Metallics TSP84M 12 x 1-1/4 in. Pan Head Phillips Sharp Point Tapping Screws - Steel Zinc - Each

A #3 Phillips bit. The recess is 0.246 to 0.259 inch in diameter and 0.141 inch deep, so a #2 bit will cam out and chew the recess under torque. Keep a #3 in the gun if you are running these by the box.

The TSP84M is a Type A tapping screw with a gimlet (sharp) point, so it needs a pilot hole in sheet metal, metal studs, or enclosure walls, then forms its own thread as it drives. It does not drill its own hole. If you want to skip the pilot hole in steel, a self-drilling (Type TEK) screw is the one to use instead. The coarse 11 threads per inch also makes this a workable screw in wood, plastic, and composition board where the sharp point starts on its own.

The head and recess geometry is built to ASME B18.6.3-2013 and the thread to ASME B18.6.4, so the TSP84M will dimension-check against a drawing calling out those standards. Note that it is not Buy American compliant and not ARRA compliant, with country of origin listed as multiple, so it will not clear a federally funded job carrying domestic-sourcing requirements.

It stands proud. A pan head is a raised bearing-surface head, not a countersinking one: this one measures 0.407 to 0.425 inch across the head with a head height of 0.139 to 0.151 inch. So budget roughly an eighth of an inch of head above the material. If the fastener has to finish flush, you need a flat or oval head screw in a countersunk hole instead.

They ship as a box of 1,000, which is the order minimum. Metallics notes that other sizes and quantities are available by request, so if 1,000 of the #12 x 1-1/4 is more than the job needs, ask about a different count or a different length.

Zinc plated carbon steel is a dry, indoor-rated finish. It handles occasional humidity in a mechanical room or a panel enclosure, but in exterior exposure, washdown areas, or anywhere near coastal salt it will corrode and bleed rust onto the surface. For wet or outdoor work, specify a stainless or hot dip galvanized tapping screw instead.

The TSP84M is a #12 diameter, 1-1/4 inch long screw. Metallics carries a #9 in the same JTSP tapping screw family, and the caveat about #9 dimensions falling outside ASME B18.6.4 applies to that size, not to the #12. Order the TSP84M when the spec or the existing hole calls for a #12.