What Bandsaw blade tension are you guys using?

[mmurray70]

Im getting gullet cracks in my blade and trying to determine the best tension to prevent this. Seems to be a large range of numbers out there. There are alot of places online recommending 15,000 PSI, some as low as 12,000 PSI. Lenox recommends up to 30,000 PSI. And our saw at work (Hyd mech S-20, no issues on this one) recommends 1000-1200 kg wheel tension on a 1" blade which works out to around 38,000 PSI. This saw works fine at that tension.

My saw at my home shop is causing the problem. It has a terrible system for tension so i normally just tighten it till it feels about right. Id like to find a better way of tensioning blades but I dont even know what force i should be aiming for. Wondering what you guys run and reccomend.

Knowing that the saw at work is working well with alot of tension and lenox reccomends up to 30,000 should i just aim for 30,000 PSI?

 

[adama]

Theres also alignment and age to consider. Used too slow at too light a feed pressure in softer low wear materials its possible for blades to simply reach there fatique life before being blunt! Alignment wise you need to check the guides, if there pulling the blade too low they make the tension uneven and amplify the stress on the gullet parts of the blade significantly.

Also wheel size is something else to consider, i have one of the small portable bench top saws for takeing to site, as saws go its not nearly as hack and DIY - toy like as it sounds, will happily chop 4" box and do it square or mitred all day long. Problem is the wheels are just too small hence the blades almost always die from fatigue before anything else.

Tension wise, i prefer less than recommend unless cutting large - wide solids, then the tension matters a lot more and does improve the cut in my experience. I try and have just enough so the blade will slip if it jams in the cut

 

[IAMATT]

Without hydraulic bandsaw pressure or a gauge youll learn eventually to play bandsaw guitar each time you install a new blade.

 

[Big Gem]

If you want a cheap and dirty check, you can just make two little clamping blocks with a flat top on the lower and a round nose on the bottom of the upper. Clamp them on an untensioned blade, start with the round nose resting on the flat, and tension. About 1 mil per inch of separation of the clamp points equals 30 ksi. If you want less, it's proportional. You can check the separation with a feeler gauge. This isn't as accurate, or pretty, as the $500 dial indicator jobs, but it'll put you in the ballpark.

My rule of thumb is to use the least tension I can get away with. I usually cut steel at less than 10 ksi and wood at less than 20 ksi. I mostly just raise the guard till I have 4 or 5 inches of blade, then tap it on the side. It's like tapping a watermelon - I don't know how I know, I just know.

 

[mmurray70]

In all honestly, this blade has done alot of cutting. But just something about throwing away a blade that is still sharp is disappointing. Small wheels could be a factor in my case too. Its just a common import 7x12 saw so wheels are not the biggest, around 11.5 inches. Seems like a pretty good bend for a 0.035 blade.

I realize there could be alignment issues as well, I plan on checking this. But the tension system (or lack of one) has to be fixed. I think im going to try a heavy duty die spring under tension knob and measure compression to set tension. Mcmaster has one that should work out to 30,000psi when compressed from 3 inches to 2.5 and its only $20 so worth a shot. Would be nice and simple if it works. At least this way when i find a tension that works well i can repeat it the next time around.

 

[adama]

Lot of saws just have a small stack of beviell spring washers, you really don't need much travel!

 

[js412000]

Maybe you need to use higher cutting speed so that the blade is dull before the fatigue life is used up.

I don't believe that I have ever seen a saw blade cracked as you describe.

With a home shop grade saw, I don't think that you will be able to tighten the blade enough to

shorten the life, without bending and destroying the frame.

At home I run 175 feet per minute for general purpose steel. At work I go faster , approx. 275-300

fpm. (since I am being paid by the hour and am not buying the blades myself.)

 

[gbent]

But just something about throwing away a blade that is still sharp is disappointing.

I could send over a former employee. I can guarantee he will make sure you never have to throw away a sharp blade.

 

[vanguard machine]

i can't find the link but there was a site that produced an octave to tune to.
you put in your parameters,ie, blade length, thickness, wheel size, etc. and it gave you track that repeated the sound repetitively so you could play it in the shop while you 'tune' to your adjusted tension. i used it a few times as a novelty thing and it seemed to work well, just don't need it with my large saw.

 

[snowman]

An S-20 with 5000 lbs of tension just doesn't compare to a 7x10 or small bandsaw. A small bandsaw will almost always fatigue before getting dull if you are using it at prescribed SFM speeds for the material to be cut. Or you'll strip the teeth by being a dumbass. Simply put, they don't have the horsepower and mass to cut efficiently. You can't even GET an aggressive blade for the small bandsaws.

How much to tension the small saw...my experience with a couple of them says that you just can't get enough tension. Your tension adjustment mechanism will start out by binding on you, then after that happens, you'll redesign it slightly so it doesn't bind...then you'll find that the frame flexes too much.

Best bet is just to use it til it goes, and always keep a couple extra blades on hand. I say a couple, because nobody is organized enough to actually order a replacement when their one on the saw goes.

My V-18 doesn't even have a scale...just a cylinder. You click it over to the "run" position and the cylinder just keeps the blade tensioned. Blades don't break on that machine unless you f it up...they just wear out.

 

[mmurray70]

I got a new blade today and had a closer look at the guides, which have never been adjusted much before. The blade was probably being pushed ahead of its free position (with no guides) by maybe 1/4 of an inch. Had to modify one guide a little to get enough adjustment, but have both setup now so blade is just barely touching the support bearing. Also the rear guide had loosened up a little and slid away from the work and closer to the wheel then it should be. So hopefully these adjustments will help too. I picked out the parts i need for a spring tensioner from mcmaster and will get them on my next order. Came to $26 for spring, threaded rod and a new knob. Ill post pics when i get it done if i remember.

Honestly im surprised how well this saw works. I got it brand new for dirt cheap. Hydraulic feed unit was mounted very flimsy so i braced that up, and bent the drain pan a little for proper coolant flow and the thing has worked perfect for 7 or 8 years. Its a pain for angle cuts but works fine for straight cuts.

Im not saying my little import saw is better by any means, but The hyd mech S-20 we have at work has been somewhat of a disappointment. It cost alot of money and has had a bunch of stupid problems that you should have to deal with for that kind of money. The frame is all welded wrong and theres no way to get coolant to drain properly without leaving a big pool somewhere to evaportate. The coolant drain filter needs to be cleaned all the time, and chips make it past anyway and clog the nozzles, pump also clogs with chips. The vise doesnt open in the fully open posiiton, has to be a few degrees back from fully open to operate. And every now and then the saw refuses to turn on and we have to turn off breaker and turn back on again. Occasionally turns off before finishing a cut too. Blade guard falls out when you move guides really close for small work. Takes too hands to move guide back and a thrid one to hold guard up to slide back in place. Other then all that BS its a good saw lol

 

[snowman]

I got a new blade today and had a closer look at the guides, which have never been adjusted much before. The blade was probably being pushed ahead of its free position (with no guides) by maybe 1/4 of an inch. Had to modify one guide a little to get enough adjustment, but have both setup now so blade is just barely touching the support bearing. Also the rear guide had loosened up a little and slid away from the work and closer to the wheel then it should be. So hopefully these adjustments will help too. I picked out the parts i need for a spring tensioner from mcmaster and will get them on my next order. Came to $26 for spring, threaded rod and a new knob. Ill post pics when i get it done if i remember.

Honestly im surprised how well this saw works. I got it brand new for dirt cheap. Hydraulic feed unit was mounted very flimsy so i braced that up, and bent the drain pan a little for proper coolant flow and the thing has worked perfect for 7 or 8 years. Its a pain for angle cuts but works fine for straight cuts.

Im not saying my little import saw is better by any means, but The hyd mech S-20 we have at work has been somewhat of a disappointment. It cost alot of money and has had a bunch of stupid problems that you should have to deal with for that kind of money. The frame is all welded wrong and theres no way to get coolant to drain properly without leaving a big pool somewhere to evaportate. The coolant drain filter needs to be cleaned all the time, and chips make it past anyway and clog the nozzles, pump also clogs with chips. The vise doesnt open in the fully open posiiton, has to be a few degrees back from fully open to operate. And every now and then the saw refuses to turn on and we have to turn off breaker and turn back on again. Occasionally turns off before finishing a cut too. Blade guard falls out when you move guides really close for small work. Takes too hands to move guide back and a thrid one to hold guard up to slide back in place. Other then all that BS its a good saw lol

You need to call Hydmech! Unless their quality has went down. Our machines are all greater than 10 years old. The coolant draining sounds familiar though, if it gets loaded up with chips it's not sloped well enough to drain good.

 

[mmurray70]

We called them about the drain issue and they admitted to a few not draining. They offered to send us some sort of a tool with a bottle jack to bend pan but i dont think it would have been the perfect fix. We adjusted the shape of the pan with a heavy piece of round stock as a hammer. Got it draining ok now but still blows my mind that they could mess this up. Water flows downhill only its not that complicated