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Ornamental turning is an old and specialized branch of turning with a unique
and interesting history. Paralleling the development of the plain
turning lathe, advanced practitioners developed complex machines to produce
highly decorative work. The art form was popular with the
aristocracy of Europe and interested George III of England, Louis XVI of France
and Peter the Great of Russia. The intricate devices made for the art include amazing mechanisms with intriguing names like rose engines, geometric and eccentric chucks, swash plates, and goniostats. Machines that are the exemplars of the art were made by the Holtzapffel family in England during the 1800's. Their machines represented the state of the art in engineering and the five volume text published by Charles Holtzapffel is to this day the authority on the subject. |
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I've been turning wood for about twenty-five years and have long had a copy of
the Holtzapffel Volume V that describes many details of ornamental
turning. However, I've found the Victorian English and exacting
descriptions of the text difficult to absorb. A few years ago, I
happened to see a demonstration of a rose engine by the master turner Gorst
Duplessis. After seeing a machine in action, it occurred to me that
the motions accomplished by the complex arrangement of shafts, gears, cams,
followers, and springs could be duplicated by simple motions produced by
motor-driven shafts and lead screws that were more familiar to me as an
electrical engineer. I began my search for parts and found a great source in eBay auctions. By careful shopping, I obtained parts surplussed or salvaged from industrial machines and constructed my simple machine so that with motion in three axes (one rotary and two linear) I could emulate the complex rocking and pumping motions of a rose engine. For control of the motors, I started with an old laptop computer, the Linux operating system with real-time extensions, and an open-source software project for enhanced machine control (LinuxCNC). I wrote my design software to emulate rose engine motions and was soon able to make the fascinating patterns that are produced by moving the lathe shaft back and forth as it slowly rotates. After some initial success, I renewed my study of the history and patterns produced in the past and realized that I could also produce designs made with other equipment like eccentric chucks and cutting frames. I am now experimenting with new designs that are only possible with a post-industrial approach and the efficacy of computer control. Currently, I'm making small boxes following the traditions of the field. I turn the basic shapes for the body and the lid by hand on my old manual lathe and transfer the parts back and forth to my emulator machine for decoration. The work is quite demanding in the precision required for the pattern work and in the extreme attention to detail needed for the many steps in the process. In addition to the unlimited possibilities for design, I've found new ways to make mistakes but each completed work adds to the learning process and my design repertoire. The traditional materials for ornamental turning are ivory and hard, fine-grained woods like boxwood and especially African blackwood. Ivory is no longer a candidate for new work and after years of woodworking, I've developed mild allergies to woods of the Dalbergia genus that includes blackwood. Though I can use the wood with extra care, the problem has motivated me to seek alternatives. In my search, I've found some very useful resins that I can cast to make cylindrical blocks that become the raw material for my boxes. This "faux ivory" material has an appearance similar to ivory and excellent machining properties that are important for the patterns and the fine-pitch screw threads used on boxes.
The old inspires the new. Dewey Garrett
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