Metallics JSS1478 Screw 1/4-20 x 7/8 SKT S-Scr Cup St- (Jar 100)

Each jar holds 100 of the 1/4-20 x 7/8 inch cup point socket set screws. Metallics ships them in a jar rather than a box, which keeps them sorted on a service van or in a shop bin.

Cup point is the general purpose holding point, and that is what the JSS1478 uses. The hollow circular rim bites into the shaft or mating part and resists loosening under vibration, which is why it is the common choice for collars, sheaves, and clamp-type fittings. If you need a point that seats into a pre-drilled dimple or a spot-drilled shaft without marring it, a cone or dog point is the better pick; cup point will leave a mark where it bears.

The JSS1478 is a steel set screw. For wet, outdoor, or corrosive locations you would want a stainless or coated fastener instead, since plain steel will corrode once exposed.

Metallics catalogs the JSS1478 as an electrical fastener, and a 1/4-20 x 7/8 inch cup point socket set screw is the size used in lugs, collars, and clamp fittings that are tapped 1/4-20. The deciding factor is the tapped hole: confirm the fitting is 1/4-20 and that 7/8 inch of thread length suits the wall thickness and the depth you need to reach.

It is a socket drive, so it takes a hex key (Allen wrench), not a screwdriver. The head is headless and seats fully below the surface of the collar or fitting, so nothing protrudes to catch.