A fully threaded, headless screw tightened through a tapped hole in a hub so its point presses on the shaft inside. Point styles do different jobs: cup point bites into the shaft and is the default, flat point suits shafts that are adjusted often, cone point seats in a drilled dimple, and dog point engages a hole or slot. Holding power depends on point style, screw size and shaft hardness, and a flat ground on the shaft keeps the raised burr out of the bore.
Pulley walked on the shaft again, the set screw had nothing to bite on, so file a flat and put a dab of blue on it.
Brits and Aussies call it a grub screw, and a cup point on a hardened shaft just skates instead of biting.
Also heard as
- grub screw
- socket set screw
Related terms
SHCS
Socket head cap screw: a round-headed, high-strength screw driven with a hex key into a tapped hole.
Threadlocker
An anaerobic adhesive applied to threads that hardens between metal surfaces to stop loosening and seal.
Allen key
Shop name for an L-shaped hex key used to drive socket head cap screws and set screws.
Jam nut
A thin nut, roughly half to two-thirds standard height, run up against another nut or part to stop it turning.