4-40 Screws in Flat, Button and Socket Head Styles
Shop 4-40 precision screws for frame and mechanical assemblies, EDC gear and tight-clearance builds that need fasteners held to close tolerances. Stainless steel Torx screws come in 25-packs, and single screws include a black oxide Phillips flat head and titanium from CKK Design and SK Design.
Every screw in this category shares the 4-40 thread, so choosing one comes down to head shape, drive, material and pack size. A flat head sits flush, a button head gives a smooth, rounded finish, and a socket head gives a secure recessed fit. Stainless steel 25-packs cover a T-8 flat head at 0.250in, a T-8 button head with 0.250in or 0.500in threads, and a T-10 shallow socket head, all with Torx drives. Made in the USA, that socket head is DFARS compliant 302HQ stainless with a 0.174in head.
The remaining screws are sold one at a time. A 0.365in Phillips flat head in black oxide coated stainless was designed with #4 finishing washers in mind and also works as a replacement or companion for #6 Chicago Screws. From CKK Design, 6AL4V titanium button and socket heads share a 0.210in head diameter and a T-8 drive, with a finish that can be heat-colored. Steve Kelly's SK Design titanium socket head comes in 0.250in and 0.375in thread lengths, and its shallow 0.060in head gives a flush, low-profile finish with little material removed.
Assemblies that take the 8-32 thread are covered back under Screws. For a 4-40 pick, message us the head height and thread length you need and we will point you to a match.