Metallics JTSS11SS 8 x 1-1/2 in. Pan Head Square Drive Tapping Screws - 18-8 Stainless - Each

A #2 square (Robertson) bit. The recess is specified as driver size 2R, measuring 0.112 inch across the flats with a gaging depth of 0.060 to 0.075 inch, so a worn or undersized bit will cam out. Keep a couple of spare #2 square bits on the job if you are running a full jar of 100.

The JTSS11SS is a Type A tapping screw with a gimlet point, so it drills in and forms its own thread in sheet metal and similar thin material. Type A screws still want a correctly sized clearance hole in the top sheet for consistent draw; the point does the threading in the base material rather than the whole stack.

Mechanically yes, but there is a corrosion caution. Metallics notes that fastening stainless steel parts to aluminum or steel can create a galvanic couple in some environments. Outdoors, in wet locations, or anywhere near salt, that dissimilar-metal contact will attack the aluminum or steel around the fastener first. For those jobs isolate the joint or use a fastener matched to the base metal; indoors and dry, the 18-8 stainless is the more corrosion-resistant choice.

No. The JTSS11SS is not Buy American compliant and is not ARRA compliant, with country of origin listed as multiple. On federally funded work with domestic-content requirements, this screw will not satisfy the clause and you need a domestic-source fastener instead.

Dimensionally the screws are built to ASME B18.6.3-2013, and the threads follow ASME B18.6.4 at 15 threads per inch for the #8 size. Minimum torsional strength is 39 lb-in, which is the spec worth checking if you are driving with an impact or a high-torque screwgun.

Metallics lists the field application as the electrical, plumbing, heating and air conditioning industries. In practice that means strapping and hangers, duct and sheet metal work, enclosure and device mounting, and anywhere an MRO or facilities crew wants a stainless self-tapper that will not rust out in a damp mechanical room. The square recess is the reason tradespeople like it overhead, the bit holds the screw without a magnet.