EZtension band saw blade tension gauge

[David Utterback]

FWW 281 has a review of the new EZtension band saw blade tension gauge for $40. They have web site by that name where you will learn that devise only works with carbon steel blades. Nonetheless, it is a nifty invention, IMHO. Has anyone tried it?

[Frederick Skelly]

Here's a little. Unfortunately, I havent had any shop time to wring it out fully. But I like the tool, FWIW.
Link (https://sawmillcreek.org/showthread.php?280492-First-impressions-EZTENSION-Bandsaw-Tensioning-Gauge&highlight=Eztension)

[Jamie Buxton]

There's a good low-cost way to measure blade tension. It uses a micrometer, which you may already have. Or if you don't, buy a $20 one, so you get both a tension meter and a micrometer. John TenEyck has posted on SMC about the method, but I'm having trouble finding that. Instead, here's Matthias Wandel https://woodgears.ca/bandsaw/tension.html

[Larry Frank]

I used the micrometer method to see where to set the tension on my bandsaw. It worked well.

[John K Jordan]

FWW 281 has a review of the new EZtension band saw blade tension gauge for $40. They have web site by that name where you will learn that devise only works with carbon steel blades. Nonetheless, it is a nifty invention, IMHO. Has anyone tried it?

David,

I haven't tried it but would like to and compare it to my Starrett tension gauge. I don't want to buy one just to test right now, maybe later. Hey, if you buy one maybe I'll stop and visit with my gauge next time I get up your way! (when it's safe to get out!)

I looked at their web site: https://www.eztension.com/ As mentioned, carbon steel blades only, not bi-metal.
Carbide? Spring steel? https://www.finewoodworking.com/2012/11/09/setting-bandsaw-blade-tension

Just thinking about it I'm curious if the magnetic detachment principle will give consistent results with with thicker vs thinner blades.

I suspect they have calibrated it for different blade widths by comparing to a gauge that measures the stretch of the steel. I wonder if the magnets they use have consistent strength, especially if they purchase a different batch. Maybe I'll ask my friend Joe who has magnetic expertise and a gauss meter.

I don't see it mentioned, but it might be important to back off on the upper and low guides before deflecting the blade.

If this proves to be useful it would eliminate the biggest issue I have with the the deflection method by finger force promoted by some without saying how to calibrate the finger! If it works well it could be a big help to many.

One oddly humorous thing - the web site touts the recyclable materials "so the body is fully recyclable at the end of its useful life" while the FAQs say "is built to last a lifetime." Maybe the end of useful life would come when you forgot to remove it before turning on the saw. :)

JKJ

[Myk Rian]

You don't need any type of measuring tool to set a BS blade. Use the "flutter method".

[Edwin Santos]

You don't need any type of measuring tool to set a BS blade. Use the "flutter method".

Browsing this forum, I have concluded the need for a tension gauge can depend on the user's personality. Those that are engineers or have an engineering mentality will usually feel much better with an instrument giving them an objective, precise measure of tension.
Others will be satisfied getting results with instinctive rule-of-thumb methods like deflection and the flutter test.
Whether one's personality cuts toward being a minimalist versus a gear and gadget collector might factor into it also.

I'm not sure one school of thought is necessarily better than the other, it may be a question of personal fit.

[Lee Schierer]

I guess I'm one of those individuals that look for more precision than just feel for making adjustments on machines. From day one with my band saw I've had questions regarding blade tension. The first thing I learned was that the scales on the tension adjustment are pretty much worthless. So then I tried the flutter test, only my blades rarely fluttered and you had to move the guides and rollers out of the way to get it to work. So next I tried the push the blade with your finger for deflection method , only how much finger pressure is enough or too much. My finger wasn't calibrated any better than the scales that came on the saw. For the most part I just tensioned it until it seemed to work for the cut at hand. I was intrigued by the tension meter at Matthias Wandel Woodgears (https://woodgears.ca/bandsaw/tension.html). I wrote to him to see if any plans were available, but so far no response has been forthcoming. Sooo, having lots of time, I printed out a photo of his tension device and proceeded to figure out the basic dimensions based on the only given dimension of 4 inches of blade between the grippers. Here is the result of my efforts.
432795
I made a few modifications to his design that I felt would increase the accuracy. I added two small brads near the blade clamps to locate the back of the blade each time. One is hidden in the notch on the upper clamp. I also designed it so that I had a spacer block that could be placed between the two arms for storage to protect the hinge element. My gauge is made of hickory.

It took me a while to work through his calculations for determining psi that were correct for my gauge. As you can see on my gauge .001 on the dial indicator equals 2,071 psi of tension. The best part of 3 hours was involved in making the gauge, including several waiting times for glue to set up. This project require no trips to the hardware store because my part bins had all the hardware that was needed.

[John K Jordan]

I like it! Nice and simple and certainly effective! Do you feel OK in providing some of the dimensions you worked out? I'd like to build one just for fun and to compare to a commercial gauge. I'm sure some people who attended my bandsaw classes would like to make one. I'm wondering how difficult it would be to design a replacement scale for the dial indicator that was calibrated in PSI for steel stretch. Or if the geometry was the same maybe photocopy an existing tension gauge dial. (I understand it's OK to do that for personal use) I suspect the people making these gauges for sale use a standard dial indicator - would be easy enough to check.
432802

I'm also one of those who prefer to get it right instead of guess. Yes, it may be the engineer/scientist/inventor in me. If bandsaw blade manufacturers, instead of saying "tension to 15,000 psi" or somesuch but instead said "tension till blade flutter goes away" or "press on the blade by some amount to deflect the blade" or "tension until you get pretty good results" I might think differently. I think they specify the numbers for various blades for a reason.

JKJ


I guess I'm one of those individuals that look for more precision than just feel for making adjustments on machines. From day one with my band saw I've had questions regarding blade tension. The first thing I learned was that the scales on the tension adjustment are pretty much worthless. So then I tried the flutter test, only my blades rarely fluttered and you had to move the guides and rollers out of the way to get it to work. So next I tried the push the blade with your finger for deflection method , only how much finger pressure is enough or too much. My finger wasn't calibrated any better than the scales that came on the saw. For the most part I just tensioned it until it seemed to work for the cut at hand. I was intrigued by the tension meter at Matthias Wandel Woodgears (https://woodgears.ca/bandsaw/tension.html). I wrote to him to see if any plans were available, but so far no response has been forthcoming. Sooo, having lots of time, I printed out a photo of his tension device and proceeded to figure out the basic dimensions based on the only given dimension of 4 inches of blade between the grippers. Here is the result of my efforts.
432795
I made a few modifications to his design that I felt would increase the accuracy. I added two small brads near the blade clamps to locate the back of the blade each time. One is hidden in the notch on the upper clamp. I also designed it so that I had a spacer block that could be placed between the two arms for storage to protect the hinge element. My gauge is made of hickory.

It took me a while to work through his calculations for determining psi that were correct for my gauge. As you can see on my gauge .001 on the dial indicator equals 2,071 psi of tension. The best part of 3 hours was involved in making the gauge, including several waiting times for glue to set up. This project require no trips to the hardware store because my part bins had all the hardware that was needed.

[Lee Schierer]

I like it! Nice and simple and certainly effective! Do you feel OK in providing some of the dimensions you worked out? I'd like to build one just for fun and to compare to a commercial gauge. I'm sure some people who attended my bandsaw classes would like to make one. I'm wondering how difficult it would be to design a replacement scale for the dial indicator that was calibrated in PSI for steel stretch. Or if the geometry was the same maybe photocopy an existing tension gauge dial. (I understand it's OK to do that for personal use) I suspect the people making these gauges for sale use a standard dial indicator - would be easy enough to check.
432802

I'm also one of those who prefer to get it right instead of guess. Yes, it may be the engineer/scientist/inventor in me. If bandsaw blade manufacturers, instead of saying "tension to 15,000 psi" or somesuch but instead said "tension till blade flutter goes away" or "press on the blade by some amount to deflect the blade" or "tension until you get pretty good results" I might think differently. I think they specify the numbers for various blades for a reason.

JKJ

John, per your request. Attached is a pdf of the cad drawing I just made of my gauge. The important thing is to get the two large holes vertically aligned and exactly 4" apart. I used #8 screws and wing nuts, making the hole through the main piece tight so the threads gripped and loose through the clamps. The clamp blocks are not show, but mine are about 1-1/2 x 3/4 x 1/2. I had to shorten the upper one to clear the block at the right side on the upper member. The "hinge" is centered left to right as you look down from the top and was made from a piece of straight grain hickory and split to a 1/16" thickness.
432810
Once you get the parts made, measure the distance from the hinge C/L to the ~C/L of the blade and then locate the center of the dial indicator probe a multiple of that distance from the hinge. Mine was 3.0 x 1-3/4

Let me know if I missed any dimensions that would be useful.

[John K Jordan]

Attached is a pdf of the cad drawing I just made of my gauge.

Thanks, I'm putting that in with my files on the Woodgears gauge.

As for the math, John TenEyck wrote it out for us.
http://www.sawmillcreek.org/showthread.php?250388-Bandsaw-blade-tension&p=2640833#post2640833

The basic calculation is Young's Modulus = Stress/Strain, where:

1) The Young's Modulus of steel is about 30 x 10^6 psi.
2) Stress, the value you are after - the tension in the blade in psi.
3) Strain = Deflection / gage length. The vernier measures deflection, and the gage length is the starting distance between the jaws under zero load.

So, you rewrite the equation as Stress = Young's Modulus x Strain = 30 X 10^6 x deflection/gage length

The gage length I started with was 4.768", so when I measured a deflection of 0.003" that was equal to a blade tension of 30 X 10^ x 0.003/4.768 = 18,876 psi.

This is his picture with the message:

432813

JKJ

[Lee Schierer]

So, just to check my math, what would be the psi per .001 if the dial is located 5.25" from the hinge and the blade is located 1.75" from the hinge.

[John K Jordan]

So, just to check my math, what would be the psi per .001 if the dial is located 5.25" from the hinge and the blade is located 1.75" from the hinge.

Hmm.. What do you think the actual clamped length is? The distance between the clamping screws is 4" but if the clamping blocks are .75 then AND they are effectively clamping the blade at the inner edges of the wooden clamping blocks without slippage then the clamped length might be 3.25" (also assuming friction for the 2" or so length sliding flat against the wood on the lower section doesn't affect the stretch).

5.25"/1.75" = 3 so assuming a simple pivot and a very small angle of rotation the gauge would measure about 3 units for each unit of blade stretch so the 0.001 gauge deflection would indicate the actual blade stretch of 0.001"/3 = 0.000333" (Am I thinking this through correctly?)

Instead of 30*10^6 Woodgears gives Young's modulus at 29*10^6 which I find matches tables for structural steel which I assume is close to a carbon steel bandsaw blade. I found this: Elastic modulus of carbon steels at room temperature is only slightly affected by changes in composition and structure.

If these are close, the numbers for a 0.001" gauge reading would be 29*10^6 * 0.000333"/3.25" = 2974 PSI. (Assuming I didn't make an arithmetic or logic mistake!)

This assumes the clamped length is the distance between the two blocks. But I'm wondering where the clamp is actually holding the blade securely. Due to flexing of the wood could it be somewhere in the middle of the blocks for a clamping distance of closer to 4"? If so, the number could be 2417 PSI, again, if the calculations and assumptions are correct.

Instead of a wide clamping block the Starrett gauge I have and other's I've seen clamp with a small diameter steel machine screw in the middle of the blade so the actual distance is well defined:

432877

It sure would be nice to compare the numbers from this design with a commercial gauge!

BTW, the Starrett instructions indicate to put a little load on the gentle spring in the gauge before clamping to the blade to take up any play in the gauge.

It's late and I was up till 4am last night so I'll try to look at this with a clearer head tomorrow evening. Or maybe someone else can double check the numbers by then.

JKJ

PS, the birds are keeping me busy - more little guineas hatched today:

432878

[Lee Schierer]

John, after reading your comments, I went back and altered the grippers to concentrate the pressure closer to the 4" distance by narrowing the tips and beveling the face that is against the gripper. I tensioned my 1/4" blade to .003 on the dial indicator and then backed off the tension. The dial returned to exactly the zero setting, so the gauge is repeatable. With those changes the tension readings would be 29*10^6 * 0.000333"/4" = 2414 PSI. So .003 on the dial would indicate about 7240 psi tension.
432908
I also shortened the bottom by 1/8" so it would fit in a cardboard storage box that I just happened to have on hand from an amazon purchase.

[David Utterback]

Browsing this forum, I have concluded the need for a tension gauge can depend on the user's personality. Those that are engineers or have an engineering mentality will usually feel much better with an instrument giving them an objective, precise measure of tension.
Others will be satisfied getting results with instinctive rule-of-thumb methods like deflection and the flutter test.
Whether one's personality cuts toward being a minimalist versus a gear and gadget collector might factor into it also.

I'm not sure one school of thought is necessarily better than the other, it may be a question of personal fit.

I agree. I like confirmation that my approximation methods are in the ball park. Most of my blades are bi-metal so the EZtension would not work for me. I have used the simple method shown by John in the past and it works quite well. I can then rely on the band saw gauge which I mark for different blades.

[John K Jordan]

...I can then rely on the band saw gauge which I mark for different blades.

That's the method I use with the gauge too - use it once for each type of blade and mark the indicator needle on the bandsaw. I think it would be good for clubs and such to have a gauge that could be loaned to members.