Make a Bandsaw Tension Gauge

Make a DIY bandsaw tension gauge:

http://www.youtube.com/watch?v=9iAkRLvLAvI

Apparently, I have been applying way too little tension on my blades. Now I have a much better idea of where I should be w/ tension.
(I was never a big fan of the pluck and listen for a tone technique.)
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On Sun, 28 Oct 2012 05:33:31 -0700 (PDT), snipped-for-privacy@garagewoodworks.com

Maybe it might be useful *once* you get your blade tensioned properly.
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I inherited an expensive bandsaw tension gauge many years ago and realized then that, at least on my bandsaw, the factory marks were way too low also. Makes a big difference when using the proper tension, so a gauge is a must if you want to get the best out of some of the older bandsaws, and this is an affordable way to go about it.
Well done.
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On Sunday, October 28, 2012 9:46:40 AM UTC-4, Swingman wrote:

Thank you Swing! I've been putting off making one for too long and regret not making it sooner.
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On 10/28/2012 7:33 AM, snipped-for-privacy@garagewoodworks.com wrote:

Good information and findings but how about a tension warning indicator that lets you know when to retention during sawing operation. When the blade warms up from simply spinning it will stretch, more when cutting, and then less when not cutting.
While we all would like to be able to narrow this down to an exact science temperature changes every thing.
On my saw the tension gauge is on the exterior in plain site while cutting. Most saws require you to turn off the saw and open up the wheel cover to recheck tension. I find it quite common to have to retention considerably after only a few minutes of sawing and after a few minutes of cooling down the blade is over tensioned.
Something to think about.
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On Sunday, October 28, 2012 10:14:13 AM UTC-4, Leon wrote:

That never occurred to me. That's is a very valid point regarding the effects of temperature. How about an internal blade cooling system that maintains 25 C? :)
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On 10/28/2012 9:41 AM, snipped-for-privacy@garagewoodworks.com wrote:

of temperature. How about an internal blade cooling system that maintains 25 C? :)

The devil is in the details. LOL. I'm looking forward to you coming up with the blade cooling solution.!
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On 10/28/2012 9:41 AM, snipped-for-privacy@garagewoodworks.com wrote:

of temperature. How about an internal blade cooling system that maintains 25 C? :)

Ok I have the solution. On a saw with the typical pointer indicating tension you mount a mercury switch. 3 wire mercury switch. When the pointer moves one direction as the blade warms up the switch tilts and a tension motor begins to increase tension until the mercury switch is again in a neutral position. As the blade cools and the pointer moves in the opposite direction the switch indicates to loosen tension. You zero the mercury switch when you initially adjust the blade tension.
What could be more simple? :~)
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Yep, making it more important to be properly tensioned to start with.
Figuring that industries relying on the bandsaw would be addressing that as a concern, this is an interesting read on the subject, which also raises the question, how do you put a "back-crown" on a bandsaw blade?
https://www.fornis.net/system/files/machining_LUS.pdf
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Best I can translate the jargon, their concern was that the toothed edge of the blade expanded from friction heat, effectively reducing the tension on the front blade edge. To maintain uniform blade tension at operating temperature, I think they are suggesting that the rear edge should be longer than the front.
I may have some OCD tendencies, but such concerns too over the top to be helpful in my shop.
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On 10/29/2012 6:59 PM, Larry Kraus wrote:

No shit ... ;)
You'd have to have a big honking blade to just "increase the tension to the tooth edge" of the blade, or some such words.
That said, I do agree that the most heat would be generated at the tooth edge, and the wider the blade, the more heat dissipation toward the back would occur, with less loss of blade tension.
IOW, use the widest blade possible, consistent with the task, and it shouldn't be a big factor on whether the cows made it home.
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On Monday, October 29, 2012 5:27:42 PM UTC-7, Swingman wrote:

If the blade tension spring is properly designed, it should compensate for the blade length changing as the blade heats and cools. Kerry
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On 10/30/2012 12:05 PM, snipped-for-privacy@gmail.com wrote:

Can you name a brand that has a properly designed tension spring? Not the case on my Laguna LT16HD.
And since tension is increased with the compression of the tension spring, how would a properly designed spring maintain the proper tension as it decompresses when the blade stretches?
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wrote:

Leon, I'm not familiar with enough bandsaws to know if any have a tension spring that does this well. A long enough tension spring would change its length by a small enough % that the force it exerts would be close to constant. Kerry
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Are you guys bottom posting... after all the hell you gave us, now you are guilty of this....hmmmmm.
A spring can be built to properly maintain tension. just like motorcycle springs, where you have springs inside of springs (coils with inner coils). The higher end springs for racing maintain almost constant tension so the bike tracks the same no matter what.

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On 10/31/2012 8:45 AM, tiredofspam wrote:

Maintaining constant tension is not the problem, as you said this has been acomplished in the transportation industry.
The trick is to have a spring maintain constant tension with limitless possible initial settings.

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On Sun, 28 Oct 2012 05:33:31 -0700 (PDT), snipped-for-privacy@garagewoodworks.com wrote:

FWIW, you will hear a lot of different thoughts on blade tension and the proper setting. One thing to bear in mind is that the right blade can affect how much tension you need. Too much sawdust caught in the gullets will force the blade to shift off line and cause rough cuts. Lower feed rates can help, but a 3 TPI blade has been recommended as a good blade and I have found it works well for me. Given that, you can use a lower tension and get good results, even in a wide resaw.
The benefit to your saw is less stress on the frame and less stress on the wheels.
Fine Woodworking has some info presented by Michael Fortune that suggests all this and also has tips to adjust blade tracking to correct for drift. If you think about it, having the blade slightly forward or slightly back of the top of the crown on the wheel will cause the blade to twist. That causes drift.
Using the adjust blade tracking technique means you don't need to adjust the fence to compensate for drift.
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On Sun, 28 Oct 2012 05:33:31 -0700 (PDT), snipped-for-privacy@garagewoodworks.com wrote:

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