New bandsaw blade question

[Bernie Kopfer]

Recently bought a new Rikon 10-347 bandsaw that they claim is professional grade. It is obviously strongly built and claims to be able to handle a 1 1/4 in blade. I stumbled across a Lennox Trimaster 1” blade, 3tpi, 1/32” Kerf blade in my length for $83 on Amazon. Brand new, so I had to buy it. Today I put it on the saw and tensioned it up and made a couple of resaw cuts and they looked great.
What I don’t know never having had a saw this big nor a blade that thick is how to know if the tension is correct. The finger flex test shows minimal give, no quarter inch of movement and the becoming solid, just solid,period. The tension release is very difficult to engage requiring both arms. The inside tension gage only reads 7/8 inch yet to tension it any tighter requires lots of effort, don’t think I can twist the wheel that much more. Makes me believe it could be overtensioned. My question short of spending money I don’t want to spend for a tension gage is what do those of you with large saws and thick blades do to correctly tension your blades? Does the flutter test work on big blades? Or is it just cut and evaluate the results?

[Melvin Feng]

Right now I just evaluate the cut and make adjustments from there as necessary. I've personally never trusted the flutter test, I tend to go much higher than the flutter test would show.

I have a laguna 18 BX and I primarily keep a 1.25" Resaw king on it. The backer is fairly thin, so it is pretty easy to tension the blade to get a nice cut. When I don't have enough tension, I tend to notice diagonal texturing, most likely due to harmonics of the blade while it is running. The higher tension is supposed to change that harmonic to a higher frequency with a lower amplitude, thus reduced texturing and a smoother end result.

I still would like to get a bandsaw tension gauge though so that I can actually do some testing and get repeatable results, I just don't want to spend the money on one either!

[Andrew Hughes]

I’ve never used a tension device on any of the saw I’ve owned. When my blades stop cutting great I believe it’s because the tips of the teeth are getting dull.
I tighten the blade a little above the factory gauge setting it does feel stiff. I don’t think it needs anymore
I have a 20 inch Bandsaw

[Brian Deakin]

You may find this link helpful

https://www.youtube.com/watch?v=wGbZqWac0jU&ab_channel=thewoodworkingshows

[Curt Harms]

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I still would like to get a bandsaw tension gauge though so that I can actually do some testing and get repeatable results, I just don't want to spend the money on one either!

If you do a search for something like "bandsaw tension gauge" you should find instructions for a homemade tension gauge. Most use either a digital or dial caliper. The homemade ones probably require a bit of math.

[John TenEyck]

Here's a shop built tension gauge I built for not much more than the cost of a dial gage:

https://sites.google.com/site/jteneyckwoodworker/current-projects/bandsaw-blade-tension-meter

Very little math involved.

When you start using carbide blades that typically cost well over $100 it makes sense to me to be sure the tension is high end for the blade to do its job properly but not too high and risk premature failure. Once you calibrate your on board tension gage against the blade tension meter for any particular blade you can just use the on board gage with confidence.

John

[Erik Loza]

My rule: Apply only as much tension as needed in order to get the cut you want. With a TriMaster, the tension needed to cut something like 8/4 wood is not going to be the same as what is needed to resaw something like a 12" tall board. The flutter test has always worked well for me but then again, I've worked mostly with big Italian saws, where "can it tension properly?" is never a question.

Bernie, just a few thoughts: First, make sure to de-tension that blade when it's not in use. You'll either fatigue the blade or possibly damage the machine if it's left under tension for long periods. You might know this already. Also, not sure what you're cutting but I've always had really good luck with Timberwolf blades. A 1/2" Timberwolf AS was my go-to blade on the MM16. Carbides are really great at a few specific things but not for general purpose use. Again, maybe you know this already. Good luck and hope this helps,

Erik

[Bernie Kopfer]

I purchased this blade because it has a good reputation and the price was right. I’d rather of had a3/4 in blade. I’m going to make a tension gage and get the tension right so that I can readily repeat it. The consensus appears to be 30,000 psi. Translates to .005 in of stretch over 5 inches. This could be fun.

[Paul Saffold]

John, thanks for the info on your shop made tension gauge. How do you know what the tension should be for the blade? I know it will be different for spring steel, bi-metal, different blade thickness, etc.

I have a Laguna 14-12 and have broken numerous blades, all at the gullet. So I assume it is a tension problem. I am very reluctant to buy an expensive blade until I find a solution to the breakage. In fact I’ve stopped buying bi-metal Lennox and Laguna blades in favor of the spring steel ones that are half the price. I use 3/8” 6 tpi mostly. Domestic hardwoods rarely more than 2” thick.

I have talked to reps from Laguna and from the blade suppliers. All think I’ve got a tension issue. I've been told too much tension or too little tension! Confusing to say the least.

The tension “guide” on the Laguna is nothing more that a magnet, think refrigerator magnet, that easily slides around.

I really like the saw except for breaking blades which I think is my problem not the saw’s.

I’ll try your guide if I can find a recommended tension for the blades.

[Erik Loza]

Paul, my feeling is that your machine is just too small for exotic metal blades. It sounds like you found a blade that works but if you want to try others, I'll shill for the Timberwolf again. They were VERY forgiving about tension range from what I recall and budget-friendly. Hope this helps.

Erik

[John TenEyck]

John, thanks for the info on your shop made tension gauge. How do you know what the tension should be for the blade? I know it will be different for spring steel, bi-metal, different blade thickness, etc.

I have a Laguna 14-12 and have broken numerous blades, all at the gullet. So I assume it is a tension problem. I am very reluctant to buy an expensive blade until I find a solution to the breakage. In fact I’ve stopped buying bi-metal Lennox and Laguna blades in favor of the spring steel ones that are half the price. I use 3/8” 6 tpi mostly. Domestic hardwoods rarely more than 2” thick.

I have talked to reps from Laguna and from the blade suppliers. All think I’ve got a tension issue. I've been told too much tension or too little tension! Confusing to say the least.

The tension “guide” on the Laguna is nothing more that a magnet, think refrigerator magnet, that easily slides around.

I really like the saw except for breaking blades which I think is my problem not the saw’s.

I’ll try your guide if I can find a recommended tension for the blades.


Hi Paul,

For the purposes of tensioning you can use a common value of 30 x 10^6 psi for the Young's modulus of steel. There are small difference depending upon the actual steel used to make a band but the difference is not great.

Band thickness makes no difference in using a tension meter like shown in the link I posted above. Nor does the width. The amount of strain applied to the blade from the spring is what results in the tension in the blade. Wider or thicker blades take more spring force to achieve a certain amount of strain than narrower or thinner ones, but at the same value of strain the tension will be the same in all blades. This is what makes using this type of meter so easy.

None of the blade manufacturers seem to actually give a recommended tension but Lennox says that their blades are made to run up to 30,000 psi, or 30 ksi. I set the 1" Woodmaster CT carbide tipped blade I use for veneer slicing to 25ksi and it runs great. Non carbide blades I run at 20ksi on that saw. The saw has no trouble applying that much tension. But my little 14" cast iron Delta can barely muster 12ksi on a 1/2" blade. Trying to apply more than that causes a lot of frame deflection which throws the upper guides out of aligment. You can easily bend of break the upper wheel axle, too. The 14" Delta still cuts well, but it cuts more slowly than the same blade on my larger saw, requires more careful set up to cut straight, and is more easily deflected by grain changes than a blade in the larger saw running almost twice as much tension.

6 tpi is quite a lot for 2" hardwood. I use a 3/8" x 3 tpi as the stock blade on my 14" Delta; it just seems like the optimal all around blade for what I do with that saw.

If you are breaking a lot of blades then either you got some bad blades, you are overheating them, or the tension is too high. Could be any of them but let's assume it's the tension. I recommend you build a tension meter and put 15 - 20ksi on it. If you get flutter at whatever tension you set it at, turn the tension up or down until it disappears and then see how it cuts and how long it lasts. FWIW, it doesn't matter to the blade if you leave it under tension indefinitely. It's the fatigue from going around the wheels, and overheating from cutting too fast or cutting too tight a radius, that causes them to break not static tension. Has anyone ever gone into their shop and found a blade broken on their saw that they left under tension? However, some saws don't like left being left under tension, either the springs or the tires, and there certainly is no harm in relaxing the tension between uses. Just remember to crank the tension back up before turning it on again.

If you don't want to build the tension meter I showed, take a set of 6" Vernier calipers and use two little C-clamps to clamp it to the back portion of the blade with the jaws open about 5". Put a blade on and apply the amount of tension you had been using before you tighten the clamps. Write down the distance between the jaws, then reset it to zero. Now relax the tension in the blade until the reading on the calipers stops changing. OK, for every 0.001" it moved the tension was 6000 psi. 30 ksi tension would require a movement of 0.005", etc. Now you'll know how much tension you were using and can set it adjust it to whatever value you want rather than guessing.

Good luck.

John

[Paul Saffold]

John,
Thanks. Lots of good helpful info in your reply. I will make the tension gauge.
Paul

[Paul Saffold]

I made the tension gauge jig with a 10" span. I was able to easily set the tension at 20 ksi on the 3/8" 4tpi (i was wrong when I said it was 6tpi) blade. Time will tell if it helps with blade life.
I do release the tension at the end of the day.

445926

[John TenEyck]

Paul, good deal. Now you know any future blade breaks were not due to over tension.

On this same topic, I put a 1/2" x 3 tpi x 0.025" gage blade on my large bandsaw to cut some bowl blanks. First time I had ever used that blade so I set up the tension meter and found that the factory indicator for a 1/2" blade resulted in almost 34ksi. Woah. So I adjusted it to give me 20ksi with the tension meter; the indicator showed just above the mark for a 3/8" blade.

John

[Robert Hayward]

Here's a shop built tension gauge I built for not much more than the cost of a dial gage:
https://sites.google.com/site/jteneyckwoodworker/current-projects/bandsaw-blade-tension-meter
John

I have looked at your tension gauge, like it and am going to build one this afternoon. One question, does the plunger on the dial gauge have to be any certain distance from the spine? Seems that the deflection amount would vary considerable depending on the spacing.

[Jon Grider]

I agree with Eric L. I tension just enough to get the cut I'm after in the piece of wood I need to cut. Different species, different thicknesses, different grain direction all play a part. I use Timberwolf's and don't ascribe to the high tension for everything theory. Too much stress on machine and blade are not a good thing imo. Not trying to start a flame war, just sayin' what works for me.

[John TenEyck]

I have looked at your tension gauge, like it and am going to build one this afternoon. One question, does the plunger on the dial gauge have to be any certain distance from the spine? Seems that the deflection amount would vary considerable depending on the spacing.

The spacing is not important, but if you want to have the dial gage close to the back of the blade there's no reason not to. The deflection will be constant regardless of where it is as long as the two halves of the jig are relatively square to the back of the blade and attached tightly enough to the blade so they don't move during use.

John

[Robert Hayward]

The spacing is not important, but if you want to have the dial gage close to the back of the blade there's no reason not to. The deflection will be constant regardless of where it is as long as the two halves of the jig are relatively square to the back of the blade and attached tightly enough to the blade so they don't move during use.

John

Thank you. Initially I thought the bottom arm moved in an arc with the blade tensioned. When I started making the tension checker the light came on as to why the bottom dowel had a loose fit in the spine, to allow linear movement. Mine is all made as I had everything needed on hand, but not tested yet. I actually put a coat of shellac on it and am waiting for that to dry.

Bob

[John TenEyck]

Thank you. Initially I thought the bottom arm moved in an arc with the blade tensioned. When I started making the tension checker the light came on as to why the bottom dowel had a loose fit in the spine, to allow linear movement. Mine is all made as I had everything needed on hand, but not tested yet. I actually put a coat of shellac on it and am waiting for that to dry.

Bob

Yes, that's right; the dowel fits loosely to allow for linear movement. It's just there to maintain alignment of the two halves.

Let us know your experience using it.

John

[Robert Hayward]

Let us know your experience using it.
John

Just finished testing the new gauge. I had never checked the tension prior, nor even knew what it was. I have always used the tension indicator on the upper wheel of my PM1500. Did the test using a Supercut 1/4"-6 .025 because that is what was on the saw. With my normal tension the bandsaw indicator is just at the edge of the high end of the 1/4" range. I had .005 movement with a 10" space between the gauge arms. So I am running 15ksi on the 1/4" blade. I used this blade to resaw 8" wide black walnut at that tension the other day and had no problems. Had just one 18" piece to resaw and did not want to change blades. Do not need a wider blade on the saw at this time but am now anxious to see what tension I am using for wider blades.