1/2" Straight Shank to 5/8"-16 Threaded Drill Chuck Arbor 1/2" Straight Shank Thread: 5/8"-16 Allows you to add a 1/2" straight shank to drill chucks with 5/8"-16 threaded back. Shank may be fully cylindrical, or have a recessed portion. Photo is for general reference only, details such as size of shoulder may vary.