5/16-18 x 5/8 18-8 Stainless Steel Flat Head Cap Screw with Nylon Insert is built for a properly cut 82-degree countersink where the head can sit flush or slightly below the surface. 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.

For walk plates, step surfaces, or low-snag equipment panels, confirm countersink geometry, thread engagement, and whether the nylon insert suits the service conditions. Plain 18-8 Stainless Flat Head Socket Cap Screws may fit torque-once joints where a nylon insert is not required.

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: 5/16-18
• Length (overall - includes head): 5/8 in.
• Head Style: 82° Countersunk Flat
• Drive Type: Internal Hex
• Locking Feature: Nylon insert providing prevailing torque
• Nylon Insert Diameter (P): 1/8 in.
• Nylon Insert Location (N): 13/64 in. +/-1/2 pitch
• Head Dimensions: ASME B18.3

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