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Bandsaw resonance

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Michael Forster 208/08/2014 07:13:31
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74 forum posts
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Anyone got any words of wisdom about this? I changed the ripping blade on my Startrite 401 bandsaw for a fine 6mm blade - adjusted the guides and tension to suit - and gave the wheel a turn by hand to check nothing was touching that shouldn't be - all delightfuly smooth and quiet. Closed the doors and started up. All seemed well. I then used a trick advised by one of Startrite's own people to tweak the tension of the blade. Looking at the blade as it ran through the table I could see a slightly fuzzy line, so gently upped the tension expecting to see the blade pull finally into line. What I got was a quite loud resonance from the machine that continued after the blade had come to a complete standstill. I checked everything over again and all seemed well. On start-up there were no problems but now I get the resonance every time I switch the machine off.

I haven't experienced this before. I have heard the term 'blade resonance' but this seems to be coming from the machine itself although clearly generated by the blade slowing down (doesn't happen when it's initially speeding up). Pinching the stationery blade doesn't stop the sound which fades away after a few seconds.

I've got some rather precise cutting to do and don't want to spoil a project at this stage - if anyone's got any advice on this I'd really appreciate it. Thankssmiley

Malcolm Alexander 104/10/2014 16:08:08
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57 forum posts
37 photos

Not sure about this, but have you checked the blade position on the top wheel? When setting up the blade and the tension, it takes a little time to ensure that not only is the blade positioned with the lowest part of the gullet in the center of the top wheel, but that it stays there once the motor has been run.

I have found from past experiance witn a couple of bandsaws, that you do need to hand turn the blade several times when tensioning the blade. Yo also need to check the top and bottom guides several times to make the correct setting.

Best practice is to move the top and bottom guides away from the blade, Adjust the tension to approximately the right setting, bearing in mind that the different size blades will need different tension. There should be something on your machine that will give a 'rough' guide on size/tension.

Only when the tension is about right and the blade positioned on the top wheel, move the top and bottom thrust bearings to just off the back of the blade, then move the top and bottom guides to just off the sides of the blade. Each time, turn the wheel by hand to ensure that the blade does not rotate, or touch the thrust bearings and you should be able to turn the wheel without the sound of any contact with the blade.

When all that is done, let the motor run for a mament and check the balade position and bearings once more. If all clear, then you should not get any adverse noises. Just remember, that when cutting, you will get contact with blade and thrust bearings, so 'be gentle' when cutting. Make sure those guides do not reach the teeth once the thrust bearing is contacted, otherwise you will ruin the blade quickly.

Let me know if this helps at all.

Malcolm

Michael Forster 204/10/2014 17:31:52
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74 forum posts
47 photos

Thanks, Malcolm - I did finally get myself sorted out! You're right to say that the alignment of the blade is critical and that did turn out to be a little less precise than I had thought with the gullets not quite centralised. Tensioning is helped on mine by a built-in tension gauge that gets it into the right general area from where it can be tweaked as necessary. The guides were all fine - I don't have any problem with those, and thanks to Startrite's good design they're easily set anyway. The resonance itself was actually coming from the machine doors - and as anyone who's tried to identify a strange sound in car bodywork knows, that can be difficult to pin down, but fitting a new blade and being more precise about alignment seems to have cured it.

Although I'm reasonably at home with machines, they're not my strongest point as a woodworker - I'm a hand-tool worker at heart - so it's always good to get advice from someone who might be able to fill in the gaps for me!

Thanks again

Michael

Malcolm Alexander 104/10/2014 18:19:12
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57 forum posts
37 photos

Thanks Michael, I'm pleased you have managed to sort it out.

I only found this site today and have only been woodworking for a few months, but love the bandsaw and have researched loads of information to know what I'm doing with it.

If you are any where local to me, near Birmingham and would like to get together for a chat about bandsaw working, I would be pleased to meet with you. Good luck

Malcolm

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