Metallics TP138SBC Screws 3/8-16 x 1-1/2 Btn Hx Pin TR M (100 pcs)

The TP138SBC is a 3/8-16 x 1-1/2 inch machine screw. The 3/8-16 is the standard coarse (UNC) thread pitch for 3/8 inch diameter, so it mates with 3/8-16 tapped holes and standard 3/8-16 nuts. Length is 1-1/2 inches of screw, so plan your grip: substrate plus any bracket or spacer has to fall within that with enough thread engaged at the far side.

A pin-in-hex (hex pin) driver bit, not a plain Allen key. The TP138SBC has a button head with a hex socket and a solid pin standing in the center of that socket, so a standard hex wrench bottoms out on the pin and will not turn it. You need a hollow hex bit sized to the socket with a bore for the pin. If your crew does not already carry pin-in-hex bits, order them with the screws or the job stalls.

Only where there is a tapped 3/8-16 hole or you are using a nut on the back side. The TP138SBC is a machine screw, not a self-tapping or self-drilling sheet metal screw, so it needs mating threads already there. For thin gauge enclosure sheet, that usually means a weld nut, a tapped boss, or a 3/8-16 nut or threaded insert behind the panel. If the hole is untapped and you cannot reach the back, this is the wrong fastener type.

Both. The TR designation on the TP138SBC means tamper resistant, and the resistance comes from the center pin in the hex socket, which defeats common hex keys and bits found in a toolbox. The button head also sits low and domed with no flats or slot to grab, so there is little for pliers to bite. It is deterrence against casual removal, which is what you want on enclosure covers, guards, grilles, and public-area fixtures.

100 pieces per box. That is a quantity sized for an MRO shelf or a repeat install where a crew is setting the same fastener across many covers or plates, rather than a handful for one repair. One box, one part number: TP138SBC.