Metallics JSPMP144SS 4-40 x 1/4 in. Pan Head Phillips Machine Screws - 18-8 Stainless - Each

4-40 is not the thread used on wiring device and cover plate screws, so these will not thread into a standard outlet box or device strap. They are 40 threads per inch on a #4 diameter, which is the small machine screw size used in control panels, instrument plates, enclosure internals and small bracketry. For device mounting you want a 6-32 machine screw.

The JSPMP144SS is flagged compliant for both Buy American and ARRA. Country of origin on record is China. On a federally funded project where the specification itself dictates domestic melt and manufacture, verify against your spec section before you submit.

A #1 Phillips driver is the correct size for these screws. The recess measures 0.115 in. across, so a #2 bit will cam out and chew the head on a screw this small. Keep a #1 bit in the pouch if you are installing these in volume.

The 1/4 in. is the shank length under the pan head, and the head itself adds 0.07 to 0.08 in. on top of the surface. Pan heads are not countersunk, so none of that length is lost into the work. Practically, you get about 1/4 in. of thread engagement total, which means thin sheet, a tapped boss, or a nut on the back side. For stacking a bracket plus a plate you will usually need a longer length.

The pan head measures 0.205 to 0.219 in. across and stands 0.07 to 0.08 in. proud of the surface. That is the footprint to check against a counterbore, a slot, or a recessed pocket before you commit. Dimensions follow ASME B18.6.3-2010, so the head geometry matches any other B18.6.3 pan head 4-40.

18-8 stainless is the austenitic grade used where plated steel would rust, so these hold up in damp interiors, outdoor enclosures and wash-down areas far better than a zinc machine screw. Pair them with stainless or non-ferrous hardware to avoid galvanic problems. They are not a marine-grade 316.

80,000 psi minimum is the figure carried on the SPMP stainless screws, with hardness listed as Rockwell BBS-B9S. Treat the tensile number as an approximation, there is no single performance standard for stainless machine screws the way there is for graded steel bolts. If the connection is structural or load bearing, specify a graded steel fastener instead.

It is a straight machine screw, 4-40 thread, blunt end. It needs a tapped hole or a mating nut, it will not form its own thread in sheet metal. For sheet without a tapped hole you want a self-drilling or sheet metal screw instead.

They ship 100 to a jar, and 100 count is the order minimum. The jar packaging is the practical part for a service van or a panel shop bench, you are not fishing screws out of a torn poly bag.

Order Metallics JSPMP144SS. It is part of the SPMP machine screw series, and Metallics offers other diameters, lengths and pack quantities in that same series on request.