Metallics JDS153M 8 x 3/4 in. 1/4 Indented Hex Head Slotted Sharp Point Tapping Screws - Steel Zinc - Each

That's exactly what a Type A tapping screw is for. The JDS153M is rated for use in thin metal less than .050 inch thick, where the sharp gimlet point starts in a pilot hole and the 15 threads per inch form their own mating thread as the screw drives. In heavier gauge steel you want a self-drilling Type TEK-style screw instead, because a Type A point will not cut through thick stock.

Either one. The head is an indented hex with a slot cut across it, so a 1/4 inch hex driver or a nut setter seats on the head (head width runs 0.244 to 0.250 inch, 0.272 across the corners) and a flat blade works in the slot, which measures 0.045 to 0.054 inch wide and 0.052 to 0.066 inch deep. The dual drive is why these are a standard electrical fastener, you can run them on a drill and still back one out with a screwdriver in a panel.

The JDS153M is flagged both Buy American compliant and ARRA compliant in the manufacturer data, which is what a government, school district, or healthcare procurement office needs on file for a federally funded project. Country of origin is listed as multiple.

Metallics specifies a #2 drill point size for the JDS153M. The gimlet point will start in that hole and form its own thread in sheet under .050 inch thick. Drill larger and the 15 TPI thread has nothing to bite; drill smaller in thin stock and you risk dimpling the panel.

Yes, there is a built-in washer face. Its outside diameter runs 0.322 to 0.348 inch with a thickness of 0.019 to 0.031 inch, and head height is 0.096 to 0.11 inch. That washer spreads the bearing load on thin sheet so the head doesn't pull through, and it means you don't need to stack a separate washer under it.

These ship in a jar of 1,000 pieces, which is also the order minimum, at about 4.5 lbs for the container. If you need a different count or a different diameter and length, Metallics offers other sizes and quantities by request.

Dimensions follow ASME B18.6.3-2010 and the thread form follows ASME B18.6.4, so a #8 x 3/4 inch Type A from any maker built to those same standards will drop into the same hole and the same 1/4 inch nut setter. One caveat worth knowing if you also buy the #9 diameter in this family: Metallics notes #9 dimensions are independent of ASME B18.6.4.

Zinc plated carbon steel is what the JDS153M is, silver in appearance, and it's built for dry interior work: electrical boxes, strut, panels, duct. Zinc plating is a sacrificial coating, so for exterior exposure, wet locations, or anywhere near treated lumber or coastal air you should move to a stainless or hot dip galvanized fastener instead.

Minimum torsional strength is 39 lb-in, with case hardness at Rockwell C28-38 on AISI 1016 to 1024 steel. In practice that means setting an impact or clutch driver to stop short of that, since a #8 tapping screw in sheet metal needs far less than 39 lb-in to seat and over-driving is what shears heads.