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Thread: How to stop wood from splitting?

  1. #1
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    How to stop wood from splitting?

    I am making two nightstands. The legs are made of 3/4x2" cherry and the aprons are 3/4"x1.5". The aprons have 2 pocket screws in either end.
    When I screw the aprons into the legs so that it is into the 3/4" thickness, the legs split. I tried clamping them first so they can't split, but they do as soon as I take the clamp off.
    I made one already. I got glue into the split and clamped it tight. It held together, so I guess it is fixed, but I would prefer to avoid the split. Any suggestions? I expect a pilot hole would help, but am not sure how that would work. You blunt nails to avoid splitting... would blunting the screws help? I could use 1" screws instead of the proper 1 1/4" screws; but it would weaken the table.
    On Facebook I saw a demo of a guy heating the screws in a propane torch first and that stopped them from splitting. Sound silly, but it worked in the demo.
    Okay, I shouldn't have made the legs 3/4", but since I did, how can I avoid splitting.

  2. #2
    Bees wax works the best ,but paraffin wax ,or even furniture paste wax helps. Use two sizes of drill bits . Largest size close as possible to size
    of beefy part . Smaller diameter bit for the threads. Test on some left over wood scraps, to “be sure you are right, then…go ahead “.

  3. #3
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    For sure you need pilot holes with something that small, no question. You barely need the threads to grab and with a little glue they'll be strong enough. I had this happen on some smaller legs made of maple and as an extra step, I had to drill a 3/8 hole and insert a longer dowel with a little glue to shore up the leg. This gave something for the screw to bite into and prevented the leg from spilling again.

  4. #4
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    What you are doing sounds no different than building face frames. That stock typically is 3/4". So I don't understand why you are having trouble. 1-1/4" screws are the right length, but they need to be the fine thread ones made for hardwood. Is that what you are using? If yes, and the problem is the leg is splitting when you drive the outboard screw, then that means that screw needs to be further away from the end. There should be no need to wax, heat, etc. the screws, but if it helps, so be it.

    John

  5. #5
    I see it in a different way. Who among us has not bought knocked down furniture that came with those skinny screws ? Did they hold?

  6. #6
    As John said above, you could have an incorrect pocket screw setup. Re-check your drill jig setting and drill bit collar setting, if they are going in too close you'll split even if using the right screws. There isn't a way to pre-drill the leg piece with pocket screws that I'm aware, but they are designed to be used without pre-drilling with the correct screw type/length. The caveat is ensuring the setup/operation procedure is followed exactly as specified.

  7. #7
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    Tom, you wouldn’t pre-drill, you would clamp (which you should do with pocket screws anyway) and then drill.

  8. #8
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    Maybe you haven't used pocket screws, Mel, or perhaps not the Kreg jig. You only pre-drill the piece with the pocket, in this case the rail. The drill has a step in it. When properly set up, it drills both the pocket and pilot hole for the threaded section of the screw, but it does not drill out the end of the piece. Then the two pieces are firmly clamped together, and the screw is inserted and driven through the remaining, unbored section of the first piece and into the also unbored second piece. It's been that way since the invention of the Kreg jig for drilling pocket holes. When set up properly they work w/o splitting, unless you get too close to the end of a piece, as discussed above.

    John

  9. #9
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    Quote Originally Posted by Mel Fulks View Post
    Bees wax works the best ,but paraffin wax ,or even furniture paste wax helps. ...“.
    Sorry for the minor thread hijack, but I have to ask this...
    Why is beeswax superior to paraffin? My Dad kept a chunk of Beeswax in his shop for greasing screws, but I never thought to ask him why he just didn't use an old candle or [canning] paraffin wax.
    So why is beeswax the "bees knees" when it comes to greasing screws?

  10. #10
    John, thanks for more detail. If I ever used those, it’s forgotten now !

  11. #11
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    Just to verify, are you using the actual pocket screws? They have self drilling cut in their tip, vs a pan head screw that might not. That feature helps with splitting when driving the screw into something without a pilot hole.

  12. #12
    When I use pocket screws on dense wood close to the end of a stile I use a 1/8" x 6" aircraft drill to drill a pilot hole. Self-drilling screws help, but they don't clear the swarf. Drill first and there's room for the screw.
    Last edited by Kevin Jenness; 01-25-2023 at 7:17 PM.

  13. #13
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    Is your jig maybe set up for half inch material?

  14. #14
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    Quote Originally Posted by John TenEyck View Post
    You only pre-drill the piece with the pocket, in this case the rail. The drill has a step in it. When properly set up, it drills both the pocket and pilot hole for the threaded section of the screw, but it does not drill out the end of the piece. Then the two pieces are firmly clamped together, and the screw is inserted and driven through the remaining, unbored section of the first piece and into the also unbored second piece. It's been that way since the invention of the Kreg jig for drilling pocket holes. When set up properly they work w/o splitting, unless you get too close to the end of a piece, as discussed above.

    John
    Quote Originally Posted by John Kananis View Post
    Is your jig maybe set up for half inch material?
    Just a slight clarification. The Kreg stepped drill bit drills a clearance hole for the screw head and for the screw. It does not, and is not supposed to, drill a pilot hole in the second piece. The cutter on the screw does that as you screw it in.

    I was curious about the dimensions of the work pieces, having joined many pieces in a similar fashion on some of my projects. So, I went out to the shop an located some scrap and prepped it to dimensions identical to those listed by Wade in his post.

    20230125_183437.jpg20230125_183454.jpg
    I drilled the holes to the proper depth using my jig

    20230125_183717.jpg
    I inserted two 1-1/4 kreg fine thread screws and drove them in with my drill.
    20230125_183849.jpg
    This photo of the completed joint shows a small crack in the 3/4" piece at the bottom of the photo.
    20230125_183837.jpg
    If you look closely in the photo below to the right on the right hand hole you can see the small crack.
    20230125_183923.jpg
    These are the screws used in this experiment.
    20230125_184002.jpg

    The root problem is the screw nearest the top of the leg is too close to the edge of the board for it not to cause the wood to crack. If you could drill the right size pilot hole for the screw at the proper angle you might be able to prevent the cracking. I'm not sure how you would accomplish this. Any angular error would likely crack the piece.

    You might be able to apply some very thin super glue to the end grain where that hole will be. The glue may wick far enough into the wood to prevent the cracking.
    Last edited by Lee Schierer; 01-25-2023 at 7:55 PM.
    Lee Schierer
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  15. #15
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    Quote Originally Posted by Kevin Jenness View Post
    When I use pocket screws on dense wood close to the end of a stile I use a 1/8" x 6" aircraft drill to drill a pilot hole. Self-drilling screws help, but they don't clear the swarf. Drill first and there's room for the screw.
    Amen, exactly. Clamp together, drill pilot with 6" bit, insert pocket screw, done. I don't do it often, but in the context of the OP's post, I most certainly would. I'd even do here if I used my Castle pocket hole router that goes in only 3-degrees vs. 15 of Kreg and other versions. I'm sort of shaking my head here thinking people don't realize YES we understand how pocket holes work! We're not the ones confused
    Last edited by Michael Burnside; 01-25-2023 at 8:19 PM.

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