Thread: Bandsaw Tension

1" blades - as high a "ting" as you can get without bending anything.
3/4" - higher "ting" than 1"
1/2" - a lot higher ting than 3/4"
1/4" - cat with b...s caught in vice "ting".
1/8" as high a "ting" as you can get without snapping the blade.

Now hows that for a set of scientific tensions.

I "ting" you sed it well Termite

Originally Posted by growl

I have just picked up and assembled a new 4300 bandsaw from Carbatec. I have read the manual but nothing is said how tight to tighten the blade. There is a scale but nothing refers to the blade width or tension required.

Growl, funny timing, I've just come inside after doing some resawing with mine a few minutes ago.

I have found that if you open the top door, reach inside very carefully with a pair of strong pliers, firmly grab the yellow indicator, and then rip it fully from its mounting, it will do wonders for your expectations.

I tighten the blade carefully, a bit at a time, watching how it tracks as I go. This way I can change the tracking and get it reasonably tight as I go. I know the general concensus is to tighten the bejeesus outta the thing, but really, all you need is it tight enough so that the workpiece has a nice vertical cut from base to top. If the cut appears bowed then you have insufficient tension.

This will apply to any blade, although, as has been said already by Termite, the smaller the blade the tighter it should be. Tension relates to the individual blade, so ensure you check it after replacing a blade with the same size.

Originally Posted by Groggy

If the cut appears bowed then you have insufficient tension.

Beg to differ, the major cause of a bowed cut is the blade out of alignment with the fence.
If the blade was slack enough to cause a bowed cut then I doubt it would be tight enough to be driven through the timber, this is assuming that you lower the top guide to suit the timber thickness.

Originally Posted by Termite

Beg to differ, the major cause of a bowed cut is the blade out of alignment with the fence.
If the blade was slack enough to cause a bowed cut then I doubt it would be tight enough to be driven through the timber, this is assuming that you lower the top guide to suit the timber thickness.

The "bow" in the vertical plane that I refer to is probably more correctly called a "barrel" cut by Duginske in the Bandsaw handbook pp57-59, however the end result is the same. Effectively the blade is tighter at the bottom than the top and it gathers a bow in the work after the cut has commenced. There is a good diagram on page 151 and explanation as well. I can scan and post this to you if you like.

cheers.

Originally Posted by Groggy

The "bow" in the vertical plane that I refer to is probably more correctly called a "barrel" cut by Duginske in the Bandsaw handbook pp57-59, however the end result is the same. Effectively the blade is tighter at the bottom than the top and it gathers a bow in the work after the cut has commenced. There is a good diagram on page 151 and explanation as well. I can scan and post this to you if you like.

cheers.

No need thanks, I am familiar with the problem, but I think you will find in practice that it only occurs with the smaller end of the blade sizes and the blade has to be fairly slack, relatively speaking. The allignment problem I mentioned is far more likely to be the cause of "barrelling" in practice.

With my bandsaw, a MJ 344C with a 2950mm blade, has a approx 25mm dia coil spring under the tension adjuster. I assume this is to absorb any shocks from maybe a woodchip getting caught between the blade & the wheel.

Trouble is, to get anywhere near the required tension to get any sort of 'ting' as opposed to a 'blaht', that spring is compressed fully removing any sort of shock absorbsion.

Also, I need to screw it up very tight to stop the blade 'slapping' inside the frame.

Are both these symptons normal?

Regards

Neil

Originally Posted by Landseka

With my bandsaw, a MJ 344C with a 2950mm blade, has a approx 25mm dia coil spring under the tension adjuster. I assume this is to absorb any shocks from maybe a woodchip getting caught between the blade & the wheel.
Trouble is, to get anywhere near the required tension to get any sort of 'ting' as opposed to a 'blaht', that spring is compressed fully removing any sort of shock absorbsion.
Also, I need to screw it up very tight to stop the blade 'slapping' inside the frame.
Are both these symptons normal?
Regards
Neil

What width blade are you using.?

Originally Posted by Landseka

With my bandsaw, a MJ 344C with a 2950mm blade, has a approx 25mm dia coil spring under the tension adjuster. I assume this is to absorb any shocks from maybe a woodchip getting caught between the blade & the wheel.

Trouble is, to get anywhere near the required tension to get any sort of 'ting' as opposed to a 'blaht', that spring is compressed fully removing any sort of shock absorbsion.

Also, I need to screw it up very tight to stop the blade 'slapping' inside the frame.

Are both these symptons normal?

Regards

Neil

Neil, I had a similar issue with mine. I bought slightly smaller blades which gave me more effective adjustment. You may be able to get the blade cut and rewelded. My personal opinion of the SBW 4300 is that with these saws the spring is under rated and the general structure is not robust enough for the tension required. Your saw may be similar.

Originally Posted by Groggy

Neil, I had a similar issue with mine. I bought slightly smaller blades which gave me more effective adjustment. You may be able to get the blade cut and rewelded. My personal opinion of the SBW 4300 is that with these saws the spring is under rated and the general structure is not robust enough for the tension required. Your saw may be similar.

I agree, My blades are 1/2 an inch shorter than manufacturer's recommendation; as I can then find the right tension, I've forgotten to refer to the manufacturers gauge. If in doubt bandsaw a peice of scrap and adjust the tension until you're satisfied with the results.

Enjoy this great machine
Sculptured Box

Originally Posted by Termite

What width blade are you using.?

I have a 6mm, 9mm, 15mm & a 20 mm and they are all the same as far as tensioning goes.

Originally Posted by Groggy

Neil, I had a similar issue with mine. I bought slightly smaller blades which gave me more effective adjustment. You may be able to get the blade cut and rewelded. My personal opinion of the SBW 4300 is that with these saws the spring is under rated and the general structure is not robust enough for the tension required. Your saw may be similar.

I initially thought the tensioner was at the end of its travel so I ordered a blade 20mm shorter, then found that it was just that the blade tensioner was over-riding the (too weak) spring tension.

Originally Posted by Sculptured Box

I agree, My blades are 1/2 an inch shorter than manufacturer's recommendation; as I can then find the right tension, I've forgotten to refer to the manufacturers gauge. If in doubt bandsaw a peice of scrap and adjust the tension until you're satisfied with the results.

My main guide for the correct tension its to try to stop the slapping which must be causing havoc to the set on the teeth.

Regards

Neil.

Thanks to all who replied. It seems as though this is a hot topic.

I think I like the idea of watching how the cut goes. If it is going wrong and I have little control. Wind up the tension.

So far I have only being cutting up scrap and had no problems withbowing or barrelling. The cuts have been relatively straight. Just operator practice is needed.

I will monitor how I go over the comming weeks.

Thanks once again. I knew you would all have the answers.

Regards

Growl

A very happy woodworker!!!!