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Thread: Ripping imperfect wood on a tablesaw.

  1. #1
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    Ripping imperfect wood on a tablesaw.

    Some wood has stress that makes the kerf close and pinch the blade or open and push against the blade (it doesn't take a lot of pressure to flex a riving knife). What to do?

    Get different wood, Sure, we're all going to do that....

    Rip on a band saw, safer but the problem is similar

    Install a half fence that goes just past the blade

    Don't cut all the way thru and finish with a hand saw

    Other?

  2. #2
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    Quote Originally Posted by Tom Bender View Post
    Some wood has stress that makes the kerf close and pinch the blade or open and push against the blade (it doesn't take a lot of pressure to flex a riving knife). What to do?

    Get different wood, Sure, we're all going to do that....

    Rip on a band saw, safer but the problem is similar

    Install a half fence that goes just past the blade

    Don't cut all the way thru and finish with a hand saw

    Other?
    I'd rip a bit on the bandsaw (no kickback potential!) then push a little wedge in the kerf to keep it open. This has worked for me.

  3. #3
    If you have a helper you can have them insert wooden wedges in the out feed side of the cut. Cabinet leveling shims work well for this. Don't try to do this if you are alone. Keep in mind that the wood may continue to move as it is processed into your project.
    Lee Schierer
    USNA- '71
    Captain USN(Ret)

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  4. #4
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    If the kerf is closing on the blade, I will sometimes stop halfway through the cut, turn off the saw, then cut from the other end of the board while holding the kerf open with my feed hand.

  5. #5
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    I knock a wedge or a screwdriver in it and march on...

  6. #6
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    Tom

    I am 6'3" and have chimp arms, so this might not work for you, but here goes;
    I keep a couple of those plastic toilet leveling wedges on the fence. If the kerf gap, starts to close, I just kind of pause and stick a plastic wedge in the kerf. My height and arm length make it so I am no where near the blade when I do this. A shorter person might have trouble with my solution.
    These plastic wedges are about 2" long and about 1-1/4" wide, kind of have a texture to them for friction. They sell them in the plumbing section of Home Depot, or lowes. I like that they're plastic.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  7. #7
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    Don't rip full to finish width in one pass, if you are making a 8" wide board into a 6" for example, do one rip at 7 and a finish one at 6.

  8. #8
    Depends on how bad it is. If bad enough, strike a line on it and cut by eye on band saw with no fence to approximate size. Edge joint one side and rip to finish size.

    Oh and cut to approximate length first. That often is enough by itself.

  9. #9
    The half fence may help if the kerf tends to open, doesn't help if the kerf wants to close. And with a half fence you have very little support of the stock for the last foot or so. Don't see that as a good solution for ripping.

    Another option that hasn't been mentioned is a track saw. Saw a bit and if the kerf is closing it's easy enough to stop and wedge it. Or, if you know the stock is wonky, you can start with a plunge cut a few inches from the end so the uncut portion remains to hold the kerf open. Then go back and finish the cut with the track saw or a hand saw.

  10. #10
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    Subscribed: I've had this happen a bunch of times on the slider. You can feel the wood starting to move as the cut relieves the stress. Kinda' scary on a 10hp saw. The toilet wedges are a great idea.

    Erik
    Felder USA Territory Representative: Central & South Texas

  11. #11
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    Any wedges should be wood or plastic in case they go into the blade.
    Bill D

  12. #12
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    Is it closing up so badly on your riving knife/splitter that you cant continue to feed it? Do you have a riving knife or splitter installed?

    Option A for me always involves forcing it through the cut. As long as you are firmly in control, the board wont kickback. If you are timidly expecting the kickback, then that is when you are going to take a board to the gut.
    Option B usually occurs after ive stalled the saw. Yes, ive done this a few times on a 5hp saw, many times on a 3hp saw, and a lot on a 1.5hp saw. Sometimes it will be clamped so tightly on the blade/riving knife after the stall that i need to pound open the kerf with a chisel before restarting the saw. Keeping wedges nearby is a good idea, but i would prefer to insert them with the saw off.

  13. #13
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    If I feel one closing up on the blade, I lift the tail end that I'm holding if there is enough of the board past the blade to help lever it up, or push down on the board tilting it on the front of the saw table, whichever is required to clear the board from the blade, and start the cut over-as many times as necessary. I'm sure this requires some feel from experience, but I've never had one lock up the saw, or kick back on me. This with 45 years pro experience, and I don't know how much before that. I've never used a table saw with any kind of safety device on it, because some don't allow you to use my method-not saying to try this at home. I wouldn't consider applying more force.

  14. #14
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    Adding wedges to a pinching cut has always sounded better than it actually works for me sometimes. Kind of need three hands at times. For me, the best control of the operation is to rip at less than half the thickness of the material from each side and then saw the remaining quarter inch or less with a hand saw. I don't worry excessively about kickback (I am positioned out of the way), but do worry about pinching a blade, jamming the wood onto a blade, stalling the motor, etc. I ruined a decent BS blade once with problematic material. Again, for me, it is worth taking the time to do the rip in three steps if it at first looks like there is going to be problems.
    David

  15. #15
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    I have when it starts to pinch the riving knife I turn the saw off pull the wood off and then start the cut again. It widens up the saw kerf on a bad peace I have had to do it more than once.
    Not sure it is the rite thing to but it can work.

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