Endpin Jack Reamer
This machined steel 2-step reamer is made specifically for enlarging a guitar endpin hole to accept a 15/32" or 1/2"-diameter endpin jack.
It won't chip the finish, and it's semi-fluted to help keep the hole round.The 3/8" shank can be chucked in a hand drill for slow reaming. The upper 1" cutting length is 1/2" diameter; the 1" center section is 15/32" diameter, and the lower 2-5/8" section has a standard 5-degree endpin taper to 1/4".