Hey guys,
I have an old Bridgeport J-head mill and it came with a JT6 taper 1/2 drill chuck made by King. However the chuck key that came with it doesn't fit properly, it is close, but pretty sloppy. It appears to have a 5/16 pilot hole.
The only lettering on the chuck is:
King
JT6-1/2
CAP-13...