Metallics JFMP105 1/4-20 x 3 in. Flat Head Phillips Machine Screws - Steel Zinc - Each

Standard 1/4-20 UNC coarse thread, 20 threads per inch, cut to ANSI/ASME B1.1. Any off the shelf 1/4-20 hex nut, coupling, or tapped 1/4-20 hole takes them. They are not fine thread, so a 1/4-28 nut will not run on.

A #3 Phillips bit. The recess on these 1/4-20 flat head screws measures 0.276 in. diameter, 0.16 in. deep, with a 0.036 in. recess width, so a #2 bit will cam out and chew the recess under torque. Keep #3 bits in the pouch if you are running a jar of these.

Fastener length is 3 inches measured from the underside of the head, and because this is a flat head that length sits inside the countersunk hole rather than on top of the work. Subtract whatever you need protruding for the nut and you have your usable grip. For a run of thinner panels, a shorter length in the same FM and FMP series is the better call.

1900 lb minimum tensile, with a hardness of Rockwell B70 to B100, made from AISI 1006 to 1022 low carbon steel. That is a standard commercial machine screw, fine for enclosures, strut, panels, and fixture mounting. For a structural or high load connection you want a graded bolt instead, not a machine screw.

These are steel with a zinc finish, which is an indoor and dry location plating. It resists handling corrosion and incidental moisture, not sustained wet exposure or washdown. For exterior, coastal, or wet locations, step up to a stainless machine screw in the same 1/4-20 x 3 in. size.

The JFMP105 is flagged compliant for both ARRA and Buy American in Metallics' data, with country of origin China. If your contract spec requires domestic melt and manufacture rather than the broader compliance flag, verify against the exact clause on your project.

They ship in a jar of 100 count, and 100 is the minimum order. The packed jar weighs 3.38 lbs. Good buy for an electrical crew or MRO stockroom that burns through 1/4-20 hardware; if you only need a handful, a 100 count jar is more than you want.

Gaging diameter is 0.424 in., with head protrusion running 0.029 to 0.050 in. above the gage. That is the inspection check that confirms the countersunk head seats to the right depth, and it is the number a QC or institutional buyer wants when the screws have to match a drawing callout rather than just hold a cover plate.