when I put the 6" chuck in place of the 4" on my 9x20 lathe I used the hardened head stock center checker with tail stock supporting the other end (mt5 I think) tightened the chuck to it backwards( jaws to the head stock side) so i could machine the recess& true it up since it was a china chuck...( totaly disassembled chuck first deburred and cleaned real good reassembled for totaly smooth movement( the china greese is used greese/oil/lube in all thier out bound equipment and is full of ****, so it must be disassembled and cleaned then refilled with proper lube if you want it to last) so i trued it up on both planes.then installed the backing plate to the lathe and trued it up and sized the resess for it also. much much better runout readings than the normal china stuff. I wish I had it in me to put a larger spindal in it...but i would be better served selling my 2 small lathes and getting 1, 12x36 0r 13x36.lathe....I probably have 3 hours run time on this one in 5 years and mostly resizing pvc pipe fittings.... yes Im a financial wizzard....NOT. it's just getting harder to do things I want to do.