Metallics QK18M 7 x 1/2 in. 1/4 Hex Head Slotted Sharp Point Self-Piercing & Tapping Screws - Steel Zinc - Each

That's what the sharp point is for. The QK18M pierces and taps its own hole in thin sheet stock, so no pre-drilling. Twin lead threads cut the driving torque, and the case-hardened steel (Rockwell C28-38, made from AISI 1018-1022) is what lets the point bite instead of walking. It's a #7 diameter screw, 1/2 inch long, with 16 threads per inch, so the working range is thin gauge material, not structural steel.

A 1/4 inch hex nut driver or nut setter. The head is hex, measuring 0.244 to 0.25 inch across, with a head height of 0.08 to 0.093 inch. It's also slotted, with a slot 0.039 to 0.048 inch wide and 0.04 to 0.062 inch deep, so a small flat blade works when you can't get a socket in. Most crews run the hex on a driver and keep the slot as the backup for tight spots or removal.

Both are flagged compliant on the QK18M, which is what a government, school district, or federally funded project needs on the submittal. Country of origin is listed as multiple, so if your specification requires a single named origin on the certification, confirm the origin on the lot you receive before it goes into the submittal package.

There's an integral washer under the hex, 0.322 to 0.348 inch outside diameter and 0.017 to 0.029 inch thick. That spreads the clamp load wider than the 1/4 inch hex alone, which matters when you're pulling down a strap, clip, or a piece of thin trim that would otherwise dimple. Below the washer is an undercut that gives you more usable thread engagement in the material.

Keep it inside. The QK18M is zinc plated carbon steel, which handles indoor conditioned space, panel interiors, and dry mechanical rooms. It is not a stainless or hot-dip coating, so wet exterior work, coastal exposure, or anywhere it sits in standing moisture will eventually rust the plating through. For exterior or wash-down duty, spec a stainless self-drilling screw instead.

It ships as a bulk box, 8,000 pieces to the order minimum. That's a stocking quantity for a shop that runs self-piercing screws daily, not a job-box handful. The full box weighs 25.6 lbs and the carton runs 7.75 x 6.75 x 6.75 inches. Metallics does list other sizes and quantities of this screw on request.

A self-piercing screw makes its own hole; a standard tapping screw needs one already there. The QK18M has a sharp piercing point that punches through thin gauge stock and then taps threads on the way in, so an electrician setting straps or covers doesn't stop to drill. One thing to know when you're matching what's on the job: head dimensions on self-piercing screws differ from standard tapping screws, and there's no single industry standard governing self-piercing screw dimensions, so treat the published numbers as a guide rather than a hard tolerance.

Case hardness runs Rockwell C28-38 on 1018-1022 low carbon steel, which is the standard range for a thread-forming fastener: hard enough for the point and threads to cut into light gauge steel, soft enough in the core that the screw doesn't snap under a driver. It won't tap thick plate or hardened stock. If the base material is heavier than light gauge, drill and use a machine screw.