I'm looking at getting a 4 jaw chuck for my lathe when I get it up and running. What size chuck would you recommend? I am looking at a 6" Shars currently, the next largest size is an 8" but I don't want to go maximum overkill if I don't need to-i'd be worried about the jaws being so large that I can't hold things without them not clearing the bed.
6" 4 Jaw Independent Chuck With1-1/2 x 8 Threaded Mounting Plate - Lathe Chucks - Toolholding & Workholding - Products
4-J also exist in 3", 4", 5", 7" or near-as dammit also - I have one or more of each of those. Two of the little ones are Chinese "San Ou" and surprisingly decent for their modest price.
Check for what comes out "even" in the metric world.
On a SB 9, - or even my nominal 10", actual 12.5" 10EE's a 6" would be as large as I'd expect to use with any regularity.
I have the 5" and smaller partly because of the high RPM a 10EE can deliver, and partly as collet systems aren't good with odd-shaped or off-centered parts. Smaller 4-J generally have thinner jaws and can "get in" where wider ones cannot.
Having one or more
faceplates and the skill and will to adapt or fab clamping and fixturing "goodies" to mount stuff to a sub-plate or angle plate if not directly may prove more useful than a larger chuck.
Not all turning and boring is of round goods that are balanced, rotationally, nor has to proceed at high RPM, after all.
Even if not on YOUR radar, think connecting-rod end boring, or a die-casting, such as a carburetor body. Faceplate work, those generally be.
