Carter, Iturra, Lenox, Starrett Comparison

[Mark Duginske]

Carter, Iturra, Lenox, Starrett Comparison

There have been a number of questions and comments on the Feb. 2007 article Woodworker’s Journal concerning the comparison between the four readily available tension gauges: the Carter, Lenox, Iturra and the Starrett and the saw’s built-in gauge.

That article is based on a number of tests that I did for my new book THE NEW COMPLETE GUIDE TO BAND SAW, which is designed to update the BAND SAW HANDBOOK, published in 1989, which is the best selling band saw book in the world but is black and white and has become outdated.

No field of woodworking has more confusion that the topic of blade tension. I acquired all of aftermarket tension gauges and tested them. The results were all over the board. I was confused. To help me sore it out I hired Aaron Gesicki who has an undergrad and Masters degree in metallurgical engineer with 30 years of experience with GM and Cat making engine parts. For the article I did the photography and the drawings and developed a series of questions. Aaron wrote the article. This is the first article that I know of that compares the gauges to each other. Our test may not be perfect but it is a start and we are open to suggestions for more testing.

One of the SMC members criticized the article because it did not give the mechanical gauge numbers compared to the electronic Carter. When Aaron tested the Carter electronic ( which is modern technology) it measured the equivalent of 15,000 psi (292 pound of wheel load) for a 1/2” blade (see the article). This was the reading when the built-in saw gauge registered on the 1/2 mark. At that setting the Starrett was in the 13,000 psi range, Lenox 10,000 psi and the Iturra was all over the board from 8,000 to 12,000 psi but usually on the low side.

Along with research by an electrical engineer we working on a technical paper covering the relationship between blade tension, sharpness, wheel alignment, pitch etc. If you have suggestions for testing methodologies let me know. Please ask questions here rather than emailing me or sending me a private message.

Mark Duginske

[Scott Thomas]

Mark, I didn't read the article, but would like to know how the psi was determined.

Was it done by measuring deflection?

ie; xxxpsi required to cause the blade to deflect .100" (hypothetical) at a given height above the table, or at the center point between the wheels.

To me that would show a true reading to actually compare the guages to each other

[Mike Cutler]

Mark.
We are beginning to get significantly away from woodworking it would appear.

Let me first premise this post by stating that I do in fact own your original "Bandsaw Handbook". I can assure you that is well worn and has been loaned out, on multiple occision, to people that have had issues with the 14" bandsaw. It is the most complete reference I know of for the bandsaw.
You are a fine author,and should be very proud of this book. I expect your update to the book to be equally as valuable as the original. I cannot comment on the magazine article, as I haven't seen it.

The area of contention, it would appear, lies with the use of the tension gauges, and the application.
From the data presented I can assume that the Starret, Lennox and Carter were repeatable, and the Itturra was not. This would tell me that the mechanical properties of hysterisis are better in the first three gauges, than the last.
The Carter, being an electronic device , is essentially the same as the two pure "mechanical devices. the difference being that the distortion of the test fixture's metal is being applied to a piezoelectric crytal changing the oscillation frequency of the crystal as force is applied or releived, or it is two pieces of known wire acting as the plates of a capacitor, and referenced to a center null wire. The difference in capacitive reactance of the two wires, relative to the center can be measured an used in an electronic circuit, as can the frequency changes of the crytal.
There are more sophisticated instruments that operate on different principles, but I doubt that they were used. They cost 10's of thousands of dollars.
To establish the actual "accuracy" of these devices. They would have to be tested to a known standard, in a lab, using NIST traceable standards. Then the OEM bandsaw tension gauge could be compared to these devices and a qualitative, and quanitative value can be assigned. for a given force applied. This testing however could cost you thousands of dollars to have done, and is not really worth it in my opinion.
The Carter, Starret, and Lennox could be used with equal effectivness. Each of them would unifromally tension a bandsaw blade in a repetive nature. The Ittura would not based on the info provided. The only thing I can't assume right now, based on info provided, is which one is actually the most "accurate"
From the Carter, Starrett, and Lennox a baseline value could be assumed, and changes made to tension could be referenced back to this baseline value and a table could be developed to indicate the effects of tension on the blade.
It wouldn't really matter which one was used, as long as only one was used , and it was used consistently. If you prefer the Carter, you should use that one.
Using Young's modulus, for the given material that the blade is made of, the amount of "strectch" could be measured using a vernier, and the data obtained from that could be compared to the indication on the Carter, and the OEM bandsaw tension indicator.
From these three devices a table could be developed. if the Carter and the vernier are in agreement, and the OEM tension indicator is at 1/2". It's an odds on bet that the bandsaw tension meter is "accurate enough".
Even though I have access to calibration labs and standards, and could easily "calibrate" any of these devices to NIST standards. I've never seen the need. I use the tension meter on the bandsaw and then look at the cut, and change tension based on what I see. I've also used the vernier method that John Steven's outlined here on the board as a cross cal. All of the tension argument goes out the window as soon as that blade heats up anyway becuase it just changed everything.

My eMail address is.

Michael_J_Cutler@dom.com


Please feel free to email, or contact me, or have Aaron email me and I can see if I can set up to cal any of those devices to NIST standards in our lab should you desire it. It may take me a little time to fabricate a cal fixture and contact the vendors for calibration procedure. Starrett would be the easiest, Starret t should actually have a comercial grade cert on the device, but it can be done.

Mike Cutler

[Pete Brown]

This thread is bumming out this Iturra gauge-owning guy! :p

Pete

[Mike Cutler]

This thread is bumming out this Iturra gauge-owning guy! :p

Pete

Don't let it Pete.
Most of my post is so esoteric,I really don't see much value in anything I wrote as applied to woodworking. In the end it's a piece of wood going through a blade,and then through a jointer,planer,or sander.
If your Itturra gauge is helping you and giving you confidence in your bandsaw setup. Keep using it. Regardless of which tension device you used, that has been mentioned, all would eventually end up in a drawer once you got a "feel" for it.

Please don't let anything I posted have any effect on how you work.

[Wilbur Pan]

Mark,

I'm an owner of The Bandsaw Book as well, and I thought it proved invaluable when I was setting up my 16" Walker Turner bandsaw. Even though I'm a novice at woodworking, I was able to get it well tuned up using your book.

But even though I'm a novice at woodworking, I do know something about research methodology. (Part of my day job is to conduct clinical medical research.) I think your Woodworker's Journal article was trying to address two separate issues, of which your tests and measurements only really addressed one.

The two issues raised in your article are: [1] does setting up a bandsaw to very high tension (>15,000 psi) affect bandsaw operations, and [2] how accurate are the meters on bandsaws and aftermarket tension gauges?

The data you've presented clearly addresses the second point. Based on your findings, I believe that there is a lot of variance when it comes to aftermarket gauge accuracy. The only thing I would add to your testing are the points Mike already made about comparing the gauges to a known outside reference. You seem to be making the assumption that the electronic Carter tension gauge is accurate due to modern technology. As a pediatrician, I can assure you that home ear temperature probes sold to parents are nowhere near as accurate as your $2 mercury thermometer, even though the ear probe is much more modern technology.

However, regarding the first point -- does increasing tension result in a better cut, or is it unnecessary -- your data so far does not address that at all. The best support for this is your reference to manufacturers recommending 15,000 psi as the tension for their blades. But I think we all know that manufacturer specs can be as accurate as aftermarket tension gauges when it comes to woodworking machine specs. In order to properly test this issue, a series of cuts need to be made at different tensions, while keeping all other parameters equal, and the results compared.

Your data supports the conclusion that aftermarket gauges can be inaccurate, and that the gauges provided on the bandsaw are at least usable for measuring blade tension in the 15,000 psi range. Your data does not support the conclusion that therefore there is no reason to tension above 15,000 psi.

On a side note, I do have a question. My Walker Turner bandsaw actually does not have a tension gauge on it at all. Is there a recommended way for setting the tension besides getting an inaccurate aftermarket gauge?

[Phil Thien]

Using Young's modulus, for the given material that the blade is made of, the amount of "strectch" could be measured using a vernier, and the data obtained from that could be compared to the indication on the Carter, and the OEM bandsaw tension indicator.
From these three devices a table could be developed. if the Carter and the vernier are in agreement, and the OEM tension indicator is at 1/2". It's an odds on bet that the bandsaw tension meter is "accurate enough".

But isn't that precisely how these gauges work? They attempt to measure the stretch in the blade, don't they?

If the devices tested give repeatable tests that don't match one another, I don't understand how introducing another device (vernier) that functions the same way is going to answer any questions???

I know I must be looking at your suggestion wrong.

[Mike Cutler]

But isn't that precisely how these gauges work? They attempt to measure the stretch in the blade, don't they?

If the devices tested give repeatable tests that don't match one another, I don't understand how introducing another device (vernier) that functions the same way is going to answer any questions???

I know I must be looking at your suggestion wrong.

Phil.
Yes they do measure the "stretch" of the blade. The vernier would measure the actual elongation of the blade. From this value the amount of lbs/force could be derived based on the known modulus of steel.
The vernier would provide another independent method of determining the amount of force.
The indication from the vernier and the aftermarket tension gauge could be compared to another and then compared to the OEM tensoin indicator on the bandsaw. From ths a rough baseline value could be derived.
I'm trying to get enough independednt measurements to form a table.

The after market tension gauges could also be checked by clamping them to a beam and suspening known amounts of weight off of them to replicate the wheel force, in lbs, applied. Then multiplied by the cross section of the blade and the modulus value. This could be a pretty accurate and cheap way of validating the values obtained from the aftermarket tension gauges.
Your last post in the original thread is correct in it's assumptions. I believe though,that three of the tension gauges are repeatable, and one was not.
Maybe I read it wrong??

[Dennis Peacock]

While this is not directly related and we are starting to dive into the "science" of tension guages.....

Please remember, no bashing of person or manufacturer or the post will be edited or deleted.

[Jim Dailey]

Hi Mike,

Not that I can shed much light on this subject 'cause your "way over my head" on the technical aspects of blade tension.

In the other thread Mark Duginske wrote these specifics regarding the tension gauges mentioned in the article;

"3.The Carter gauge is the most accurate for this application (a tired woodcutting band saw). The spring gauge in the saw is adequate and more accurate than the mechanical gauges. Of the mechanical gauges the Starrett was the most accurate in terms of psi reading. The Lennox was most precise (repeatable). The worst is Itura which has a calibration problem and often does not return to zero. With the faulty Itura gauge we got 15,000 psi readings as low as 8,000. Which means that if you use the Itura gauge you could be almost doubling the tension on your saw. No wonder parts are bending or being broken."

Of course of the 3 mechanical gauges... which one do you think I own....:(

From my prospective; I just want to repeatably tension my saws for the proper tension for what ever size blade the job calls for....

It's like my television...I don't care how the picture got there....

It's like my computer... I just want it to work... of course this is why I fired Bill Gates and bought an Apple :D

jim

[Al Willits]

"""""""""
The best support for this is your reference to manufacturers recommending 15,000 psi as the tension for their blades.
"""""""""

Consider I'm a newbie, and of the tighten it till it works, method of setting tension, the people I bought my TimberWolf blades from said, I needed less tension than normal, does seem to work though.
??

Al

[Phil Thien]

Phil.
Yes they do measure the "stretch" of the blade. The vernier would measure the actual elongation of the blade.

I've been guessing (wildly assuming) that part of the difficulty w/ the blade-based gauges has been getting them correctly installed, and extrapolating their measurement over just a few inches of blade to the rest of it.

When you suggested using a Vernier, I pictured a set of calipers c-clamped to the blade as has been discussed here and elsewhere before.

I just can't imagine this is a good way to measure how much a 80+ inch blade is stretching. But again, I will qualify this by saying I've only done some redumentary experiments on my own bandsaw w/ a digital caliper.

It does seem to me that the Carter gauge is actually the equiv. of a digital scale. It is measuring force applied rather than trying to measure the blade. Which is probably a smarter way to do it if the option is available to you.

I will continue to use the built-in gauge and my gut.

[Mike Cutler]

Hi Mike,

Not that I can shed much light on this subject 'cause your "way over my head" on the technical aspects of blade tension.

In the other thread Mark Duginske wrote these specifics regarding the tension gauges mentioned in the article;

"3.The Carter gauge is the most accurate for this application (a tired woodcutting band saw). The spring gauge in the saw is adequate and more accurate than the mechanical gauges. Of the mechanical gauges the Starrett was the most accurate in terms of psi reading. The Lennox was most precise (repeatable). The worst is Itura which has a calibration problem and often does not return to zero. With the faulty Itura gauge we got 15,000 psi readings as low as 8,000. Which means that if you use the Itura gauge you could be almost doubling the tension on your saw. No wonder parts are bending or being broken."

Of course of the 3 mechanical gauges... which one do you think I own....:(

From my prospective; I just want to repeatably tension my saws for the proper tension for what ever size blade the job calls for....

It's like my television...I don't care how the picture got there....

It's like my computer... I just want it to work... of course this is why I fired Bill Gates and bought an Apple :D

jim

Jim.
It was never my intent in my post above to infer that any of those tension devices were of a lesser or greater quality. I was trying to limit my resonse solely to the instruments that Mark currently has available for use.
To the best of my knowledge. Louis Itturra does not make the tension device that bears his name in his basement. It is being made by someone for him.
It works on the same principle as the Starrett, and should be a pretty rugged little device. The particular one that Mark has may be damaged, or did not adhere to the spec's that Louis specified. If it were mine I would have returned it, regardless of manufacture, or origin.
Mark and company have 4 tension devices available to them, by four different vendors. It would be difficult to state that each one is a statistical representation of that product, and that every device each manufacture produced, of the same product line, would yield the same result. As with all things, sometimes you get a great one and sometimes a not so great one right out of the box. It would be unreasonable to expect Mark to purchase 10 or 20 of each one and do a comparison across the devices.
Unless you have reason to believe that your tension gauge is not working properly, keep using it. If you have reason to believe that it is not working contact Louis Itturra. In the conversation I had with Louis a few years back, I found him to be a very engaging individual that cared about the services he provided, and the products that bear his name.

I guess the point is. "If it ain't broke, don't fix it"

[Ken Garlock]

I said that I would not post again on this subject. So much for that.:rolleyes:

First off, Mark, I plan on buying your new book. ( I have the BS book by Mr. Bird and was underwhelmed by it. )

I too, as you may have guessed, own the Ittura gauge. I was surprised and dismayed that it performed so poorly. I accept your comparison, and will at some point get the Starrett gauge.

So now the new question: I have been puzzled for sometime about the claim by Suffolk Machinery that their blades require lower tension to operate satisfactorily. It seems to me that the science of steel making is well understood. If Suffolk Machinery had a new and better blade, the rest of the world would also have it, via industry publications, or metallurgical analysis.

I spent one afternoon using google to explore for silicon steel blade material, and didn't find anything. Maybe it is so common, that it is not worth mentioning? Yes, I could have missed something important...

Soooo, why does the Timber-Wolf blade require/use lower tension as opposed to other brands?:confused:

Any metallurgists out there?:)

[Al Willits]

"""""""""
Soooo, why does the Timber-Wolf blade require/use lower tension as opposed to other brands?
""""""""

Well I now know I'm not the only one wondering.....:D

Al

[Mike Cutler]

I said that I would not post again on this subject. So much for that.:rolleyes:


Actually Ken, I was hoping that you would post again on the subject.

[Mark Duginske]

This is the discussion I was hoping to generate.

I will try to address some of the questions but first I would like to make a comment particularly to Mike C. and Ken G. because you guys are more technical than I am. The article did not address the issue of the discrepancies between the gauges because that is a whole another issue. I wondered about the discrepancies and speculated on it but Aaron S (in a phone conversation) and Ken G. corrected me which is good.

Mike C. Thanks for participating. Also thank you for your email address. I will contact you before we do more testing. I appreciate your input and your willingness to participate in this discussion.

I had mixed emotions about giving out the numbers because it is possible that there is something wrong with one of the gauges. Perhaps I should get another Iturra gauge. However, I have two Lennox gauges (one is new and the other is 18 years old) and they both read exactly the same every time. If all of the gauges had the same results we would not be having this discussion. We want to do more testing and I’m open to suggestions. Aaron and I talked about buiding a framework from which we could hang a piece of blade which could hold the gauges. On the bottom of the blade
we would make something that would hold a weight. That way we could exactly duplicate the amount of weight for each test. What do you guys think of that? Should we do something different?

Aaron and I have talked about having a conference where we would do various test and demonstrations. Unfortunately there is not a lot of usable testing or research being done.

We are going to be working with an electrical engineer to do a number of test. We are open to suggestions. At this point I have more questions than answers.


Thanks,

Mark Duginske

[Mark Duginske]

Ken: I went to the text file for the new book and copied this.

Silicon Steel Blades

One variation of the carbon steel blade is blade stock from Sweden which has a high silicon content. Silicon steel blades have a carbon content similar to C1074 spring steel. That is, it's carbon content ranges from .74-.79%. It's silicon (Si) content is high at around 1.5% whereas regular carbon steel has a silicon (Si) content of .16-.19%. The reason for high silicon content is its ability to tolerate heat. It is appropriately named "Friction" band and is used primarily for “friction sawing” when cutting metal at speeds of around 6,000-14,000 feet per minute. This technique is used to cut through different types of steel and compound materials. The material being cut is heated by the cutting action of the blades and softens in front of the cut. Even though the blade is not designed for woodworking it is aggressively marketed at a premium price. These blades have teeth in the 60 Rc range with a 30 Rc body. They are initially sharp and cut well in the beginning, but I don’t think that they are as durable as a high quality carbon steel blade. These blades are advertised as requiring less tension but there is not a good technical explanation for using less tension than usual.

Note to Ken G.
I was told by someone in the blade business that these blades have a tendency to stretch if too much tension is applied. I can not confirm that but that is one of the things I would like to test.

[Jim Dailey]

Mark,

When it comes time for testing if you'd like another Iturra gauge... you can can use mine.

Just send a PM & I'll send you my email address.

jim

[lou sansone]

Some how I feel that the discussion of blade tension gages is not complete without a sound engineering reason for using them. I did explore this issue in a previous post. In my mind there are a couple of things going on with the band saw blade and a couple of reasons for trying to measure the tension.
From my previous post

" it turns out that many steels tend to yield at about 1/3 of 1% strain. so it looks like band saw blade mfgs simply play it real safe with the blade tension in the 15kpsi to 30kpsi range ( 1/20 to 1/10 of 1% strain ). this gives the blade a decent amount of tension, but pretty far away from actually yielding the steel for plastic deformation. "

the other issue is related to harmonic vibrations and a standing wave on the taught steel band. I seems to me that the flutter test is trying to get to this issue.

any thoughts ?
Lou

[Mark Duginske]

Response to Wilbur Pan

“does increasing tension result in a better cut, or is it unnecessary”
Not necessarily, the analogy that I use for the band saw is that it is like a soup, there are a number of ingredients and they have to work together. Tension is one important ingredient but more is not necessarily better (like salt). If too much tension is applied the spring will compress completely and the shock absorber function is lost. The top wheel hinge will bend or break as shown in the photo in the article, or the wheels twist or are pulled out of alignment. There is a wide range of “functional tension”. On my 14” saw I can resaw with a sharp 1/2” blade with the saw set at the 1/4” mark although I usually use the 1/2” mark. As the blade dulls I move it to the 3/4” mark. A lot of the tension requirements depends on blade choice and sharpness. Ultimately, with or without a gauge you should experiment a little bit to find the sweet spot.

If I remember correctly Walker Turner was bought by Delta in 1953. They are very nice band saws. For tensioning I would not recommend the clamp on gauges. There is a thread now on using the dial caliper to measure the amount of blade stretch and that makes sense if that appeals to you. That is one option. The other option is the flutter method but I would give it more than one turn. The other method is just to experiment. As I said in another thread there is the misconception that the “correct” tension is a very narrow band like between one 49 yard line and the other 49 yard line. It is more like the middle of the field with quite a wide area of acceptable tension settings.

I think that a lot of using the clamp on gauge has to do with the “placebo affect”. I took a pill 30 minutes ago and my…….now feels better. I used the tension gauge so I must have the right tension.
It is a confidence builder. I worked as an R.N. in peds for two years. I actually learned a lot more about writing being a nurse than an English major.

Good Luck,
Mark

[Dennis Peacock]

Ken: I went to the text file for the new book and copied this.

Silicon Steel Blades

One variation of the carbon steel blade is blade stock from Sweden which has a high silicon content. Silicon steel blades have a carbon content similar to C1074 spring steel. That is, it's carbon content ranges from .74-.79%. It's silicon (Si) content is high at around 1.5% whereas regular carbon steel has a silicon (Si) content of .16-.19%. The reason for high silicon content is its ability to tolerate heat. It is appropriately named "Friction" band and is used primarily for “friction sawing” when cutting metal at speeds of around 6,000-14,000 feet per minute. This technique is used to cut through different types of steel and compound materials. The material being cut is heated by the cutting action of the blades and softens in front of the cut. Even though the blade is not designed for woodworking it is aggressively marketed at a premium price. These blades have teeth in the 60 Rc range with a 30 Rc body. They are initially sharp and cut well in the beginning, but I don’t think that they are as durable as a high quality carbon steel blade. These blades are advertised as requiring less tension but there is not a good technical explanation for using less tension than usual.

Note to Ken G.
I was told by someone in the blade business that these blades have a tendency to stretch if too much tension is applied. I can not confirm that but that is one of the things I would like to test.


Hey Mark D.
I can tell you from experience that the Timberwolf Blades that I use will cut better and out last any other brand of BS blade of the same type and size. I used to use Lenox blades, but after I was pointed towards the Suffolk Machinery blades? I have never looked back.
I know there are other brands of BS blades out there, but I've tried 3 of them and I have settled on one that works long and cuts well for me without costing me an arm and a leg. Just my experiences with blade. ;)

[Art Davis]

Okay, a newbie here---one who owns Mark's book as well as the one by Lonnie Bird, and have benefitted from both.

When I purchased my Grizzly G0555, I ordered Timberwolf blades. Tried their "flutter method," but all I could get was a heart flutter. Called them, and the rep there said, "Well, if it won't flutter, it doesn't really matter. Just set it up according to the tension adjustment on your saw." I have been doing that, and don't have any complaints. Resaw works fine, etc. (I have the six inch riser block and ordered the longer blades.) I do like the Timberwolf blades.

So, here's my question: how do those of you who have a lot of experience with the band saw adjust your blade tension? Frankly, after a long professional career of being a theoretician, here I find myself wanting the practical viewpoint. You can talk about stress, strain, Young's modulus, Hooke's law, etc, but it all boils down to a question of what will saw my wood the best. And I think that is an empirical issue, but one that seems to be "underaddressed" in the literature---including Mark's own fine book.

Anybody with any responses?

Thanks.

Art

[Pete Bradley]

Mark,

I think the answers may lie in the application of these gauges. Precision measurement is 5% about the tool and 95% about how it is used. It's really a science in itself, and few of us do enough to become experts.

My thoughts/questions:

1. Contact Starrett, explain who you are, and ask them about tension gauges. Starrett should be able to hook you up with someone who is expert not only with their gauge, but who can shed light on your questions.

2. Since the Carter gauge measures wheel load rather than measuring band strain directly, I expect it has to be calibrated somehow to account for band thickness and width (or c.s. area). How is this done?

3. When testing the Carter gauge, how did you determine the actual PSI at the band?

Pete

[Mark Duginske]

Good, then keep using them. I have used them and like them. I also like the Highland Woodslicer. Both give a good cut but I use the band saw a lot and I wish they would stay sharp longer. I think that for a serious hobbiest who isn't spending all day sawing they are a good choice. I think it is a good idea to experiment.

I now use a bimetal blade almost all the time because they last so long.
One of the experiments that I would like to do is on blades and test cut quality versus longevity. Also, there may be enough variation (speed, power)in saws that may make a difference in the performance of the blade.

[Mark Duginske]

Response to Pete Bradley

Your point is well taken. Aaron has a masters in metallurgical engineering so I assume he knows how to use the gauge.

I talked to the tech people at both Starrett and Lenox and was under whelmed by the response. No one could explain how the gauges we calibrated and/or tested. Also I talked to the engineer at Delta who says that now that he read the article he wants to do some test. One of the problems these days is that the "corporate memory” is short. The people who designed and built the 14” Delta
In 1933 or 34 in Milwaukee are long gone….. same with the Lenox and Starrett gauges. Getting good technical information these days can be a real challenge. The engineer at Carter was very knowledgeable and very helpful.

The Carter measures wheel load in pounds at the bottom of the tensioning rod. Aaron calculated the blade load to be 146 pounds
for a blade with that cross section at 15,000 psi. If you study the drawing you can see the blade in the corner of the one inch square.
15,000 psi is what both the blade and saw manufactures recommend for tension on a 14” band saw.

Mark D

[Mark Duginske]

No area of woodworking has more confusion among hobbyist woodworkers than blade tension. If you visit a professional woodworking shop or factory or a metalworking shop and look at the band saws they will be tensioned to the setting on the gauge. If you told these people who use saws all day long that the gauge was off or not accurate they would laugh at you. They are practical and the gauge has worked for them.

This whole tension controversy thing started about 18 years ago with the late Jim Cummin's article in Fine Woodworking Magazine which said that the gauge was erroneous, that the spring weakened, and the spring should be replaced with a stiffer spring.
HE WAS WRONG ON ALL ACCOUNTS, and knowledgeable practitioners disregarded the article. Cummins assumed that the Lenox gauge he was using was accurate not realizing the gauge was reading 15,000 psi in the 10,000 psi range. Which means that if you use that gauge you are overtensioning the saw by 50 percent. That article is the seed for the mistrust of tension gauges.

However, author’s and merchants have continued to pass on the false information without doing any research or testing. This wrong information (that the gauge on the saw is erroneous) is now accepted as fact in some circles and this poor quality information keeps getting quoted over and over.

I'm a fourth generation woodworker. Both my father and grandfather had businesses making patterns. I grew up in a shop with 3 different 14" Deltas and much bigger saws, all set at the gauge mark. That 14" Delta saw has been the standard of the industry for 75 year (often working 24 hours a day during WW2 in pattern shops). It astounds me that anyone who has used that 14" Delta saw a lot could believe Jim Cummins article that said the gauge is off, the spring is week and doesn't provide enough blade tension. That article is the seed for the mistrust of tension gauges.

USE THE GAUGE, AS THE BLADE DULLS YOU MAY WANT TO INCREASE THE SETTING. I USE THE GAUGE AT THE 1/2” SETTING FOR THE 1/2” BLADE BUT INCREASE THE SETTING TO 3/4” WHEN THE BLADE GETS DULL.

Don’t be afraid to experiment and change the tension .

Mark D

[David Rose]

Art,

I also started with TW blades. I couldn't get them to flutter (or to quit?) either. They were not steady, but never changed. This was on a Delta 14" US last model. This is my only rip saw and I ate those TW blades fast.

A fellow on the B. Pond found me a Lenox carbide blade at a good price. He convinced me to try it.

It took 1/32" or LESS planer cut to clean up the saw cut! I just used the minimal settings that TW recommended for their blades. That was about 3/8" blade if memory serves. It worked VERY well with no tracking adjustment. That may have been due to the teeth being wider than the band, but it was true.

Due to a "visitor" turning on the saw with no tension, I got a kink in the blade which I never could quite smooth out. I'm not sure that the new blade gives me quite the cut that the old one did, but it hasn't really been "tested" yet. I have tensioned it all the way up to 1/2" on the factory scale. I can tell little to no difference. I'm sure that the tension is fairly low. I have set the wheels as co-planer as feasible, added a riser block, use Cool Blocks adjusted well, changed the motor to 1HP with pulleys to up the speed to recommended, installed a brush, added half decent dust collection port, added a better table with tight insert, added link belt, squared up everything, basically I super tuned the saw. The saw will easily pass the nickel test.

This saw saw 6 TW blades in about 4 months before the carbide ones. The first carbide ran about 4 years before the accident. The new blade has seen little use. But if history repeats, tension will end up at around 3/8" with the factory spring. This is for resawing and ripping.

Oh, and I do release tension after each use. And I haven't broken a blade yet even on the 14" saw. One blade may not tell much, but we'll see with the second one.

David


Okay, a newbie here---one who owns Mark's book as well as the one by Lonnie Bird, and have benefitted from both.

When I purchased my Grizzly G0555, I ordered Timberwolf blades. Tried their "flutter method," but all I could get was a heart flutter. Called them, and the rep there said, "Well, if it won't flutter, it doesn't really matter. Just set it up according to the tension adjustment on your saw." I have been doing that, and don't have any complaints. Resaw works fine, etc. (I have the six inch riser block and ordered the longer blades.) I do like the Timberwolf blades.

So, here's my question: how do those of you who have a lot of experience with the band saw adjust your blade tension? Frankly, after a long professional career of being a theoretician, here I find myself wanting the practical viewpoint. You can talk about stress, strain, Young's modulus, Hooke's law, etc, but it all boils down to a question of what will saw my wood the best. And I think that is an empirical issue, but one that seems to be "underaddressed" in the literature---including Mark's own fine book.

Anybody with any responses?

Thanks.

Art

[Ken Garlock]

Your information on the silicon steel is the first write up I have seen. :) But. I will stick with my Lenox bi-metal blades.:cool:

[Mark Duginske]

Ken,

Please see the note to Dennis Peacock. There are a lot of good blades out there but I also have been using bimetal blades (Olsom MVP).

I got that info from the metal working field where that blade is used for friction sawing.

Regards,

Mark

[Mike Cutler]

Response to Pete Bradley

Your point is well taken. Aaron has a masters in metallurgical engineering so I assume he knows how to use the gauge.

I talked to the tech people at both Starrett and Lenox and was under whelmed by the response. No one could explain how the gauges we calibrated and/or tested. Also I talked to the engineer at Delta who says that now that he read the article he wants to do some test. One of the problems these days is that the "corporate memory” is short. The people who designed and built the 14” Delta
In 1933 or 34 in Milwaukee are long gone….. same with the Lenox and Starrett gauges. Getting good technical information these days can be a real challenge. The engineer at Carter was very knowledgeable and very helpful.

The Carter measures wheel load in pounds at the bottom of the tensioning rod. Aaron calculated the blade load to be 146 pounds
for a blade with that cross section at 15,000 psi. If you study the drawing you can see the blade in the corner of the one inch square.
15,000 psi is what both the blade and saw manufactures recommend for tension on a 14” band saw.

Mark D

I also spoke with the engineer at Carter yesterday about the Carter ETG, and asked him to send me whatever info on their device that he was able to.
He seemed like a decent guy. We talked about the differences between the Starrett,and the Carter.

The Starrett, Lennox and Itturra all work on the same principle. As the blade is tensioned, the distance between the two fixed points becomes greater.
The point on top is fixed,and the point on the bottom of the gauge is free. The bottom point is a lever that moves on a pin. As the distance between the two points expands the lever exerts force on the bottom of a dial indicator, that has been graduated in pressure.
The lengths of the lever arm(s), or pivot arm according to Starrett, relative to the fulcrum point would be a math function to represent blade stretch.
The dial indicator is just a graduated usable scale. It's no different than any other dial indicator. The amount of deflection, represents the amount of distance between the two contact points, and the math fuction of the lever arm. Minus mechanical hysterisis of the dial indicator, and the lever arm, and friction of the pivot arm on the pin. the rest of it is all a math function.
If I were to use these instruments I would make sure that the dial indicator was already pre loaded though to remove the mechanical hysterisis of the device at the zero point.

The Carter is an electronic strain gauge that is looking at the amount of force being placed on a point of contact, and converting it to an electrical output, millivolts, frequency, resistance . Carter wouldn't tell me the exact type of strain gauge that they were using, proprietary I assume. Strain gauges are nothing new though, and this one is basically the same type used in a load cell for cranes,and electronic bathroom scales. Beyond the zeroing there isn't much that can be done to one. normally zero and span calibrations are performed on the electronics modules themselves. Then a known amount of weight, or force is applied to the sensor to check the operation of the cell.
If you wanted to check the Carter. zero it and then apply a known weight to the contact point. It appears it is just measuring the weight of the downward force in lbs.
The info that Carter sent me has a table for common bandsaw widths and the corresponding range of lbs force for each width of blade.

The following info is the document I recieved from Carter, on their ETG. I deleted the marketing type stuff. I have the entire document in a PDF file if anyone would like it, including installation/operation instructions. I have not found similar info for the Starrett, Lennox, or Ittura or I would have also post that. If someone has that info, it might help the discussion by providing a "common language" so to speak, if it could be posted.

I'm posting this info because there have been a few questions regarding the operation, and basis of the Carter device.

ELECTRONIC TENSION GAUGE (ETG™) Patent Pending
from Carter Products Co., Inc.
Overview
The following is a suggested range of ETG TM settings and readouts for various size
blades that you may wish to use as general guidelines to start with. You should revise
these values based on your particular saw and style of cutting.
CAUTION: The ETG displayed value is primarily intended to provide a relative indication of
tension and a method of achieving repeatability. ALWAYS take into account the
characteristics of your saw model and cutting conditions as well as any information available
from the saw’s manufacturer or your blade supplier when determining appropriate tension
levels to use for your particular application.
The output of the ETG closely approximates the bandsaw WHEEL LOAD in pounds force.
Please note that the ETG does NOT read directly in units of BLADE TENSION since for any
given load the tension will vary depending on blade size. Blade tension, often expressed as a
value of PSI (pounds per square inch) is a function of the size of the cross sectional area of the
blade. For those that want to explore this further, the Appendix at the end of this document gives
more detail about the relationship between TENSION and LOAD.
Blade Width Range of ETG Readout
1/8” 150-175
3/16” 175-200
1/4” 200-225
3/8” & 1/2” 225-250
3/4” plus 250 +


APPENDIX: THE RELATIONSHIP BETWEEN LOAD AND TENSION
Simply speaking, LOAD is the force, usually expressed in pounds, applied to an object.
In the case of a bandsaw, the wheel tensioning device causes the saw’s frame to exert an
upward force on the top wheel. It is this WHEEL LOAD that is being measured by the
ETG Electronic Tension Gauge’s sensor, which is positioned in the load path between the
saw’s frame and the upper wheel.
This upward load is resisted by a downward pull from the blade. Since there are two
strands of blade pulling on the wheel, one on the left and one on the right, each blade
strand is seeing ½ the force that the wheel is seeing. Therefore:
BLADE LOAD = ½ the WHEEL LOAD
However, the effect that any given load will have obviously depends on the size of the
object to which the load is applied. Larger objects can withstand large loads that might
deform or destroy a smaller object. Therefore, it is often helpful to calculate a parameter
called STRESS, which very simply is defined as the LOAD applied to an object divided
by the CROSS SECTIONAL AREA of the object. If we know the STRESS an object is
experiencing, we can often predict the object’s behavior even if we don’t know its size.
Stress which acts in such a way as to tend to pull things apart is referred to as TENSION.
Therefore, the stress pulling on a bandsaw blade is called BLADE TENSION and is
usually expressed in units of PSI, Pounds of load per Square Inch of blade cross sectional
area. The cross sectional area of a bandsaw blade is simply the thickness of the blade (in
inches) multiplied by the width (in inches) of the blade at its narrowest point, usually at
the bottom of the gullet. Therefore we can say:
BLADE AREA = THICKNESS X WIDTH
and
BLADE TENSION = BLADE LOAD / BLADE AREA
So by knowing the approximate load being applied by the wheel of the bandsaw (through
the use of the ETG) and by knowing the cross sectional area of your bandsaw blade
(through direct measurement), you can estimate the BLADE TENSION (STRESS) and
compare it to the blade or saw manufacturer’s recommended values.
EXAMPLE CALCULATION:
Suppose we have an approximate wheel load of 250 pounds and that we are using a ½” x
.025” blade. If we were to measure this blade’s narrowest point and find it to be .41”
wide, we have enough information to calculate the blade’s tension or stress level by use
of the following equations:
BLADE LOAD = ½ WHEEL LOAD = 250/2 = 125 pounds
BLADE AREA = THICKNESS X WIDTH = .025 X .41 = .010 in2
BLADE TENSION = BLADE LOAD / BLADE AREA = 125 lbs / .01 in2 = 12,500 PSI (lbs/in2)
This value, 12,500 PSI, is the number you should then compare to the blade manufacturer’s
recommended tension level to determine if you are operating your saw within proper guidelines.

[James Carmichael]

Lots of good info out here, but I'm afraid Mark is giving his book away:-)

The trouble with any "scientific" test is that unless all conditions are precisely duplicated with the same object definitions for "quality of cut" and "outlast", you're comparing apples to oranges.

Bottom line is, go with what works for you.

[Mark Duginske]

Mike,

Thanks to Mike Cutler for long explanation, I hope you type faster than I do. When I asked the people at Lennox and Starrett about using their gauge for woodworking machines they both seemed surprised and commented that it was designed for older metal working saws without a gauge.

Now to be practical

I personally use the gauge on the saw and fine to tune the set-up.
We never talk about blade sharpness in this discussion but it is a huge factor. A sharp blade on saw with coplanar wheels doesn’t require that much tension. A lot of people, like Ken G. and I use bimetal blades because they last longer than the others. Another factor for resawing is the flat (European design) wheels versus the America crowned wheel. The flat wheel really supports the blade well. For the BAND SAW HANDBOOK I put chalk on the tire of a Sears saw and then ran it with 1/2” blade. I was amazed that I only removed about 3/16” of the chalk which means that blade is
balancing on the crown.

I’m not picking sides, I don’t care if people spend money or not on gauges. But, from my experience with the clamp on gauges I have to question their usefulness (especially considering the discrepancies) for woodworking. However I think they provide a useful tool for people who are not confident with another approach such as using the built-in gauge and then fine tuning it. There are some people who really like numbers and the gauge gives a number. There is such a wide range of “functional tension” that I’m sure the gauges “work” for the people that use them.

If one is a “love numbers type of guy” and want to spend money I think the Carter gauge is the answer. It is a really neat device. First of all, once it is installed there is nothing else to do. It provides a constant readout as the saw is running which is very interesting. Since I put it on a 14” saw that is now my gauge because it is easier to use than the built-in saw gauge. In many situations it would be very useful such as a shop with multiple users, schools, etc. Now the bad news….at the moment it is made only for 14” saws. The other factor is the $200 price. I talked to Alex Snodgrass, who is the inventor, and he said they are working on the price to get it lower. He also told me that he had a new tensioning system that is less expensive. He wouldn’t say much about the new device. I suggested that he work on something that would work on all the types of band saws but that is a problem because they are all different. The Carter ETG works well on the 14” saws because it clamps onto the frame under the space where the tension rod contacts the frame. Rather than contacting the frame the point at the bottom of the rod contacts the top of the of the ETG sensor. Mike Cutler is right about the bathroom scale analogy.
The sensor is essentially measuring the WHEEL LOAD of the top
Wheel. Study the drawings in the Feb. 2007 Woodworkers Journal article by Aaron G and myself.

Thanks Mike C.

Mark Duginske

[Mark Duginske]

There is some confusion about the origin of the psi recommendation.

Most saw and saw blade manufacturers recommend 15,000 psi. I think Delta on their new 14" 5X saw recommends 13,000 ???. It looks like Carter recommends 12,500 (read Mike C's comments).

This number keeps getting refered to but I have not been able to track down where the number came from.

IF SOMEONE READING THIS POST (MIKE C. OR KEN G.) KNOWS WHERE THAT NUMBER CAME FROM PLEASE LET US KNOW.

Mark

[Mark Duginske]

Thanks for your concern about giving the book away but the article material is not in the book because the book was too far along.

Also, for the average woodworker this discussion is "pointy headed"
as they say here in Wisconsin. A lot of readers want to know where to set the gauge, period. As my father would say, "Tell me the time, not how to built a watch". This discussion is deeper than the average book reader wants to go.

And I agree with your apples and oranges comment. The article was an attempt to sort out some of the confusion about blade tension. Unfortunately, no one that I know of has really done testing and research that is practical to the average woodworker. I would like to do a lot more testing and I'm getting good feedback from the technical types reading and contributing to this thread.

There is a lot of unsubstantiated material in articles and catalog copy and no one seems interested in sorting it out. I talked to the people at Fine Woodworking about correcting the misinformation in previous articles but they want to “move on” with new material.
This kind of discussion on the web really is a good source of feedback for people. We are discussing the idea of the new book having a website so we could update readers on new developments etc. I’m hoping this new book I applicable for a long time but to keep it current it needs to be supplemented by the web.

Traditional publishing is a very large, powerful and entrenched industry that does not always serve the group that wants to go a "little deeper" into a subject.

Mark

[Ken Garlock]

If I were to use these instruments I would make sure that the dial indicator was already pre loaded though to remove the mechanical hysterisis of the device at the zero point.


Mike, the Ittura gauge instructions specify at least one full revolution of the dial indicator when tightening the lower clamp. It appears that loading of the gauge didn't help in the tests.:(

[Mark Duginske]

Jim Dailey has offered to lend me his Iturra gauge for more test. I would like to test three gauges attached at the same time so if someone has an Iturra gauge that they would lend me I would appreciate that.

I'm think about building a fixture from which I would hang the blade and design something that would allow me to a add weights to the bottom of the blade. That way, when I apply weight to the blade, it will always be exactly the same for each test.

I'm open to suggestions for testing.

Mark

[Ken Garlock]

in the night.

Personally, I came to the 25-30,000 pound number after reading the tension article in the Ittura Designs catalog. In that article, Lou Ittura states that he contacted Lenox tech people, and that they "frequently recommend" 30,000# for their blades(2005 catalog, page 33.) I also know from various posts on this forum and others that people run their Lenox carbide blades in the area of 30-35,000#. These numbers seem reasonable since 30,000# is within the elastic limit for steel. It seemed reasonable that the more axial tension on the blade, the less lateral deflection there would be, and hence less potential for blade drift.

[Joe Mioux]

I have been scaning this thread with some interest.

Iturra's product has been beaten up pretty good here.

Is he a member here, if not, I would sure like to hear his response to some of the previous comments.

Joe

[Pete Bradley]

I'm open to suggestions for testing.

Well, since we're already in the spirit of academic endeavor:

Based on my back of the envelope calculations, it seems to me the challenge of the mechanical gauges is that they have to measure a very small delta, a few thousandths at most. A minute amount of slack or bend in the band when you start or any slippage will cause error. It doesn't make sense to me that anyone else would be marketing such a thing to the average weekend woodworker.

You might be able to find a college nearby with an Instron machine and an inclination to help. This machine will apply a controlled load to a piece of band, and at the same time it measures the strain.

Failing that, your idea of the weights has potential You'd want the top end clamped solid, and the bottom end to go through a slot, then attach to something of moderate weight that will carry the real weights. That would minimize slack while attaching the gauge. You're going to need a very accurate measurement of band thickness and minimum width too.

Pete

[Mike Cutler]

I have been scaning this thread with some interest.

Iturra's product has been beaten up pretty good here.

Is he a member here, if not, I would sure like to hear his response to some of the previous comments.

Joe

Whoa.... This is definitiely what I did not want to have happen. I have spoken to Louis only once on the phone, and found him to very engaging and articulate individual that really cared about the products and service he provided. I also believe that if others are having problems they should contact him. He may not be aware of the issue(s), if they exist.

Any remarks or observations I have made on the Ittura tension gauge can only be confined to the one that Mark currently has in his possesion, which I believe has been damaged somehow, or not manufactured to Louis' spec's.

If my lack of typing,or english skills have implied that I somehow believe the Ittura tension devices, as a whole, to be inferior. I absolutely do not.

[Alan Schaffter]

I have read Mark's article and the two SMC threads with interest.

I thought I wanted an after market tension gauge until reading and thinking about these threads. I think what too many of us are/were searching for is a more precise, repeatable, and QUICK and EASY way to adjust our bandsaws to some likely totally illusive goal- a number representing the "correct" tension that takes our own abilities out of the equation.

As Mark and others have alluded, in reality there are no precise standard tension- because of differences in blades (steel, size, teeth, etc.), saws, tires, wheels, etc. We are trying to replace experience, knowledge, and, yes, craftsmanship (with all that entails) with a number from a gauge.

We may also be forgeting about the size and properties of the material (wood) we are cutting as well as the condition of the blade at the time. I really like this quote from the Carter gauge info (the most accurate gauge according to Mark's article): "CAUTION: The ETG displayed value is primarily intended to provide a relative indication of tension and a method of achieving repeatability." (I added bolding). Think about what that means. It doesn't sound too good, but beyond that it only affects the blade being set to some previous setting - but what setting, and how was it determined? It is also without regard to the current condition of the blade or the material being cut.

So, except for Mark and those of you who have weighed in here, who are successfully setting their tension by testing and experimenting (with experience gained over- years?) and getting good cuts, or at least ones that satisfy you, the rest of us need more experience. In my mind, that pretty much negates the need for an after market tension gauge. I still want an easy way to do it that I can trust more than my own craftsmanship if someone can come up with one - it appears no one has figured out how to do that yet.

Also, in order for any gauge comparison test to be valid, the test samples and conditions have to be identical - identical blades (same run of steel, same tempering, age, handling, welded exactly the same way, on the same saw under the same conditions.

[Mark Duginske]

Ken Garlock and Jim Dailey have offered to lend me their Iturra gauges.

So I'm planning on building a fixture from which I can hang a 1/2" blade (like the one in the article). I plan to hang 146 pounds from the blade with the three gauges installed. This will duplicate the set up in the Woodworker's Journal article.

I'm not singling out one manufacturer or retailer of these gauges in particular but the fact that all three do not read the same does mean something. I was reluctant to give the numbers but the article was also criticized for not giving the numbers. By doing more test we can see
if one of the gauges is damaged. Even forgetting the Iturra, what accounts for the big difference between the Lennox and the Starrett.

I plan on doing 10 test with the gauges installed and 10 test with the gauges reinstalled each time. Mike C. and Ken G: how does that sound?

I will also use the set-up to check the two Lennox gauges which thus far given identical results.

I got the number of 15,000 from Starrett for woodworking band saws.

If you have testing suggestions let me know.

Mark Duginske

[lou sansone]

There is some confusion about the origin of the psi recommendation.

Most saw and saw blade manufacturers recommend 15,000 psi. I think Delta on their new 14" 5X saw recommends 13,000 ???. It looks like Carter recommends 12,500 (read Mike C's comments).

This number keeps getting refereed to but I have not been able to track down where the number came from.

IF SOMEONE READING THIS POST (MIKE C. OR KEN G.) KNOWS WHERE THAT NUMBER CAME FROM PLEASE LET US KNOW.

Mark


I did a little more research which confirmed what I had suspected about the flutter method and bandsaw tension gages. Namely, all of this has to to do with the harmonic vibration of the blade. Much of this research is in the area of "vibrations" ( all you mechanical engineers must remember these undergrad courses with joy ). There have been many technical articles written in various journals about bandsaw blade vibration which results in "wash-boarding" or other types of poor cuts. Unfortunately I don't subscribe to any of those journals and don't live close to a good university library that would carry them. But even looking at the abstracts, one can see that all of the blade tension stuff is really concerned with suppressing the fundamental or higher order harmonics in the blade. If someone has access to these articles, here are a couple.


http://www.springerlink.com/content/l4114136h2052t7j/

http://www.thinkerf.com/Downloads/StrainResp.PDF you can read this one

http://apt.allenpress.com/aptonline/?request=get-abstract&issn=0735-6161&volume=010&issue=01&page=0019

there are many other articles as well that one could spend lots of time on.

It does look like blade tension is a critical factor in cut quality, the problem is determine that tension and adjusting it for the conditions. It seems that just throwing out a value of 15000 psi is just way to vague if you really want to get to the heart of the problem, which is vibration and natural resonance of the blade. It is obvious that a certain amount of tension is needed to make sure you have a stiff blade, but that is only one part of the total solution. If mike is still working on his book, I would think that someone from thin kerf technologies might be good to get in touch with.

lou

[Mike Cutler]

To "calibrate" any of the mechanical tension shouldn't require an elaborate setup. Everything about the mechanical devices, is a math function.

If I were to calibrate these I would remove the independent variables. The blade, and the human. We are trying to quantify that the device is capable of providing an accurrate representation of force for a given change in distance between the two points.
Once this is established, any unexpected value can be traced back to the user, or the blade.
Using Youngs Modulus value for Carbon Steel, 29,000,000 and trying to achieve 15,000 psi. The amount of strain in inches would be 15,000/29,000,00 or .00051724 in/in.
The value referenced in the Carter Info of 12,500psi would be 12,500/29,000,000 or 0.00043103 in/in.

Multiply the in/in values by the distance between the two clamps on the mechanical gauges, after preloading the device, and this would be the change in distance bewteen the two points that should correspond to a change in tension gauge indication of the calculated amount. A calibrated, or even commercial quality inside micrometer could be used to make these measurements.
Any blade tension value in psi (strain) can be worked using Youngs Modulus, as long as the measurement falls within the linear range of the metal, and doesn't enter the plastic range.
Using the blade cross sectional/width formula provided by Carter, and working it backwards would result in the expected Carter indication in wheel load, or lbs. This is all math, there are no variables yet. Once we know that the device is "accurate" we can look for discrepancies somewhere else.
I'm thinking of a test fixture to this. I think one of the MicroFence Router guides could be used/adapted as quick test fixture to change the distance between the two contact points in a controlled linear fashion. The threading is 50tpi, and there is enough strength between the parts. An independent measurement device could also be incoporated. A possibility.

The variables as I see them are these.

The mechanical tension gauges were designed around the particular steel that was in use in steel bands when Starrett first made the device (The Lennox and Ittura are copies o the Starrett). Differing types of steel are going to have different properties and Youngs Modulus values. This would throw the scale readings off. The amount of difference in the Youngs Modulus values could be established and a bias factor algebraically summed with the tension gauge indication to give a better approximate value for that particular blade.

If we just hang weight off the bottom of a bandsaw blade we can get a fairly decent comparison. Attaching all three simultaneously to a single band and then suspending the weight could be effected by the non linearity of the area between the clamp points, and the clamps themselves. Although I doubt very much.
Additionally the blade would have to be new. An old one would be suspect of micro cracks and stress induced fatigue. Once again the blade could be non linear throughout the range that the devices are attached.

Just some thought. It looks as if it's going to be a nice day outside today. Hopefully I can get some yardwork, or shop time in. LOML has a little project for me.:eek:

[Steve Rowe]

...
I thought I wanted an after market tension gauge until reading and thinking about these threads. I think what too many of us are/were searching for is a more precise, repeatable, and QUICK and EASY way to adjust our bandsaws to some likely totally illusive goal- a number representing the "correct" tension that takes our own abilities out of the equation.

As Mark and others have alluded, in reality there are no precise standard tension- because of differences in blades (steel, size, teeth, etc.), saws, tires, wheels, etc. We are trying to replace experience, knowledge, and, yes, craftsmanship (with all that entails) with a number from a gauge.

...
So, except for Mark and those of you who have weighed in here, who are successfully setting their tension by testing and experimenting (with experience gained over- years?) and getting good cuts, or at least ones that satisfy you, the rest of us need more experience. In my mind, that pretty much negates the need for an after market tension gauge. I still want an easy way to do it that I can trust more than my own craftsmanship if someone can come up with one - it appears no one has figured out how to do that yet.

...
Alan - well said. I have been using bandsaws (3 different ones) for 27 years now and have always used the scale on the saw to set tension. If the setting didn't give an acceptable cut (and this has been rare), all that was ever required was a minor adjustment to the tension. I personally don't see the need for a $150+ gadget to adjust tension to a specific PSI setting as I have yet to purchase a BS blade that even had a recommendation of tension in PSI. I have read on other forums reports of folks snapping their expensive carbide tipped BS blades by using these "accurate" devices making these expensive gadgets even more expensive.
Steve

[lou sansone]

"[quote=Mike Cutler]Using Youngs Modulus value for Carbon Steel, 29,000,000 and trying to achieve 15,000 psi. The amount of strain in inches would be 15,000/29,000,00 or .00051724 in/in.
The value referenced in the Carter Info of 12,500psi would be 12,500/29,000,000 or 0.00043103 in/in.

The variables as I see them are these.

The mechanical tension gages were designed around the particular steel that was in use in steel bands when Starrett first made the device (The Lennox and Ittura are copies o the Starrett). Differing types of steel are going to have different properties and Youngs Modulus values. This would throw the scale readings off. "


My response

I think most steels are close to 29 mega psi and thus have little effect on the reading.

The big sawmill type bandsaws ( two sided blades ) often have hydraulic upper wheel tension mechanisms, which make measuring blade tension a snap. The clamp on Gage will get you close to some supposed value, but what use are they really? If they are not repeatable, then they are not useful at all. An instron would be ideal to test these gadgets. ( maybe someone has already offered to do that ).

lou

[jim gossage]

in response to Mark's plan to do more testing of the gauges, you might ask for advice from the staff at consumer reports. they are extemely experienced in devising jigs and machines to test anything from drill torque to force of car crashes.

[Tom Hamilton]

Facinating discussion, thanks for sharing all this info. And Mark, thanks to you for you first book. Mine is saw-dusty, creased and dog-eared from use in the shop.

And my Duginske set-up Griz 513X performs to my great satisfaction.

Best regards, Tom

[JC Bagley]

I am working with Louis Iturra on resolving and understanding the issues with his gauge and my G0513X. I sent him an email about this thread and suggested he chime in. He replied with:

"Attached to this email is my response to Mark Duginski's article published in Woodworker's Journal Feb. 2007 issue. You may post it online in any internet forum you see fit."

It's a VERY long reply and the SMC server is forcing me to split it up into smaller segments. Here's part one.

===================

01/22/2007

“Letters”
Woodworker’s Journal
4365 Willow Drive
Medina, MN.
55340

Dear Sir,

I read with interest the complimentary issue of your February 2007 magazine and I would like to take this opportunity to respond to the two bandsaw myth busters, Mark Duginski and Aaron Gesicki. But before I do, I would just like to say thank you for the complimentary issue. Your magazine is very informative and gives the home-shop woodworker a new and different perspective to the world of woodworking. I especially appreciate the way your magazine presents difficult and controversial issues that other magazines tend to shy away from. Of particular note, Ron Johnstone’s article on the challenges China’s manufacturing has on domestic sources hits close to home since my company is in the business of manufacturing. I can only say that I understand why most major woodworking manufacturers have moved overseas but I don’t see the war as being already lost. There are still many smaller manufacturers such as my company, Iturra Design, that have been successful due to listening to the voices of the average woodworker and offering innovative products and services that fulfill their needs. It’s only one mans opinion but I believe the larger manufacturers lost out due to their reluctance to change quickly enough. When the Asian invasion first began, larger companies like Delta and Powermatic refused to accept the challenge. They simply refused to improve machine designs which were almost 50 to 60 years old. Since their utility and design patents had expired years ago they had no protection against off-shore manufacturers copying their designs right down to the last nut and bolt. When they finally woke up, they found their foundations severely eroded and in order to save themselves from total collapse they gave in and moved their manufacturing overseas. It’s the same story with our vaporizing automotive industry, domestic manufacturers haven’t moved quickly enough to changing market forces therefore surrendering more and more market share to imports. Confirming my premise is the fact that many of these importers have become domestic manufacturers by opening production plants here on American soil. They’re simply more responsive to the American consumer and what they want. Such is the game of capitalism.

Many experts say we’re simply moving from a manufacturing economy to a service/technology economy. Americans will no longer have to worry about that pesky and dirty business of making things to sell to others, we can simply sell our services and technology to everyone. Frankly, I don’t see it working, most of the high-tech companies are moving manufacturing and R&D overseas and I don’t think selling insurance, flipping hamburgers, or endless telemarketing is good for this country’s economic future. So the way I see it, the fights not over, many small American manufacturers will continue to thrive and prosper. I hate to think about what it will mean for America when that day comes to an end. So please give kudos to Rod Johnstone for a great article that was long overdue.

Before I comment on the article “Blade Tension” let me just point out that I have known Mark Duginski for a number of years and consider him one of my bandsaw mentors. His book, “The Bandsaw Handbook” has been one of the best-selling books written on home-shop bandsaws and I highly recommend it. He has also written several other books and magazine articles on the subject of bandsaws, produced videos and even conducts woodworking classes. As the prior owner of Fasttrak Woodworking, he invented the popular “Cool Blocks” along with other great products designed to make the life of woodworking easier for all of us involved in the field. But unfortunately, after reading his article, “Blade Tension”, there was little I agreed with, which is unusual, because Mark is known for doing his homework. So lets take each of the author’s five questions they chose to answer one by one.


The first, “How accurate are the standard built-in gauges on band saws?” The authors found that the standard tension gauges built into bandsaws are accurate enough to provide proper blade tension readings. I disagree because of the simplistic way they work. In order to build a tension gauge of this type you’re forced to make certain assumptions which may not correspond with reality. First, you must determine a correct blade tension level for all of the wide variety of bandsaw blades being produced today. In this case, Mark and Aaron reported that industry sources for both band saw blades and saws said the optimal value was 15,000psi. Then you must assume that all of the bandsaw blades are going to be of the same thickness because you only want one mark for each blade size. Then you must assume that all the tension springs you install in the band saw will have the exact same spring rate and will never wear out or shorten in length. Then you must assume that the markings you place on the band saws scale will be understandable by the end user. That’s a lot of assumptions! Way too many for my taste, for we all know what can happen when we assume something. So lets take the first of these assumptions, the 15,000psi benchmark for optimal blade tension. This 15,000psi benchmark is not consistent with what we have been told nor what has been published by several blade manufacturers in the past. We’ve been a distributor of Lenox bandsaw blades for many years now and Lenox has always recommended 30,000psi as their ideal tension. Up until just recently they have published this recommendation in their blade catalogs. Also, if one looks closely at the Lenox tension meter pictured on page 66 of the article, you can see that Lenox color codes their gauge indicating their recommendations, green zone starts at 25,000psi and goes up to 32,500psi. Starrett, which has been manufacturing tension meters for several decades, and was one of the four meters tested, provides tension recommendations included in the meter’s instructions for their bandsaw blades. Their recommendations range from 20,000psi for carbon steel blades and up to 35,000psi for bimetal blades. Other sources such as the popular “Timberwolf” blades which are marketed as “low tension blades” do recommend 15,000psi although their main distributor Sulfolk Machinery recommends using a flutter test to set tension. The manufacturer of our “Blade Runner” thin kerf blades recommend 15,000 to 17,000psi as does Highland Hardware’s “Wood Slicer”. Olsen recommends 9000 to 12,000psi for their blades. All of these blade tension recommendations are a bit dated, having been obtained from the manufacturers back in 2000 when we launched the introduction of our own blade tension meter, the Blade Gage which the authors tested in the article. They may have since changed, I called Lenox tech. support and was told that Lenox now recommends 30,000psi when using their blades on a metal-cutting bandsaw and 15,000 to 20,000psi when using a woodcutting bandsaw with the caveat emptor of “if your bandsaw is capable of such tension levels”. As a matter of fairness, I have sent letters to all the current blade manufacturers requesting official clarification on this matter and I’ll publish their responses in our next catalog issue next month. Now remember the authors reported that the saw manufacturers also agreed on this benchmark as well. So refer to an article posted on their website and published in June 2003 by Popular Woodworking magazine titled “Steel-frame Band Saws” written by David Thiel. He quotes Kendall Smith, product manager for band saws at Delta Machinery, “tensioning capacity of the saws also is important, and Delta’s tensioning spring (recently upgraded to a die spring) will tension a ¾” blade to 12,000psi”. Why did he say 12,000psi? According to Mark it should be 15,000psi but one could argue that was in 2003, they may have changed their minds…reconsidered. If so, has Delta once again up-graded their tension springs or re-calibrated their built-in tension gage? I haven’t seen any evidence of this yet in their band saws, if Mark has, please let him point it out to me so I can pass it on to my customers.

Now lets examine the second assumption, for the built-in tension gauge to be accurate, the manufacturer had to assume that all blade thicknesses would be the same. Why? Because listing other blade thicknesses on the gauge would make the scale complicated and hard to read. To be accurate, instead of having just one mark for a ½” blade, you would now need 4 or 5 different markings corresponding to each blade thickness. Blade manufacturers produce ½” blades in .018”,.020”,.022”,.025”, and .035” thicknesses. A .018” thick ½” wide blade would require less force to tension to 15,000psi than a .035” thick ½” wide blade. So they each would require a different marking on the built-in tension gauge of the bandsaw.

The third assumption that all the tension springs would have the same spring rate and wouldn’t wear out or shorten would have to be true if the gauge is to remain accurate. If the bandsaw manufacturers used milled springs it would be an accurate assumption to a degree, but they don’t. A milled spring is cut out by CNC lathes from a solid piece of round bar stock. All current springs used for bandsaws utilize wound springs, which are wound with wire on CNC lathes to form a spring. The best wound springs have a 10 to 15% variance in spring rate and will shorten (more on this later). This variance is for the best-made springs, most manufacturers are using poorer quality springs. The greater spring rate variance there is and any change in spring length due to various factors will degrade the accuracy of the built-in tension gauge.

Continued in another post...

[JC Bagley]

Louis Iturra's reply continues...

============

The last assumption boils down to whether or not the end user understands what the markings on the gauge mean and how to use them. Most manufacturers utilize blade width markings but I have seen some European saws whose scales have no correlation at all to blade width, or use metric scales, leaving the end user in the dark. To conclude, the built-in tension scales used on bandsaws are a low tech. method of determining proper blade tension. Simply put, the manufacturer arbitrarily determined what the tension should be for several different blade sizes and provided marking on a scale for same. This method doesn’t take into account the many different ideal tension levels recommended by different blade manufacturers nor does it take into account the variety of blade thicknesses available for today’s band saw blades nor does it take into account the differences in spring rates from one spring to another nor the different scales used.


Their second question, Are these gauges adequate for the average user? is subjective but is partially answered above. The average user needs and wants a reliable gauge that gives them usable information. Truthfully, I don’t believe these built-in gauges can do that in all cases.


The third question, Is there a problem with the built-in blade tensioning components, as some authors suggest? More specifically, is there a problem with the blade tension spring? Well, back in the year 1999, my company was the first to offer improved tension springs for the Delta and JET 14” bandsaws. We began advocating their use due to some disturbing results we found when testing these bandsaws. With a ½” blade installed, neither machine was capable of properly tensioning the blade to the blade manufacturers recommendations. We published these results in our catalog, listing exactly what tension levels were obtained at each of the blade size markings these machines use for a tension gage. Surprisingly, the maximum tension levels we obtained for a ½” blade at the ½” marking on the saw’s tension gauge was only 5600psi, well below Mark and Aaron’s magical 15,000psi benchmark. But for arguments sake lets assume Mark is correct and all blade and saw manufacturers do indeed agree on 15,000psi as the optimal tension for a bandsaw blade. We have tested many bandsaw springs and have found many unable to obtain 15,000psi for the maximum width blade the manufacturer recommends for their bandsaw. Take the current Delta’s X5 14” bandsaw model 28-475X, since its introduction several years ago it comes equipped with an up-graded spring (die spring) and even with this spring it still can not properly tension a ¾” bandsaw blade to the author’s benchmark 15,000psi. This is why I and many other experts advocate the use of a ½” blade on these smaller bandsaws. Can Mark or Aaron explain why Delta hasn’t up-graded its other current 14” models with this new spring? There are several models which still use the older tension springs such as the 28-206 and 28-276 models made in China or all the previous Delta 14” bandsaws which have been produced by Delta since 1937 when the 14” machine was first introduce. As I’ve stated above, we tested these older springs and have published our results for all our customers to see in everyone of our catalogs since 2000. One of our customers took us to task back in 2001 when he performed his own test on his JET 14”. His results contradicted ours and we were at a loss to explain why his reading were almost twice as much as ours. After he sent us his spring we discovered why. JET had obviously been reading our reviews on this bandsaw and had decided to upgrade their springs! We again published photos showing the upgrade compared to the older OEM spring JET had previously been using and informed customers of the newer (2001 or newer) JET 14” bandsaws not to buy our high tension spring until they experienced problems with the upgraded JET spring. We also have to note here that JET also beefed up their tracking arm to prevent such problems that Mark illustrates is caused by too much tension in the top photo on page 67 of the article. In a nutshell the point is: the bandsaw manufacturers knew their original OEM springs couldn’t obtain the necessary tension levels for the maximum blade width they currently advertise their bandsaws can handle! Also, Mark knew this if he read the many copies of our catalog that have been sent to him and by the many phone conversations we have had on this very subject!

The authors also said, ”Contrary to what you may have read elsewhere, even if the spring is fully compressed, such that the coils are actually touching, the spring will never go bad, get tired, or lose strength. Actually, if the spring provides adequate tension on the first day you use the saw, it will always provide adequate tension.” Those of you that have sleep on an old worn out mattress would probably take exception to this statement, but according to the authors, if I read it correctly, you should never have to replace that spring filled mattress again. I use this example only because my wife and I are currently shopping for a replacement mattress for our girls bedroom. You see, when they were little and had a sleepover with their friends, they used their mattress as a trampoline. Yes, we would tell them not too but you can’t police them every minute. So now as I inspect their mattress, what I see is compressed springs in the middle which don’t spring back to their original length anymore, causing the mattress to sag in the middle. So I had to chuckle just a little when I originally read the author’s statement. But on a more serious note, going back to the JET spring upgrade I mentioned earlier, we tested this spring, measuring its uncompressed length (free length) before and after it was fully compressed (solid height) only once and found the spring had decreased in length by approximately ¼”! This happens when the elastic limit is exceeded and the spring doesn’t return to its original length when the load is released, spring manufacturers call this “Permanent Set”. Now what do you believe will happen in terms of providing accurate readings if this shorten spring is used to determine proper tension levels with the built-in tension scale supplied with the bandsaw? Will it be accurate? I should note here that all the high tension springs we sell for the Delta and JET 14” bandsaws come with a tension chart which we have made up using a tension meter that indicates what tension level is present at the bandsaws tension gauge markings using all the current width blades that can be utilized for that bandsaw (1/16” to ¾”). But these charts are only accurate to 10-15%, since that’s as accurate a spring rate as we can get from one spring to the next without milling the spring from solid instead of coiling (milled springs of the size and spring rate needed would be cost prohibitive). It also doesn’t take into account the shortening of the spring if it exceeds it elastic limits. Even our high quality high tension springs will shorten if fully compressed for an extended period. So why would a woodworker buy one of our high tension springs? Well for the same reason one buys better parts for their auto, to get better performance and reliability from it. Our springs are made from the finest steel, vacuum degassed, valve spring quality chromium vanadium in accordance with ASTM-A232 specifications. The ends are closed during the coiling operation to provide a large bearing surface and finished square by grinding. This allows the spring to stand on their own base and compress evenly under load. The modified trapezoidal cross section changes to a “D” cross section during coiling which significantly lowers maximum stress levels compared to springs using flattened round wire which so many of the bandsaw manufacturers use. Our springs are also subjected to several additional manufacturing steps including heat treating, tempering, shot peening to reduce working stresses, and presetting by compressing to solid for increased set resistance and greater fatigue resistance. Woodworkers buy our springs because they are of higher quality than the OEM springs and in most cases, if properly selected, they will provide them with higher tension levels compared to the OEM springs which will allow them to utilize wider bandsaw blades and/or operate their blades closer to blade manufacturers recommendations (15,000psi ?). This does not mean the woodworker should ever operate their spring at close to full compression. At no time have I ever heard or read any expert advocate fully compressing the tension spring on a bandsaw. The spring must be able to act as a shock absorber as well as providing the necessary tension on a bandsaw. Mark simply needs to tension a ¾” wide blade on the JET 14” bandsaw pictured in the article and tension it to 15,000psi. He would find that the JET spring would be at full or close to full compression, ( the JET 14” bandsaw we tested couldn’t obtain 15,000psi without fully compressing the spring) yet JET documents this machine can handle up to a ¾” blade. If what Mark says is correct about the blade and saw manufacturers believing 15,000psi is the optimal value for bandsaw blades, why can’t the JET bandsaw properly handle the ¾” blade?


The fourth question, Do aftermarket tension gauges provide accurate, useful information that is valuable to band saw users? Mark and Aaron can only recommend the Carter electronic version. This is the only conclusion where I half-way agree with them. I love the Carter tension meter, I wish that the bandsaw manufacturers would incorporate this meter in all the bandsaws they make in the future. It’s great to watch the blade tension while the bandsaw is actually in operation, in many cases you can actually see how blade tension is effected by the blade heating up and expanding. But Carter’s electronic meter doesn’t actually measure blade tension, it simply measures the force directly under the tension rod with a load cell. This eliminates the stick-slip problem (I‘ll explain this later), making the readings extremely linear and repeatable. But there’s several limitations to this meter that Mark and Aaron failed to tell your readers about. First, it can be used only on cast iron 14” bandsaws since it’s specifically designed only for them. This leads to its second limitation, it’s not portable. It can only be used on one bandsaw, unlike the three mechanical versions which can be used on a wide variety of different bandsaws without limitations. The third limitation is the fact that it’s not measuring actual blade stretch or tension, as I said before, its measuring the force under the tension rod only. I discovered this can be a limitation when I was releasing the tension on a Delta 14” bandsaw. After releasing the tension by watching the reading on the electronic display return to zero, I noticed that the blade still had tension on it and couldn’t be removed. After closer inspection I discovered that the bottom of the tracking arm had caught on the opening on the upper wheel guard preventing the sliding bracket from dropping down and releasing the tension on the blade. A fourth limitation is that the electronic display doesn’t read out in psi like the mechanical versions, almost all the blade manufacturers express blade tension in psi requiring the owners of Carter’s electronic tension meter to convert the reading to psi thru manual calculation.

========

Continued in another post...

[JC Bagley]

Louis Iturra's reply continues...

============

I find it difficult to comment on the test results of the mechanical tension meters since neither of the authors describe how they were obtained. They did report that they carefully compressed the spring in measured increments from zero to 15,000psi and back to zero. So I’ll make the assumption they simply counted the number of turns on the tension rod in applying incremental tension on the spring. If this is true, then their results are invalid since they didn’t take into account a phenomena known as stick-slip. This is basically the frictional element between two sliding members, in this case the sliding bracket that contains the tension spring and the ways machined into the upper arm casting of the bandsaw. Stick-slip makes the up and down movement of the sliding bracket nonlinear and probably accounts for the non uniform results obtained in their testing. For example, they may find that 5 complete revolutions of the tension knob may result in 8000psi on the ½” blade but when they attempt to repeat the test they may have to use a total of 5-1/4 complete turns to again obtain 8000psi. Why? Because the friction between the sliding surfaces may change due to the loose tolerances machined in the ways, the sliding bracket may temporarily jam and require more force to move it again. Does this make the mechanical tension meters unless? No, these mechanical tension meters are measuring tension where the rubber meets the road, at the blade. A better test would have been to measure tension with a known quantity of dead weight suspended from a short length of blade attached to a fixed point. This is how we actually calibrate our own tension meter, the Blade Gage. This method eliminates any frictional resistance in the system being tested. Any discrepancies between the three tension meters to each other in their readings may be attributed to improper mounting of the tension meter on the blade. One must ensure that the captured length between the clamping thumbscrews is not curved when comparing the tension meters to each other. If one tension meter captures a straight length of de-tensioned blade and another captures a length with just a small amount of slack in the blade its readings will not be accurate. Also improper handling either during shipment or rough handling in service can adversely affect their calibration. Even the way the tension meter is stored can affect accuracy if corrosion is allowed to develop within the moving parts. This is why we have a policy here at Iturra Design that allows the original owners of our Blade Gage to ship it back to us and for $5 (cost of return shipping) we will check and/or recalibrate the gage (this is a life-time guarantee). These gages are extremely precise instruments measuring blade stretch in 0.0001” graduations which makes them very expensive and delicate. But all of these gauges have distinct advantages over built-in tension gauges, they’re not affected by weak or shorten springs, they’re not affected by differences in blade widths or thicknesses, and they allow the user to adjust the blade to the blade manufacturers ideal tension recommendations. Worldwide, mechanical tension meters have been used successfully for decades in industry, setting up production bandsaws to produce reliable consistent cuts day after day. Almost all bandsaw blade techinians recommend their use.


The last question the authors attempt to answer, What is the most efficient way to properly tension band saw blades? The authors recommend simply using the built-in tension gauge; that you can get top-notch performance right out of the box. In many cases, this may be true, if the user knows what the ideal tension is for the blade they’re using and the bandsaw they purchased can obtain those tension levels and the built-in tension gauge has been calibrated for those tension levels. Lots of “ifs”, and judging from customer feedback and commonly asked questions here at Iturra Design, it’s a subject that sorely needs addressing by your magazine and others. So many subjective methods for properly setting blade tension have been given by so called experts, such as pushing on the side of the blade and looking for ¼” deflection, plucking the blade and listening for a pure musical note and watching for flutter in the blade. All of these methods are just that, subjective, which means it depends on the person performing the test. An example of this would be: I may push on the side of the blade with 5 pounds of pressure to obtain ¼” deflection but you on the other hand may apply 10 pounds of finger pressure. We would both end up with different tension levels on the same blade. In order to be consistent, a bandsaw user must have a measuring device that can obtain accurate and repeatable results. He can only obtain that with a blade tension meter. I often use the analogy of car tires to explain this aspect of bandsaws to woodworkers. If one purchased new tires for their car and the tire manufacturer recommends 32psi for maximum performance and life, how would one know when the tires were properly inflated? Simple, they would use a tire pressure gauge because they’re readily available and inexpensive. But years ago, before they became commonplace, people would simply kick the tires to check for proper inflation. Was this an accurate method? No. Did users get maximum life and performance from their tires? Probably not. But someone somewhere saw a need for an accurate way to measure tire pressure and the tire pressure gauge was born. We are slowly approaching the same period with blade tension meters, very few woodworkers have used them since their cost has been extremely expensive. Here at Iturra Design we saw a need for an inexpensive tension meter, a tension meter any woodworker could afford and introduced the Blade Gage which sells for $150, which is half the cost of what was currently on the market. We still believe that this is still too expensive and are currently working on a second version which hopefully will retail for half the cost of our Blade Gage. So the real question one needs to ask themselves when properly tensioning their bandsaw blades is this. Do I want to be a tire kicker or do I utilize tools and components which enables me to obtain accurate blade manufacturers tension levels? Thus achieving optimal performance and longevity from their bandsaw blades.

The authors attempted to answer five questions and in every instance drew questionable conclusions. The authors blame over-tensioning as the cause of component failure and provide photos of broken components attributed to over tensioning. They don’t recommend high tension springs believing the OEM springs are adequate. Truth is, many of these components are substandard even if you believe in Mark’s benchmark optimal blade tension of 15,000psi. Fact is, some manufacturers such as JET beefed up their tracking arms when they up-graded their tension springs several years ago because of component failure in this area. But buyer beware, because many manufacturers haven’t followed suit. So is it wrong to offer customers improved and stronger made parts to replace OEM components that constantly fail, I think not! Is there a problem with the OEM tension springs? In most cases the answer is uncertain without actually testing the bandsaw with the widest blade recommended by its manufacturer with a tension meter. In the case of the JET 14” bandsaw pictured in the article, even the improved OEM spring is incapable of providing Mark’s 15,000psi to the maximum width blade(¾”) JET claims it can handle!

The authors state,” So there you have it. We’ve found no good technical reasons for over tensioning. We suspect it has more to do with compensating for other tune-up issues rather than blade tension system deficiencies.” Mark and Aaron, no one has ever recommended over tensioning! We simply believe that if a woodworker purchases a bandsaw whose manufacturer claims can use a certain maximum width blade, then that bandsaw should properly tension that blade. If you want to agree on a benchmark of 15,000psi then that bandsaw should be able to apply 15,000psi to that blade width. If it doesn’t, don’t blame us for selling the woodworker a spring that can or selling improved components that won’t break. Instead of myth-busting, experts such as yourselves should be advocating that blade manufacturers disclose on the packaging what they consider to be optimal blade tension for their blades. Have saw manufacturers disclose what ideal or average tension level was used to calibrate their built-in tension gauges. Also have saw manufacturers disclose what tension level was used to determine the maximum width blade recommended for the bandsaw.


Unfortunately, in this day and age, disinformation is everywhere, which is why we publish our catalog with information we believe to be true and correct. At anytime, anyone can take us to task on the validity of this information and if we believe it furthers the efforts of providing a better understanding of bandsaws we’ll publish their arguments. This provides a forum to our customers so they can decide for themselves which is the better course of action to improve bandsaw performance. A healthy suspicion of popular opinion is a valuable intellectual quality but one has to closely examine the rational for that popular opinion. Weigh the reasons it came about and then make an appropriate choice, for no one likes living in a fools paradise.

I sincerely hope that Mark and his friend reconsider their conclusions on blade tension.

Sincerely,
Louis A. Iturra

[lou sansone]

long article by Mr iturra. I still don't see anyone providing a sound engineering reason for the 15000 psi value, except my attempt in a few posts back. What good does it do to spend several pages saying that any meter can read the magic 15kpsi value, when the value is really the question in the first place.

still wondering

lou

[Dennis McDonaugh]

I think everyone with a dog in this fight has his own fish to fry. How's that for mixing metaphors? They are all salesmen whether they are selling books or bandsaw springs. In the end you have to evaluate the claims and make your decision on who to believe. I tuned Mr. Duginski out when he called Louis Iturra a self promoter. How many times has Mr. Duginski mentioned his new book in these threads? I find it pretty convenient that he mentioned several times how he hates to visit these forums yet here he is. Kinda like watching the movie stars make the rounds with Jay Leno and Lettermen when they have a new movie coming out. Having to retract statments made as fact just reinforced my opinion. But then again, maybe I've become too cynical.

[Jim Dailey]

Dennis,

I think you are making a personal attack. If I an reading this wrong... my apology. :o

I had the opportunity to have lunch last week with Mark Duganiske. He was very down to earth. I did also have a chance to look very briefly at his new unpublished book. His updated book appeared to be very well polished, incredible graphics and much more substantial then his previous book on bandsaws.

I have also on several occasion spoke to Louis Iturra over the phone. And have purchased a number of items from him it the past, and will both purchase & recommend him in the future.

I have gained insights from many sources... experts, tradesman & novices.... no one has a monopoly on good ideas.

Personal attacks however are not appropriate. Please keep an open mind.

Again if I an reading this wrong... my apology. :o

jim

[Dennis McDonaugh]

Dennis,

I think you are making a personal attack. If I an reading this wrong... my apology. :o

I had the opportunity to have lunch last week with Mark Duganiske. He was very down to earth. I did also have a chance to look very briefly at his new unpublished book. His updated book appeared to be very well polished, incredible graphics and much more substantial then his previous book on bandsaws.

I have also on several occasion spoke to Louis Iturra over the phone. And have purchased a number of items from him it the past, and will both purchase & recommend him in the future.

I have gained insights from many sources... experts, tradesman & novices.... no one has a monopoly on good ideas.

Personal attacks however are not appropriate. Please keep an open mind.

Again if I an reading this wrong... my apology. :o

jim

Apology accepted Jim. I am merely pointing out what went on earlier in this thread and made an observation. I didn't accuse anyone of anything. I have his book and use it regularly. I also buy from Louis Iturra. PM me if you'd like to discuss it off line.

[lou sansone]

long article by Mr iturra. I still don't see anyone providing a sound engineering reason for the 15000 psi value, except my attempt in a few posts back. What good does it do to spend several pages saying that any meter can read the magic 15kpsi value, when the value is really the question in the first place.

still wondering

lou

Still wondering .... are there any engineers out there ?

[Dick Sylvan]

Mark,
Since we met in Sacramento I have been looking for your book, but it doesn't seem to be out yet. Do you have any more details?

[Tom Hamilton]

Hi Dick: The book vendor we use at our Church Bookstore shows that Mark's new book is due in May 07.


The New Complete Guide to the Band Saw: Everything You Need to Know about the Most Important Saw in the Shop
Contributor(s): Duginske, Mark (https://ipage.ingrambook.com/ipage/servlet/ibg.product.search.br8000?productType=All&productLimit=INGM&N=0&Ntk=Contrib&Ntt=Duginske, Mark)(Author) https://ipage.ingrambook.com/ipage/servlet/ibg.common.titledetail.imageloader?id=1565233182&ean=9781565233188 ISBN: 1565233182 EAN: 9781565233188 https://ipage.ingrambook.com/images/spacer.gifPublisher: Fox Chapel Publishing Company https://ipage.ingrambook.com/images/spacer.gifUS SRP: $ 19.95 US - (Discount: REG) https://ipage.ingrambook.com/images/spacer.gifBinding: Paperback https://ipage.ingrambook.com/images/spacer.gifPub Date: May 2007 https://ipage.ingrambook.com/images/spacer.gifPublisher Marketing: This essential guide to woodworking's most versatile tool includes a thorough analysis on everything needed to know in order to purchase, setup, use, and maintain a band saw. This book details what woodworkers need to know before purchasing a saw--including the eight questions to ask before buying a used saw--along with topics such as a part-by-part overview of every component of the saw, techniques of set-up and alignment, choosing the right blade, and understanding hand positioning to provide any woodworker with the most complete guide to a band saw. Special sections are devoted to band saw accessories, how to deal with common problems, and how to maintain a band saw to keep it running effectively and efficiently for years.Should be in the stores fairly soon.

Best regards, Tom, in Houston, with a copy on order!

[Dave MacArthur]

Good information in this thread, and good discussion. After reading all the information, I strongly feel that Mr. Iturra's response has been the most logical, well reasoned, and scientifically sound. I was very impressed with the obvious research and thought he has put into the subject. As someone with a master's degree myself in probablility and statistics, and a good bit of study in test design and data analysis, I must say that his conclusions ring true to me, and I was quite pleased to see previous descriptions of him as engaging, articulate, and caring borne out by his thoughtful response.

Can't say when I've enjoyed reading an internet thread so much, and I am also impressed with the maturity and respect demonstrated by the forum readers here!

[Alan Schaffter]

I'm with Lou- what is the correct tension (psi) for a particular blade, and how was that figure obtained- I would suspect there may be some trade between metallugical/mechanical requirements and material cut quality requirements. So how important is it for the tension to be set accurately (as opposed to precisely), and how much variance is acceptable?

I think the best and easiest tension method might be a combination of a well designed bandsaw tension/tracking mechanism that doesn't have "stick-slip" and a direct reading (in psi) gauge similar to Carter's that can be used/monitored while the saw is in use- and all included in every saw for minimum additional cost.

How have we all survived using the bandsaw for the last XX years without accurated springs and tension gauges?

[lou sansone]

Still wondering .... are there any engineers out there ?


I am still wondering if there are any sound engineering reasons for the recommendation about 15kpsi.

lou

[William Falberg]

Being new to Sawmill Creek's forum I'd like to introduce myself as another band saw "expert". I make and sell specialized portable bandsaws for timberframers. I've been following BS threads on several general-WW forums for a year now and just recently found Sawmill Creek. This particular thread caught my eye because it highlights the confusion surrounding the subject of re-sawing. I once owned a Delta BS and immediately chopped it down to a frame with three wheels. Mark Duginske, Lonnie Bird, and others have far more experience setting up standard two-wheeled bandsaws to perform re-sawing than I do so I defer to them in all matters related to the commercial machine-dynamics side of resawing. The emphasis of my research has been directed towards making flat cuts in the 16" depth-of-cut range; two to four times what most of you consider tough cuts. There just aren't any blades that worked, no matter how much tension was applied, and in the end I had to make my own machine for re-setting commercial blades to match the variety of cut parameters my customers demand. I'm not skilled enough at writing to describe exactly how tension, tracking, blade speed, HP, set angle, and wheel alignment interact to produce flawless resaw cuts so I'm inviting any recognized author (Mark?) or BS expert to bring their favorite blades, tension gauges, band saws, fences, gnarly workpieces, whatever, and (especially) a typewriter to my shop to see for yourself why my on-line postings always contradict your learned advice. You are ALL correct, insofar as the dynamics of the band saw is concerned, but equally wrong where blade dynamics is concerned. I'd like you to see what happens when a blade is "tweeked". I think an open-minded, face-to-face exchange of this nature could, if properly described and published, dispel the last remaining "mysteries" on the subject. I'm easy to find on Google, so please feel free to contact me in any manner you wish. My shop, my mind, and my heart are open. I have no dogs, just kids.

[Bill White]

What time is it? Well, you first take a billet of stainless steel, mill the outside shape of the watch you want, contact a swiss watch movement mfg. co.,............
Now that I feel better, I tension 'til I get the smoothest cut, cut the part, and get on with stuff.
I have had good luck running the Timberwolf blades with my standard settings.
Bill

[Jay Fields]

Hello Mr. Falberg,

I read an article about your test methods, results, and conclusions a while back in either Woodshop News or Woodworker West. Interesting conclusions. A bit counter to everything else you read on the net and in print.

A search for your name at SMC found the following posting;
http://sawmillcreek.org/showthread.php?t=52942 (http://sawmillcreek.org/showthread.php?t=52942)

I may try some similar tests on my own bandsaw someday when I find some time.

JF

[Rick Markham]

Ok, gentlemen... now maybe I understand just enough of the physics to toss the proverbial "monkey wrench" in this conversation. Please bear with me... In a shop environment, where you are changing blades, i.e. different manufacturers, different steel, even blades from the same manufacturer might be steel from different foundries/ore, yielding albeit minute subtle differences in the metalurgy, even in separate runs from the same foundry is there not going to be environmental factors that contribute to the molecular make up and hence the physical properties of the steel? Even with the highest quality control, environmental factors fluctuate, minute uncontrollable changes, i.e. Ore characteristics etc. Even the minute amount of welding on the blade, should change it's characteristics slightly (it might be small but... it's still there)

So now my point, for true repeatability I would think measuring the load on the single point on the machine (the tension rod) is going to yield the most repeatable results. Granted I am not talking about true tension of the blade, since from my perspective, there are too many variables to eliminate. Obviously recording the setting for each blade by the best result gives you an excellent reference point for the next time you set up that blade. At some point this becomes a semantic argument. It seems to me that for repeatability sake, measuring the point with the least amount of variables is the best idea. It might not be true "blade tension" it's the force exerted on the wheels, but since the blade make up and type are not a constant there is little more than a "ballpark" figure that you can ask from any instrument.

Just a thought, don't know if my bucket holds any water

[Van Huskey]

Rick, I have read a TON of posts here and other forums, articles and books and watch too many engineers that know far more than I argue ad naseum about tension, aftermarket tension gauges and the gauge on the saw. I have finally come to the conclusion that OP, Mark (one of the BS gurus) supports:

"USE THE GAUGE, AS THE BLADE DULLS YOU MAY WANT TO INCREASE THE SETTING. I USE THE GAUGE AT THE 1/2” SETTING FOR THE 1/2” BLADE BUT INCREASE THE SETTING TO 3/4” WHEN THE BLADE GETS DULL."

He is talking about the gauge on the saw, I go up a blade width for carbide because they require more tension. If I have any issues with a particular blade I may play with tension and mark that blades "tag" (I keep one for each blade with some info I see as valuable).

In the end I love tools and measuring devices but when it seems I have already paid for the only tensioning device I really need when I bought the saw I would rather spend that money on a really nice carbide resaw blade.

So for me I had the same questions as you but the more people that "knew what they are talking about" chimed in the more I realized there was no clear cut answer though each person felt like they were right. So I just figured I would go with the easy route recommended by someone that knows more and is more proficient with a BS than I will ever be.

[kenneth kayser]

For testing tension gauges, why not just take a few feet of blade material and hang a known weight from it. Cross sectional area can be easily be measured with a micrometer.

[Howard Klepper]

I am neither an engineer nor a bandsaw expert, but there is another method of tensioning a blade that I don't see mentioned here, which is listening to the pitch when it is plucked between the wheels on the column side. I listen for a musical sound in the 40-50 Hz range. For a given tension, this will vary from saw to saw with the distance between wheels, but since tension is directly proportional to the unit weight of the blade, the pitch remains a constant (for a given tension and wheels spacing) as blade width changes, so long as blade thickness remains the same.

[Tom Walz]

A couple great posts here. They do a nice job of illustrating the complexity and uncertainty of tool science and tool testing.

In the industrial world the following book is widely respected. Maybe not as directly applicable to the average forum member as Mr. Bird’s but it may have some valuable crossover information.

The Complete Guide to Your Industrial Bandmill & Bandsaw
111 pages, 52 illustrations

Wijesinghe, Ralph
4688 Sunland Pl
Burnaby, BC V5J 2R4
(604) 437-4610.
ridw@shaw.ca
www.datasystech.com

[Neil Brooks]

I've been following this thread with ... a RIDICULOUS amount of attention :)

I still don't have all the pieces that MY brain seeks:

a) What's the problem that we're trying to solve. For ME, it's ease and accuracy of cut, safety, blade life ... in no particular order;

b) What impact do various blade tensions have on the above;

c) How do we know this;

For ME, I'm tripping over dollars to pick up dimes without that info.

I've got Mark's first book (love it). Do I need to go back to that to find my answers? DO they live there?

ARE these questions well and thoroughly answered, already -- if elsewhere ??

[James White]

What happened to this? Was the retesting ever done?

[Will Blick]

> I would think measuring the load on the single point on the machine (the tension rod) is going to yield the most repeatable results.


in the end, its blade tension you are after, nothing else. Itura's new 2011 book writes about this subject in detail. Its a great read, and its 2011 catalogue is quite updated vs. some of this outdated tests.


I have the higher end Ituro test gauge, which reads in 1/10k of on inch... (current ones do not, unless you replace with a higher-end dial indicator, which is what Starett and Lenox has installed) Louis claims he has all these meters, and tests them, and its the Carter electronic which he has the hardest time keeping matched with the 3 gauges, his, Starett and Lennox. When using the gauge, assuming the dial indicators are working, and not sticking, it does not appear the readings should be far apart. considering you are trying to read variances in 1/10k of an inch, IMO, any faults would probably be in the dial indicator, as these are quite precise instruments vs. the more commonplace 1/1k inch versions.


you also have to be careful using the saws gauge. In most cases, they are rudely calibrated, and often calibrated thin blades...whereas you may use thicker blades. The Lennox Tri Masters I use are 2x thicker than what the MM20 scales are for. Double blade thickness = double tension, so in theory, when I use a 1" blade, I would need to set at 2" setting, but the saw only goes up to 1.5" setting max. which as it turns out, with the Ituro guide, reads 13k pounds of pressure. TriMaster 1" blades are suggested to run up to 30k pounds of pressure, so I just max. out the crank when using that blade...

[ian maybury]

Hi Mark, guys. I've not read all the posts, but the perspective that strikes me is that we're a little at risk of presuming we know what's needed in terms of chassis, blade tension and the like. Which may not be the case - it's more like there's a recipe that usually works, but it's not necessarily clear why.

One issue I ran into in trying to get a high end 18in hobby band saw to re-saw well was that there clearly was lots going on by way of vibrations in the blade. These were largely invisible, but could be felt if it was touched with a piece of wood and seemed to interplay with vibration in the chassis and worsening to correspond with the onset of drift.

My sense was that there's probably lots of modes of vibration involved - ripples running up and down the blade, torsional/twisting movements in the blade, and also longtitudinal movements involving rotational oscillations of the blade and wheels. Then there's the various modes of vibration the chassis may be capable of in the many dimensions in which deflections are possible.

All this on top of the static/load induced deflections taking place which may give rise to tracking and blade guidance issues too. The tensioning mechanism/spring, and the stub shafts on which the wheels are cantilevered are no doubt capable of various modes of vibration in their own right too. I've acquired a 24in Agazzani which I'm about to start up - it'll be interesting to see how it compares to its predecessor....

Another complicating factor is the reality that when vibrating systems interact they can reinforce or cancel each other's effects. There's also the little matter of resonance.

Getting a saw working well is probably (just theorising) about (a) getting to set up that maintains correct alignment of the blade, wheels and guides, and (b) getting into some sort of sweet spot where the worst effects of vibration (i.e. resonance) in certain critical modes is tuned out. Blade tension is perceived as being critical, but probably because in the context of a given saw and blade set-up/system it's probably the single biggest factor available to (a) re-tune the multiple modes of vibration, and (b) adjust static deflections/alignments.

Steel fabrications like are found on most modern band saw chassis are especially prone to vibration (unlike cast iron the material has minimal internal damping) - maybe they need filling with concrete or a similar damping medium. It looks like maybe the close multi point contact guide systems like Laguna's and Cool Blocks produce improvements in cut quality by maybe acting to damp/choke off vibration in the blade.

This is of course all pretty speculative, but judging by the saw mentioned above they are the sort of issues in play. One thing that seemed fairly clear was that it simply didn't seem to offer the possibility of a dead (minimal vibration) zone for deep re-sawing within the available adjustments. No matter how it was set up significant vibration was always present. Deep re-sawing (over 6in in oak) seemed to trigger a sharp worsening which could be heard as a nasty and harsh metallic almost scream.

It's hard to know how best to approach the problem of creating a 'dead' saw. Chances are that modern CAD modelling coupled with finite element analysis may open the way to predicting a lot of what's going on - I'm not up to speed, but suspect that it's possible to predict modes of vibration pretty effectively these days. (think aircraft and vehicle structures and the like) On the other hand when there's multiple systems and multiple modes of vibration in play it may get somewhat beyond accurate theoretical prediction.

It's also quite likely to be the case that some variables become hypersensitive to adjustment within certain narrow ranges, while appearing largely inconsequential for much of the time. There's also the issue of how the variables change between and with wear to blades and the like.

The other approach is the empirical - getting a series of saws hooked up with all sort of instrumentation to figure out what's going down in practice. With a view to tuning out the problems in a new design through repetitive testing and modifications. My inclination would be to focus on finding out what's actually happening when saws stop performing/get outside of the sweet spot first - with a view to figuring out what improvements are likely to give the best bang for the buck.

The outcome might be a set of requirements to be delivered when designing and setting up a saw - maybe some design improvements and a methodology and some tools for delivering the requirements too.

All in all (depending on the project is scoped) it's potentially quite some undertaking - maybe time to call NASA. Good luck with the project.

ian

[Will Blick]

Ian, good post, and yes, I should have touched on some of this as well... running a saw at 15k - 30k pounds of tension is nothing to sneeze at. So there is certainly more to the equation than getting blade makers reccommendation on blade tension, buying a gage and setting to that tension. It's the weak link in the chain principle...if the saw itself is the weak link, all the set-up will not produce the best cuts. This is why lots of hardcore re-sawers buy very old BS's and overhaul them, as back in the old days the big units weighed a ton, and they still weigh the same today :-) Weight adds stability, absorbs vibration and resists flexing as much of the metal is in all the vulnerable support zones. This seems to be the "claim to fame" of the Italian makes today, they have maintained the robustness of the saw vs. the Asian makers. Then of course you need good bearings, the right guide blocks, the right set up, a blade that does not walk (in n out), as not all blades are created equal. I have had blades that walk, (.025") and I replace them with an identical blade, and it will walk only .004". Blades have lots of variables, including the human variable as each one is welded together.

Then you need to follow some fundamentals on cutting.... I follow the 3-6-19-12 Rule - IMO, very effective... Lennox also supports this... Idealy, select the tpi of the blade so you always have 3-6 teeth in the wood at all times. If softer wood, you can go as low as 3, VERY hard wood, up to 12. Too many teeth in the wood = too much heat and insufficient waste removal (creating more friction heat). Heat is the enemy of all blades, specially BS blades. Not enough teeth in the wood = slower cutting = heat build up from excessive friction as the blade is in the wood longer than it needs to be.

This is why its a 3-6-9-12 rule, its flexible. The wood type and power of the saw, which are two variables that vary for each set up... so clearly, re sawing is part science, part feel, part equipment, part user knowledge of feed rates, etc. And you hit the nail on the head, this power tool is not heavily researched, much is trial and error. And as blade technology continues to advance, the documentation doesn't seem to follow it. The best resources are those who work in the BS field full time such as Louis and some of the big shops that re-saw wood all day - they have lots of wisdom you will not find in books....

[Wes Grass]

One option not generally available is varying the blade speed. This is one of the first things to try in the metal shop, lathe, mill, etc., when chatter is an issue. Might turn out to be a valid reason to just go 3 phase from the start.

As for the metallic screaming, I've been assuming it's induced by friction with the rear thrust bearing (Euro guides). I don't remember ever hearing this with my Laguna and the ceramic guides.

[Kirk Howard]

Carter, Iturra, Lenox, Starrett Comparison
... suggestions for testing methodologies let me know. Please ask questions here rather than emailing me or sending me a private message.

Mark Duginske

I have not read the article yet, but I am curious and will try to look it up this weekend.

So my comment/question are without knowledge of the test setup. As mentioned in an earlier post, this is a very difficult test to administer. Can you discuss the measurement system analysis?

[David Kumm]

I have been reading this and other threads about bandsaw tension over time and opinions are varied and temper can flare. I recently purchased a starrett gauge because I had no way to judge my iturra gauge. That gauge took a lot of criticism in Mark Duginske's article some years back and stirred up a big debate with Louis Iturro. Louis had cleaned and tested his gauge but curiosity - and a good deal on ebay- led me to the starrett. I tested both at the same time on my Oliver 217, one above the other. They read within 1000psi of each other from 0 to 35000. Yes the old ollie could tension a one inch lenox trimaster to that point. At least in my case the two gauges were reading the same. As to results, which are all that is important, at 15000 I got a great cut on 8 inch hard maple although the blade pushed back against the rear bearing and spun it pretty hard. At 25000 the cut was slightly better- slightly being the only choice becasue the first was so good. The veneer ranged from .055 to .061. My fence probably flexes more than that. More importantly, the blade did not move into the bearing. That alone will keep my tension for that blade at that point as running the bearing hard heats up the blade and leads to much shorter life. I have been there and done that. I have no incentive to run higher because the cut can't get any better. The surface looked like a planer with straight knives set just a tad off. Take this for what it is worth. Both gauges could be off but at the end of the day, I tension to the point the blade doesn't move back much and I have not bottomed out the spring. Dave

[Daniel Berlin]

I have not read the article yet, but I am curious and will try to look it up this weekend.

So my comment/question are without knowledge of the test setup. As mentioned in an earlier post, this is a very difficult test to administer. Can you discuss the measurement system analysis?

This is some impressive thread necromancy

[ian maybury]

Thanks guys. I saw you post of FOG too David, you've done lots of investigation of blade tension. In general I have to defer to experience like yours.

My perspective is more that of a manufacturing/process engineer from industry. Through the repetitive manufacturing lens the objective is normally to achieve a piece of equipment that will reliably produce to a specified level of quality when a defined (and not overly complex) set-up procedure is followed. This to move away from the dark art/only Mr. X can do it school of machine set up, and the attendant issues of loss of run time and production of defective parts to a situation where it's possible to just hit the button and run to spec. Basically the SPC/total quality line of thinking in Lean Manufacturing.

By this measure most of the bandsaws we encounter are pretty crap pieces of equipment - in that they need all sorts of finessing to get them working right. Especially on deep re-sawing - the high blade forces involved seem to by triggering all sorts of vibrations and other issues to give hobby and lower end professional saws the fits. Some can't be made to work well on deep cuts at all it seems. I wasn't for example impressed to discover last year that there wasn't a hope of finding a set up on my last saw that would enable it to re-saw to anything remotely approaching its stated 12in vertical capacity - it simply couldn't apply enough blade tension to handle the forces. Saw literature meanwhile seems often to purposely blur the distinction re-saw depth capability and vertical capacity.

There's of course always going to be those that benefit from the 'dark art' situation and will want it to continue, but in the end the objective in any programme to put band saw set up on a firm and fact based foundation must surely be to deliver the basis of the putative 'hit the button and run to spec' saw.....(provided the work t's being asked to do is within the limits of its specified capability)

It'd be very easy to end up stuck in the mire that is chasing around in circles trying to define some highly elusive set-up sweet spot on what is in fact often an unacceptably tempermental piece of equipment. It'd be so much better to bounce the manufacturers into delivering modern robust* designs ....

* a robust design is one that will keep on performing to spec despite widely varying and less than optimum end use conditions - this was what Japanese quality did for cars, motorcycles and consumer electronics for example. The products became extremely good at tolerating what previously would have been termed 'abuse'.

[David Kumm]

Ian, I am wondering what companies made old cast iron saws in your world. I am a little familiar with Wadkin and Robinson but have very little knowledge. Over here there were a number of cast iron saws to choose from. Yates, Tannewitz, and Oliver being the most prominent. The yates snowflake is really impressive in action, as is the Oliver 115 resaw with the rolling feeder assembly that sits all the way to the floor. I am hard pressed to come up with any reason not to go the old route if resawing is a big part of the equation. As to the test, I'm an accountant in real life so my only point was to quantify some number that works with each blade on each saw. The 1/4 bimetal I run on my yates y20 is set closer to 30000 becasue it works really well cutting tenons. For curve cutting I go a little lower. I come from a numbers background so I tend to convert what works into them. Any knowledge about old euro stuff is hard to find but very interesting to me. thanks, Dave

[ian maybury]

I've unfortunately got even less knowledge probably David, in that I bought the 18in saw mentioned above about ten years ago, and was perfectly happy with it because I was using it to make profile cuts in thinner material. It actually did that very well, was easy to set up (guided by the procedures in Mark Duginske's original book - thanks Mark) and lasted well.

This too by the way I suspect is the historical context of most DIY and lower end professional band saw designs - it's only quite recently that deep re-sawing (= high HP and high blade tension) is being asked of the larger saws in this space.

My background is mechanical engineering - machine design and development, and in recent years a manufacturing management consulting business.

It was only late in 2009 (when I set out to upgrade my still WIP shop to go professional and started to think of some veneer based projects) that the re-sawing issue arose. We simply don't have the sort of high end woodworking community here in Ireland that you guys have, so my reaction was to seek troubleshooting and subsequently buying help through a UK forum, and on here.

Robinson and especially Wadkin were the brands that the professional users on the UK forum (nice guys) kept bringing up (most UK DIY users are on much smaller saws though), and several reported very good experience with them - including on re-sawing. They also come up pretty regularly in dealers lists. The Italian saws don't have much of a profile at DIY level in the UK as in the US - too expensive. What stalled me on a Wadkin was that while nice ones were coming up at good money I couldn't get to try one out, or to make contact anybody with an engineering approach and experience of the big Italian saws as well. Plus I really didn't need another rebuild project.

They (Wadkins) seem to be built very solidly with lots of cast iron, but to typically run quite small motors which made me a little cautious about their likely re-saw capability - I'm sure they were designed back in the day when if you wanted to re-saw you bought a re-saw. :) There were questions about wheel camber, blade guidance and the like that needed answering too.

I spent some time looking at a couple of 22 and 24in saws made in Taiwan in the same factory and to a very similar spec as the high end Grizzly's, and got great help from the guys here who couldn't have been more helpful. In the end though getting more than isolated and not very specific instances of good feedback became an issue. Eventually I was offered a very fresh UK spec 3 phase Agazzani B-24 (NRA600 over here) locally at very good money, and given the consistently good and precision re-saw specific feedback on the big Italians for re-sawing here I bought it. It's eventually (lots of shop set up work had to get done in the meantime) going to get fired up on a rotary converter next week.

Pardon the round the houses. What I can offer if you have an interest is to dig up the names of a few UK dealers that sell used Wadkin, and the company doing spares and service. I could also try raising the UK user contacts I made last year for you if you would like - just pm and describe what you would like...

ian

[David Kumm]

thanks, Ian. Let me know how it works. As to motors, keep in mind that the direct drive saws used low rpm motors, typically 700 to 900 rpm. Accordingly they have more torque for the hp rating. A 3hp 700 rpm saw is more than a match for a 6hp 1750. Dave

[ian maybury]

Will do David. I'd need some convincing that a direct drive motor is going to make much difference to cutting performance unless it's the case that such motors were rated in proper 'old time' horses that were more powerful, or that the power losses in the belt drives used on modern saws are more substantial than the few % I think they are - or something like that. The maths surely suggest that it all must grind back down to a target blade speed - which in turn is equivalent to a given drive wheel rpm. Power = torque x HP, so a given HP will eventually (regardless of the means by which it's driven) surely deliver a given torque (= pull on the blade) at the drive wheel at a given rpm?

It's no doubt possible to get away with less HP on a saw if the blade is geared to run more slowly, but that will presumably be at the expense of slower cutting? (= doing less work = reduced HP requirement)

ian

[bob hertle]

Will do David. I'd need some convincing that a direct drive motor is going to make much difference to cutting performance unless it's the case that such motors were rated in proper 'old time' horses that were more powerful, or that the power losses in the belt drives used on modern saws are more substantial than the few % I think they are - or something like that. The maths surely suggest that it all must grind back down to a target blade speed - which in turn is equivalent to a given drive wheel rpm. Power = torque x HP, so a given HP will eventually (regardless of the means by which it's driven) surely deliver a given torque (= pull on the blade) at the drive wheel at a given rpm?

It's no doubt possible to get away with less HP on a saw if the blade is geared to run more slowly, but that will presumably be at the expense of slower cutting? (= doing less work = reduced HP requirement)

ian

Hate to be a nitpicker, Ian, but Power = Torque x speed or more correctly Power = f(T x RPM)

Regards

Bob

[James White]

>

in the end, its blade tension you are after, nothing else. Itura's new 2011 book writes about this subject in detail. Its a great read, and its 2011 catalogue is quite updated vs. some of this outdated tests.
.

Can someone PM me if you have the 2011 catalog in PDF or other digital format.

I am a bit disappointed that the OP dropped this bomb shell and then abandoned this thread.

James

[David Kumm]

Ian, Bob is correct and that is why a 700rpm 3hp motor has 2.5 times the torque of a 1750 rpm motor of the same rating. Torque is what you need on a bandsaw. As to the Iturra catalog, I to would like to see the updates on tension. Again, my point is not about the correct number but rather a reliable method to establish the tension at which each blade seems to work best on each saw. As a numbers guy it helps me to quantify it that way, but then I don't use the scale on my jointer to set its depth either. Dave

[Mike Cutler]

What happened to this? Was the retesting ever done?

James

I haven't seen this thread in quite awhile.
I am not certain what retests you are referring too?
I did the testing of aftermarket tension gauges for Mark during the initial thread and for some time afterward. Most of it is pretty dry and is nothing more than spread sheets with all types of calibration data tables and methods of calibrations.
The testing was done using NIST calibrated force gauges, mechanical standard dimensioning tools ( also NIST traceable ) and a frame fixture stand that allowed me to tension a length of blade roughly equivalent to the unsupported length of a 14" bandsaw, and compare the force gauge readings the aftermarket bandsaw meter readings. If memory serves me correctly, I tested three Iturra tension meters, one Starrett, and a Lennox. Carter supplied Mark with an ETG for me to test also.
If I were going to use a tesion meter, it would be the Carter. The mechanical hysterisis and quality of machining in the tension meters was inconsistent. The Carter ETG is repeatable. The mechanical tension meters were not.
Bottom line is that Mark's assertion on the use of the supplied tension gauge on the 14" bandsaw is correct. It is entirely usable as a measurement device.

[bob hertle]

Ian, Bob is correct and that is why a 700rpm 3hp motor has 2.5 times the torque of a 1750 rpm motor of the same rating. Torque is what you need on a bandsaw. As to the Iturra catalog, I to would like to see the updates on tension. Again, my point is not about the correct number but rather a reliable method to establish the tension at which each blade seems to work best on each saw. As a numbers guy it helps me to quantify it that way, but then I don't use the scale on my jointer to set its depth either. Dave

But a 1750 rpm motor of the same HP rating as your 700 rpm motor, belt driving the same wheel at 700 rpm, will drive it with the same torque. (minus the belt inefficiency~the work required to flex the belt) With a properly designed drive the difference is negligible. Biggest difference is now we've got additional drive components rotating, for which we have to worry about balance. The drive sheave wants to be as large as practical from the standpoint of drive efficiency, but from a vibration standpoint, smaller is better since it's rotating at 1750 rpm. Imbalance forces increase with the square of the rotational speed, so the drive sheave and the motor rotor balance becomes critical. (2.5 x speed equates to 6.25 x the imbalance force!)

Bob

[ian maybury]

Oops. No problem and thank you Bob, not sure how I got it wrong. I meant power = torque x rpm - the f (function of?) disappears when the units are correctly chosen. The remainder was based on that. i.e. for a given HP the torque increases as the 'gearing' is changed to reduce the rpm and vice versa.

[David Kumm]

Thanks, Bob. I forgot to specify that it is direct drive saws that can be misleading when judging their power. I have to admit though that the belt driven torque thing makes more sense to me from the perspective of reducing torque when increasing the drive pulley size than the other way around. Your point is that if the saw wheels are rotating at 700 rpm, a 3hp provides the same torque-power- whether direct drive 700, 1750 or 3500 geared down by belts, even though the amp draw is significantly different on the motors. Help me if I still have it wrong. Dave

[bob hertle]

David,

You've pretty much got it. I would alter your wording as follows:

Quote: ".......direct drive 700, 1750 or 3500 geared down by belts...."

change to: .....direct drive 700, or 1750/3500 geared down by belts......

A 3 hp motor's amps should be the same, regardless of rpm, if it were not for efficiency. HP= (V x I x Eff)/746

BTW, your 700 rpm example, is this a real world motor? I ask this because in 35 years as a professional machine designer, I've never seen, or heard of one. Maybe an eight pole on 50 Hz whose synchronous speed (120 x F / # of poles) is 750 rpm. 700 rpm would be nearly 7% slip but entirely possible.

Regards
Bob

[David Kumm]

Bob, My oliver 217 has an 860 rpm direct drive 3hp rated motor and pulls 9.8 fla. My oliver 116 has a 690 rpm 5hp rated motor and pulls 19.4 or 19.6 fla. My yates has a 900 rpm 1hp motor and pulls -I'm remembering now- 3.8 fla. Those have been my examples. The yates is surprisingly strong although I don't use it for much resawing. Will resaw 6 to 8 inches but slowly. The 217 will resaw up to about 14 inches effectively at moderate hand feed rates. The 116 will resaw 20+ inches about as fast as I can feed. Those are with lenox carbide blades that take a pretty good kerf. My laguna -acm- with the 3 hp belt drive wasn't even close to handling what the 217 will. Some of the errors in my thinking are probably the result of those experiences- or just being dumb. Dave