Metallics QK510M 8 x 1/2 in. 1/4 Hex Head Slotted Sharp Point Self-Piercing & Tapping Screws - Steel Zinc - Each

No pilot hole. The QK510M is a sharp point self-piercing and tapping screw, so it pierces thin sheet metal and forms its own thread as it drives. Twin lead threads cut the driving torque, and the undercut under the head lets more thread engage the material.

Half an inch of overall length is all you get, so plan on light gauge sheet metal work: electrical boxes, duct, hanger straps, plates. Thread count is 15 per inch, and with an undercut below the head most of that 1/2 inch is usable thread engagement. If your stack-up is deeper than the screw, step up to a longer length in the same JQK series.

Metallics lists the QK510M as both Buy American compliant and ARRA compliant. Country of origin is recorded as multiple, so if your specification demands documentation for a specific mill or country, request the certification with the order.

Two options on the same screw. The head is a 1/4 inch hex, measuring 0.244 to 0.25 inches across, so a 1/4 inch nutdriver or hex socket fits it. It also has a slot in the top (0.045 to 0.054 inches wide, 0.052 to 0.074 deep), so a flat blade works when you cannot get a socket in. Head height runs 0.096 to 0.11 inches.

The screw is case hardened to Rockwell C28-38 and made from AISI 1018 to 1022 steel, which is what lets the sharp point punch through light gauge sheet without a pilot. That hardness is for piercing thin material, not for driving into structural steel.

It spreads the load. The integral washer measures 0.322 to 0.348 inches outside diameter and 0.019 to 0.031 inches thick, which gives bearing area over sheet metal and slotted holes. There is no gasket or bonded sealing washer, so for weather exposure you need a separate sealing washer or a different screw.

The QK510M is zinc plated steel, which is a dry-location and mildly damp finish. It is fine inside boxes, panels, and covered areas. For direct weather, coastal, or wet locations, specify stainless or a coated exterior fastener instead.

They ship in a box with a 10,000 piece minimum, and the packed box weighs 29.52 lbs. That is a bulk contractor quantity, not a small shop pack, so size your order accordingly.

No. Metallics notes that self-piercing screw head dimensions differ from standard tapping screws, and there is no single industry standard governing them. The figures given for the QK510M head, slot, and washer are a guide and small deviations can occur, so if you are matching an existing fastener in a slotted or countersunk hole, check the head against the part in hand.