Metallics JTEKD20V 12 x 3/4 in. 5/16 Indented Hex Head Self-Drilling & Tapping Screws with Washer - #3 Drill Point - Steel Zinc - Each

The washer on the JTEKD20V is an integral metal washer formed with the head, 0.398 to 0.432 inch outside diameter and 0.022 to 0.039 inch thick. It spreads bearing load and keeps the head from pulling through thin flange material. It is not a rubber or neoprene sealing washer, so for exposed roof or wall penetrations that need to be watertight you want a bonded-washer screw instead.

Zinc plated carbon steel, per AISI 1016-1024 material. That is a dry interior finish, fine for strut, panel enclosures, duct hangers, and framing inside the building envelope. For exterior exposure, coastal air, or wet process areas, go to a stainless or coated-steel self-drilling screw rather than this zinc one.

Minimum torsional strength on the JTEKD20V is 92 lb-in, with case hardness at Rockwell C32-40. That is enough for a standard drill/driver at normal speed. The common failure is over-torquing after the screw seats, so back off the clutch once the washer pulls tight. Manufacturer data notes drill time of about 2.5 seconds through a 1 mm plate.

Both the ARRA and Buy American compliance flags on the JTEKD20V are marked compliant, with country of origin listed as multiple. For a federally funded spec that requires documented domestic origin on a specific lot, ask for the mill paperwork on the shipment you receive.

At 3/4 inch overall on a #12 shank, the drill point and the flutes consume part of that length, so plan on the point fully exiting the back of the material before the threads can engage. Within the rated 0.110 to 0.210 inch panel thickness that leaves plenty of thread. Stacking two heavy plates at the top of that range, or fastening through a spacer or insulation layer, calls for a longer screw in the same series.