Bandsaw tension

[John Lanciani]

How critical is it to have a blade tension that's absolutely 'perfect'? I must be doing it wrong, because I only ballpark mine. What I can't figure out, though, is why my cuts come out fine. While the stock gauge may not be 'right', isn't 'right enough' in this case?

I'm a numbers guy too, but is this or is this not a case of perfect-for-the-sake-of-saying-i'm-perfect? Don't mean to be glib by that.

I guess it depends what you use your saw for. If you're cutting veneer from a $30 or $40 (or more) per board foot piece of 4A quilted maple then good enough is not neccessarily good enough. I regularly cut 12" - 16" wide veneers and they go directly into the vacuum bag, they're that perfect every time and I don't make test cuts. If that's in your ballpark that's great; I'll continue to quantify my setup in the name of accuracy and repeatability.

[Georg Zudoff]

Hi John, of course you're right and tension gauge still in my wish list. But for my purposes - coarse ripsawing and after I do remaining jog with handtools only, I no need to use tension gauge. For veneer resawing you are right for 200%.

[Sam Layton]

Thank you everyone for your response and help. David, and Van, I have read the information, and views of Duninski. I do not agree with his views in all cases. I think that Iturra got a bad rap in that deal.

I have been using Timberwolf blades. When I resaw with a 3/4" Timberwolf, the results are good. However, the cuts are very rough, and not satisfactory. So I would like to get a carbide blade, and do some serious resawing. First, I am going to work on my saw in order to increase my tension. In addition, I am a numbers guy as well. I like to dial in, and see where I am at. I am just not happy not knowing what tension my saw is producing.

Damon, your on. However, I believe it is my turn to buy lunch.

John, what kind of saw and blade are you using?

Thank you very much for all of the help, I do want to purchase one of the three gages. I am just not sure which one.

Sam

[Thomas Hotchkin]

Sam
Not to highjack your post. But has anyone here used [The Thien Audible Tension Gauge for Bandsaws (Beta)] for bandsaw blade tensioning? Can be found at.
http://www.cgallery.com/jpthien/tg.htm Tom

[John Lanciani]

Sam,

I have a Minimax MM20 with a 1" Lenox tri-master blade. You can see my resaw setup here; http://www.sawmillcreek.org/showthre...t=#post1838654 at post #11

[ian maybury]

Must say (as a non expert) that I find this is a very confused subject. I'm another that's all for having an objective and repeatable method of measuring blade tension.

My experience suggests the following:

(1) Tension is a very different matter on your average 14in lightweight saw, and on a large industrial (e.g. Italian) machine.

So far as I can tell it's as much about having a method of finding a setting that avoids unwanted vibration and harmonics as anything on the former. Which given that saws are different probably leads to the often conflicting varieties of black art one hears of for finding a workable tension setting.

On the latter with carbide and larger blades the tension gets high enough that it's tough to judge by subjective means - which points to the advisability of a gauge.

Against that large saws seem to be less bothered about the precise setting once you have 'enough' tension. They don't for example seem (if at reasonable tension levels) to suffer from blade flutter to any significant degree, or to get into the sort of vibrational melt down that occurred on my last saw on rip cuts much above 5in....(no matter what the tension setting - caused by inability to tension the blade enough, and chassis flex?)

(2) OEM bandsaw tension gauges that rely on uncorrected and mechanically indicated spring deflection cannot be accurate over time - there's always going to be the issue of sag in springs that are regularly loaded. i.e. the spring gets shorter in its relaxed full extension condition, and likewise needs additional compression to deliver a given force.

Perhaps if regularly calibrated and the scale marked up accordingly using an accurate tension gauge.....

(3) Friction in the mechanism, and the possibility that it can vary means that (despite our tendency to use it as an indicator) the force to turn the tensioning wheel isn't necessarily a very good indication of what's going on either.

(4) 'Proper' tension gauges that measure blade stretch (technically 'strain') have the potential to work, but only if used correctly, and if the required tension is well above that required to pull all bowing/sideways deflection out of the blade. (which is going to be rather more than at first might appear to be the case) Otherwise all it's going to measure is lengthening between the clamping points due to the straightening effect.

The other issue is that if you do the maths it becomes clear that a tension gauge needs a high accuracy (expensive) dial gauge measuring down to about 1/10 thou if it is to be accurate enough to do the job.

All of which may mean tension gauges are less applicable to lightweight saws...

None of which is 100% satisfactory.....

ian

PS Maybe one of these: http://www.tensitron.com/strap_band.html

[Sam Layton]

Thomas, I have heard of the audible method, but don't know anything about it, nor know anyone that has used it.

John, you have a great set up. That sure is a super resaw set up. I can see that you put a lot of work in that device, and it sounds like it paid off for you.

Ian, I'm with you, it is a very confusing subject to me as well. Everyone has their own theory. A lot of different methods work for a lot of people. So, I guess what ever method works for an individual is good. Like David said, he can not feel the difference between 20,000 and 30,000 psi. For me, I don't know what any psi feels like. So, for me a gage is what I will have to rely on. Even if it is not total accurate, but repeatable, that will be good.

Sam

[Alan Lightstone]

I guess it depends what you use your saw for. If you're cutting veneer from a $30 or $40 (or more) per board foot piece of 4A quilted maple then good enough is not neccessarily good enough. I regularly cut 12" - 16" wide veneers and they go directly into the vacuum bag, they're that perfect every time and I don't make test cuts. If that's in your ballpark that's great; I'll continue to quantify my setup in the name of accuracy and repeatability.

Yeah, but you built the greatest resaw fence/guide in the history of the world.

What's the downside in over tensioning a blade?

BTW, just looked at the price for the Starrett. OMG!!!!

[David Kumm]

Sam. Can you clear some room for PM. Dave

[Sam Layton]

Sure will David

[Bruce Wrenn]

For me, I don't know what any psi feels like. So, for me a gage is what I will have to rely on. Even if it is not total accurate, but repeatable, that will be good.

Sam

Grab yourself a $9.99 HF dial indicator and a couple of 1" C clamps. With blade only slightly tensioned, open caliper to 5". Clamp jaws to blade. As tension is increased, blade will elongate. A little research will show amount of elongation over 5" to achieve the desired tension. Before breaking out the CC to buy a carbide blade, I would try a bi-metal blade.