5/16-24 x 3/8 Socket Set Screw Cup Point Alloy . A headless screw threaded the entire length. It has a hexagonal drive at one end and a cup-shaped indentation at the other end. The cup point is the most used style set screw. Designed for fast, permanent and semi-permanent location of parts on shafts with hardness differential of 10-15 Rockwell C points and where cutting in of cup edge on the shaft is acceptable. Hardness: Rockwell C45-53.