Metallics JDS172V 12 x 1-1/4 in. 5/16 Indented Hex Head Slotted Sharp Point Tapping Screws - Steel Zinc - Each

Either one. The JDS172V has an indented hex washer head with a slot cut in it, so a 5/16 nut driver or a flat blade both work. Head width measures 0.305 to 0.312 in. across the flats and 0.34 in. across the corners, and the slot is 0.056 to 0.067 in. wide by 0.077 to 0.093 in. deep. On a ladder with a cordless driver most crews use the nut setter; the slot is there for a final snug or for tight spots where a socket will not seat.

The JDS172V is a Type A tapping screw with a gimlet (sharp) point, so it starts itself in thin sheet steel, sheet metal boxes, strut accessories and similar light gauge material without a pilot hole. In heavier stock, pre-drilling keeps the point from walking and keeps you under the screw's torsional limit.

83 lb-in minimum torsional strength, with the body heat treated to Rockwell C28-38 from AISI 1016-1024 steel. That is plenty for hand driving or a clutched impact driver set low, but a full torque impact gun into heavy steel will twist the head off a #12 tapping screw. Back the clutch off and let the point do the work.

11 threads per inch, to ASME B18.6.4 for the thread and ASME B18.6.3-2010 for the head dimensions. If a drawing or submittal calls out a #12 Type A tapping screw to those standards, the JDS172V meets the callout.

Steel with zinc plating is a dry interior and protected finish. It handles indoor panel, box and fixture work fine, but zinc on carbon steel will bloom white and then rust in weather, wash down, or coastal air. For rooftop, exterior, or wet locations specify stainless or a hot dip or mechanically galvanized fastener instead.

Metallics lists the JDS172V as both ARRA compliant and Buy American compliant. Country of origin is recorded as multiple, so on a federally funded project where the AHJ or owner wants mill documentation, request the certification against the specific lot you receive.

Overall screw length is 1-1/4 in. and the threads run nearly the full body on a Type A, so subtract whatever you are fastening through to see how much engagement is left in the base material. Thin gauge steel needs at least two or three threads past the back face to hold. Head height adds 0.139 to 0.155 in. above the surface, which matters if a cover plate or trim has to sit flat over the screw.

They ship in a jar of 500, and 500 count is the order minimum. The jar runs about 5.85 lbs. Handy for a shop shelf or a van bin rather than a loose handful, so if you only need a dozen for one panel you are still buying the jar.