A socket set screw is also called a grub screw. It has no head and is typically tightened or loosened with a square or hex key, although a slotted set screw can be adjusted with a screwdriver. Socket set screws prevent movement of a pulley or similar machine part relative to a shaft. A cup point set screw has a rounded tip that offers excellent grip while also resisting deforming of the shaft surface. A flat point screw provides more contact with the shaft. Buy socket set screws from Grainger to keep machinery running safely and smoothly.