I too have a 5C collet chuck bought it used when I still had my 14 1/2" South Bend lathe. Kept it when I used the SB as a partial trade for my Logan.
The previous owner would mount it in a 4 jaw and indicate it in, which I found kinda weird. It has some marks from the 4 jaw on the OD and one day I may take a skim cut to clean it up, maybe. Does not affect function so that's way down the to do list.
I bought a new D1-4 (I think) spindle adapter made sure its back and the spindle nose were as clean as possible, made witness marks, then machined it to fit the back of the chuck. It been dead on ever since.
I considered ER collets, but I also have a 5C indexer so the economics worked out in favor for the 5C chuck. It's certainly much easier to change out ER collets V the 5C versions. On the other hand the 5C's can be used with a stop inside the collet, a very handy feature.
The previous owner would mount it in a 4 jaw and indicate it in, which I found kinda weird. It has some marks from the 4 jaw on the OD and one day I may take a skim cut to clean it up, maybe. Does not affect function so that's way down the to do list.
I bought a new D1-4 (I think) spindle adapter made sure its back and the spindle nose were as clean as possible, made witness marks, then machined it to fit the back of the chuck. It been dead on ever since.
I considered ER collets, but I also have a 5C indexer so the economics worked out in favor for the 5C chuck. It's certainly much easier to change out ER collets V the 5C versions. On the other hand the 5C's can be used with a stop inside the collet, a very handy feature.