Metallics JTMSP103 Screw 1/4-20 x 1-1/2 Truss CD MS St- (Jar 100)

The JTMSP103 is a 1/4-20 x 1-1/2 inch truss head machine screw. The 1/4-20 means a 1/4 inch diameter with 20 threads per inch, which is the standard coarse UNC thread for that diameter, so it mates with any 1/4-20 nut or tapped hole. Length is 1-1/2 inches.

That is exactly what a truss head does. The JTMSP103 has a truss (oven) head, which is wider and shallower than a standard round or pan head, so it spreads load over a larger area and sits lower above the surface. Electricians use that where a pan head would stand too proud or where the hole is slightly oversized and needs covering. If you need the head flush with the surface, you want a flat head countersunk screw instead, not a truss head.

It is a machine screw, not self-tapping. The JTMSP103 has a blunt, fully threaded 1/4-20 machine thread, so it needs a tapped hole or a nut. If you are driving into unthreaded sheet metal without a nut on the back, a sheet metal or self-drilling screw is the right part instead.

One hundred screws per jar. The JTMSP103 is packaged as a jar of 100, which is how Metallics sells these for van stock and shop benches rather than loose count.

That is the intended use. These are cataloged as electrical fastener stock, and a 1/4-20 x 1-1/2 truss head machine screw is a common size for mounting hardware, brackets, and covers into tapped holes in enclosures, strut, and box ears. The 1-1/2 inch length gives enough reach to pass through a spacer or a thicker bracket before engaging the threads.

If you are not threading into an existing tapped hole, you need 1/4-20 nuts, and most electricians add flat and lock washers. The jar of 100 JTMSP103 screws ships as screws only, so nuts and washers get ordered separately.