I need to adapt a couple of chucks to my DSG lathe, which has a simple spigot and 4-stud flange on the spindle. The only thing I have to fit the spindle so far is the 3-jaw which is probably the original,52 years old. That's not too bad if I tweak the different key positions a bit, but I can't just put in a piece of bar and assume it'll be running true.
First off is a 16" 4-jaw which originally had an integral L2 fitting. I bought it unused or almost so 6 years ago, it's had very little use since. I adapted it to fit my TOS, with C6 spindle, by hacking off the threaded projection and machining the C6 taper direct into the body. This I did by clamping the chuck backwards onto a 3-jaw in the lathe and indicating it true from the body before machining. That wasn't a huge success, parts held in the jaws would 'wobble' slightly relative to the axis. My guess is that I didn't have it quite as true as I had thought, but it makes me think twice about doing the same again. The alternative is to bore and face it on the mill, but that'll require some *very* careful setting up, tramming etc to get a decent result. Either way assumes the face of the body is square to the jaws, but it is a decent quality (Pratt, I think) chuck. Any recommendations, anyone been there before? After I've done the 4-jaw I have a faceplate and 12" 3-jaw to do, but at least by then I'll have the added option of setting them up in the4-jaw.
Thanks Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service