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The Pith

Discussion in 'Woodturning Discussion Forum' started by William Rogers, Nov 28, 2017.

  1. William Rogers

    William Rogers

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    Or should I say evil pith. I know you want to avoid the pith. I had a small elm about 8" down that had been on the firewood pile for a year and noticed very little cracking around the pith. Just for practice turning hollow forms I turned two pieces, one pith to pith and one through the pith. Just some minor cracking around the pith after 4 months finished.

    So are there woods that you can leave the pith? I've heard NIP is one. Does anyone remove and plug the pith (thinking hollow forms and not bowls). Are there treatment for leaving the pith?

    Here is a vase turned for practice ( and some small bowls) I was practicing. The cracking extension out some what, but seem to be stable. Some would not want any cracking, but some it would be "character".

    Opinions?


    IMG_0461.JPG
     
  2. odie

    odie

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    Nice job of it, Wm......:D

    You got away with it, and ended up with a nice vase. For myself, I avoid the pith like the plague! In times past, I did try to incorporate the pith into turnings, just for character and interest sake, but I've had more failures than successes with it. I just avoid it now......not worth the gamble.

    This is one of my few successes......
    Walnut Natural Edge #653.jpg
    Sorry about the bad photography.......was awhile ago! :oops:

    -----odie-----
     
  3. hockenbery

    hockenbery AAW Advisor Staff Member

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    I leave pith in some greenwood turnings.
    If it is turned thin with curve it will dry without cracking most of the time since the wood can move.
    Often some woods wil
    Each want to dry to a smaller diameter than the rim side it. So something has to give.
    Turned thin with a curve allows the drying to telescope out as the rings dry by pushing the one inside outward.


    One issue here is that bump will distort the curve of the piece.
    Smaller diameter logs will be more successful.

    A bowl like Kelly showed will often work since the bottom bumps out in the curve so distortion is less obvious and the curvature allow the rings to push the inside ones out.
     
    Last edited: Nov 28, 2017
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  4. john lucas

    john lucas

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    Several people have done wonderful hollow forms with the pith in the base, removing it a plugging. If you remove the pith and dry it very very slowly it is less likely to crack. What I did was cut off that portion of the base and dried the pith by putting it in a plastic bag and turning inside out every day for about 3 months. It was about 3/8" thick. Don't remember the species off hand. I then hollowed the vessel and drilled through the pith that remained. After it dried and the pith piece dried I trued up the drilled hole and then carved the pith plug to fit. You could barely see it once I got it all sanded and finished. learned that from John Jordan.
     
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  5. hockenbery

    hockenbery AAW Advisor Staff Member

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    Here are two NE bowls in progress.
    Both have some spalting so the wood will be less likely to crack.
    Both are sanded to 320 except of the rim. No finish.

    This one is red bay It doesn’t show well but the two bumps at the pith make the curve funky.
    33FE8BE0-3791-4A95-A624-0FB189ADB8C6.jpeg 3E75E84A-E914-4201-8C1D-472ADC717831.jpeg

    This one is citrus three piths. I haven’t worked on the rim yet.
    45269363-5787-4F94-8205-7538E8DF71E3.jpeg
     
    Last edited: Nov 28, 2017
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  6. Gerald Lawrence

    Gerald Lawrence

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    Have not done a lot with pith in as I try to avoid it. I did have success with 2 methods.
    1. drill out the pith with small drill bit and use a contrasting or similar wood dowel to plug
    2. drill out and use colored epoxy.
    Preferable to use 1/4" or less drill. If in the bottom of a hollow form the fix will be almost not be noticeable.
     
  7. Zach LaPerriere

    Zach LaPerriere

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    I've had moderate luck leaving the pith in with mountain ash/rowan, even with twice turned bowls. Its a remarkable wood for resisting cracking when dried slowly. I'll often oil just the heart area and any knots with the pith.
     
  8. RichColvin

    RichColvin

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    I like mixing the heart and pith when turning cedar or juniper. In particular, I like to turn it with the grain going parallel to the bed, and I've found that by selectively picking where I transition from the pith to the heart, the piece can look like it's fire (if you look hard and turn your head to the side in just the right way ...).
     
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  9. Mark Wollschlager

    Mark Wollschlager

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    I have done a bunch of natural edged branch vase forms, pith intact.
    The greatest success was with a 'turned in one session', consistent thin wall, off setting the pith from the center of the base and slow drying.
    Pith on the rim of a bowl...not much luck.
    I prefer not to use fillers or ca. Warping is to be expected, pieces with bad cracks end up in the 'what not to do next' pile
     
  10. charlie knighton

    charlie knighton

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    surprised no one mentioned this wood
     

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  11. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I thought that it was common knowledge that everyone knows about mesquite. :D
     
  12. William Rogers

    William Rogers

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    No mesquite in Indiana. What is it? Just kidding.
     
  13. hockenbery

    hockenbery AAW Advisor Staff Member

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    NE goblets and vases are forms that work well with the pith in the bowl.
    As Mark mentioned.
    The curvature in the bottom let’s the pith squeeze the rings outward rather than crack.
    If the pith is in the stem it will be weak and likely break.

    A Holley vase. Apologies or the poor photo

    92D6D882-0E0A-4CEC-884E-FF4D0E97BC3D.jpeg
     
  14. Zach LaPerriere

    Zach LaPerriere

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    All I know, is if you add an "O" to the end of mesquite, it's likely to bite you. The mesquite-o-s don't even care if I'm wearing a face guard. I think they could even get under the neck of a turner's smock! Not that I own a smock...that's what the beard is for.
     
  15. charlie knighton

    charlie knighton

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    no 1stand experience....but I have read that it only takes 2 mesquit-oes to carry a gold miners mule off with all his gear
     
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  16. Bill Boehme

    Bill Boehme Administrator Staff Member

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    When we were in Alaska on vacation, I thought that I saw a swarm of helicopters, but I was told that they were mosquitos. :D Mesquite is much nicer.
     
  17. Mark Wollschlager

    Mark Wollschlager

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    Thanks Al, I am away from home and didn't have a good picture.
     
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  18. john lucas

    john lucas

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    Dave Barriger was the one who taught me that if you turned a cone shaped piece with the pith in the bottom it wouldn't crack. When the wood dries and shrinks the cone gets smaller and longer. The ability for the wood to move freely is what keeps the wood from cracking. I think Dave was doing the the tall vases on a wooden spring back in those days.
     
  19. William Rogers

    William Rogers

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    Since I don't know, what is the orientation of the cone?
     
  20. hockenbery

    hockenbery AAW Advisor Staff Member

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    Pointy bottom to the form
    Similar to the shape of the vase I posted above. While the pith in the case is slightly off center the shape allow the outside rings to push the inside rings outward as them wood dries.

    The issue with pith cracking is that a that the wood shrinks more around the rings than it does across the rings.
    So each ring wants to shrink to a smaller diameter than the ring inside it shrinks. This usually causes the pith to crack.
     

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