Metallics JDS5161 5/16 x 1 in. 1/2 Indented Hex Head Slotted Sharp Point Tapping Screws - Steel Zinc - Each

The JDS5161 has a 1/2 inch indented hex head, measured 0.489 to 0.500 inch across the flats, with 0.545 inch across the corners. A 1/2 inch socket or nut driver seats it. There is also a slot in the head, 0.072 to 0.084 inch wide and 0.100 to 0.122 inch deep, so a standard flat blade will start or back the screw out in tight spots where a driver won't fit.

A Type A tapping screw like the JDS5161 has a gimlet (sharp) point and wide-spaced thread, so it cuts its own thread in thin sheet metal but needs a pilot hole already there. It does not drill its own hole. If you are fastening straight through steel with nothing pre-punched, you want a self-drilling screw with a drill point instead. For knockout boxes, strut, duct and sheet steel that is already punched or drilled, the Type A is the usual pick.

Metallics lists the JDS5161 as both Buy American compliant and ARRA compliant. Country of origin is recorded as multiple, so if your contract requires a specific documented origin per lot, that is worth confirming against the shipment paperwork rather than the catalog entry.

Dimensions are to ASME B18.6.3-2010 and the thread is to ASME B18.6.4. Material is AISI 1016 to 1024 carbon steel, case hardened to Rockwell C28-38. One caveat straight from Metallics: dimensions for the #9 diameter are independent of ASME B18.6.4. That does not affect the 5/16 x 1 inch JDS5161.

Yes, the head carries a washer face with an outside diameter of 0.624 to 0.676 inch and a thickness of 0.035 to 0.055 inch. That gives you a larger bearing surface than a plain hex head, which is why these get used on thin sheet and slotted strut where a bare head would pull through or distort the material. No separate washer is needed.

These ship in a jar of 100 pieces, and 100 count is the order minimum. The packed jar runs 2.9 lbs. Metallics lists other diameters and lengths in the same JDS indented hex head slotted tapping screw family on request, so if 5/16 x 1 inch isn't your size the configuration exists elsewhere in the series.

The JDS5161 is zinc plated carbon steel, which is a mild indoor and sheltered corrosion finish. It is fine in mechanical rooms, ceilings, duct runs and interior strut. For direct weather exposure, wash-down areas, or coastal work, zinc plating will eventually bloom and you should be specifying stainless instead.

Length is 1 inch overall measured from under the head, with head height running 0.208 to 0.230 inch. Since a tapping screw needs several threads engaged in the receiving material to hold, plan on the clamped layer being well under 1 inch so there is thread left to bite. Stacked sheet over strut or channel is the normal use; for thicker assemblies step up to a longer screw in the same JDS series.