Metallics JDS179SS 14 x 2 in. 3/8 Indented Hex Head Slotted Sharp Point Tapping Screws - 18-8 Stainless - Each

Either works. The JDS179SS has an indented hex head measuring 0.367 to 0.375 in. across the flats, so a 3/8 in. socket or nut driver seats on it, and the head is also slotted (slot width 0.064 to 0.075 in., depth 0.083 to 0.101 in.) if you need to finish or back it out by hand. Width across corners is 0.409 in., which is what matters if you are driving in a tight pocket.

It is a Type A sharp (gimlet) point screw with 10 threads per inch, so it starts in thin sheet metal, and it forms its own thread as it drives. In heavier gauge or structural steel you still want a pilot hole sized to the thread, because Type A is a thin-sheet thread form, not a self-drilling screw. There is no drill point on this one.

Metallics lists the JDS179SS as both Buy American compliant and ARRA compliant. Country of origin is recorded as multiple, so if your spec requires a documented single origin, confirm on the lot you receive.

They can be. 18-8 stainless in contact with aluminum or steel can set up a galvanic couple in wet or coastal environments, which corrodes the softer base metal rather than the screw. For exterior or damp locations, isolate the joint or use a fastener matched to the base metal. Indoors and dry, the 18-8 stainless is the point of the screw, it won't rust out like a plated carbon screw.

The head is an indented hex with an integral washer face, listed at 0.480 to 0.520 in. outside diameter and 0.030 to 0.050 in. thick. That gives you a bearing surface wider than the 3/8 in. hex, so you generally don't need to add a separate flat washer on sheet metal.

Sold in a jar of 100 count, which is the order minimum. Shipping weight on the jar is 2.69 lbs. Other sizes and quantities in the JDS series are available by request.

Head dimensions follow ASME B18.6.3-2010 and the thread form follows ASME B18.6.4, which is the tapping screw standard. Hardness is Rockwell C28-38. That combination is what a submittal on an electrical or sheet metal package usually asks for.

Overall fastener length is 2 in., threaded for essentially its full length under a head that stands 0.172 to 0.19 in. tall. Subtract the thickness of what you are fastening through to get your thread engagement in the base material; a #14 at 10 TPI needs several threads engaged to hold, so for thick standoffs go to a longer screw in the JDS series rather than relying on the tip.