Drill a perfectly centered hole in your pen blank directly on your lathe. Thread chuck onto your lathe's headstock spindle. Mount a drill bit in a drill chuck in your lathe's tailstock. Advance drill bit into blank while lathe is spinning. Chuck is pre-threaded to 1" x 8tpi. Weighs 1. 2 lbs. Diameter 2. 5". Chuck will secure blanks up to 1" square x 4" long. Dedicated jaws are 2" long. Includes (2) tightening levers to open and close the chuck jaws.