Metallics JDSP157 8 x 1-1/2 in. 1/4 Hex Head Phillips Sharp Point Tapping Screws - Steel Zinc - Each

The Metallics JDSP157 uses a gimlet point, which is the sharp, drill-bit-like tip that starts itself in thin sheet metal, so light-gauge steel studs, duct, and enclosure flanges generally take it without pre-drilling. It is a Type A tapping screw with 15 threads per inch, a coarse thread built to form its own mating thread as it drives. Heavy or thick stock still wants a pilot hole sized to the screw's root diameter.

Either. The head is a 1/4 inch hex with a Phillips recess in the top, so you can run it with a 1/4 inch nut driver or socket, or drop a #2 Phillips bit into the recess. Head width measures 0.244 to 0.25 in. and head height 0.096 to 0.11 in. The Phillips recess diameter is 0.168 in. with a gaging depth of 0.090 to 0.115 in., which is why a #2 bit seats properly and a #1 will cam out.

Metallics flags the JDSP157 as compliant under both Buy American and ARRA, with China as the country of origin. If your contract enforces a domestic melt-and-manufacture clause rather than the ARRA/Buy American designation, verify against your specific contract language before you commit the material.

Yes, it is a hex washer head. The integral washer runs 0.322 to 0.348 in. outside diameter with a washer thickness of 0.019 to 0.031 in., so it spreads the clamp load wider than the 1/4 in. hex alone and helps keep the screw from pulling through thin sheet or soft strap. That bearing face is why these get used on box mounting and bracket work where a plain hex head would dimple the material.

They are rated to 39 lb-in minimum torsional strength and case hardened to Rockwell C28-38, made from AISI 1016-1024 steel. That hardness is what lets the gimlet point cut its own thread in sheet steel. On a high-torque impact driver you can still twist the head off a #8 once the screw bottoms, so back off the clutch or finish with a nut driver on the 1/4 hex.

The finish is zinc plating over steel, which is a mild indoor corrosion coating. It holds up fine in dry interior work, panel and enclosure mounting, framing and strap. For exterior exposure, wet locations, or coastal air, go to a stainless or hot-dip galvanized fastener instead; zinc plate will rust through and stain the surface it's in.

These ship 100 to a jar, and 100 count is the order minimum. Metallics also builds the JDSP series in other diameters and lengths on request if 8 x 1-1/2 in. isn't the size you need.

Two apply. Head and drive dimensions follow ASME B18.6.3-2013, and the thread follows ASME B18.6.4, the tapping screw standard. One caveat Metallics states outright: dimensions for #9 diameter screws in this series fall outside ASME B18.6.4. The #8 covered here is within it.

A Type A like the JDSP157 has a gimlet point, coarse 15 TPI thread, and it forms its thread in sheet metal or into a pre-punched hole. It starts fast in thin gauge but has no drill flute, so in heavier steel it walks or work-hardens instead of cutting. A self-drilling screw carries an actual drill tip that bores its own hole through thicker stock in one pass. For light-gauge electrical work, boxes, straps, and duct, the Type A is the normal choice; for structural or heavier-gauge steel, use a self-drilling point.