by Jo Miller
Glenn Schmitt – Green Wood Turning – from Log to Bowl
Glenn is an active member and director of the CMW board and, after serving as an assistant instructor at the John C Campbell Folk School, he was scheduled to teach his own classes in 2020 and 2021. Hopefully COVID will allow students to take advantage of his expertise in the coming year.
Glenns demonstration focused on taking a green log through cutting, bowl turning, and reshaping the bowl after drying.
Examining the green log:
Remember that wood will shrink about ½% vertically, ~8% at end grain and 4% at side grain. Thus, the initial size of the green bowl will need to take this into account.
Glenn cuts a tree up into 4 foot lengths (this fits into his truck), and anchor seals each end. He uses a tarp under the tree when it is taken down to help him get it into his trunk. When cutting the green log, draw a line through the pith and extending to the outside of the bark. This allows you to adjust your cut so that all the crack lines are vertical to the log. He uses a 13” electric chain saw from Harbour Freight for his cuts. If the log is larger, he makes a notch on each side at the cut lines, cuts from one side ~ 85% through the log – cutting all the pieces you need, then turning the log around to finish cutting from the other side.. He uses several aids for cutting the wood
A support rack made from scrap wood with notches
Plastic wedges from Northern Tools to keep the wood from binding on the chain saw blades. Plastic is better than metal wedges since plastic wont hurt the chain saw blades
Template for drawing the circles. He uses clear plastic bathroom sheets (4×8) and has circles with diameters from 4-24 “. Put a nail hole in the center to allow you to see if you are making a symmetrical circle.
Once the circular blanks have been cut, remove the corners and the bark.
Turning the green bowl:
Place blank between centers:
Use a 4-prone drive center – since a 2-pronged center is more likely to split the wood. To drive the center into the wood, he uses scrap pipe (Lowes will give you left over pieces), puts a cap on it and uses this to pound in the drive. Its important that 2 of the prongs line up with the grain while the other 2 prongs go across grain.
Remove the pin out of the live center
Line up the blank with the “X” centered at the bottom of the bowl. Check on both sides of the blank to make sure the Grains line up. You can use a laser on the tool rest to help with this as the blank is adjusted. Since the pin has been removed from the live center, the blank can be more easily adjusted. Level the edge if you want to make a platter.
Turning the blank:
Using a slow speed and a 5/8th gouge , round the blank going from head to tail stock. Cut in from the bottom until you have smooth wood. Look for cracks and take out as much as needed. This will determine the size of the bowl top.
On the bottom (head stock), rough shape the bowl and put on a tenon. Since the wood will move when drying, remember to make the tenon oversized- both in depth and diameter. Shoot for ~15% greater than the smallest size of your chuck. He doesn’t recommend making a recessed tenon since it is more likely to split the wood. On green wood, compressive force is stronger than expansive forces. Once the tenon is formed and bowl round, you can increase the speed of the lathe. Continue to look for cracks or flaws. You may have to change the shape of your bowl as you go to accommodate these. If you are making a functional bowl, you will want the base to be ~40% the size of the top diameter.
Once you have the shape you want, reverse the blank and put into your chuck. Line up end grain with your chuck jaws since the end grain is more dense. Thus, the end grain is positioned going from top to bottom of the chuck. Glenn uses a golf ball with a 3/8thinch hole over the tail stock when positioning and tightening the blank in the chuck. Once the blank is secured, he removes the golf ball from the tail stock
Hollowing out the bowl: Once in the chuck, check to make sure your bowl is running true. Adjust if necessary. Your final thickness of the green bowl should be ~ 10% the diameter of the blank – i.e. a 13 ¼ bowl should have a wall thickness of ~ 1 3/8thinches. Flatten off the top of the bowl. Create an arc over the edge of the bowl and then mark you 10% thickness line inside the rim. Hollow the bowl keeping the thickness even – remember that the bottom of the bowl is flat. Glenn uses a relief cut on the back edge of the gouge to prevent bruising of the wood – especially important with Cherry. Glenn also prefers using spring-loaded calipers to check the thickness. Once finished, he uses a shear cut to take off any rough spots.
Drying the blank and returning:
Wood dries at ~ 1 inch /year, thus a 1” thick bowl would take ~ 6 months to air dry ( the wood is drying from both sides). To speed up the process, you can use a dehumidifier set at 50%. Turn it on intermittently – ½ hr on then 1 ½ hr off for a total of 2 hours/day.
Reverse chuck the bowl using suede leather in the bowl. Glenn gets his leather as coarse hair padding cut-offs 5/8thinch thick from Jackson leather. Turn the tenon down to round and shear scrape the bottom lightly. Rough cut the outside of the bowl minimizing the amount removed and avoiding going right to the edge of the bowl (remember you still have to cut on the inside).
Reverse the bowl and secure in the chuck. Use a cone Center to support the bowl until the weight is even all around. Go across the rim first. Remove the cone and finish the inside of the bowl to the desired thickness. Then remove the tenon. For a functional bowl , finish with Mahoney’s oil 2 x 24 hr apart.