4-40 x 2 1/2 18-8 Stainless Steel Flat Head Cap Screw with Nylon Insert pairs ordinary moisture resistance with a nylon pellet for thread-friction locking. A countersunk head bears on the cone rather than a broad underside, so clamp load should not be treated like a full socket head cap screw. Overall-length measurement matters on countersunk joints because the head occupies part of the thickness stack.

For bracket faces, panel-mounted hardware, or smooth machine surfaces, confirm countersink geometry, thread engagement, and whether the nylon insert suits the service conditions. Where strength matters more than stainless material, Alloy Steel Flat Head Socket Cap Screws with Nylon Insert may be the better route.

Slight magnetism from cold working can be normal for 18-8 stainless, so final material selection should reflect the assembly conditions. Cold Headers can help verify the exact 18-8 flat head nylon-insert configuration before quoting pricing and availability.

Technical Highlights

• Material: 18-8 Stainless Steel
• Thread Size: 4-40
• Length (overall - includes head): 2 1/2 in.
• Head Style: 82° Countersunk Flat
• 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.