Metallics JTSF36 12 x 1-1/2 in. Flat Head Phillips Tapping Screws - Steel Zinc - Each

The JTSF36 is a #12 x 1-1/2 inch Type A tapping screw with a flat head and Phillips drive, made of zinc-plated steel. Type A means a gimlet point that cuts its own thread as it drives, so it goes into sheet metal or similar material with a pilot hole and no tapping. Metallics lists it for the electrical, plumbing, heating and air conditioning trades, which is where it shows up most: mounting boxes, straps, hangers and brackets.

Yes, that is what the flat head is for. The head measures 0.38 to 0.412 inch across with a head height of 0.112 to 0.132 inch, so it seats flush in a standard 82 degree countersink for a #12 screw. In plain sheet metal with no countersink it will stand proud by roughly the head height, so use a pan or hex head there instead.

No. These are flagged as not Buy American compliant and not ARRA compliant, with country of origin listed as multiple. If the project specification carries a domestic sourcing requirement, this part will not satisfy it.

A #3 Phillips bit. The recess on the JTSF36 runs 0.262 inch diameter, 0.144 inch deep and 0.035 inch wide, which is sized for a #3 driver. Using a #2 in it will cam out and chew the recess, especially since these are driven into metal.

Yes. Both the dimensions and the thread conform to ASME B18.6.4, the 1998 revision, so head geometry, thread form and point match anything else built to that spec. The steel is AISI 1016 to 1024. One caveat from Metallics: dimensions for the #9 diameter in this family are independent of ASME B18.6.4, though that does not affect the #12.

They are case hardened to Rockwell C28-38 with a minimum torsional strength of 83 lb-in, which is the ASME figure for a #12 tapping screw. That is enough to tap sheet metal without shearing, but an impact driver will exceed 83 lb-in easily once the screw bottoms out. Drive with a clutch-set drill or a screw gun and back off as the head seats.

Size the pilot to the screw's gaging diameter, which is 0.362 inch on the JTSF36, less the thread depth. The thread is 11 threads per inch, a coarse Type A form, so in thin sheet metal a pilot around the root diameter lets the gimlet point start and cut cleanly. Too large and the threads strip out; too small and you risk twisting the screw off.

The JTSF36 is carbon steel with a zinc finish, which handles indoor and normally dry conditions. Zinc plating is a sacrificial coating, not stainless, so in wet, coastal or chemically aggressive locations it will eventually corrode. For those openings go to a stainless or hot dip galvanized fastener instead.

They come in a jar of 100, and 100 is the order minimum. The jar weighs 0.92 lbs. Metallics notes other sizes and quantities in this flat head Phillips tapping screw line are available by request.