"Turning Wood into Art"

"Nothing is better for a man than that he should eat and drink,
and that his soul should enjoy good in his labor...."
-Ecclesiastes 2, 24

Friday, January 15, 2010

From Tree to Table, Part 2 - Rough-Turning

In our last post, we went through the initial steps of creating a wooden bowl that, with proper care, will last for generations.  We selected the parts of the tree most likely to yield the best bowl "blanks" and cut those blanks to maximize both beauty and longevity. 

In this post, we explore final blank preparation, mounting the blank on the lathe, rough-turning it into basic "cut-rimmed" bowl and setting it aside to dry before re-mounting on the lathe and turning it to its final dimensions.

But before we continue, a word from my legal advisor: As discussed previously, lathe-turning is inherently dangerous and should be NOT undertaken without proper instruction, experience (i.e., knowing your limitations(!), and adherence to the rules of lathe safety.  (The American Association of Woodturners provides a practical set of lathe safety guidelines at http://www.woodturner.org/resources/safety.cfm.  A good read!)  That said: the following is provided for your information only.  Because of the many variables involved, I assume no responsibility for any incidental or consequential damages that might be suffered as a result of your attempting to duplicate these steps.

Now on with the post....

Our first objective - and one of the most important - is align the blank so that the wood grain is centered in the bowl.  We accomplish that by laying the blank on our bench with what used to be the center of the log facing up.  We then use a compass to draw a circle around the most interesting part of the blank, which describes the basic bowl.  We want the circle as large as possible while staying within the boundaries of solid wood.  (Depending on the species, we may - or may not - include sapwood in our bowl.  For lighter woods like ash and maple, I like to include sapwood, but for dark woods like walnut, I stay within the heartwood. The white ash bowl on the right is a good example of what we're looking to achieve.)

We next round off the portions of the blank that fall outside our circle. (Note: this is another "do not attempt without proper training, experience and following appropriate safety rules!" Cutting green wood - and especially THICK green wood like a bowl blank - requires a somewhat different set of skills and precautions.  Be safe....)

We now mount our rounded blank on the lathe and bring up the tailstock to ensure maximum support. (We use a threaded cast iron fitting called a "faceplate" to affix our workpiece to the lathe because it provides the most secure means of affixing large and/or out of balance workpieces.  Other woodturners, whose opinions I respect, use different techniques, but we will stick with this approach.)  With the workpiece mounted on the lathe, we rotate the workpiece by hand to make sure it clears the toolrest, toolrest holder, lathe bed - and double-check that there are no loose objects that will go flying around when we power on the lathe.  (Don't laugh - it's happened!)  We start the lathe at its lowest speed setting and adjust the speed to the point where the lathe is running smoothly.   

Using our bowl gouge, we turn the exterior of the bowl into the approximate shape of our finished bowl.  Because in this example, we are only want a rough-turned bowl that will warp and distort as it dries, we aren't too concerned about achieving a perfect shape or finish.  We will address final finishing in our next post.  (There are several techniques that can be employed here - all are beyond the scope of this post.  Distinguished turners like Richard Raffan, David Ellsworth, Mike Mahoney (and others) have books and videos that drill down on these techniques, if you have an interest in pursuing.  Full disclosure: I have no commercial interest in any of them.)

Once the exterior is done, we reverse the bowl on the lathe and proceed to hollow out the interior.  Our objective at this point is to achieve a uniform wall thickness that is approximately 10% of the total bowl diameter.  (For example: a 12" bowl will have about a 1-1/4" wall thickness.) That leaves enough material to allow for final turning while providing a consistent surface area that minimizes the risk of cracking during the drying process.  (Again, there are several ways of hollowing-out a bowl - see Raffan, Ellsworth, at al. for further information.)

As final steps, we write the wood specie and today's date on the bottom of our bowl, apply a liberal coating of "Anchorseal(r)" or an equivalent coating to control the drying process and set the piece in a climate-controlled space for 6 - 12 months to dry. (Again, there are innumerable techniques - and variation of same(!) - for drying rough-turned bowls.  The above folks discuss at length.  Enough said....)

Well, if you've stayed with me this long - congratulations!  I hope you have found this informative and at least mildly entertaining!

Next time: Finish Turning.

Until then....

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