A Geometric Chuck (sometimes called an Epicycloidal Chuck) is used for cutting patterns made up of rolling centres.
Additional pictures of this device
Examples of work produced with this device
Examples of this device in use
- This YouTube video from Chuck Bommarito (aka, outsidescrewball) shows a Leinhard Rose Geometric Chuck in use. The video is a bit long, but does show the chuck well, as well as a piece made on it.
- This YouTube video shows an Ibbetson Geometric Chuck on Holtzapffel rose engine lathe No. 1636.
How it works
Basically, it is achieved by rolling one object around another, forming a composite of two perfectly circular motions. The geometric mathematics behind this chuck's movement are explained by Dr. Frank Farris in his 1996 paper, "Wheels on Wheels on Wheels-Surprising Symmetry". There is also a nice article on this at Wolfram MathWorld.
Frank Dorion gave a lecture on the design and functions of a geometric chuck. He also built an oversized wooden model of one, helping to explain it's function. This is one of the best overviews presented to date.
Notes on making one
- Designing 'Geo-Flowers' with a Geometric Chuck by Joshua Salesin. The Society of Ornamental Turners Bulletin 144, Spring, 2021, pg. 21
- Geometric Turning: The Manufacturer and Builder, by (unknown). Ornamental Turners International Newsletter, Volume 20, No. 1 - Spring, 2013, pg. 5
- Plant's Geometric Chuck, by (unknown). Ornamental Turners International Newsletter, Volume 25, No. 1 - Summer, 2018, pg. 19
- There is also an article about one in the "English Mechanic and Mirror of Science", Vol VII, No. 171 (03 July 1868).
- Specimens in Eccentric Circular Turning with Practical Instructions for Producing Corresponding Pieces in the Art, by John Holt Ibbetson (1884).
- Index to the Geometric Chuck, by Thomas Bazley. The Bazely book also has some nice pictures showing what can be produced on such an apparatus.
This chuck is so complicated that John Jacob Holtzapffel never got around to putting it into his last published work, .
- The details are difficult for me to explain, and are far better explained by John Edwards' document. John captured this and more in what he calls the "Holtzapffel Volume 6", which you can get from the The Society of Ornamental Turners
- Design and functions of a geometric chuck by Frank Dorion.
Disclaimer: eMail comments to me at OTBookOfKnowledge @ Gmail.com. The process of woodturning involves the use of tools, machinery and materials which could cause injury or be a health hazard unless proper precautions are taken, including the wearing of appropriate protective equipment.