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  1. 3rd September 2006, 11:07 PM #1
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    Default Bandsaw 25mm blade breakage.

    I've had a few blades break on me now and it is really no big deal - a bit of a bang, reach for the switch and get a new blade.

    For the last few days I've been resawing a fair bit of timber that was given to me. Using a 3tpi hook-tooth 25mm blade, tensioned as tight as it goes, I guess I've cut a few hundred feet.

    With the flitches that are the offcuts, I've been docking them at 300mm lengths for the missus to use on the fire. These are free handed through and dropped into a box beside the machine.

    While doing a handful of these there was a snap as one of them rolled off the fistfull and fell to the table, causing a jolt in the saw. Then a bump became apparent and, as I was reaching for the switch - BANG. It was time to fetch the brown trousers.

    This thing really let go, I had the saw off a second later and fitted a 12mm 3tpi. Now though, the wheel seems a little rougher, like it is out of balance or running with a slight buckle (like a bike with some loose spokes).

    Not happy Jan
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  3. 3rd September 2006, 11:58 PM #2
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    Hi Groggy...

    Bad luck on losing a big blade. I'm not clear on what caused the breakage though...what or where did the off cut jam?

    Some questions: Can you detect an out of balance condition on the lower wheel/drive belt/motor by running without a blade?

    Are your wheels balanced with weights, and is it possible that one of them shifted/detached?

    Any damage to the tensioning mechanism when the blade broke?

    Regards

    Greg
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  4. 4th September 2006, 12:09 AM #3
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    Quote Originally Posted by gregoryq
    Hi Groggy...

    Bad luck on losing a big blade. I'm not clear on what caused the breakage though...what or where did the off cut jam?

    Some questions: Can you detect an out of balance condition on the lower wheel/drive belt/motor by running without a blade?

    Are your wheels balanced with weights, and is it possible that one of them shifted/detached?

    Any damage to the tensioning mechanism when the blade broke?

    Regards

    Greg
    Greg, the offcut rolled off a handfull of strips I was cutting as a bunch. It rolled down the group and caused the blade to 'jar' as it contacted the piece.

    The out of balance is on the top wheel only.

    Wheels were balanced by drilling plugs out.

    Tensioning seems the same (it was never great).

    Greg
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  5. 4th September 2006, 12:17 AM #4
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    I'm trying to picture what would happen at the upper wheel in that split second. When the blade momentarily jammed on the offcut, does it make sense that the upper wheel briefly would have become untensioned, and risen on the spring, then slammed back down when the blade broke through the offcut? I am wondering about damage to the casting that supports the tensioning mechanism and the upper wheel bearing.

    Also, is it possible that one of those holes once had a plug that's now missing?

    I got scotch for Father's day...so please excuse the incoherence.

    Greg
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  6. 4th September 2006, 12:21 AM #5
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    Quote Originally Posted by gregoryq
    I'm trying to picture what would happen at the upper wheel in that split second. When the blade momentarily jammed on the offcut, does it make sense that the upper wheel briefly would have become untensioned, and risen on the spring, then slammed back down when the blade broke through the offcut? I am wondering about damage to the casting that supports the tensioning mechanism and the upper wheel bearing.

    Also, is it possible that one of those holes once had a plug that's now missing?

    I got scotch for Father's day...so please excuse the incoherence.

    Greg
    So long as you're not flying me to Sydney tomorrow - forgiven

    There were never plugs in the holes, I suspect the wheel casting has bent when the tension unloaded. I'm off to sleep on it, g'nite
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  7. 4th September 2006, 12:26 AM #6
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    Might have done a bearing on the top wheel
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  8. 4th September 2006, 06:51 AM #7
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    What type of bandsaw are you using? This could have a bearing on your breakages. Rockwell Deltas have a roller bearing sitting behind the blade as a stop guide. Continual pressure on the blade may cause it to run against the bearing creating heat. Was the balde hot when it broke? Also the type of guides on the bandsaw? Are they properly adjusted? Knowing the type of bandsaw may be a help in answering your question>
    Gerald
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