Damaged Band Saws from Overtensioning

[Mark Duginske]

Enclosed is a picture of bend or broken top wheel hinges from over tensioned 14 inch band saws. I'm wondering how many people have bent the top wheel hinge by over tensioning the blade. The broken hinge on the left is from a Taiwanese saw, the one in the middle is a new Delta replacement
and the bend one on the right is a 14" Delta.

69601

[Roy Wall]

Not defending those who really overdue the tightening.......but why not make these parts stronger/beefier?? aka PM 141 / General 490-690.....

[Vic Damone]

I have a circa late forties early fifties 14" open frame Delta that was running poorly for many years (my neglect). Earlier this year I installed a Carter spring, release lever, tires, and a DIY cleaning brush for the lower wheel. I raised the motor to decrease the new link belt length, gave it a thorough cleaning, lubrication, full tune up, and a new blade, the results were stunning.

Without a tension gage I generally run it just past the scale marks and check deflection with my thumb. Using the lever I release the tension when not in use mostly to save the tires. No problems so far.

Vic

[Matt Meiser]

Mark, I haven't bought your book and I'm sure this is answered in there, but short of buying a tension gauge for a ridiculous amount of money, how do I know if I'm overtightening?

Someone told me once to tighten by sound, when you pluck the blade and it sounds good it is tensioned properly. That seems to give me good results, but am I overtightening?

[Dick Rowe]

Mark,

I had an old Buffalo 14" BS on which I broke the hinge (it looked exactly like the one in your lower left example).

The replacement parts for a 14" Delta (don't remember the model) were an exact fit and I was able to fix the Buffalo using the Delta part. A good thing because I was unable to locate any Buffalo parts.

I've since sold that saw and the new user hasn't had a problem, and since I learned my lesson on the Buffalo, I haven had any problems with the Grizzly 14" with riser block I bought to replace it.

Dick

[Ken Garlock]

Mark, I have to agree with Roy.

I bought your new book when it first came out, and for various reasons, I have only gotten through the first 60 pages. I must say that I am very impressed with the detail of the book, and the illustrative color pictures. Your's is the best I have seen on the subject of band saws. Congratulations on a winner.:cool:

If you Creekers haven't bought Mark's book, I recommend it. It is worth the price you pay, and may save you from problems in the future. :)

[Jack Ganssle]

Matt,

I bought & read Mark's book and then reread it. It's great. In it he claims that the tales of inaccurate tensioning mechanisms are way overblown, at least for 14" saws. My take was to just use the scale on the saw. He also doesn't buy into the idea that springs lose their compressability.

Jack

[Mark Duginske]

Mark, I haven't bought your book and I'm sure this is answered in there, but short of buying a tension gauge for a ridiculous amount of money, how do I know if I'm overtightening?

Someone told me once to tighten by sound, when you pluck the blade and it sounds good it is tensioned properly. That seems to give me good results, but am I overtightening?

Matt.

Thanks for the note. There is more research since the book was published. I acquired all of the gauges and sent them to Mike Cutter for testing. He is a frequent contributer to SMC. He has done extensive testing of the gauges and will give a report that will be placed on this thread.

This is a good place to gather information and experiences.

I think the goal is to give people commonsense ways of measuring the
tension. There is a lot of misinformation and Mike's testing will help clarify
some of the tension myths.

[Jim C Bradley]

Hi Mark,
I'm going to Barnes & Nobel to check out your book.

Enjoy,

Jim

[Chuck Lenz]

Not defending those who really overdue the tightening.......but why not make these parts stronger/beefier?? aka PM 141 / General 490-690.....
Roy, I have a JET JWBS-14CSW and JET has beefed up the upper axle assembly considerably. I kind of feel cheated that I had to buy a part that they obviously under engineered in the first place. I think it ran me about $50. I really don't feel that I over tightened the blade when the part failed. It was a 3/4" blade, and the manufacturer of the saw claims up to 3/4" can be used. http://i25.photobucket.com/albums/c89/Woodchuck_/JETjwbs14csw.jpg

[Roy Wall]

Roy, I have a JET JWBS-14CSW and JET has beefed up the upper axle assembly considerably. I kind of feel cheated that I had to buy a part that they obviously under engineered in the first place. I think it ran me about $50.

Chuck - I think I'd feel the same way! I wish they would consider the old defective part as a "recalled item" (like in the Auto business)....and make it right. The part probably didn't cost $10 to make it. At least have some internal memo flagging the part.....and if it did break....send the customer a new one.......

That particular band saw is pretty good though...once tuned up. I used to have one and the only drawback was "vibration" traced back to the motor....other than that...with a good blade...it cut well.

I have learned much reading Mr. Duginske's book(s)......looking forward to the new edition.

[Stuart Johnson]

The one on my Grizzly broke but I don't think it was from over tension. I did not detention it and it got pretty cold. The pot metal gave way. The replacement seems much stronger.

[Chuck Lenz]

Here is some pictures of what I'm talking about when I say JET beefed the part up. On the left is the new part, on the right is the old failed part. http://i25.photobucket.com/albums/c89/Woodchuck_/JETaxle1.jpg

[Chuck Lenz]

As you can see they also beefed up the back side of the shaft hinge also. http://i25.photobucket.com/albums/c89/Woodchuck_/JETaxle2.jpg

[Randy Denby]

A few months ago I saw some pictures of some failed top wheel hinges. On the outside skin,the metal looked ok, but underneath the surface in the broken joint you could see all sorts of voids. Metallurgy has been the problem for cheap knock-off tools/imports for forever....IMHO They can copy the tools we used to make, but not the quality.....not yet it seems

[Chuck Lenz]

Side view of the failed part. The shaft hinge is bent out, causeing it to hit the spokes of the upper wheel and makeing one heck of a racket. You will know when it goes bad. http://i25.photobucket.com/albums/c89/Woodchuck_/JETaxle3.jpg

[Bart Leetch]

I have read & heard many times that older style Delta & Delta knockoff 14" saws widest blade should only be 1/2". Having tried a 3/4" TW blade I can understand why. I have stayed with 1/2" blades on my 14" saw with riser block for re-sawing & rounding out bowls & have not had any problems. I also have a 12" saw with either a 1/4" or 3/8" blade for general use.

I have Mark's previous book.

[Chuck Lenz]

Bart that may be the word on the street, but the JET manual for this saw states maximum blade width as 3/4". I generally expect a piece of equipment to do what it claims to do without breaking parts. There are NOT alot of miles on this saw. Performance of cuts is one thing, durability of parts is another.

[Tom Cowie]

Hi Mark

Love the books. Keep them coming. Glad to see you post on the forum.


Tom

[Mark Duginske]

Earlier this evening I looked at this thread I read Mike Cutler's
post about the results of his test of the mechanical tension gauges.

When I went to reread it it was gone. What became of it??

Mike: can you post it again? The reason I started this thread was so Mike could post the test info.

Thanks,

Mark

[Chuck Lenz]

I would like to see the test results, if there is a better way to fine tune the tension on different widths of blades I'd like to know about it. I think the stock tension scale on the bandsaw will get you close, but I'm not sure that it's dead on as most of us would like it to be.

[Mike Cutler]

Earlier this evening I looked at this thread I read Mike Cutler's
post about the results of his test of the mechanical tension gauges.

When I went to reread it it was gone. What became of it??

Mike: can you post it again? The reason I started this thread was so Mike could post the test info.

Thanks,

Mark


Mark.

For some reason the cut and paste function from a word document scrambles any data tables. Without the tables the post doesn't make much sense.
I'll try to post again when I figure out how to import tables from a word doc.
I hope I don't have to manually recreate them. Ugghh.

Mike

[Roy Wall]

Here is the General 690 wheel tensioner mechanism....

I have seen the old PM 141's and they are at least the equal if not beefier....

[Mark Duginske]

Mike,

Thanks for getting back with an explanation. I know you did a lot of work testing the Lenox, Iturra and Starrett gauges.

I’m also sending you the Carter ETG electronic gauge.

There was a lot of information in your text and unless one has a good machinist or engineering background a lot of it is “Greek”.

Although you provide a lot of technical information the average reader on SMC wants to know the practicality of the test. No area of woodworking has more contradictory “information” than band saw tension.

Here are some questions that you may answer with the information you have.

Are these mechanical gauges relevant to a woodworking band saw?

Are the aftermarket clamp on gauges a better way of tensioning the saw than the gauge on the saw?

Does this group of gauges have problems measuring the amount of tension used on a woodcutting band saw because they were designed for very large metal cutting band saws. Is this the equivalent of using a gallon jug to measure a spoon of liquid?

What is the significance of the three Iturra gauges have different results and results that are not repeatable?

Do band saw tension springs lose their ability over time as some books, magazines and catalogs suggest?

Thanks,

Mark

P.S. If any of the SMC group has tension questions this is a good thread to ask them on.

[Carl Oresick]

This seems like a good, cheap way to accurately measure tension.

http://www.sawmillcreek.org/showthread.php?t=22144&highlight=caliper+bandsaw+tension+guage

[Mike Cutler]

Mark.

You are correct, the post was very technical, and without the data tables difficult to understand exactly what was going on.

For background. During this past winter a thread was started here on the board concerning the relative use, and a comparison between three bandsaw tension gauges. The Iturra, the Lennox, and the Starrett.

http://www.sawmillcreek.org/showthread.php?t=50949

Following this thread Mark sent me 5 bandsaw tension gauges to test. 3 Iturra's, 1 Lennox and 1 Starrett. I performed a mechanical dimension checks/ calibrations of all five gauges. and then an actual pull test with an electronic force gauge, or load cell. All of the devices used were traceable to NIST standards. I spent many, many hours at the bench with these devices, before they ever saw a bandsaw blade. Here is a basic outline of the mechanical checks;

Method of mechanical calibration checks for all of the tension gauges.
The instruments were mechanically cal checked by removing the dial indicator from the tension assemblies.
The dial indicators were them held in a jig and a calibrated Mitutyo outside dial micrometer was used to determine the range of travel of all dial indicators and determine the distance of travel for one revolution.
The range of calibration was then divided into inputs based on readability of the scale range of interest.
The input points were then mathematically divided into the full “One revolution” range to determine the percentage of scale based on one revolution.
The desired range of travel was then multiplied by these percentages to achieve the ideal “desired” input of stem travel to dial indicator readings.
In some instances a “reverse calibration” method was utilized based on the readability and resolution of an individual dial indicator , and mathematically worked “backward” to extrapolate a value.

The dial indicators were then re-installed into their respective Tension gauge assemblies.
The tension gauge assemblies were mechanically cal checked by measuring the distance of the Thumbscrews “ctr-ctr” and applying a corresponding inputs of 0.001”-0.004” + the ctr-ctr value by use of a Starrett Model 124 inside micrometer.
The desired pressure readings in psi were derived by dividing the desired indictor psi value by Young’s modulus of 29E6 and multiplying the value by the ctr-ctr value.
Formula used for determining input.
Desired PSI Indication/29E6 x 3.5475”

Example (Iturra tension Indicator)
Desired input for 8000psi.
8E3/29E6=0.0002758
0.0002758x 3.5475”= 0.0009784”
0.0009784” of input, with 3.5475” as a zero point. Is expected to yield a dial indicator reading of 8000psi.
Formula can be worked backward to apply readable inputs from cal check device.

It should be noted, that without exception, all of these devices are being operated at the extreme low end of their respective full scale ranges. This is an undesirable attribute from a measurement and test philosophy.
The algebraic sum of errors. Dial indicator, Tension fixture ctr-ctr deviations, distances of lever arms, mechanical friction, mechanical hysterisis and the inherent accuracy specs of the test devices coupled the limited range of input motion (< 3 thousandths of an inch ). Make quantifying, and repeatability of. the resultant output indication extremely difficult, even under ideal conditions.

The gauges were cal checked at cardinal points from 0-30,000 psi, or reversed cal'd based on the readability of each gauge.

I'll Take Mark's questions one at a time.

"Are these mechanical gauges relevant to a woodworking band saw?"

No. In all cases the total range of measurement of these devices is too large. The actual measurement range is less than 6% of the total span of the device. Simply stated, they are too large.

"Are the aftermarket clamp on gauges a better way of tensioning the saw than the gauge on the saw?"

No. The range of these devices, when coupled with mechanical hysterisis of the devices, makes them too inaccurate. The best performance was obtained with the Starrett, but the resolution of the indicator is too large to really be usable in this range.
Hysterisis prevents the others from being repeatable, even under ideal conditions.

"Does this group of gauges have problems measuring the amount of tension used on a woodcutting band saw because they were designed for very large metal cutting band saws. Is this the equivalent of using a gallon jug to measure a spoon of liquid? "

Yes. The total range, resolution, and mechanical hysterisis have too significant an effect when trying to measure inthese ranges.

"What is the significance of the three Iturra gauges have different results and results that are not repeatable?"

Ahh.. The softball. The Iturra gauges have a design problem in my opinion. The bearing face of the dial indicator plunger makes contact with the fulcrom arm on the edge.
This is causing wear of the fulcrom arm. the fulcrum arm is a much milder material than the bearing face.
Additionally the physical relationship of the contact point presents a non linear response. As the fulcrum arm moves up, it also rotates and travels back along the bearing face. Instead of all motion occuring in a single plane. it is rotating. The resultant output is a mathematical representation of the curvature of the sphere, and the movement of the fulcrum arm.
I'm not singling out the Iturra's. The Lennox has a problem also. The machine faces of the fulcrum arm to the tension gauge body are aluminum, and have a lot of friction and drag due to the lack of polishing these surfaces.

"Do band saw tension springs lose their ability over time as some books, magazines and catalogs suggest?"

Not really. I think a lot still depends on the initial quality of the material, but the forces involved aren't that great,and the spring sholud retain it's strength .
The spring that was initially supplied with my Jet was only capable of providing ~ 8500psi to a blade max. Jet also came out with an upgrade, but by then I had installed a Carter spring that was ~ 3/4" longer.

I eventually got to the point where I could get repeatable results with the Lennox, and the Starrett. The three Iturra's I could not because of the fulcrum/ bearing face relationship. I could essentially get any value I wanted with these. None were repeatable.

Many photos were taken of the process and emailed to Mark, along with multiple data tables that recorded the results. The photos are too large in size to post, but I will email them to any one interested. I will also prepare a complete word document,with photos if anyone is interested . Be forewarned though. it will be a large file, and reads like a White Paper summary.

I have seen the photos of bandsaw failures that Mark sent me, and I see some of the same types of failure in other photos in this thread. While some of this may be attributed to faulty design/workmanship. Over tensiniong the blade could certainly cause problems.
I applied the equivalent of 80,000 psi to a 1/2" bandsaw blade during testing and did not break the blade. I bent the C-clamp in my test fixture, and sheared a stainless steel 8-32 screw, but the blade was intact.
On the 14" bandaws if the blade is tensioned beyond the range of the spring, the spring is "bottomed out", the pressue increase become non linear, and more exponential. A half turn of the tension knob will add 50-60,000 psi. Watch the spring. If it's bottomed out, don't keep applying tension.

[Mark Duginske]

Carl Oresick

Thanks for bring up that previous thread. I disregard that whole idea because there are too many false assumptions.

The Fine Woodworking article which the thread is based on that was republished in John White’s book which if full of questionable information.

White is following the line of thought that Jim Cummins did when he was an editor at Fine woodworking. 20 years ago Cummins wrote an article in which he state three false assumptions:

1. The spring weakens over time.
2. The saw gauge is not accurate
3. An aftermarket gauge (the Lenox) is more accurate than the saw gauge

Cummins had acquired an aftermarket Lenox gauge and when the
Lennox gauge and the saw gauge did not match he assumed that
the saw gauge was off and the Lennox gauge was right. I had a conversation with him when I was at Fine Woodworking working on my first article for them. He did no testing, he wrote the article on an assumption.As it turns out he was wrong on all three of the above assumptions.

White’s article is based on the same false assumptions that Cummins had which is that a clamp on gauge is more accurate than the saw gauge which is not true. For a test I made the simple gauge in the FWW article and also used that caliper as the thread suggested but I tested it against the Carter ETG electronic strain gauge. Although I did get some numbers none of them were accurate or repeatable. White’s idea for the gauge is to mimic the aftermarket gauges made by Lenox and Starrett or the less expensive gauge by Iturra. The Iturra gauge is so inaccurate that one could throw dice and pick a number with about the same accuracy and repeatability as the Iturra gauge.

As Mike Cutler will verify the clamp on gauges are not easy to use.
Also the tension on the blade has to be taunt but not too taunt. Also the clamping process is touchy. It would take expensive testing equipment to know at what tension the blade should be at before
the clamp is attached. All of this beyond the back yard mechanic.
Using the White gauge and the caliper will give you a number. The
number will not be correct but it will give the placebo effect.

I did this thing (took a pill), and got this number: now my band saw will feel better. My testing shows that the band saw gauge on a 14 saw is much more accurate than trying to measure tension with a feeler gauge or a caliper.

To quote my friend Toshio Odate, “Americans love numbers, they do not know what they mean but they want a number.”

I think that White’s article fulfills the fantasy of doing something on the cheap, duplication of what a $300 tool does for a couple of bucks. And that is what it is, a fantasy. Even more of a fantasy is that the $300 tool is the answer.

Ben Franklin said, “Folly is wisdom spun too thin.” That is a good
description of this feeler gauge/caliper idea. The reality is that one would get much better results from the gauge on the saw. I think that it is very naive of author’s to assume that manufacturer’s of the 14” do not know what they are doing.

[Mike Cutler]

I resized the photos of the Iturra and Lennox gauges to hope clarify more.

This is a photo of the Iturra from the side. You can see that the bearing is on the edge of the fulcrum arm69673

This phot shows the relationship of the fulcrum to the bearind as seen from thr front.69674

This photo shows the wearing of the edge at the point the bearing surface is contacting the fulcrum arm69676

This next photo shows the wear of the lennox gauge at the fulcrum pivot point. The shiny section(s) are wear friction is being generated.69675

[Chuck Lenz]

Mike you say Jet also came out with an upgrade. Is it for the 14" bandsaw ? Could you tell me what that upgrade consists of and is it still available.

[Mike Cutler]

Mike you say Jet also came out with an upgrade. Is it for the 14" bandsaw ? Could you tell me what that upgrade consisted of and is it still available.

I would assume it's already incorporated into their current generation(s) of 14" bandsaws. My saw is a few years old, and came with a spring the was too short in length. The machines that came after mine had a longer spring.
I replaced my OEM spring with a Carter aftermarket spring. This was 5-6 years ago though. I've since given up trying to resaw with my Jet, and have a Rikon 18", with a 1" Tri-Master, set up specifically for that task

[Chuck Lenz]

That particular band saw is pretty good though...once tuned up. I used to have one and the only drawback was "vibration" traced back to the motor....other than that...with a good blade...it cut well.

I have learned much reading Mr. Duginske's book(s)......looking forward to the new edition.
Roy I may have to play around a bit with it, maybe some rubber motor mounts and a Fenner Drives PowerTwist link belt would get rid of some of that vibration you talk about. I wrote JET a e:mail yesterday about how I felt about paying for that part when I feel the original part was under engineered and so did they aparently by looking at the new one. They are going to issue me a credit for half the price of the part and shipping.

[ray connors]

Regarding band tension gauges how about switching over to hydraulic tensioning on the band saw it self? Probably cost prohibitive at the $300 machine level but the $500-$800 14" may benefit.


Redundant info.
Force is force and measuring the result (strain) is prone to accuracy issues.
Off to the real world now. As bands warm up they stretch in length. Tension drops. Hydraulic tensioning with the addition of a mechanical pressure gauge allows changes to be monitored and compensated for while in use. Most folks running band mills do this already. Granted these are $20-50k machines but the hydraulic tensioner run $100-$200 less if home made.

The down side of using one is a bit of math is required stress(psi) =force/area (insert smiley).

Its been my experience when using the clamp on strain measuring techniques that its easier to do so on wider bands.

Regarding the casting failure.I've experienced this and chalked it up to inadequate material selection (poor engineering) for the part.
Replaced failed part with a home machined one 6061 aluminum not cast.

Interesting topic band tensioning. Virtually every cut I make has my eyes glancing at the tension gauge --its a relative thing if its falling bands heating up probably dulling if its increasing bands cooling feed faster.

[Maurice Ungaro]

Mike & Mark:
Thanks to the both of you for the thorough studying that you have done on the subject. This is the kind of stuff that really cuts through the bull and gets to the meat of the matter.

I too, have questioned some of FWW's testing methods.

[Mike Cutler]

Ray.

Welcome to Sawmill Creek. Please'd to meet ya'

Your obsevation about the wider band is correct. The tension gauges got more repeatable as the band got wider, and the tension increased. There is a lot of twist and flex in a 1/2" blade.
The Lennox and the Starrett were both "usable" on a 1" blade.
I had 2 Marvels and 3 Do-All's to play around with also.while I was checking out these devices. The Marvels have 1 1/2" blades that are hydraulicly tensioned, and the Do-All's were the "lighter" version with really big springs.
Someday I'll happen by when the PM's are being performed on the Marvels, and maybe play around some more. Lot of tension on those bands, and they twist 90 degrees at the top and bottom.

Once again. Welcome to Sawmill Creek. Nice to see more people from CT. I'm in Griswold.;)

[Pete Bradley]

Regarding band tension gauges how about switching over to hydraulic tensioning on the band saw it self? Probably cost prohibitive at the $300 machine level but the $500-$800 14" may benefit.

[...]

Off to the real world now. As bands warm up they stretch in length. Tension drops.

Theoretically true, but it's not clear to me that it matters in the real world for woodworking machines. The coefficient of expansion for steel is in the neighborhood of 8-11 microinches/inch*degree F. In other words, for each increase of a degree, a 1-inch section of band will lengthen 11 millionths of an inch. Figure a 14" machine with 1" of spring travel and an 87" band (divided by 2), you're in the neighborhood of a percent or two change in tension.

Pete

[John Schreiber]

This may be way off the mark, but has anyone tried something like this?

69684

It's a "Loos Tension gauge" used to measure the tension of the shrouds on sailboats. It claims to give an absolute measurement, which I think would be a challenge, but I would think a realistic relative measurement could be made with a tool with a similar design.

Just another idea.

[John Schreiber]

Here are some drawings of how such a gauge might look.

The positions and shape of the pivot pins and the spring tension could be determined by trial and error. The indication could be calibrated or just given some reference numbers.


69693 69694
In position ready to measure . . . . . . . . Measuring tension


Not much, but better than pushing it with your thumb to see how it feels.

[Warren Clemans]

I moved a few years ago and my bandsaw (and everything else) went into the basement of our new house until I could get the new shop built. I finally got the bandsaw in the new shop this spring. To my dismay, I found that I had left the saw tensioned for over 2 years. It worked fine before, but the hinge pins had broken out of the casting while in storage, just like in the pictures posted above. The saw is a 8 or 9 year old Grizzly 18" piece of junk. My grandfather had a Grizzly 16" saw that suffered the same problem. I know, just back off the tension to avoid it. Sometimes that's easier said than done. I'm pretty sure the problem was not overtensioning, since I can barely get adequate tension with a 1/2" blade. I've had to add spacers in the tensioning mechanism. Not sure what causes that--bad spring, maybe?

I won't go into all of the other problems I've had with that saw, but suffice it to say that I'm saving pennies for a MM16.

[Pete Bradley]

I have to admit, I'm mystified by the amount of discussion tension gets in threads like this. Maybe I'm just lucky, but I started with the "flutter method" and now do it pretty much by feel and eyeball. I can crosscut, rip, and peel off veneers with no problems. If I'm doing a tall resaw I give the handle and extra crank. Does tension really have to be that complicated?

Pete

[Mark Duginske]

Does tension really have to be that complicated?

Pete[/quote]

As a band saw author the most frequently asked questions concern blade tension.

Tensioning does not have to be complicated. I'm a fourth generation woodworker and we have always used the saw gauge. However
Jim Cummin's article and the mutant offspring of that article have unfortunately caused a lot of confusion. It is complicated by very slick salesman with something to sell.

I spent a lot of money (way over $1000) and time (along with Aaron Gesicki and Mike Cutler) learning that the after market clamp on tension gauges are not applicable to woodworking. I have the Carter ETG on my Jet and will be doing some test with Mike in the future on that item. For now my conclusion is this statement:

USE THE GAUGE ON YOU SAW FOR NEW SHARP BLADES AND ADJUST IT TO ONE SETTING HIGHER AS THE BLADE DULLS.

I started this thread to start a discussion with Mike so that we could clarify a lot of the misinformation that is out there. I hope that it has helped.

[Andrew Williams]

i read a previous post here that covered a homemade tension gauge using two clamps and a dial caliper, based on the modulus of elasticity of steel. As I used this and tensioned it to 15,000, sure enough, it was exactly on the mark of the saw's tension gauge.

[John Stevens]

Maybe I'm just lucky, but I started with the "flutter method" and now do it pretty much by feel and eyeball.

Pete, who manufactured your bandsaw? I'm just curious whether your saw is old iron, or a newer Italian model, or if it's something along the lines of Delta, Jet, PM, etc. Thanks.

Regards,

John

[Jack Delaney]

Hello everyone. I am new to this forum and found this thread interesting. There is an inexpensive way to check tension that should work well. Plucking the blade while under tension and using a musical instrument tuner should give a frequency that relates very well to tension. The frequency would be different for different blades but calibration should be possible. Once the frequency of particular blade is known, increasing tension until it is "tuned should yeild very good results. This is the method used to tension guy wires on a tower. With guy wires, the frequency is so low that one can use a wrist watch to measure the frequency by timing the return wave.

Mark, do you know if this method has ever been investigated?

Cheers.

[Pete Bradley]

Pete, who manufactured your bandsaw? I'm just curious whether your saw is old iron, or a newer Italian model, or if it's something along the lines of Delta, Jet, PM, etc.
Old Iron. It's a Delta 20" light industrial machine built in the late 40s. I've used various Delta 14s also.

Pete

[Mark Duginske]

Roy had the idea (and Ken agreed) that the top wheel hinge part could be built more heavily. That is probably true and from the before and after photos that Chuck supplied it appears that Jet has done that.

I will pass this thread on to my metallurgical engineer friend Aaron Gesicki
for his perspective. I think that the manufactures designed that part to be the "weak link", thus the part that fails first and with some visual or auditory warning. I have replaced bottom shafts on on band saws and would much rather replace the top wheel hinge.

Here is a photo of a Delta where the owner bent the top wheel hinge and then cut the back wheel cover out to make room for it. Apparently he did
not have the Delta 800 number for replacement parts.69772

[Chuck Lenz]

Mark, you need to ask yourself, is this common with larger saws also ? So far from what I can tell it's largely limited to 14" saws. I'm still thinking it's a design flaw, especially after JET beefed their part up.

[Phil Pritchard]

He also doesn't buy into the idea that springs lose their compressability.
Experience from industry in general as well as the automobile market refute that absolutely. Springs lose their tension over time (under compression) and will also flatten (compress). I've now rebuilt seven older bandsaws over ten or so years. All have needed the tension springs retempering probably because of the habit of former owners of leaving the maines constantly under tension. I've discussed this with the spring maker who hase retensioned all the springs - he also doesn't buy intoi the concept that "springs don't lose their compressability".

Phil

[Rick Christopherson]

I haven’t followed these discussions until I came across the posting of a dial caliper clamped onto a blade. What troubles me about these concepts is that you are attempting to correlate one parameter by measuring another parameter. And while that may be possible under the correct conditions, there is an unknown variable that separates the two measurements--namely the blade itself.

These methods are based on the assumption that all blades will extend the same amount with the same tension. I am not a metallurgist, but I do not believe this is true. The blade stretch will vary with the quality and type of steel. I would suspect that this may even vary over the length of the blade depending on the quality controls of the processing and tempering of the blade.

The most accurate method for measuring the tension on a blade is the hydraulic force gauge a previous poster mentioned. This reads the direct forces on the blade, and eliminates the blade itself as a variable.

Those bandsaws that use a compressive spring to set tension should actually be fairly accurate so long as the indicator of the spring’s compression is calibrated (or designed). The correlation between a spring’s compression and the amount of force the spring is applying is fairly consistent. I don't know if this concept is applicable to the design of the 14" bandsaws because I don't own one and have not examined the design. However, on the larger bandsaws where the tensioning spring is pressing upward on the axle, in-line with the blade, this method should be reasonably accurate.

[Allen Bookout]

I have one of the last American made Delta 14" bandsaws with a riser and the documentation states that this saw will handle a 3/4" blade just as the poster stated for his Jet. I have three 3/4" blades that I have never used. Am I better off just junking the new blades and staying with 1/2" and smaller or am I safe with the 3/4" blades that require higher tension?

[Herbert Granger]

Mark,I have an old Rellant 14",Don't know if you ever heard of that or not, it is an off the wall brand, But belive me I think it is a great saw, The only thing is I can't get parts for it. I would like to get a riser block for but I can't find one. But the saw is really good, I resaw on it all the time down 1/16 and never had any problem .I tighten my blade with a sliding square,I set the sq. blade to 1/4 " and hold it even with the saw blade and then push the blade to the sq. It sould just about touch,And then it is right ,But that is on my saw are all saws the same or do thay all have a life of there own.Thank you so much, Oh!! by the way is there any web sight that I can get your book from ,,Thanks again,,Herb Granger

[Mark Duginske]

One of the goals of doing my new bandsaw book was to sort out all of the contradictory "information" especially from the people selling a product. I starting using a band saw at age 5, (I also stated driving an Allis Chalmers C picking up hay at age 5) my bandsaw experience is from working in a shop. My father and grandfathers were woodworker who made their living as patternmakers making the tools that make tools which is both a science and and art that we are quickly loosing. I was an English major and then went to nursing school and worked as an RN in peds and intensive care.

I am not an engineer so I'm dependent on others for engineering expertise.
I this thread you have read material from Mike Cutler who I have asked to check the aftermarket gauges. The other engineering person that I use is
Aaron Gesicki who has an undergraduate and masters degree in metallurgical engineering. For the article in Woodworker's Journal earlier this year Aaron helped me test the gauges.

Mike and Aaron have tons of expertise and also have the very rare ability
to explain a complex idea in simple terms.

Aaron is out of the country at the moment but emailed these comments.


I can't post a comment. My membership privileges have not yet been
activated.

Maybe after I get back.

Or - you can post this on my behalf:

In my opinion the problem with bending the bracket has, I think, been
explained by Mike Cutler earlier in this thread. On most 14" saws, it's
relatively easy to increase tension spring compression to the point that the
spring effect has been lost because all the coil loops are now in contact.
When this occurs, the spring becomes a rigid structural member. Any
additional "compression" now adds huge amounts of stress to the overall saw
structure - blade, frame, wheels, shafts, brackets. Something will fail
first, and apparently it's the top wheel shaft bracket.

I doubt that this bracket has been intentionally designed as the weak link,
although that is possible. I would think that it is more likely that the
blade should be the weak link, and perhaps it is until blade sizes exceed
1/2".

Finally, about the bracket itself - it's a non-ferrous die-casting, and
could be either an aluminum or a zinc alloy. The fact that it's a casting
does make it problematic. As for metallurgy, either Al or Zn can be quite
serviceable, since the tensile strengths of both alloy families are usually
well above that of cast iron and quite often comparable to that of mild
steel.


Aaron Gesicki

[Mark Duginske]

This is a response to the following comment. I have include it here so
I can easily quote from it.

Quote:
Originally Posted by Jack Ganssle View Post

He also doesn't buy into the idea that springs lose their compressability.

"Experience from industry in general as well as the automobile market refute that absolutely. Springs lose their tension over time (under compression) and will also flatten (compress). I've now rebuilt seven older bandsaws over ten or so years. All have needed the tension springs retempering probably because of the habit of former owners of leaving the maines constantly under tension. I've discussed this with the spring maker who hase retensioned all the springs - he also doesn't buy intoi the concept that "springs don't lose their compressability".

Phil
Last edited by Phil Pritchard : Yesterday at 4:08 AM.
Reply With Quote


From =Mark Duginske

I also have refurbished many band saws. In your comments
you use a number of terms that I am not familiar with.

"All have needed the tension springs retempering". What is
retempering?

"I've discussed this with the spring maker who hase retensioned all the springs". What is "retensioned"

Since I am not familiar with these terms (retempering and retensioned) and since the commenter referred to the automotive industry I thought I would pass on these comments to Aaron Gesicki who is a metallurgical engineer working in the automotaive industry.

This is Aaron's bio:

With undergraduate and masters degrees in Metallurgical Engineering from the University of Wisconsin in Madison, Aaron Gesicki has been working with engine components his entire career. He’s done research and development at Caterpillar’s Technical Center, process engineering at Marathon Electric, melting and metallurgical production management in General Motors foundries, product and quality engineering and management for American Motors. He helped to build and launch a new foundry for Neenah Foundry , and currently is Technical Director for the Sparta Manufacturing Division of Slinger Manufacturing Company, which produces engine components (cast iron cylinder sleeves). Along the way, he has become a Certified Quality Engineer, a Registered Professional Engineer, written and presented national technical papers, acquired several patents, and continues to be very active on several national technical committees within the American Foundry Society. He is a charter member of the Coulee Region Woodturners Chapter of the American Association of Woodturners and does his woodworking in Sparta, WI. He owns two band saws.

These are Aaron's comments:

Here are my comments, after his excerpted statements.

“All have needed the tension springs retempering”
Really? All metallurgists know that “retempering” does not bring back the properties if indeed they changed to begin with. Assuming, of course, that the word is properly used – that is, the part is tempered again.

“hase retensioned all the springs”

What exactly is the procedure for “retensioning” a spring? I am not aware of what this is, much less how it’s done.

I maintain my previous statements, as published in Woodworkers Journal – “if the spring is operating in the elastic region [those are normal operating conditions], it will not lose any of it’s properties regardless of how much time has passed.”.

Aaron Gesicki

The conclusion:

Phil,

Please provide substantiated data using standard terms (and technical data) or your comments will not be taken seriously.

Response from Mark Duginske

[Mark Duginske]

I was puzzled by the "retempered" spring comment. Since I had
not heard of it I sent off these questions to Mike Cutler and Aaron Gesicki.


1. Is this guy using the right terminology?
2. Can a spring be "retempered" ?
3. " I've discussed this with the spring maker who hase retensioned all
the springs". Is there such as retensioning a spring.

I posted Aaron's responce earlier.

This is the email I got from Mike Cutler:

Mark

I'm certain that Aaron can explain it a lot better than I ever could.
I've never heared these terms used with reference to springs. If something like this could be done, it would almost certainly have to be done at the manufacture of the spring. It would require some pretty expensive, and large equipment.

The springs that I have to deal with are very large. The force is measured
in 10's of tons. They are used to operate large pneumatically operated
valves, inline check valves, relief valves, etc. These are lifetime
components. The springs in small pneumatically controlled process
instrumentation are also lifetime components. The only reason they are
replaced is because they are sometimes "matched" to the control device that they are part of.

The only plausible explanation for a spring "fatiquing" would be due to the
initial quality of the material being poor. Round wire can be drawn, and formed into a coil, but this doesn't make it a spring. It would perform the function of a spring, but it still wouldn't be a "spring".

In the reference that I have made to the spring that I replaced on my Jet.
That particular spring was only capable of tensioning a blade to ~ 8500
psi. It was just a poor component selection for that application. It was
literally "bottomed out" at about the 1/2" blade tension mark on the 14"
Jet.The Carter that replaced it was a much stiffer spring and it was
longer. I still use the tension marks on the bandsaw, but I know that I
have a spring still in the tension mechanism capable of performing it's
intended function.

I'm not certain how your thread evolved into a discussion on spring force
and rate. I guess it's just an evolutionary development. I'd like to see
the focus come back to overtensioning and the risk of damaged involved.

Mike

[Jack Ganssle]

Mark, Mike and all,

I appreciate all of your engineering analysis. This sort of insight, plus your experiments, sure clarify a lot of things for those of us!

Jack

[Al Willits]

""""""""""""
The only plausible explanation for a spring "fatiguing" would be due to the
initial quality of the material being poor. Round wire can be drawn, and formed into a coil, but this doesn't make it a spring. It would perform the function of a spring, but it still wouldn't be a "spring".
"""""""""""

Doubt the springs on a top fuel, pro stock or any high performance motor are just plain round wire, and they will fatigue after a few runs, worked on several pit crews and and springs were checked on a regular basis and did lose their original spring rate.

Don't much care if you believe that or not, but those in the automotive high performance field see it on a regular basis.

Blanket statements like springs do not weaken over time are misleading, they can weaken...least in the real world they can.

Al

[Glenn Clabo]

Springs made of metal will "fatigue" which means that tiny cracks in the metal move around and lump up into bigger cracks. A metal that has been stressed frequently becomes more brittle which requires more force to stretch it or commpress it... which damagages it faster. How any streches/compressions before the spring breaks? Depends on how tightly coiled it was to begin with, it's size and what metal it was made of.

For those who want to see this in more technical terms...
http://www.efunda.com/designstandards/springs/calc_comp_fatigue_eqn.cfm (http://www.efunda.com/designstandards/springs/calc_comp_fatigue_eqn.cfm)
http://www.efunda.com/designstandards/springs/calc_comp_fatigue.cfm (http://www.efunda.com/designstandards/springs/calc_comp_fatigue.cfm)

[Matt Meiser]

Wouldn't springs tend to work-harden over time? Any other time you have a metal part which is flexed repeatedly you get work hardening?

Also, Phil didn't say how old his bandsaws were, but wouldn't the metalurgy on an older spring tend to be poor compared to modern metalurgy--meaning those old springs might be more like round wire rolled into a spring-like shape than today's springs?

Phil, can you explain what you've done to your springs?

[John Thompson]

""""""""""""
The only plausible explanation for a spring "fatiguing" would be due to the
initial quality of the material being poor. Round wire can be drawn, and formed into a coil, but this doesn't make it a spring. It would perform the function of a spring, but it still wouldn't be a "spring".
"""""""""""

Doubt the springs on a top fuel, pro stock or any high performance motor are just plain round wire, and they will fatigue after a few runs, worked on several pit crews and and springs were checked on a regular basis and did lose their original spring rate.

Don't much care if you believe that or not, but those in the automotive high performance field see it on a regular basis.

Blanket statements like springs do not weaken over time are misleading, they can weaken...least in the real world they can.

Al

I believe you... I sold 2 sets yesterday to replace old springs on "muscle cars" that have weakended over time. When you see a vehicle sitting 2" below factory specified "ride height", it doesn't take much convincing to understand they do weaken and fail when subjected to heavy load.

I was curious and called Kim (operations manager) at Eaton-Detroit Spring for their take. When asked if they felt if auto springs weaken, the reply was "if they didn't, Eaton-Detroit would not have been in the replacement spring business since 1937 and pegged by GM and Ford as a source of OEM replacement springs". That about says it all to me.

But.. when ask at what point would they weaken, the answer was that your guess is about as good as mine as they are not aware of any concrete evidence that has been presented. Many unknowns.. did you over-load with boats, trailers, etc. High torque engines, fat hinny buddies on board and the list goes on and on.

So.. will a spring on a BS that was indeed engineered to deliver proper load rate for the given maximum blade for that BS weaken if you don't over-load it is the question as I see it.... ?

I personally think that a poor quality spring that was not engineered hefty enough to handle a given blade load is more apt to stress and weaken over time even though with a BS and non-commercial, the time that is over-loaded will be much shorter than in an automobile and not as critcal to spring life.

In chosing a BS.. I look for hefty springs that won't come close to fullly compressing with a maximum width blade on-board. Then I look to see if what the spring is anchored too is engineered well enough to properly support that spring over time. If not... I move to the next model and look some more.

My theory is not based on advanced technology and similar to yours. just common machinery sense based on having "walked the walk" and not just having "talked the talk"! What ya hear can be good or bad and sometimes decieving if not un-raveled properly.. what ya see is hard to dispute!

Regards...

Sarge.. john thompson

[Chris Friesen]

Wouldn't springs tend to work-harden over time? Any other time you have a metal part which is flexed repeatedly you get work hardening?

Something that hasn't been mentioned yet is the fatigue limit. This is the stress value that will not cause failure regardless of the number of applied cycles, and is generally well below the elastic limit.

Different metals behave differently--aluminum, for instance, doesn't actually have a fatigue limit, but steel and titanium do.

So if you were to take a steel spring and keep the stresses below the fatigue limit, it would never wear out. If you increase the stress (but still keep it below the elastic limit) it will work for a while but eventually fatigue and need replacement. Finally, if you stress it beyond the elastic limit it will immediately fail and will not return to it's original shape.

[Glenn Clabo]

From the website...
By definition, objects that are loaded under purely oscillatory loads (smean = 0) fail when their stresses reach the material's fatigue limit sfatigue.
Conversely, objects that are loaded under purely static loads (salt = 0) fail when their stresses reach the material's yield limit syield.

For objects that have a mixture of smean and salt stresses, the Soderberg Criterion provides a way to calculate a failure limit. The Soderberg Diagram plots mean stress on one axis, and alternating stress on the other, and draws a line between the smean = syield and salt = sfatigue points, as shown here,
http://www.efunda.com/designstandards/springs/images/soderberg.gif

We then plot the stress state our object of question as a point on the Soderberg Diagram. If the stress state is below the line, then we are OK. If the stress state is above the line, then failure in the part is likely.

[Brett Baldwin]

My informed layman's reading of all this and particularly Chris F. and Glenn C. posts leads me to these two understandings about overtensioning:

1. If the spring material/manufacture is inferior, the spring could be too weak in spring rate or too short from the start, leading to the potential for coil-bind and from there a quick possibilty for overtensioning.
2. If the spring is only "adequate" for the "normal" tensioning and not over engineered to handle the tension required for larger blades and thicker materials and it is constantly used beyond its fatigue point because of this, it will weaken and probably coil-bind leading to the overtensioning again.

So that leads me back to the gist of Mark's orginal position that the guage on the saw is good enough for average use. What I am getting out of all the disussions is that this is probably true as long as the spring in the tensioner is up to design specifications and you are using a blade whose tensioning needs don't exceed the capacity of the tensioning system on the saw.

Does that seem like an accurate summarization of all this?

[Greg Mann]

My informed layman's reading of all this and particularly Chris F. and Glenn C. posts leads me to these two understandings about overtensioning:

1. If the spring material/manufacture is inferior, the spring could be too weak in spring rate or too short from the start, leading to the potential for coil-bind and from there a quick possibilty for overtensioning.
2. If the spring is only "adequate" for the "normal" tensioning and not over engineered to handle the tension required for larger blades and thicker materials and it is constantly used beyond its fatigue point because of this, it will weaken and probably coil-bind leading to the overtensioning again.

So that leads me back to the gist of Mark's orginal position that the guage on the saw is good enough for average use. What I am getting out of all the disussions is that this is probably true as long as the spring in the tensioner is up to design specifications and you are using a blade whose tensioning needs don't exceed the capacity of the tensioning system on the saw.

Does that seem like an accurate summarization of all this?

Seems pretty close from my point of view, but, I might question the term "up to design specifications". We tend to think that there are some real brilliant and wise designers who know exactly what "design specifications" are needed. One of the reasons we all tend to rhapsodize over 'old iron' is that, quite often, those guys had no clue what size spring, bolt, axle, motor, etc. was needed so the overkilled their choice. Subsequently, most components never got overstressed and the tools still work today. (At least the ones that had the excesses built in. All the mediocre versions have long been discarded. We don't hear much about them and our ignorance of them feeds the notion that "They don't build 'em like they used to.") I think Glenn's chart is very useful. If the design of the tool keeps the spring in the safe zone we will probably never need to worry about it failing. OTOH, even well engineered and crafted springs can fail (in muscle cars for example) if taken across the line in his chart. And, of course, that is exactly where they are taken 'in just a couple runs'. In the end, I believe that if a spring is engineered correctly for the application, the saw is buttressed for the tension by good design and so on then we should be able break the largest blade designated as proper for any given saw EVERY TIME without damage to any other saw componentry. Someone asked if they should junk their 3/4 blades for use on a Delta 14, IIRC. Well I have that saw (older American made) and it allows for 3/4 blades but, if I find it really isn't engineered for that big a blade, I won't use one.

My summary would be: Try a blade at tensions you are comfortable with. If it works to your satisfaction, make note of the tension. If not, use a smaller blade and repeat. If none of this is to your liking get a bigger saw. I am reasonably sure I will find applications for which my 14 inch Delta will be insufficient. If it is with blades for which it was 'designed' to work then I will conclude it was under-designed.

[Phil Pritchard]

Wouldn't springs tend to work-harden over time? Any other time you have a metal part which is flexed repeatedly you get work hardening?
To an extent, yes, but the rate of work hardening varies with the composition of the steel used.


Also, Phil didn't say how old his bandsaws were, but wouldn't the metalurgy on an older spring tend to be poor compared to modern metalurgy--meaning those old springs might be more like round wire rolled into a spring-like shape than today's springs?
All the machines I've rebuilt were post-1930. I don't believe that modern steel is that much better. Part of the skill in tempering a spiral spring is in the art of the springmaker


Phil, can you explain what you've done to your springs?
In two cases I've had to replace them as the old springs had, indeed cracked. These were machines made in the early to mid 1940s, so maybe the war was the reason (poorer steel). Mostly the springs have been annealed/detempered, pulled slowly out to length then retempered by the springmaker.

Phil

[Mark Duginske]

That saw was sold by Trendlines and they are no longer in business. It is one of the generic Taiwanese saws. I'm glad to hear that you are happy with it. Most of these saws are very similar and often take the same replacement parts. For example, I get involved with a lot of saw repairs or restorations.
I recently fixed an "Elephant" brand top wheel hinge (the broken one in the original photo in this post) with a Jet part.

I would see if a local dealer, Home Depot, Woodcraft or Rockler has a riser in stock. If it is not too far a drive I would take the top casting of the saw off and take it to the store and see if it fits. Chances are that it will fit.
Good luck.

[Bart Leetch]

Does anyone know where I can purchase 5/16" round cool blocks. I have an 1950's Sears 12" band-saw that came with round 5/16" steel blocks & I would like to replace them with manufactured cool blocks. I have been using pieces of hardwood dowel.

[Alan Schaffter]

Mark can you or someone else address the below issues-

I read this thread and the one a few months back, and no where do I recall seeing a discussion about how desired blade tension figures (for sawing wood) are determined and how do we know they are correct, assuming there is or will be a bandsaw gauge to measure them.

Are these numbers theoretical or were they determined by testing and experimentation by the blade manufacturers? To me, an accurate tension gauge is only half the problem.

I realize, it would be nice to have a tension gauge to help prevent bandsaw damage from over-tensioning, but can we trust the tension numbers given for these blades? Do all blade manufactures provide recommended tension figures ? I thought some like Timber Wolf recommend the "flutter test" As a blade is used won't the tension need to be adjusted to account for blade elongation and dullness? And what about adjusting blade tension for differences in material being cut? If so, by how much?

So what is the answer to proper blade tensioning? Might there be another whole methodology, simple or complex, we have not even touched on?

[Ralph Lindberg]

Mark,I have an old Rellant 14"..

Herb, I put a Grizzly block on my old one, it did take a little work, as they were not 100% the same. But it was doable

I also upgraded the guide system, it helped (but not enough), or why I own a Grizzly G0457 now.

[Matt Meiser]

Does anyone know where I can purchase 5/16" round cool blocks. I have an 1950's Sears 12" band-saw that came with round 5/16" steel blocks & I would like to replace them with manufactured cool blocks. I have been using pieces of hardwood dowel.

Bart, Olson lists Cool Blocks "For Gilliom and old Sears Band Saws using round guides" but it doesn't say the size. Here's (http://www.olsonsaw.com/cb.html) their list of part numbers. You might try giving them a call and seeing if they are what you need. The phone number is on their contact us (http://www.olsonsaw.com/contact.html) page.

Re: Riser blocks for generic saws--I had a no-name 14" for my first saw which I put a Ridgid riser block on. I ran into a couple problems. First, the alignment pins didn't line up, so I just took them off and used a long straight edge to align everything. Second, the replacement bar for the guide was the wrong size. My dad is an amateur machinist so he just turned it down for me. Alternately, I could have bought some bar stock in the right diameter, though it would probably have been metric and thus harder to find. That saw worked well once I replaced the wimpy stock motor with a 2HP motor from Harbor Freight, but when I found a great deal on an old Rockwell 14" I bought it and sold the generic saw.

[John Thompson]

Mark can you or someone else address the below issues-

I read this thread and the one a few months back, and no where do I recall seeing a discussion about how desired blade tension figures (for sawing wood) are determined and how do we know they are correct, assuming there is or will be a bandsaw gauge to measure them.

Are these numbers theoretical or were they determined by testing and experimentation by the blade manufacturers? To me, an accurate tension gauge is only half the problem.

I realize, it would be nice to have a tension gauge to help prevent bandsaw damage from over-tensioning, but can we trust the tension numbers given for these blades? Do all blade manufactures provide recommended tension figures ? I thought some like Timber Wolf recommend the "flutter test" As a blade is used won't the tension need to be adjusted to account for blade elongation and dullness? And what about adjusting blade tension for differences in material being cut? If so, by how much?

So what is the answer to proper blade tensioning? Might there be another whole methodology, simple or complex, we have not even touched on?

Alan, you have "ask" the most pertinent questions I have seen ask in this thread. I'm curious if Mark will answer and what his answers will be!?

I personally don't have an a tension guage other than what are on my 2 BS's. I buy BS's that I know have over-sufficient springs and all components (upper case.. column.. hub and pulley mounts,, etc.) are re-enforced well enough to support them throught years of use.

I just crank it to BS tension guage reading for a given blade, then make a test cut. It gets cranked up or down a notch to find the tension that will deliver properly on a given blade with a given type stock. Only takes a few minutes. Never had a problem using this "Kentucky windage" approach. :)

Again... great questions and anxious to see a reply from Mark!

Sarge..

[Jeff Clow]

My take on the discussions here are:

Aftermarket tension gauges are not accurate/repeatable
The clamped on dial caliper method is not accurate
The flutter method is not accurate
The Built in gauge on the bandsaw is accurate enough

My old (late 1940's) bandsaw does not have a built in gauge. What should I use to tension my saw? The saw also does not have a de-tension lever either, so I must manually de-tension when not in use. This requires re-tensioning every time I use it.
Is there an aftermarket gauge, or some other method that I can use to properly tension blades?

Jeff

[Allan Brown]

Mike,
Just wanted to say thanks for your latest book. Just got it in from Amazon and can't put it down. Just bought my first bandsaw this weekend, although I won't pick it up for a week or so. Your book will give me a big jump on getting everything adjusted and ready to go@
Allan

[Mark Duginske]

I haven’t followed these discussions until I came across the posting of a dial caliper clamped onto a blade. What troubles me about these concepts is that you are attempting to correlate one parameter by measuring another parameter. And while that may be possible under the correct conditions, there is an unknown variable that separates the two measurements--namely the blade itself.

These methods are based on the assumption that all blades will extend the same amount with the same tension. I am not a metallurgist, but I do not believe this is true. The blade stretch will vary with the quality and type of steel. I would suspect that this may even vary over the length of the blade depending on the quality controls of the processing and tempering of the blade.

The most accurate method for measuring the tension on a blade is the hydraulic force gauge a previous poster mentioned. This reads the direct forces on the blade, and eliminates the blade itself as a variable.

Those bandsaws that use a compressive spring to set tension should actually be fairly accurate so long as the indicator of the spring’s compression is calibrated (or designed). The correlation between a spring’s compression and the amount of force the spring is applying is fairly consistent. I don't know if this concept is applicable to the design of the 14" bandsaws because I don't own one and have not examined the design. However, on the larger bandsaws where the tensioning spring is pressing upward on the axle, in-line with the blade, this method should be reasonably accurate.

I think that this is well put and a good explanation. The gauge on the saw is about as usable as the gas gauge in you car. It is accurate enough. If the blade is dulling or cutting thicker material one can set the tension for the next high setting. For a 14" saw that would mean setting a 1/2" on the 3/4" setting.

[Mark Duginske]

I have one of the last American made Delta 14" bandsaws with a riser and the documentation states that this saw will handle a 3/4" blade just as the poster stated for his Jet. I have three 3/4" blades that I have never used. Am I better off just junking the new blades and staying with 1/2" and smaller or am I safe with the 3/4" blades that require higher tension?

Bart Leetch also ask about this.

Although the owner's manuals often say that one can use a 3/4" blade it is not a good idea.

The 3/4" blades are usually .035" thick and that band is too thick to bend over that diameter wheel. I've seen these blades crack prematurely.

Also the 14" crowned wheels do not support wide blades the way the bigger flat wheel saws do.

Also some springs do not tension the bigger blades as well as the 1/2"
blade.

For a number of reasons the largest blade that is practical for the 14" saw
is the 3tpi hook tooth.

[Mark Duginske]

Mark can you or someone else address the below issues-

I read this thread and the one a few months back, and no where do I recall seeing a discussion about how desired blade tension figures (for sawing wood) are determined and how do we know they are correct, assuming there is or will be a bandsaw gauge to measure them.

Are these numbers theoretical or were they determined by testing and experimentation by the blade manufacturers? To me, an accurate tension gauge is only half the problem.

I realize, it would be nice to have a tension gauge to help prevent bandsaw damage from over-tensioning, but can we trust the tension numbers given for these blades? Do all blade manufactures provide recommended tension figures ? I thought some like Timber Wolf recommend the "flutter test" As a blade is used won't the tension need to be adjusted to account for blade elongation and dullness? And what about adjusting blade tension for differences in material being cut? If so, by how much?

So what is the answer to proper blade tensioning? Might there be another whole methodology, simple or complex, we have not even touched on?

When I talked Starrett and Lenox they said that the 15.000 psi rating for woodworking is an international standard by an industry group. Chuck Olson from Olson Saw doesn't use a psi number.

The most important factor concerning overtensioning in not to compress the spring completely. At other places in the post I state that I use the gauge and that I set it one setting higher when resawing or when the blade dulls.

[Mark Duginske]

Hello everyone. I am new to this forum and found this thread interesting. There is an inexpensive way to check tension that should work well. Plucking the blade while under tension and using a musical instrument tuner should give a frequency that relates very well to tension. The frequency would be different for different blades but calibration should be possible. Once the frequency of particular blade is known, increasing tension until it is "tuned should yeild very good results. This is the method used to tension guy wires on a tower. With guy wires, the frequency is so low that one can use a wrist watch to measure the frequency by timing the return wave.

Mark, do you know if this method has ever been investigated?

Cheers.

This is another one of these theoreticals. Since I am not musical
and don't know a musical note from a post-it-note it would not suit me.
All things are relative and for wires on a tower that makes sense.

[John Shuk]

Jack,
I use a strand dynomometer. It is alot more accurate for tensioning.

[Mark Duginske]

My take on the discussions here are:

Aftermarket tension gauges are not accurate/repeatable
The clamped on dial caliper method is not accurate
The flutter method is not accurate
The Built in gauge on the bandsaw is accurate enough

My old (late 1940's) bandsaw does not have a built in gauge. What should I use to tension my saw? The saw also does not have a de-tension lever either, so I must manually de-tension when not in use. This requires re-tensioning every time I use it.
Is there an aftermarket gauge, or some other method that I can use to properly tension blades?

Jeff

There are a lot of theoretical ways to tension the saw. As noted above the methods other that the gauge are questionable. I would use a new high quality blade and experiment. For starters I would get a cheap ruler and
stick it on the saw by the spring the same way that the gauge is applied.
Start by compressing the spring half way. That is a good stating point.
From that point experiment with the tension up or down. Make some notes for further reference. The sharper the blade the less tension is needed.

Good luck.....

[Jeff Clow]

There are a lot of theoretical ways to tension the saw. As noted above the methods other that the gauge are questionable. I would use a new high quality blade and experiment. For starters I would get a cheap ruler and
stick it on the saw by the spring the same way that the gauge is applied.
Start by compressing the spring half way. That is a good stating point.
From that point experiment with the tension up or down. Make some notes for further reference. The sharper the blade the less tension is needed.

Good luck.....

I understand that this would be making my own gauge for this saw. Good as far as that goes, but I'm missing something here....What would I make notes of? I still don't see any way to accurately measure the tension. If I could borrow an accurate gauge (there must be such a beast), I can see how this would work to calibrate the scale. But lacking an accurate gauge, the aftermarket ones still sound better than nothing in this instance.

Jeff

[John Shuk]

Mark,
What do you think of the flutter test suggested by Suffolk Machinery for Timberwolf blades?

[Mark Duginske]

I understand that this would be making my own gauge for this saw. Good as far as that goes, but I'm missing something here....What would I make notes of? I still don't see any way to accurately measure the tension. If I could borrow an accurate gauge (there must be such a beast), I can see how this would work to calibrate the scale. But lacking an accurate gauge, the aftermarket ones still sound better than nothing in this instance.

Jeff

Tension is only one ingredient like a soup. Think of the tension as one of 8 factors affecting band saw performance. I think that blade choice and
blade sharpness are more important that tension. If a blade is sharp it requires only moderate tension. What you are trying to establish is a "baseline" or stating point. Use a new 3tpi 1/2 blade. Compressing the spring half way is a good starting point, then note the number on the scale. Use scrap for the test. Does it cut 3/4 material at that setting? Does it cut 2" and then 4" and then 6".

If you start to have trouble cutting the material straight increase the tension and experiment some more.

[Mark Duginske]

Mark,
What do you think of the flutter test suggested by Suffolk Machinery for Timberwolf blades?

Some people use that thest with good result and if it work for them that is great. I have tried it and have not had particularly good results. To quote one of my previous post:

“No field of woodworking has more misinformation than the band saw as it relates to tension and the standard tension mechanism. Although the feeler gauge and caliper (AND THE FLUTTER METHOD) of measuring tension is theoretically valid the actual usefulness of this technique is doubtful. How many of you measure tire pressure to know how much fuel is in your tank? Theoretically you could measure either your car weight or the tire pressure to determine the amount of gas in the tank. Why not use the gas gauge?

90 percent of the time you can use the gauge on your saw with good results. For cutting thick material or if the blade is dulling
go to the next higher setting. Just like the gas gauge in your car
it is a “good enough” device.”

[Alan Schaffter]

No one answered my questions above. :confused: :confused:

[Mark Duginske]

Mark can you or someone else address the below issues-

I read this thread and the one a few months back, and no where do I recall seeing a discussion about how desired blade tension figures (for sawing wood) are determined and how do we know they are correct, assuming there is or will be a bandsaw gauge to measure them.

Answer from Mark:
When I talked Starrett and Lenox they said that the 15.000 psi rating for woodworking is an international standard by an industry group. Both of them use the same 15,000 psi number for wood but neither tech person could explain where the number came from. Chuck Olson from Olson Saw doesn't use a psi number. They (Olson Saw) have a testing machine and test welds up to several multiple of the 15,000 to test if there computerized machine is still "doing its thing". As far as giving a psi number it just is not "relavent" according to chuck Olson.

Are these numbers theoretical or were they determined by testing and experimentation by the blade manufacturers? To me, an accurate tension gauge is only half the problem.

Answer from Mark:
As I said, these 15,000 psi numbers are established by a trade group. If you look at the Feb 2007 Woodworker's Journal article that Aaron Gesicki and I did for a 1/2" 3tpi blade that blade load at is 146 lbs and the Wheel load is 292 lbs. When the blade was tensioned to read 292 (wheel load pounds) on the Carter Electronic gauge (Carter ETG) the standard saw scale measure was adjusted to the half inch blade mark. So there is a correlation between the saw scale and the Carter Electronic. Mike Cutler will be giving us more details as to the accuracy of the Carter ETG. The Starrett Gauge averaged in the 12,000psi range , the Lennox
in the 11 to 12 range and the Iturra was all over the board and some of the Ittura reading were quite low which would result in overtensioning.

I realize, it would be nice to have a tension gauge to help prevent bandsaw damage from over-tensioning, but can we trust the tension numbers given for these blades?

Answer from Mark:
These are two different questions: The most important factor concerning overtensioning in not to compress the spring completely. At other places in the post I state that I use the gauge and that I set it one setting higher when resawing or when the blade dulls.

Do all blade manufactures provide recommended tension figures ?

Answer from Mark:
Some manufactures such as Lenox and Starret do provide a 15,000 tension number but others don't. Olson recommends using the saw gauge rather than a psi number which is much less confusing to the "laymen"

I thought some like Timber Wolf recommend the "flutter test" As a blade is used won't the tension need to be adjusted to account for blade elongation and dullness? And what about adjusting blade tension for differences in material being cut? If so, by how much?

Answer from Mark:
The "flutter test is fairly simple but I prefer the saw gauge. The tensioned should be increased (I increase the 14" saw from 1/2" to 3/4"" for thicker material or as the blade dulls.

So what is the answer to proper blade tensioning?

Answer from Mark:
The proper blade tension is the one that works without hurting the saw.

Might there be another whole methodology, simple or complex, we have not even touched on?

Answer from Mark:
Of course there are a lot of different methods and the latest is the Carter Electronic ETG.

[Alex Shanku]

I dont understand how you can take a semi-scientific approach to testing aftermarket tension gauges, yet when asked what to do when the saw in question has no built in gauge you tell him to compress the spring halfway and start from there.


Why is the flutter method not better than compressing various sized/strength springs halfway?

Also, as one poster mentioned, why does this topic receive so much debate. Ive never had a problem with centering the blade, cranking the tension knob until its pretty tight, and cutting away. Am I the only one who sees this as a non-issue?

Alex

[Steve Clardy]

I dont understand how you can take a semi-scientific approach to testing aftermarket tension gauges, yet when asked what to do when the saw in question has no built in gauge you tell him to compress the spring halfway and start from there.


Why is the flutter method not better than compressing various sized/strength springs halfway?

Also, as one poster mentioned, why does this topic receive so much debate. Ive never had a problem with centering the blade, cranking the tension knob until its pretty tight, and cutting away. Am I the only one who sees this as a non-issue?

Alex


Nope. I think its a non issue also. Just my .02 :D

[Gary Keedwell]

Me three:D

Gary K.

[Mark Duginske]

Also, as one poster mentioned, why does this topic receive so much debate. I've never had a problem with centering the blade, cranking the tension knob until its pretty tight, and cutting away. Am I the only one who sees this as a non-issue?

Alex[/quote]

As one has more experience and if one has a higher quality saw one learns to intuitively adjust the band saw. No doubt that experience, comfort with machines and hand-eye-coordination play a part. IF YOU GET GOOD PERFORMANCE-GREAT. I've had students who were professional athletes,
Surgeons and other highly trained individuals who were getting into woodworking and did not have the time to develop the "heuristic" skill of
using the band saw. I do encourage people to "learn" the skill rather than buy some gadget that often doesn't work.

Just because it is easy for you it doesn't mean that it is as easy for everyone else.

[Gary Keedwell]

Just because it is easy for you it doesn't mean that it is as easy for everyone else.[/quote]


I think that it does generate more debate then is necessary. There is a learning curve but no more then there is in jointing a long board on a jointer.;) :)

Gary K.

[Steve Clardy]

Also, as one poster mentioned, why does this topic receive so much debate. I've never had a problem with centering the blade, cranking the tension knob until its pretty tight, and cutting away. Am I the only one who sees this as a non-issue?

Alex

As one has more experience and if one has a higher quality saw one learns to intuitively adjust the band saw. No doubt that experience, comfort with machines and hand-eye-coordination play a part. IF YOU GET GOOD PERFORMANCE-GREAT. I've had students who were professional athletes,
Surgeons and other highly trained individuals who were getting into woodworking and did not have the time to develop the "heuristic" skill of
using the band saw. I do encourage people to "learn" the skill rather than buy some gadget that often doesn't work.

Just because it is easy for you it doesn't mean that it is as easy for everyone else.[/quote]


True.
I don't consider a bandsaw my first go-to machine.
Its far down the line of use in my shop.
So I do not put a lot of extra though/thinking into that machine. It performs well, does what I expect from it when I use it.

[Mark Duginske]

I dont understand how you can take a semi-scientific approach to testing aftermarket tension gauges, yet when asked what to do when the saw in question has no built in gauge you tell him to compress the spring halfway and start from there.

Alex

On most saws (but not all) the setting for the 1/2" blade usually correlates with the spring (that the manufacturer chooses) being half way compressed. On most saws, especially with a sharp blade one will get acceptable performance with the spring half way compressed and not run the risk of compressing the it completely and thus negating the "shock absorber" aspect of the standard spring. He has to start somewhere and that is a good place to start experimenting.

People who get good performance (or achieve a certain level of success) take it for granted. The surgeon or professional may or may not get good performance with their band saw but they may get better performance out of their bank account than the average woodworker. That is a skill to.

Everyone is different and has spent time learning different things.

[Ken Fitzgerald]

Gary,

As you are probably aware, last year the members here primarily turners sent me a lathe, tools, videos etc. I also on the advice of turners here bought several books. I learned to turn on my own. The nearest turning club is 110 miles north of here. I'm very mechanically and electronically inclined. I install and repair CT scanners, MR scanners and x-ray equipment for a living. I've overhauled car engines, ground and lapped the valves....I started working on oil rigs full time when I was 15. I worked morning tower 11-7 for my Dad and went to HS days. In the Navy I worked Air Traffic Control maintenance and repaired equipment used aboard Fast Attack Subs..... I learned to turn on my own and I was more than just a little nervous the first time I put the gouge on the tool rest and then "heel and toed" it into the spinning chunk of wood.

Not everybody has my experience or natural talents. If I had my druthers, I learn to turn from an experienced turner. I'd learn to use my b/s from someone with a lot of experience.

Reallistically, most springs,and other mechanical things are designed to work about mid-way through their range of their mechanical range. So telling someone if they don't have a tension gauge on the b/s to compress the spring about 1/2 way through it's range.....sounds pretty sage to me.

Giving somebody like myself, totally ignorant about bandsaws, a starting point isn't a bad thing.

BTW a friend is sending me Mark's video and first book.

BTW..I'll be ordering my first b/s in about 4 weeks. Though I have a specific b/s in mind, I'm still looking at options.

[Mark Duginske]

I

Why is the flutter method not better than compressing various sized/strength springs halfway?

Alex

I have experimented with the flutter method and noticed that there are many variables. It works fine for some people and that is "great". I recently helped a friend tune up a Jet saw that he go at an auction. Just for the fun of it I tried various test including using a Carter ETG electronic gauge.

The saw needed help. Initially it would "flutter" with very low tension on the saw. The bottom wheel and top wheel were out of alignment by 1/4".
When the "riser" was added it the wheel misalignment was even worse. With each improvement the tension at which the blade would flutter would change. My unscientific observation is that saws with a riser block flutter at a different tension than those without. Could it be the longer span of the blade? Perhaps, some one could add some engineering or physics to this conversation.

"Flutter" is an easy technique which is good. However, my experience is that it is on the low end of tension required to use the saw for heavy use such as resawing. Initially to blades from the source who recommend that method are quite sharp. But, as the sharp blades dull, more tension may be required and thus the "flutter" method may require more than the initial rotation of the tension knob after the saw blade stops fluttering.

[Gary Keedwell]

Gary,

As you are probably aware, last year the members here primarily turners sent me a lathe, tools, videos etc. I also on the advice of turners here bought several books. I learned to turn on my own. The nearest turning club is 110 miles north of here. I'm very mechanically and electronically inclined. I install and repair CT scanners, MR scanners and x-ray equipment for a living. I've overhauled car engines, ground and lapped the valves....I started working on oil rigs full time when I was 15. I worked morning tower 11-7 for my Dad and went to HS days. In the Navy I worked Air Traffic Control maintenance and repaired equipment used aboard Fast Attack Subs..... I learned to turn on my own and I was more than just a little nervous the first time I put the gouge on the tool rest and then "heel and toed" it into the spinning chunk of wood.

Not everybody has my experience or natural talents. If I had my druthers, I learn to turn from an experienced turner. I'd learn to use my b/s from someone with a lot of experience.

Reallistically, most springs,and other mechanical things are designed to work about mid-way through their range of their mechanical range. So telling someone if they don't have a tension gauge on the b/s to compress the spring about 1/2 way through it's range.....sounds pretty sage to me.

Giving somebody like myself, totally ignorant about bandsaws, a starting point isn't a bad thing.

BTW a friend is sending me Mark's video and first book.

BTW..I'll be ordering my first b/s in about 4 weeks. Though I have a specific b/s in mind, I'm still looking at options.
Ken...Don't know where your going with this....what I'm trying to say is that almost 90 posts on how to tighten a blade seems out of proportion as compared to the many skills needed to be a skilled woodworker. But apparently there are alot of people having a hard time ...so there must be something to all these posts. Sorry about all my unfocused english this morning...coffee hasn't kicked in yet.:o I don't mean to demean anybody because I've had days where resawing doesn't go like I want it to. But I found out that most of my solutions were that I was using the wrong blade for the job at hand.:rolleyes: :)
Gary K.

[Mark Duginske]

Ken...Don't know where your going with this....what I'm trying to say is that almost 90 posts on how to tighten a blade seems out of proportion as compared to the many skills needed to be a skilled woodworker. But apparently there are alot of people having a hard time ...so there must be something to all these posts.
Gary K.

Gary,

Looking back this thread was not about "tightening the blade", it was about trying to get a feeling for how many people had accidently damaged their band saws by overtensioning. I thought that there may be a couple of post showing pictures of bent top wheel hinges and broke top or bottom shafts (which we still have not gotten). Since the thread was titled "...overtensioning..." the discussion move to overtensioning and then tensioning in general.

I to am surprised at the number of post but I think that it shows the interest in (or confusion about) the band saw. Unlike the other circular saws the band saw needs to be "tuned" like a musical instrument
and that is a skill not easily communicated.

[Al Willits]

Been enjoying the topic, not so sure I'd say its gotten to be a little much though, some like to know the who, what, where, when and why of a product, and I think that could get pretty involved.

Then there's people like me, who at this state of the learning curve are perfectly happy with starting at the half way point of the spring and making cuts to see what happens and adjusting from there.

Personally with the Wolf blades I find I can set the tensioner at just shy of what it says to and it cuts just fine.
Also think no matter what ya use to set a tool up, the proof is in the using.
Unless of course your an engineer.....:D :D :D

Al

[Ken Fitzgerald]

Ken...Don't know where your going with this....what I'm trying to say is that almost 90 posts on how to tighten a blade seems out of proportion as compared to the many skills needed to be a skilled woodworker. But apparently there are alot of people having a hard time ...so there must be something to all these posts. Sorry about all my unfocused english this morning...coffee hasn't kicked in yet.:o I don't mean to demean anybody because I've had days where resawing doesn't go like I want it to. But I found out that most of my solutions were that I was using the wrong blade for the job at hand.:rolleyes: :)
Gary K.

Gary,

I've been looking at b/s a lot the past couple of weeks. I'm pulling the trigger on a b/s in the last week of September. I've looked at inexpensive and what I consider expensive. Some have tension indicators, some don't. All I was trying to say that I didn't think Mark's giving a general starting point for tensioning was a bad thing. That's all I meant to say.

1st cup of coffee too!:o

[Mark Duginske]

Been enjoying the topic, ..............

Also think no matter what ya use to set a tool up, the proof is in the using.
Unless of course your an engineer.....:D :D :D

Al

I think that Al Willits makes a very good point. The proof is in the using and this thread has given the SMC group a chance to share their experience and concerns. The statement..."the proof is in the using"...
shows a lot of midwestern common sense.

Until one "learns" the nuances of tuning the band saw it is a temptation to
use "engineering" solutions such as the clamp on gauges etc. After reading Mike Cutler's comments in this thread the point is that these are not applicable to the woodworking band saw.

The saw gauge, the "flutter test" and compressing the spring half way are places to start. The band saw user has to realize that the saw requires experimentation and performance may change as the blade dulls or heats up and that one has to keep an eye on the saw and possible "dial in" a change. A little experimentation with the saw is a good thing.

[Alan Schaffter]

Mark thanks!

Maybe repeating parts of a previous summary, but for me it sounds like first, follow the saw's tension markings (or half spring compression if there are no markings) which will get you in the ball park, then adjust the tension as necessary. Take note of what setting you are using and build up some experience as you go. Different wood, thicknesses of wood, and blades will act differently. But, by all means, don't bottom out the spring.

This brings up another question (already addressed?) that gets back to Mark's original issue- seems improbable, but has anyone damaged the tension mechanism (hinge, pins, etc. etc.) of their bandsaw by tensioning it without bottoming out the spring?

[Chuck Lenz]

Mark thanks!

Maybe repeating parts of a previous summary, but for me it sounds like first, follow the saw's tension markings (or half spring compression if there are no markings) which will get you in the ball park, then adjust the tension as necessary. Take note of what setting you are using and build up some experience as you go. Different wood, thicknesses of wood, and blades will act differently. But, by all means, don't bottom out the spring.

This brings up another question (already addressed?) that gets back to Mark's original issue- seems improbable, but has anyone damaged the tension mechanism (hinge, pins, etc. etc.) of their bandsaw by tensioning it without bottoming out the spring?
Ummm Alan, I believe my hinge shaft was damaged because it's a under engineered part, not because I tightened it too tight. The new hinge shaft I got from JET was beefed up considerably where the old one had failed. I'm sorry but this whole thread of blameing everyone for over tightening bandsaw blades has gotten wayyyyyyyyyyy too deep. Who's got the time to play mad scientist with clamps and calipers everytime they use their bandsaw ? You wouldn't get any woodworking done ! It's not the operator, it's the saw part thats to blame. You don't see anyone breaking or bending hinge shafts on bandsaws larger than 14" do you ? Someone in here mentioned that they had broke their hinge shaft on a certain brand and they got one for a different brand saw and it looked just like the one he had, and it fit his saw. The 14" saws are all geting to be that they have the same castings but are branded different. Someone has also mention in here that you shouldn't use a blade wider than a 1/2" in these saws, hogwash ! JET says I can use a 3/4" blade and I expect them to stand behind that claim.