Metallics JRM135 3/8-16 x 4 in. Round Head Combo Machine Screws - Steel Zinc - Each

Either one. The JRM135 is a combo head, slotted and Phillips in the same round head, so a #4 Phillips driver or a flat blade both work. The slot runs 0.081 to 0.094 inch wide and 0.117 to 0.155 inch deep; the Phillips recess is 0.374 to 0.387 inch across and 0.202 to 0.228 inch deep. Practical upshot for an electrician working overhead: whatever is already on your belt drives it.

The thread is 3/8-16, that is 16 threads per inch on a 3/8 inch diameter, which is the standard coarse machine screw thread in that size. It will engage any 3/8-16 tapped hole or nut. At 4 inches of length you get plenty of reach for stacking strut, backing plates or spacers; just confirm your nut or tapped hole is 16 TPI and not a fine thread.

The JRM135 is zinc plated steel, AISI 1006 to 1022 low carbon stock. Zinc plating is a mild corrosion barrier suited to dry indoor work: panels, enclosures, device mounting, HVAC and plumbing fixings inside the building. For wet, washdown or exterior exposure, step up to a stainless machine screw of the same 3/8-16 x 4 size instead, since plating wears and scratches through at the drive and the threads.

No. The JRM135 is not Buy American compliant and is not ARRA compliant, with country of origin listed as multiple. On a federally funded project with domestic sourcing language in the spec, this screw will not qualify and you will need a domestically produced fastener instead.

The round head measures 0.67 to 0.708 inch across and stands 0.237 to 0.256 inch above the surface. Round head means it sits proud rather than flush, so it needs no countersink in the panel, but allow about a quarter inch of clearance if anything mounts over the top of it. If you need the fastener flush, a flat head screw is the right choice instead.

Minimum tensile strength is 60,000 psi, with a case hardness of Rockwell B70 to B100. That is standard low carbon machine screw strength, fine for mounting panels, boxes, brackets and equipment. It is not a structural or high strength bolt, so for load bearing or seismic bracing work specify a graded hex bolt rather than a machine screw.

They come in a jar, with a 50 each minimum order quantity. Shipping weight on the jar is listed at 5.65 lbs. For a shop or truck stock item the jar keeps the 4 inch screws together rather than loose in a bin; if you need a different count or a different size in this series, Metallics lists other sizes and quantities as available by request.