Metallics JDSP174 12 x 2 in. 5/16 Hex Head Phillips Sharp Point Tapping Screws - Steel Zinc - Each

Not in sheet metal or wood. The JDSP174 is a Type A tapping screw with a gimlet (sharp) point, which pierces and forms its own thread in thin material. Thread count is 11 per inch, which is the coarse Type A spacing, so it bites fast. Where you do need a pilot hole is thicker steel or hardwood, and in masonry or concrete these are the wrong fastener entirely.

Zinc plating over carbon steel is a mild corrosion finish, suited to dry interior and protected work. The JDSP174 is steel with a zinc finish, made from AISI 1016 to 1024 carbon steel. For sustained exterior exposure, wet locations, or anything coastal, specify stainless or a hot dip galvanized fastener instead. For interior electrical work, strut mounting, enclosure and box attachment, the zinc finish is what is normally called out.

These ship in a jar, 100 count, and 100 is the order minimum. Jar weight is 1.66 lbs for the 100 pieces. If you need a different size or a different count, Metallics makes the JDSP series in other diameters and lengths.

Yes, it is a hex washer head. The integral washer measures 0.398 to 0.432 in. outside diameter with a thickness of 0.022 to 0.039 in., and head height runs 0.139 to 0.155 in. That washer face spreads the clamp load, so you do not need a separate flat washer when fastening sheet metal, straps, or box ears.

Head dimensions are built to ASME B18.6.3-2013 and the thread form to ASME B18.6.4. Case hardness is Rockwell C28-38, with a minimum torsional strength of 83 lb-in, which is what keeps the shank from twisting off when it is driven into gauge steel. Note that Metallics states dimensions for the #9 diameter are independent of ASME B18.6.4; the #12 covered here follows the standard.

Metallics lists the JDSP174 as both ARRA compliant and Buy American compliant, with country of origin China. Specifications differ in how they treat those two designations, so match the compliance language in your project documents against those entries before you commit a large quantity on a government or institutional contract.

Fastener length is 2 in. on the JDSP174, measured under the washer head. That gives real embedment into wood framing or through a layer of sheathing, but in thin gauge steel or strut the extra point sticks out the back. Where that exposed tip is a problem (behind drywall, inside an occupied space, against conduit), step down to a shorter length in the same #12 diameter rather than cutting these.