A set screw is a threaded fastener that is typically used to hold a sleeve, collar or gear on a shaft to prevent relative motion. It is a threaded member that normally does not have a head. Unlike most other threaded fasteners it is basically a compression device normally used to generate axial thrust. Various socket types are provided to allow the set screw to be rotated. These types include hexagon socket, fluted socket, screwdriver slot and square head. Various point designs are available (the part of the set screw that rotates against the shaft being secured) and include: Cup - Hollowed end, is the most commonly used point style. Used when the digging in of the point is not undesirable. Cone - Pointed end, this type generates the highest torsional holding power and is typically used for a permanent connection. Oval - Rounded end that is typically used when frequent adjustment is required. The oval end prevents/reduces indentation. Flat - Cause little damage to the shaft and are used when frequent adjustment is required. Dog - Flat end with the threads stopping short of the end with the end fitting into a hole.

A small screw in the shank of a knob that is tightened to fix the knob on the spindle. Old set-screws varied widely in diameter and thread count.

n. a screw used to fasten a component in a fixed position relative to another component