4-40 x 1/4 18-8 Stainless Steel Button Head Socket Cap Screw with Nylon Insert uses a low-dome head for exposed fastening where a smooth, reduced-profile shape matters. The nylon pellet presses against the mating thread for prevailing torque without changing the head geometry.

The rounded button head can reduce exposed edges, spread bearing load over a broader face, and avoid counterbore machining when the assembly accepts a raised dome. Typical applications include machine guards, removable covers, and service panels, where exposed hardware benefits from a smooth dome and exact thread-length match.

The 18% chromium and 8% nickel austenitic stainless material is commonly chosen for general corrosion resistance, clean appearance, and ordinary moisture exposure. For chloride-heavy or saltwater-adjacent service, 316 stainless with nylon insert is a non-catalog request Cold Headers can quote. Cold Headers has supplied specialty socket fasteners since 1962 and helps buyers source exact stainless sizes and uncommon lengths.

Technical Highlights

• Material: 18-8 Stainless Steel
• Thread Size: 4-40
• Length: 1/4 in.
• Head Style: Button Head
• Drive Type: Internal Hex
• Locking Feature: Nylon insert providing prevailing torque
• Nylon Insert Diameter (P): 1/16 in.
• Nylon Insert Location (N): 7/64 in. +/-1/2 pitch
• Head Dimensions: ASME B18.3

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.