Metallics JDS159 Screws 8 X 2 Ih Hx 1/4Hd Sl TS St-zn (Jar 100)

The Metallics JDS159 is a Type A thread forming tapping screw with a gimlet point, intended to self-start in metal from 0.015 to 0.050 inch thick, or in resin-filled plywood. Thicker steel needs to be pre-drilled or you need a self-drilling screw instead. Thread pitch is 15 threads per inch, the wider spacing that is characteristic of Type A versus Type AB.

That is the stated application: light metal assembly such as electrical outlets, framing and other sheet metal work. At #8 x 2 inches long it suits standoff situations where a shorter screw will not reach the steel. For thin-gauge steel only, in the 0.015 to 0.050 inch range.

Dimensions are to ASME B18.6.3-2010 and threads to ASME B18.6.4, with material to AISI 1016-1024. Note that country of origin is listed as multiple, and it is neither ARRA nor Buy American compliant, so it will not clear a federally funded job that carries domestic sourcing requirements.

Either works. The head is an indented hex with a slot, so it takes a 1/4 inch hex driver or a flat blade. Head width runs 0.244 to 0.250 inch across the flats with 0.272 inch across the corners, head height 0.096 to 0.110 inch. The slot is 0.045 to 0.054 inch wide and 0.052 to 0.066 inch deep, so a cabinet-tip blade seats better than a wide carpenter's tip.

Yes, there is a washer face under the indented hex head, with an outside diameter of 0.322 to 0.348 inch and a thickness of 0.019 to 0.031 inch. That gives you roughly a third of an inch of bearing surface, which is what keeps the head from pulling through thin sheet or a punched mounting hole.

Torsional strength is 39 lb-in minimum, with case hardness at Rockwell C28-38 on AISI 1016-1024 steel. That is enough to form threads in thin sheet under a drill or driver, but 39 lb-in is not much torque, so back off the clutch on an impact driver and stop as soon as the washer face seats. Over-driving a Type A screw in thin metal spins the hole out before it snaps the shank.

The JDS159 is steel with a zinc finish, which is a mild indoor corrosion coating. It is fine for interior electrical and sheet metal work. For exterior exposure, wet locations, or contact with treated lumber, specify stainless or a heavier coated fastener instead.

Type A screws like the JDS159 have wider spaced threads and a gimlet point, which lets them start themselves in thin sheet and in resin-filled plywood without a pilot. Type AB uses a finer, closer thread pitch, which holds better in slightly heavier material and in plastics. If you are fastening to sheet in the 0.015 to 0.050 inch range, Type A is the one you want; above that range go to an AB or a self-drilling screw.

These ship in a jar of 100 pieces, and one jar is the order minimum. Other sizes and quantities are available by request.