From Trees to Turning Blanks
Preparing the log
What woodturner can drive by a downed tree without thinking, "Hmmm, turning stock!" In this article, you'll learn how to cut up and preserve such finds for bowl blanks.
While experienced turners use features such as knots and eccentric growth rings of branches to great advantage, those features can cause blanks and finished turnings to crack or warp excessively. So when selecting wood for turning blanks, avoid limb wood and look instead for trunk logs with minimal knots.
Because the ends of a log start to dry immediately after cutting, seal them right away to avoid checking. Use a commercial green-wood sealer. (Available from Packard Woodworks. Call 800/683-8876, or go to packardwoodworks.com.) These sealers clean up with water, dry clear, and are superior to paraffin, which can flake off, and paint, which may require several coats for a good seal.
If there is checking on an old unsealed end, make a fresh crosscut to expose an unchecked surface; seal it immediately. Leave the logs in long yet manageable lengths until you are ready to cut them into turning blanks. This limits potential checking (and waste) to just the two ends of the log rather than both ends of multiple blank-length sections.
Leave tight bark in place. Bark slows moisture loss, helps prevent checking, and leaves the option of using the stock for a natural-edge vessel.
When ready to cut blanks, saw the log into sections about 4" longer than its diameter. This way, if you find any checking after sealing and storing the blank, you'll have ample stock to trim from both ends, exposing check-free surfaces.
When chainsawing a log section lengthwise to form bowl blanks, lay the log on its side, and support it to prevent rolling. Cut along the grain, as shown above. Do not stand the section on its end and cut across the end grain. Doing that takes longer and can overheat and dull the chain.
Removing the pith
At the center of a log is the original tree stem, called the pith, surrounded by a zone of very unstable wood. You'll usually be able to recognize this unstable zone by a change in wood-grain color. The size of this zone varies more with wood species than log diameter. Because this unstable wood may cause uneven drying and splitting, remove it.
When slicing log sections with a small-diameter unstable zone (1" or less) into turning blanks, make your cut through the pith. For log sections with a larger-diameter zone, remove additional wood adjacent to the pith, as shown below. To guide you when removing the unstable zone from a log section of irregular shape, draw potential bowl shapes on its end, as shown below right.
Working with the end grain
Not all log sections must be sliced lengthwise to make bowl blanks. You can leave some log sections whole for turning end-grain bowls, which allows you to get the largest possible bowl from a given diameter log. Be warned: End grain is more difficult to turn than face grain, and end-grain bowls have a greater tendency to crack than face-grain bowls.
Seal the end grain of blanks, as shown above. If the wood is particularly prone to drying stress, such as some fruitwoods, coat the entire piece. When the sealer dries, mark each blank, as shown below. Because the sealer leaves a waxy surface, mark blanks that will be completely coated before applying the sealer. Store blanks off the ground in a dry, well-ventilated area.