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Rough turned bowls cracking

Discussion in 'Woodturning Discussion Forum' started by John Hicks, Jun 17, 2020.

  1. Mike Adams

    Mike Adams

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    Hit youtube for videos of people prepping blanks or moving logs without machinery. You can do more than you think with some rope and long, sturdy levers.


    View: https://www.youtube.com/watch?v=awjSqpUQUVQ


    The next two are from The Survival Sherpa - Good stuff.

    View: https://www.youtube.com/watch?v=HkV7-jf1pEM

    www.youtube.com/watch?v=QFDGGht3CQU
     
    John Hicks likes this.
  2. John Hicks

    John Hicks

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    I turned this yellow old growth cedar bowl today. 12% moisture reading, and it still cracked like grandma's skin. I could literally see the shallow cracks appear as I sanded it. To the junk pile yet again!
    IMG_7273.JPG IMG_7277.JPG
     
  3. Gary Beasley

    Gary Beasley

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    Looks a bit like the cracks were there before you put it on the lathe.
     
    hockenbery likes this.
  4. Timothy Allen

    Timothy Allen

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    Are those cracks or are they some sort of ray? Look carefully at how they interact with the grain -- maybe those are a "feature" not a defect?
     
  5. Don Wattenhofer

    Don Wattenhofer

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    Ya beat me to it! The dead giveaway is the dust in the cracks
     
    hockenbery likes this.
  6. hockenbery

    hockenbery AAW Advisor Staff Member

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    Agree that the cracks were there before you turned it.
    given that it was 12% MC. It had to crack as it was drying.

    Heat from sanding can sometimes cause similar small cracks.
     
  7. John Hicks

    John Hicks

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    They were not there when I started sanding. They developed about half way through 80 to 120 grit
     
  8. hockenbery

    hockenbery AAW Advisor Staff Member

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    Not visible perhaps. cracks like those are hard to see until the surface becomes smooth and heat from sanding can cause them to open up.
     
  9. Mark Jundanian

    Mark Jundanian

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    From the photo those cracks seem shallow and tight. Unless you feel that the bowl is going to fail, I agree it's still worth finishing.

    Out of curiosity, @John Hicks, how fast are you turning when you sand?
     
    John Hicks likes this.
  10. John Hicks

    John Hicks

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    350 rpm with a kinetic sander. The wood was outside in the weather and I probably did not let it stabilize long enough.
     
  11. Gerald Lawrence

    Gerald Lawrence

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    Put black CA in them and will add a feature
     
    John Hicks likes this.
  12. Donovan Bailey

    Donovan Bailey

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    I'm not sure what kind of cedar that you are turning here but there might not be anything you can do to stop it from cracking. As I have stated on many occasions, the Red Eastern Cedar that we have here in Virginia is the "king of cracked wood." You just can't stop it from cracking. On several occasions I have heard it cracking while it was just sitting on the lathe (not turning and my shop tunes were turned down a bit). It is a beautiful wood and I'm always experimenting with it (right now I have a chunk rubbed in cedar oil)...but it is definitely going to crack no matter what you do to stop it. My best fix so far is to do what Gerald recommends...expect the cracks, get to know your cedar cracks (ha), and then flood the heck out of them with black CA glue and hope it looks "artsy" when you put some finish on it. Sometimes it works...
     
    John Hicks likes this.
  13. John Hicks

    John Hicks

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    Cracking accepted; but of course the mortise failed and it went flying. I've had that happen to several pieces of cedar; guess I should have used a big tenon.
     
  14. robo hippy

    robo hippy

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    Well, if I was there while you were turning it, before you started sanding, I may have been able to see those cracks. I will agree that they look like they were already there. Being able to see them is a skill you develop as you get more experience. The heat checking you get from abrasives tend to look similar, but they are generally much smaller checks, and more wide spread. You can 'thump' a bowl on the lathe to see if it has cracks. One with no cracks will ring like a bell. One with cracks will just have a dull thump sound. Some times you can hear the cracks rattle.

    robo hippy
     
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  15. hockenbery

    hockenbery AAW Advisor Staff Member

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    The mortise is high risk with wood like cedar that is easy to split.
    You can break a mortise in cedar with too heavy a cut and most minor catches will break it.

    a tenon will hold better but will still fail with a catch.

    keep paying attention to the tools.
    It takes practice and you will get to the point that one day you will think, “ gee I can’t remember the last time I had a catch” , Because it will have been many months or a few years past.
    Catches are not part of Woodturning. They are the result of poor instruction. When we teach ourselves ( I was self taught) we have a pretty inexperienced teacher....
     
  16. Lars Hansen

    Lars Hansen

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    Well said - both parts!
     

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