An Oblique Chuck is used in conjunction with a dome chuck or a rectilinear chuck to position objects in ways that a dome chuck cannot do. The details are difficult to explain, and are better explained by John Edwards' document.
Lindow Machine Works makes a very nice one that they call an oblique dome chuck.
Antique Oblique Chuck
Additional pictures of this device
Examples of work produced with this device
Examples of this device in use
How it works
Notes on making one
- Amplitude Adjuster for an MDF Rose Engine by Rich Colvin. Ornamental Turners International Newsletter, Volume 26, No. 2 - Winter, 2019, pg. 23
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.