John K Jordan >>>
I believe that is called a donut chuck and IMO is an easier to build and safer than a Longworth chuck ...
I agree. Just last week I was demoing at a club where a gentleman described how a Longworth chuck came apart and injured him. He said he barely escaped serious injury. I've heard several such reports over the years. As with Cole jaws, one recommendation is sometimes not followed: keep the speed low.
For an excellent source of how to make and use a variety of the much simpler and safer donut chucks (and many other useful things) take a look at chapter 7 in Doc Green's "Fixtures and Chucks for Woodturning." A valuable book for any turning shop.
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