Metallics JTSS83 12 x 3 in. Pan Head Square Drive Tapping Screws - Steel Zinc - Each

A #3 square (Robertson) bit. The JTSS83 uses a square recess with a 3R driver size, the recess measuring 0.133 across the flats with a gaging depth of 0.080 to 0.095 inch. Square recess is what keeps the bit seated when you are driving a 3 inch screw overhead, which is why this style shows up on electrical and mechanical work.

The JTSS83 is a Type A tapping screw with a gimlet point, so it forms its own thread in sheet metal, wood or soft materials without tapping. A pilot hole sized to the root diameter is still normal practice in thicker or harder stock. With 11 threads per inch and a 3 inch length, it is a coarse-thread screw meant for deeper pull-in, not thin gauge sheet alone.

Pan head sits on top of the surface, it does not countersink. On the JTSS83 the head runs 0.407 to 0.425 inch across and 0.139 to 0.151 inch tall, so it gives a wide bearing face against a strap, clamp or box ear. If the drawing calls for a flush surface, you want a flat head countersunk screw instead, not this one.

Yes. The JTSS83 is built to ASME B18.6.3-2013 for dimensions and ASME B18.6.4 for the thread, with material per AISI 1016-1024. Note for procurement: 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 language.

They ship in a jar of 100, which is the order minimum. Jar weight is listed at 2.44 lbs and the container measures 3.5 x 5.75 x 3.5 inches, useful if you are stocking a van drawer or a shop bin.

The JTSS83 is carbon steel with a zinc plated finish, which is a general indoor and dry-location coating. For sustained wet exposure, coastal air or direct ground contact, a stainless or hot dip galvanized fastener is the right call instead.