Metallics JTSF26 8 x 2-1/2 in. Flat Head Phillips Tapping Screws - Steel Zinc - Each

The JTSF26 is a #8 by 2-1/2 inch Type A tapping screw with a gimlet point. A gimlet point Type A thread is made for forming its own thread in sheet metal, resinous plywood and similar softer sheet materials in a pre-punched or drilled pilot hole. It is a thread-forming screw, not a machine screw, so it does not run into a tapped nut or threaded insert.

Metallics lists the JTSF26 as both ARRA compliant and Buy American compliant. Country of origin is recorded as multiple, so if your submittal package requires a specific mill country per lot, that is worth confirming against the shipment paperwork.

Yes. Dimensions are to ASME B18.6.4-1998 and the thread is to ASME B18.6.4. Material is AISI 1016 to 1024 steel, case hardened to Rockwell C28-38, with a minimum torsional strength of 39 lb-in. One caveat Metallics states: dimensions for #9 diameter screws in this family fall outside ASME B18.6.4, though the JTSF26 itself is a #8.

A #2 Phillips bit. The recess is a Phillips drive measuring 0.182 inch diameter and 0.11 inch deep, so a #2 seats fully; a #1 will cam out and a #3 will not bottom in the recess.

Flat head means it is designed to finish flush in a countersunk hole. The head measures 0.285 to 0.312 inch across with a head height of 0.084 to 0.1 inch, so you need an 82 degree countersink of roughly that diameter in the top material for a flush finish. Drive it into a flat, uncountersunk surface and the head will stand proud by about the head height.

They ship 100 to a jar, and 100 count is the order minimum. The filled jar weighs 1.05 lbs.

The JTSF26 is carbon steel with a zinc plated finish. Zinc plating handles indoor and dry or occasionally damp conditions, but it is not a stainless or hot dip galvanized screw. For sustained exterior exposure, coastal air, or contact with treated lumber, specify a stainless or hot dip galvanized fastener instead.

Size the hole off the gaging diameter, which Metallics lists at 0.267 inch for the JTSF26, and the 15 threads per inch thread form. In sheet metal the clearance hole goes in the lower material at roughly the screw's minor diameter so the thread can form and grip, while the top sheet gets a clearance hole plus countersink for the flat head. Thinner gauge takes a smaller hole; too large a hole and a Type A will spin without holding.

At 2-1/2 inches of overall length, the JTSF26 passes through 5/8 inch board and still leaves well over an inch and a half of thread in the substrate, which is more than enough engagement into framing or track. Keep in mind this is a Type A gimlet point tapping screw, so it is thread forming for sheet and soft sheet material rather than a self drilling point for heavy gauge steel.

A flat head measuring only 0.285 to 0.312 inch across has limited bearing area, so in very thin gauge sheet or soft panel the head can pull through under load. Where the head is carrying load rather than just locating a part, a pan or washer head, or a flat head with a finish washer, gives more bearing surface. The flat head is the right choice when you need the fastener flush with the surface.