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Bowl blanks

Discussion in 'Getting Started' started by Duane Douglas, Feb 13, 2010.

  1. Duane Douglas

    Duane Douglas

    Joined:
    Nov 3, 2009
    Messages:
    2
    This is my first post. Although I have gotten some good tips in the past.
    The problem I have is that I bought some bowl blanks from my local W.C. store, I cleaned the wax off and turned them round to get ready to rough out a couple bowls. That was about 2 weeks ago. Today I thought I would go and get them to the rough shape that I wanted and they were all cracked. The only thing I can think of is that my house is so dry that it sucked the moisture right out of them. What I was wondering if there is anything I could have done to prevent this?
    Thanks
    Duane
     
  2. Rick M

    Rick M

    Joined:
    Mar 11, 2009
    Messages:
    180
    No need to clean off the wax ahead of time--it comes off with the shavings as you turn. Once you begin turning, you have several rule-of-thumb options, which include turning to final shape, or turning to ~5 to 10 percent of original thickness then storing (by various methods to control drying, including just re-coating after rounding) until dry enough to turn to final dimension, or . . .

    How bad is the cracking? Minor checking or major separation? Can it be rejoined or strengthened with proper adhesive or perhaps turn the affected portion away and have enough good wood left to complete something?

    Some woods are more prone to checking and cracking than others, requiring additional precautions to prevent problems if you stop turning for more than a few minutes. Keeping the wall thickness uniform is good practice, too.

    Shift into salvage mode to ponder what you can do with what's left, chalk the experience up to the learning curve, keep reading what you can about wood movement as it relates to turning, and consider using less expensive wood to develop a prototype which will help build the muscle memory and skills to achieve the result you're after with your costlier blanks.

    Other turners in your area or a club would be good sources of information, especially as apply to your local environment, available woods and characteristics, and technique.
     
    Last edited: Feb 13, 2010
  3. Steve Worcester

    Steve Worcester Admin Emeritus

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    Location (City & State):
    Plano, Texas
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    Unless you ask and get an honest answer, assume all wood is wet, wet when you buy it. Which means it has to dry, then equalize to your environment before turned. Every piece I buy, I date and then assume an inch/year for drying. Or at least that is my best way to set it up to dry.

    Most exotics, African, Asian, Australian, or South American woods, come over to the US freshly cut, waxed and on the shelf.

    Depending on what I am doing with it, say an open form bowl, it gets turned to a fat thickness (10% of the diameter) and then set to dry. After sufficient drying, usually 6 mos to a year, then it gets turned to a final thickness. Even then, the stresses of removing more wood, can make it warp and crack. It depends highly on species and the environment it is in.
     
  4. odie

    odie

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    Location (City & State):
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    Rick has got it right! This may seem overly precautious to some, but I've had severe cracking occur within hours.

    Best plan is to completely rough out your bowl, and reseal for seasoning......IN ONE STEP.....NO STOPPING.

    I've had other examples of severe cracking, EVEN WHEN I'VE FOLLOWED THE RULES!.....so, with green wood, no general rules will work ALL the time! :mad:

    ooc
     
  5. MichaelMouse

    MichaelMouse

    Joined:
    May 16, 2005
    Messages:
    3,540
    Let's all add the words to final dimension at the end and say "Amen!"

    I'll go even further, and say that any piece of wood over 6/4 in thickness should be treated as if it were wet unless it has been in a controlled humidity environment for a couple of months.

    So you were your own worst enemy, removing the covering that slowed moisture loss and shrinking unto cracks. Probably stored them indoors, with the low relative humidity that heating outside air causes in the winter, and forced it to lose from the outside only, rather than a more stable bilateral loss from a hollowed blank.

    Here's why it happened, mostly in chapter 3. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf So turn a blank to a thicker version of what you want to make and keep it in a controlled humidity regime of some sort while it equalizes with the surroundings. Bag it, box it, coat it or neglect it on the floor, makes little difference. If you have a favorably-shaped blank of around 3/4 thick, you can expect to re-turn in three-four months by the neglect method, half that if you push.
     
  6. Duane Douglas

    Duane Douglas

    Joined:
    Nov 3, 2009
    Messages:
    2
    Thank you for all the info. I thought the moisture would come out, but not that fast. I'll know better next time.
    Tanks again
    Duane
     

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