Metallics JRM135SLT 3/8-16 x 4 in. Round Head Slotted Machine Screws - Steel Zinc - Each

The JRM135SLT is a 3/8-16 machine screw, meaning a 3/8 inch nominal diameter with 16 threads per inch. That is the coarse (UNC) pitch for 3/8, so it mates with standard 3/8-16 nuts, tapped holes, strut channel nuts and threaded inserts. Overall length is 4 inches.

Neither. The JRM135SLT is a low carbon steel machine screw rated at 60,000 psi minimum tensile, made from AISI 1006 to 1022 steel with a hardness of Rockwell B70 to B100. That is general fastening strength, not structural bolt strength. For a load path that calls out Grade 5 or Grade 8 on the drawing, use a hex cap screw instead, not a slotted round head machine screw.

It does not sit flush. A round head is a domed, above-surface head, so no countersink is needed and no countersink will hide it. The head stands 0.237 to 0.256 inches proud and spans 0.67 to 0.708 inches across, so leave that much clearance around the hole. Drill a clearance hole for the 3/8 inch shank, typically a 25/64 inch bit. If the head has to finish flush with the surface, use a flat head machine screw with a countersunk hole instead.

They ship 50 to a jar, and 50 count is the order minimum. If you need a smaller count or a different length, Metallics notes other sizes and quantities are available by request.

These are zinc plated carbon steel, which is a mild indoor and dry-location finish. Zinc handles general humidity and incidental moisture, but in exterior, washdown, coastal or chemical exposure it will eventually bloom white and then rust. For those openings, specify a stainless machine screw in the same 3/8-16 x 4 size instead.

The JRM135SLT is slotted only, with a slot 0.081 to 0.094 inches wide and 0.117 to 0.155 inches deep. A flat blade in a slot has no self-centering, so overhead or one-handed work is slower and more prone to cam-out than a Phillips or combination head. Metallics does offer a full combo line, so if you are driving these overhead in a panel or box, a combo head 3/8-16 x 4 is the easier screw to run. Slotted is still the right choice when you are matching existing hardware or finishing a visible plate.

No. The 50 count jar of JRM135SLT is screws only. A 3/8-16 machine screw either threads into a tapped hole or needs a matching 3/8-16 nut, and if you are bolting through sheet metal or a soft substrate you will want flat washers under the head and nut as well. Order those separately.

The JRM135SLT is flagged compliant for both Buy American and ARRA in the manufacturer data, while country of origin is listed as China. On a federally funded project where the specification or the contracting officer requires domestic melt and manufacture, that origin is the controlling fact, so confirm the requirement wording before you submit these.

The 50 count jar weighs 5.65 lbs. That is a real weight for a tool bag, so for a long overhead run most electricians decant into a pouch rather than carry the jar.