A set screw is a threaded fastener that normally does not have a head. Unlike most other threaded fasteners it is basically a compression device normally used to generate axial thrust.

Set Screws are also known as grub screw.

It is used to hold parts like sleeve, collar, coupling, gear etc. on a shaft to prevent relative motion.

The most obvious point of distinction between grub screws and other types of standard screws and bolts is that true grub screws tend not to feature a protruding head.

Instead, they’re usually threaded right to the top, and are the same diameter all the way along their length, meaning that the grub screw can be fully driven into its hole to sit flush with (or even countersunk into, depending on the application) the workpiece.

They’re almost always found being used in mechanical systems where two or more metal surfaces rub or press directly together, and where there isn’t room to fit a bolt or other type of protruding head between the two flush surfaces without limiting proper functionality or movement of the part(s).

Socket set screws offer three types of holding power: torsional (resistance to rotation); axial (resistance to lateral movement); and vibrational.

Size selection is an important factor in holding power.

Grub Screws are available with different point options.