Metallics JDS83 12 x 3 in. 5/16 Indented Hex Head Slotted Sharp Point Tapping Screws - Steel Zinc - Each

The JDS83 takes a 5/16 inch hex socket or nut driver. Head width across the flats measures 0.305 to 0.312 inch, and across the corners 0.34 inch, so a standard 5/16 magnetic nut setter seats it. The head is also slotted, with a slot 0.056 to 0.067 inch wide and 0.077 to 0.093 inch deep, so a flat blade works when you cannot get a socket in.

It is a Type A tapping screw with a gimlet (sharp) point, so it starts on its own in soft materials like sheet metal, wood and plastic without a pre-drilled pilot in thin stock. Type A threading is coarse at 11 threads per inch, which is what lets it cut and hold in thinner gauge material. For hard or thick stock, drill a pilot sized to the root diameter.

The JDS83 is a #12 diameter screw, 3 inches long under the head. With 11 threads per inch across that 3 inch shank, it is a long-reach fastener for anchoring boxes, straps or supports through furring, sheathing or shimmed gaps rather than a thin sheet metal screw.

The head is an indented hex with an integral washer face, outside diameter 0.398 to 0.432 inch and 0.022 to 0.039 inch thick. That washer face spreads the load and bears flat against a flange or strap, so you generally do not need to add a separate flat washer. Head height is 0.139 to 0.155 inch, so it sits low.

The JDS83 is carbon steel with a zinc plated finish. Zinc plating handles indoor, dry and lightly damp interior conditions such as mechanical rooms and electrical rooms. For sustained exterior exposure, washdown areas or coastal work, a stainless or hot dip galvanized fastener is the better call.

The JDS83 is flagged as both ARRA compliant and Buy American compliant in Metallics' product data, which is the documentation a public agency or institutional procurement office typically asks for. Country of origin is listed as multiple.

They come in a jar, with a minimum order of 100 count. Packed weight is 2.47 lbs. That jar format is what you want on a cart or in a gang box rather than a loose bag.

Head dimensions follow ASME B18.6.3-2010 and the threading follows ASME B18.6.4, which is the tapping screw thread standard. One note for spec writers: Metallics states that #9 diameter dimensions in this family are independent of ASME B18.6.4. The JDS83 is a #12.