Metallics JQK1 7 x 1/2 in. 1/4 Hex Head Slotted Sharp Point Self-Piercing & Tapping Screws - Steel Zinc - Each

No pilot hole needed in thin sheet metal. The JQK1 is a sharp point self-piercing and tapping screw, so the point punches through and the thread forms its own mating thread as you drive. Twin lead threads cut the driving torque, which is what keeps the point from walking on light gauge steel.

Two options on the same screw. The head is a 1/4 inch hex, measuring 0.244 to 0.25 inch across, so a 1/4 inch hex driver or nut setter fits it. The head is also slotted, with a slot 0.039 to 0.048 inch wide and 0.04 to 0.062 inch deep, and the specified driver size for that slot is a #8. Most electricians run the hex and keep the slot for tight spots where a nut driver will not reach.

No. The JQK1 is not Buy American compliant and is not ARRA compliant, and country of origin is listed as multiple. On federally funded or domestic-preference work, these will not satisfy the clause and you need a domestically produced fastener instead.

It is heat treated to Rockwell C28-38 from AISI 1018 to 1022 steel, which is the case hardness range a tapping screw needs to form threads in mild steel rather than deform against it. That hardness is also why you should not over-torque it with an impact driver; the point and lead thread can snap before the head gives.

Zinc plated carbon steel is what you get here, which handles indoor and protected-damp service such as mechanical rooms, plenums and duct chases. For direct weather exposure, salt air or wet locations, a zinc plating is not a long-term corrosion answer, and a stainless fastener is the right call instead.

They ship in a jar of 100, and 100 is the order minimum, so this is bought by the jar rather than by the piece. Figure roughly 0.32 lb for the packed jar.

Thread-wise the sizes are similar, but the heads are not interchangeable in a spec sense. Metallics notes that head dimensions of self-piercing screws differ from those of standard tapping screws, and that no single standard governs self-piercing screw dimensions, so the published values are a guide and deviations can occur. If the detail calls for a self-piercing screw with a sharp point, order the JQK1 rather than a conventional tapping screw.

The undercut area beneath the head frees up more of the 1/2 inch shank for thread, so you get a greater length of thread engagement in the material than you would with a thread that runs straight into the head. On thin stock that is the difference between a couple of threads holding and the screw actually clamping.