Metallics JRM121 10-32 x 4 in. Round Head Combo Machine Screws - Steel Zinc - Each

The Metallics JRM121 is a 10-32 thread, 4 inch long machine screw, so it gives you about 4 inches of usable thread past the round head. That is the length people reach for when a device or fixture has to be held off a box through stacked extension rings, plaster rings, or thick finish material. For a flush box with just a mud ring, 4 inches is far longer than needed and the excess has to be cut or run into free space behind the box.

Yes. 10-32 with 32 threads per inch is the standard machine screw thread used in outlet box mounting holes, device yokes, ground screw holes, and fixture straps across the electrical trade, so the JRM121 mates with that tapped prep directly. It is a machine screw, not a self-tapping screw, so the hole must already be tapped 10-32.

Either one. The JRM121 head is a combo recess, slotted and Phillips in the same head, so a flat blade or a Phillips bit both work. Metallics calls for a #2 driver size on the Phillips side. The slot runs 0.05 to 0.06 inch wide and 0.065 to 0.087 inch deep, so a cabinet-tip blade seats better than a wide carpenter's screwdriver. The Phillips recess is 0.182 to 0.195 inch across with 0.093 to 0.119 inch depth.

It stands proud. The JRM121 has a round head measuring 0.334 to 0.359 inch across and 0.123 to 0.137 inch high, with no flat underside taper, so it bears on top of the surface rather than pulling flush. For anything that has to finish flush, such as a countersunk cover plate, you want an oval or flat head machine screw instead.

The JRM121 is AISI 1006-1022 low carbon steel with a zinc finish. Zinc plating handles dry interior work, box mounting, and panel interiors. It is a sacrificial coating, so for wet or exterior locations, coastal air, or anywhere washdown chemicals are in play, go to a stainless 10-32 machine screw instead.

Minimum tensile strength on the JRM121 is 60,000 psi with a hardness of Rockwell B70 to B100, which is ordinary low carbon steel machine screw territory. Fine for holding devices, straps, covers, and fixture hardware. It is not a structural or high strength fastener, so do not treat it like a Grade 5 bolt or lean on it with an impact driver in a tapped hole, especially at 4 inches of length where bending and snapping are the real risks.

Metallics lists the JRM121 as both ARRA compliant and Buy American compliant, with China given as country of origin. On a federally funded job, submit those compliance designations with your package, since compliance program and origin are evaluated separately by the contracting authority.

They ship in a jar, 100 count, and 100 is the order minimum. That is the usual way a shop or MRO storeroom buys a single size to keep on the truck or in a bin rather than counting out loose pieces.

Metallics publishes 2.81 lbs for the JRM121 jar of 100, with carton figures of 5.75 in. height and 3.5 in. length and width. Useful if you are building out a storeroom order or checking freight on a multi-size fastener pull.