Metallics JSS3838 Screw 3/8-16 x 3/8 SKT S-Scr Cup St- (Jar 100)

The JSS3838 is a 3/8-16 thread socket set screw with a 3/8 inch length, cup point. The 3/8-16 designation means a 3/8 inch nominal diameter with 16 threads per inch, which is the standard UNC coarse pitch for that diameter.

At 3/8 inch length with a 3/8 inch diameter, the JSS3838 is a 1:1 length-to-diameter screw. That means it will seat flush or near flush in a tapped boss of roughly its own depth and reach very little past it. If your lug or collar wall is thicker than about 3/8 inch, the screw will bottom out before it clamps and you need a longer 3/8-16 screw instead.

Each jar holds 100 pieces. Metallics packages this one in a jar rather than a box, which is the usual format for small loose fasteners kept on a service truck or at a parts bench.

Yes, it is a socket set screw, so it drives with a hex (Allen) key in the internal socket, not a screwdriver. The business end is a cup point, which bites into and slightly deforms the shaft or surface it clamps against. That gives good holding against rotation and slip, but it marks the part, so use it where the mating surface does not need to stay unblemished.

Cup point, like the JSS3838, is the general purpose choice and what most electrical and mechanical lug, collar, and coupling applications call for. Use a flat point instead when the screw has to seat against a hardened or finished shaft you cannot afford to scar, or when the part will be repositioned. A cone point is for permanent location in a drilled or spotted seat. For routine clamping where a little indentation is acceptable, cup point holds best.