March Meeting: Wood Turning with Virgil Leih
The March meeting was a presentation by Virgil Leih on large scale woodturning. Virgil brought several samples of his work, including a vase approximately six feet high and a foot in diameter. Virgil began his presentation by showing a recording of the `Minnesota Original' public television series that featured an interview and video clips of his shop and work. The video is about 10 minutes long and well worth watching if you were unable to attend the meeting. An additional video about Virgil and his work is available here.
Virgil turns whole logs. He starts with green wood which is often at 100% to 125% moisture content (ratio of water weight to weight of completely dry wood). These log sections may weigh more than a ton. To help him deal with pieces of this scale an overhead chain hoist, a forklift and other unconventional woodworking tools are a part of his shop . The beginning of the turning process is the most dangerous - he has a massive log, still out of balance, held between the headstock and tailstock of the lathe.
The lathe Virgil uses is an Oliver model 26, built in Grand Rapids, Michigan in 1917. It was originally sold to a manufacturing company on the east coast and was used for tank production during World War II. The lathe is powered by a five horsepower electric motor that is geared down for slower speeds. The size of these turnings necessitates very slow turning speeds, especially when initially rounding the piece The bed of the lathe moves out and down such that it is possible to turn an object of approximately 7x7x7 feet.
Virgil pointed out the need to find tools up to the tasks that he performs. Standard turning tools simply will not work on this scale. Instead he uses a pivoting electric chain saw with a 48" bar and a powered chain grinder for the initial rounding - see the MN Original video to see how these work. He then uses a Milwaukee grinder mounted on an X-Y axis holder fitted first with 16 grit sandpaper discs and then steps through the grits until he reaches 320 grit.
These turnings are hollowed all the way through but it is difficult to see inside the deep openings. Virgil uses extra long calipers to measure wall thickness when he can, otherwise he has to depend on sound and feel to gauge how he is doing. Once the piece is roughed out it is dried prior to final turning.
Initially Virgil thought his biggest problem would be how to handle the large pieces on the lathe, but he discovered that dealing with drying has been even more of a challenge. When he started exploring this work his loss rate due to moisture cracking was staggering. Even today he still looses as many as one in four turnings during the drying process. A piece that does not dry at a uniform rate warps and develops large cracks.
The solution to creating a slow and controlled drying time is a microwave oven that Virgil built himself. He uses four magnetrons in a steel box of approximately 4x4x8 feet. A lazy susan turnstile slowly rotates the piece for even heat distribution. He wraps each piece in plastic and adds water to keep the surface wet as the oven slowly dries the wood from the inside out. The drying process in this microwave oven takes weeks, during which he monitors and adjusts the process. The microwave magnetrons start running at approximately a 5% duty cycle (on for 5 seconds, off for 95 seconds). His goal is to dry the pieces to approximately a 7% moisture content. Even after attaining the desired moisture content, he will wait and watch the piece for up to six months before finishing it to allow for further warping or wood movement.
Virgil prefers to finish with shellac. He uses approximately seven coats of shellac followed by automotive rubbing compounds. He always uses magnifying glasses when rubbing out the finish.
Work on Display
These words and pictures do little to convey the scope of what Virgil has accomplished. His work (40 pieces) will be on display at the Minnesota Landscape Arboretum April 13th through May 8th.
This meeting was a joint event of the Minnesota Woodworkers Guild (mnwwg.org) and the Minnesota Woodturners Association (woodturner.org). Over 175 members of the two organizations attended. For show-and-tell Steve McLoon brought along a turning he made from a tree branch, cleverly and artistically turned to highlight the color differences between the heartwood and the sapwood.