Metallics JRM131SLT 1/4-20 x 3-1/2 in. Round Head Slotted Machine Screws - Steel Zinc - Each

The JRM131SLT is a 1/4-20 machine screw, meaning a 1/4 inch nominal diameter with 20 threads per inch, which is the standard UNC coarse pitch for that diameter. It will thread into a 1/4-20 nut or a tapped 1/4-20 hole, and it will not mate with 1/4-28 fine threads.

Length is 3-1/2 inches measured under the round head, so the full 3-1/2 inches is usable grip plus thread engagement. That covers deep box extensions, stacked spacers, or thick fixture canopies where a 1 or 2 inch screw bottoms out short. The round head is low, 0.16 to 0.175 inch high and 0.443 to 0.472 inch across, so it sits on the surface rather than countersinking.

No. The JRM131SLT is listed as not Buy American compliant and not ARRA compliant, with country of origin recorded as multiple. On a federally funded project with domestic sourcing language, you will need a domestically produced fastener instead.

No. A round head has a domed top and a flat bearing face, so it stands proud of the surface by roughly 0.16 to 0.175 inch. If the plate or cover is countersunk, you want a flat head instead. Round head is the right pick for plain drilled holes and flat cover plates where a raised head is acceptable.

Slotted drive. The slot is 0.064 to 0.075 inch wide and 0.082 to 0.109 inch deep, so a standard flat blade tip matched to that width is what you want. Slotted heads cam out easily under power, so hand driving or a low-speed clutch gives better results than an impact driver.

Minimum tensile strength is 60,000 psi, with a hardness of Rockwell B70 to B100, made from low carbon steel in the AISI 1006 to 1022 range. That is standard low carbon machine screw material, fine for fixture mounting, cover plates, and general electrical assembly. For structural or high load joints you want a graded bolt rather than a machine screw.

These are zinc plated low carbon steel, which is a mild indoor corrosion coating. Dry interior work, panel and fixture assembly, and protected boxes are fine. For wet locations, coastal exposure, or washdown areas, step up to a stainless machine screw of the same 1/4-20 x 3-1/2 size.

They come in a jar with a 100 count order minimum, so the buying unit is 100 screws. That suits a shop or truck stock item rather than a one-off repair. Metallics lists other sizes and quantities as available by request.

No, the JRM131SLT ships as screws only, 100 to a jar. You thread them into a tapped 1/4-20 hole or supply your own 1/4-20 nuts and washers separately.