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Thread: Too pith, or not to pith?

  1. #1
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    Too pith, or not to pith?

    I found some 1x12 that was a nice cross section cut to make a small cupboard with (by hand of course). I was able to cut and use quarter sawn pieces for everything but one of the boards had some pith running right down the center and I thought it might make a good door since it can be centered. The pith doesnít run through both sides of the board - just one face - is there a way to seal it or make it stable so that it would function as a door to the little cupboard Iím building or should I just use another section with no pith running through it?

  2. #2
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    That board will most likely cup like crazy eventually. I would reject it and use another board.
    Can you rip out the pith and glue up the straight grain on either side? Wide enough?
    ---Trudging the Road of Happy Destiny---

  3. #3
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    If you are short of material, or for some other reason really want to use this as a panel, you could run a groove along the pith partway through the board, then leave that on the inside of the door. It won't look great when opened, but the door will be stable.

    It's not really the pith itself that is the problem, it's the curvature of the growth rings in the board around this point. So if you fill the groove with other wood, you will have the same problem as leaving in the pith. The gap would leave room for expansion and contraction without distorting the entire panel. So Brian's are really better approaches.

  4. #4
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    Thanks for the feedback. So, just to be sure I understand...even if I find a 1x12 without the pith, it it has a plain sawn section of grain in the middle of the board it is likely to cup? Best option may be to glue up a wide enough board for the door from two or more sections of quarter grain material?

    On a different note - I've been toying with the idea of making a shaker style door panel. I have a router table and could purchase a spiral upcut bit to make grooves in rails and stiles for a panel but I'd really like this cupboard to be entirely hand made. Only problem is I don't have a groove plane to make the groove by hand. Any other options? I could make rebates on the inside back edge and set a panel into it but I'm not sure if that would work.1

  5. #5
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    The general rule is that flat sawn stock will nearly always cup when drying, and can certainly continue to move after it is milled again to finished thickness. The reason quartersawn or riftsawn stock does not warp or cup (as much) is that wood fibers shrink the most tangentially in relation to the growth rings. Wood does not shrink much radially, and a quartered-cut is a radial cut and therefore is far more stable. Flatsawn (or through-and-through sawn) stock is cut tangentially to the grain by definition and therefore almost guaranteed to cup as it dries out.

    How much it moves after you mill it and put it in your project depends upon several factors: how dry the wood actually was when you started, what the species is, how you finish it, where and how you use the board in your project, how close the board was to the outside of the log when it was originally cut, etc.

    If you do actually have pith in your board, then the grain to either side of the pith is true radial grain and will yield stable quartersawn stock. I would guess that what you really have is seriously flat sawn grain from the outside of the log and there is a dark streak from one of the annular rings on the inside face that looks like pith. It’s not likely that you would only have pith on one side of a 4/4 board that is 12” wide. The pith would show on both sides. I mean it’s certainly possible, just not likely.

    Setting a panel into a frame like you mentioned does help to keep the panel flat. The rabbet will not help because the panel needs to float in the frame to be allowed to move with seasonal expansion and contraction. I suppose you could cut a rabbet, lay the panel in loose, and add a retaining moulding strip to hold it in place (like you would for a piece of glass).
    Last edited by brian zawatsky; 04-16-2018 at 9:56 PM.
    ---Trudging the Road of Happy Destiny---

  6. #6
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    Brian,

    thanks for the info. It is definitely a cross section cut - the pith (the dark very center part anyway) is just offset from the center of the faces so it only shows on one face. I definitely have gotten some good true quarter sawn stock out of the boards for use though. Iíll look into getting another board and creating a large enough panel that doesnít include any of the pith.

  7. #7
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    Quote Originally Posted by Brian Eaton View Post
    Brian,

    thanks for the info. It is definitely a cross section cut - the pith (the dark very center part anyway) is just offset from the center of the faces so it only shows on one face. I definitely have gotten some good true quarter sawn stock out of the boards for use though. Iíll look into getting another board and creating a large enough panel that doesnít include any of the pith.
    Can you put up a picture of the end grain of the board? That would probably be the easiest way for those knowledgeable on here to help you. (Truth in advertising, Iím definitely not including myself in the knowledgeable person category.)

    Also, the traditional method of putting grooves in boards for frame and panel work is a plough plane.

  8. #8
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    ‘‘Tis better to be pithed off than pithed on” (anonymous).
    It's wood dust. Saw dust would suggest a problem.

  9. #9
    Quote Originally Posted by Rob Luter View Post
    ‘‘Tis better to be pithed off than pithed on” (anonymous).
    Be nice or my dog will pith on your shoe!
    Fair winds and following seas,
    Jim Waldron

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