Metallics JTSS35 12 x 1-1/4 in. Pan Head Square Drive Tapping Screws - Steel Zinc - Each

A #3 square (Robertson) bit. The recess is specified as driver size 3R, measuring 0.133 inch across the flats with a gaging depth of 0.080 to 0.095 inch. The square recess has slightly tapered side walls and a conical bottom, which is what keeps the bit seated without camming out when you are driving one-handed off a ladder.

The JTSS35 is a Type A tapping screw with a gimlet point, so it has a sharp tapered tip that starts itself in thin sheet metal and soft materials. In heavier gauge steel you still want a pilot hole sized to the screw's minor diameter. The thread runs 11 threads per inch to the thread standard ASME B18.6.4, which is the coarse, widely spaced thread that Type A screws use to bite thin stock.

No. The JTSS35 is flagged as not Buy American compliant and not ARRA compliant, with country of origin listed as multiple. If your contract carries a domestic sourcing clause, you need a fastener with a stated domestic origin instead.

Head height runs 0.139 to 0.151 inch and head width 0.407 to 0.425 inch. That is a low, broad pan profile, so it seats flat against sheet metal with plenty of bearing surface but it does not countersink. If you need a flush surface, a pan head is the wrong head type for that opening.

They run Rockwell C28-38 with a minimum torsional strength of 83 lb-in, made from AISI 1016-1024 carbon steel. That is case-hardened enough to cut threads in sheet steel while keeping a core that resists shearing. Back off your impact driver clutch anyway, since torsional strength is a minimum rating, not a licence to overdrive.

They ship in a jar of 100, and 100 is the order minimum. The packed jar weighs 1.28 lbs. Metallics lists other sizes and quantities as available by request if 100 of the 12 x 1-1/4 inch is not the count you need.

Head and recess dimensions follow ASME B18.6.3-2013 and the threads follow ASME B18.6.4. Material is AISI 1016-1024 steel. One caveat worth noting on a submittal: Metallics states that dimensions for #9 diameter are independent of ASME B18.6.4, so that size does not sit under the same thread spec.

The JTSS35 is steel with a zinc finish, which is a general indoor and protected-location plating. It handles the humidity of a mechanical room or crawlspace fine, but direct weather exposure, coastal air, or wet locations will eventually take it. For those, specify stainless rather than zinc plated steel.

Metallics lists the JTSS series for the electrical, plumbing, heating and air conditioning trades. Typical work is fastening to sheet metal: duct, panel enclosures, strut accessories, box mounting, and hanger brackets. The square drive is the reason it is popular on that work, since the bit holds the screw on the driver when you have one hand free.