Metallics JTRM99 1/4-20 x 1/2 in. Round Head Tri-Drive Machine Screws - Steel Zinc - Each

The JTRM99 is a 1/4-20 machine screw, 1/2 inch long. That means a 20 threads-per-inch coarse machine thread, so it mates with a 1/4-20 tapped hole or a 1/4-20 nut. The short 1/2 inch length suits thin sheet metal boxes, enclosure covers, and strut fittings where there is little room behind the hole.

Whatever you already have on the truck. The JTRM99 round head is cut for three drives at once: slotted, Phillips, and square. An electrician can set it with a flat blade, a #2 Phillips, or a square-drive bit without changing tips, which is the whole point of the tri-drive head on panel and device work.

Yes for dry, indoor use. The JTRM99 is steel with a zinc plating, which handles normal interior panel, box, and enclosure duty. Zinc-plated steel is not a wet-location or exterior fastener, so for outdoor, washdown, or corrosive areas go to a stainless 1/4-20 machine screw instead.

It depends on your stack-up. At 1/2 inch of overall length under the round head, the JTRM99 gives you enough thread for sheet metal plus a nut or a tapped hole, but not for stacking brackets or thick material. Add your material thickness plus the thread engagement you need and compare against the 1/2 inch before ordering; if it comes up short, step up to a longer 1/4-20 in the same series.

It stands proud. A round head bears on top of the material rather than sinking into it, so no countersink is needed and you get a wide bearing surface against sheet metal. If you need the fastener flush with a cover or plate, a round head is the wrong choice; specify a flat or oval head instead.

They ship in a jar, which is how most shops want a loose machine screw on the bench or in the van bin rather than in a strip or a carded pack. The part number to order is JTRM99.