Metallics JSTSP32 12 x 1-1/2 in. Pan Head Phillips Tapping Screws - 18-8 Stainless - Each

You can, but be aware of the corrosion risk. Fastening 18-8 stainless parts to aluminum or steel can set up a galvanic couple in some environments, which attacks the less noble metal around the fastener. In dry interior electrical work that is rarely an issue; in wet, coastal, or exterior locations, isolate the joint or pick a fastener matched to the base metal.

Pan head, so it sits on top of the surface, not flush. Head width runs 0.407 to 0.425 in. and head height 0.139 to 0.151 in., which is what you want when you need bearing area against sheet metal or a strap but it does mean roughly an eighth of an inch of standoff. For a flush finish you need a flat head countersunk screw instead.

No. These are not Buy American compliant and are not ARRA compliant, with country of origin listed as multiple. If the job carries a domestic sourcing clause, you need a different fastener.

The JSTSP32 is a Type A tapping screw with a gimlet point, so it drills its own way into a pre-punched or pilot-drilled hole in sheet metal rather than needing a tapped thread. The gimlet point and 11 threads per inch let it form its own mating thread as it drives. Size the hole so the thread engages, not the major diameter.

A #3 Phillips bit. The recess runs 0.246 to 0.259 in. in diameter and 0.141 in. deep, so a #2 bit will sit shallow and cam out under load. Keep a #3 in the pouch if you are running a jar of these.

The JSTSP32 carries a minimum torsional strength of 83 lb-in. Stainless work-hardens and twists off more readily than hardened carbon steel, so set an impact driver or screw gun clutch well below that figure when driving into heavier gauge metal.

Yes. The JSTSP32 is built to ASME B18.6.3-2013 for head dimensions and ASME B18.6.4 for the tapping thread. One caveat worth knowing across the series: dimensions for #9 diameter screws fall outside ASME B18.6.4. This #12 size is covered.

They ship in a jar of 100, which is the order minimum. Jar weight is listed at 1.37 lbs. Handy for a van stock item rather than a loose count at the counter.

Metallics lists the JSTSP series for the electrical, plumbing, heating and air conditioning trades. Typical use is hanging straps, boxes, brackets and duct components to sheet metal where the 1-1/2 in. length gives you reach through insulation or a spacer and the stainless holds up in damp mechanical rooms.