The Fabled and Legendary Universal-Independent 3-Jaw Chuck?

I have 2 of these chucks... an 8 inch Union and a 9 inch Rohm, for my South Bend 14 1/2.

The first time you try to get them centered, it is a real pain... but after doing it a few times, it becomes very easy... I can get a part indicated within a half thousandth in less than 2 minutes now.

Both of mine have a lot of wear in the scroll, so I have to indicate everything that I chuck up... It tends to repeat within about .010, so I get a lot of experience adjusting the jaws.

Now, I actually prefer these chucks over a standard 3 jaw or a 4 jaw...

I would still love to have a set-tru chuck, but these work well enough that I can't justify paying the price for a set-tru.

-Bear
 
A number of individuals use the Bison 4 jaw 8" combination chuck, the repeatability of the scroll is about 0.001", the independent jaws allow you to take out any remaining TIR quickly. Very easy to remove and reinsert stock, and get it spot on as far as runout, you also can adjust for the non-uniformity of stock or the piece you are working on. The jaws are 0.2" at the tips so it hold smaller round stock munch better than a 3 jaw, although I usually use a collet chuck. I use my collet chuck probably 50% of the time, combo 40% and 3 jaw set-true 10%. A set-true will not necessarily hold its tolerance over a wide range of diameters, I usually set up mine with some 1" stock. SThe combo cost is similar to a 6J Set-True type. If you consider you would not need a 4J independent and a 3J scroll set-true, it is a less expensive alternative. I purchase my 3J first, and then the combo, but almost never use my 3J anymore.
 
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