Metallics JTEKD24 10 x 2-1/2 in. 5/16 Indented Hex Head Self-Drilling & Tapping Screws with Washer - #2 Drill Point - Steel Zinc - Each

No pilot hole. The JTEKD24 is a Type BSD self-drilling and tapping screw, so the #2 drill point cuts its own hole and the 16-TPI thread taps it in the same operation. Keep it inside the rated 0.035 to 0.110 in. panel thickness and run it with steady pressure.

The JTEKD24 is AISI 1016-1024 carbon steel with a zinc finish, which is a dry-location, indoor-grade coating. For exterior runs, damp mechanical rooms, or anywhere washdown or salt air is a factor, specify a stainless self-drilling screw instead. Note that minimum torque values are the same for stainless and steel self-drillers, so you don't give up drive strength by switching.

No. The JTEKD24 is not Buy American compliant and not ARRA compliant, with country of origin listed as multiple. On a federally funded project with domestic sourcing requirements, you'll need a domestically produced fastener instead.

A 5/16 in. hex driver or nutsetter. The head is an indented hex washer head measuring 0.305 to 0.312 in. across the flats, 0.34 in. across corners, with head height of 0.105 to 0.12 in. Standard 5/16 magnetic nutsetter in an impact or screwgun drives it.

The washer is formed as part of the head, not a loose piece. Outside diameter runs 0.384 to 0.414 in. with a washer thickness of 0.019 to 0.031 in., so it spreads load over the hole and seats flat against sheet metal or strap without adding a part to drop on the floor.

Sold in a jar of 100 pieces, which is the order minimum. The jar weighs 1.57 lbs. One jar covers a typical day of strut, box, and strap mounting for a single installer.

Threads follow SAE J78-2013 and head dimensions follow ASME B18.6.3-2010. Core hardness is Rockwell C32-40 with a minimum torsional strength of 61 lb-in. Steel is AISI 1016-1024. Those four values are what a spec reviewer normally asks for on a self-drilling tapping screw.

Length gives you reach through stacked material, not extra holding power in the steel itself. The thread only grips the 0.035 to 0.110 in. panel it taps into, so a 2-1/2 in. #10 is the choice when you're passing through standoffs, insulation, strut, wood blocking, or a thick box flange before reaching the sheet steel. If there's nothing to span, a shorter screw does the same job in less drive time.

They're specified for electrical, plumbing, heating and air conditioning work. In practice that means hanging boxes and panels to metal studs, fastening strut and strap, duct and sheet metal connections, and securing equipment to metal framing where the installer wants a hex drive he can seat hard without cam-out.

Drill time is 2.5 seconds through a 1 mm thick plate. If a screw is spinning much longer than that without advancing, the point is burnishing rather than cutting, usually from too little pressure, too high an RPM, or material thicker than the rated 0.110 in. maximum.