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Thread: better a clamp and a blade than a hand or fingers

  1. #1
    Join Date
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    better a clamp and a blade than a hand or fingers

    I was kerfing a slot on a piece of walnut to make a handle. I had made this cut earlier in the day, but on a bigger piece. My work was clamped to the fence using three clamps and some scrap pieces.

    I felt a pop in the wood and immediately pushed the saw back. This is when I should have stopped the saw and investigated the situation, though I did verify that the walnut didn't move from it's clamped position. Instead I slowly restarted the cut and the piece of walnut blew apart into two pieces. I lost four teeth from the blade and destroyed a clamp. I don't know where the other half of the walnut is. You can see the saw mark on the half I did find; an identical whole piece is on the far left to show the starting piece.

    Click image for larger version. 

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    I had my left hand completely off the workpiece in order to keep me out of the line of fire. This plan was successful - I have a very minor abrasion from shrapnel (didn't even draw blood). My blade vibrated pretty bad while spinning down. Hopefully this is a blade balance issue and not bearing damage or anything.

    The reason this accident happened was operator error - I should not have continued the operation after that first abnormal wood reaction. Having said that, proper engineering controls prevented serious injury - clamping the work to the fence kept my body out of harm's way.

    Now I need to find someone who replaces carbide.

  2. #2
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    Kudos on having things set up for safety and for being aware of the line of fire.

    Looking at the picture, it appears that you weren't using a negative rake blade on your radial arm saw. Could that be a contributing factor to the wood blowing up?
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  3. #3
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    I don't think so. If the blade grabbed the work to pull it back, I think that would have happened right when I felt the pop in the wood the first time without a chance to react. I think I just hit some inner tension or internal defect.

    I don't feel too shaken, but have decided to be done for the night anyhow. Maybe finding the other piece will shed light on what happened. Tomorrow.

    By the way, do you know of any negative rake glue line rip blades?

  4. #4
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    Quote Originally Posted by Mark Kosmowski View Post
    ...By the way, do you know of any negative rake glue line rip blades?
    Offhand, no, but if you drop Charles McCracken a note (e-mail would probably be seen first) I'll bet he can steer you in the right direction.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  5. #5
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    Goes to show you that even when taking proper precautions something crazy can happen. Glad you are OK.
    I think I'd toss the blade myself.
    Faith, Hope & Charity

  6. #6
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    Phew glad to hear you survived it ok Mark.
    cheers

  7. #7
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    Used the RAS today with the non-ferrous blade to cut some brass for the sliding bevels. All went well, no apparent damage to the saw.

  8. #8
    You showed the aftermath but failed to show how it was originally set up for the cut. Yess clamping and stepping aside was a good measure, obviously you knew going in that you were setting up a dangerous operation. Would like to see how you were setting up and what you were trying to do.

    I too have been known to stretch the abilities of the saw and had similar reactions, Would be nice to see what you did and add to the list of what NOT to do.

  9. #9
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    Title Says It All !

    Scary stuff right there ! Glad it wasn't worse.
    Don Orr

    Woodturners make the World go ROUND

  10. #10
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    Quote Originally Posted by Bill Simpson View Post
    You showed the aftermath but failed to show how it was originally set up for the cut. Yess clamping and stepping aside was a good measure, obviously you knew going in that you were setting up a dangerous operation. Would like to see how you were setting up and what you were trying to do.

    I too have been known to stretch the abilities of the saw and had similar reactions, Would be nice to see what you did and add to the list of what NOT to do.
    You are absolutely correct.

    Click image for larger version. 

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    This is enough to give you an idea what I was doing. The brass was still at my machinist friend's stash and the bag of hardware wasn't on the RAS table.

    The blade (the 12" FTG in the original pic) was much, much higher and the piece shown was successfully kerfed using three passes of sequentially lower blade height. I clamped the piece directly to the fence using the middle clamp, and I clamped a piece of wood to either side of the piece for extra stability. Maybe the piece that blew up was just too small to be stable for this cut.

    As an aside, would this cut be described as a through-mortise, a groove through the end or is there another word for this cut?

    I still feel like an idiot for not ceasing the operation with that one piece of wood when it tried talking to me. At least I made the right safety decision by keeping my hands out of the picture.

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