Stainless Flat Head Socket Cap Screws

Stainless steel flat head socket cap screws (inch series) combine the flush-seating countersunk head of a standard flat head socket cap screw with the corrosion resistance of 18-8 or 316 stainless steel. They conform to ASME B18.3 with the same 82° countersink angle as alloy inch-series fasteners, making them a direct material substitute in applications where corrosion resistance is required. Eugene Fastener stocks 18-8 stainless flat head socket cap screws in a full inch size range from stock in Eugene, Oregon.

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Stainless Steel Flat Head Socket Cap Screws — 18-8 and 316, Inch Series

Shop Stainless Flat Head Socket Cap Screws

Stainless steel flat head socket cap screws are used wherever countersunk installation and corrosion resistance are both required. Conforming to ASME B18.3 with an 82° countersink angle — the same as alloy inch-series — they are a direct material substitute in applications where the environment precludes plain or black oxide alloy steel. Available in 18-8 (302/304) for general corrosion resistance and 316 stainless for chloride and marine environments.

18-8 Stainless Steel (302/304)

18-8 stainless steel — also designated 302 or 304 — provides excellent resistance to oxidation, moisture, and many chemicals. It is the standard choice for food processing equipment, pharmaceutical and laboratory fixtures, outdoor structures, and general washdown environments. Tensile strength is approximately 85,000–125,000 PSI depending on size, which is lower than alloy steel FHSCS. Verify load requirements before substituting stainless for alloy in structural joints.

316 Stainless Steel

316 stainless steel adds molybdenum to the 304 alloy, providing superior resistance to chlorides, salt water, and acidic environments. It is the correct choice for marine hardware, coastal outdoor structures, chemical processing equipment, and medical or food-grade applications requiring the highest corrosion resistance. 316 SS flat head socket cap screws are available in select sizes — contact us for availability on specific thread sizes and lengths.

Anti-Galling with Stainless Fasteners

Stainless steel is prone to galling — a form of adhesive wear that causes threads to seize during installation, particularly when driving stainless fasteners into stainless tapped holes. To prevent galling: apply a small amount of anti-seize compound (Never-Seez or equivalent) to the threads before installation, avoid high-speed installation with power tools, and never force a fastener that has begun to bind.

Frequently Asked Questions

What is 18-8 stainless steel?
18-8 refers to the approximate alloy composition: 18% chromium and 8% nickel. It is also designated Type 302 or Type 304 stainless steel. 18-8 provides good general corrosion resistance for most indoor and outdoor non-marine environments and is the most common stainless steel grade for fasteners.

What is the difference between 18-8 and 316 stainless flat head socket cap screws?
316 stainless contains approximately 2–3% molybdenum in addition to the chromium-nickel base of 18-8/304. This addition significantly improves resistance to chlorides, salt water, and acidic solutions. Use 316 for marine, coastal, chemical, or food-grade applications. Use 18-8 for general corrosion resistance where chloride exposure is not a factor.

Are stainless flat head socket cap screws as strong as alloy?
No. 18-8 stainless flat head socket cap screws have a tensile strength of approximately 85,000–125,000 PSI depending on size — compared to 170,000–180,000 PSI for alloy ASTM A574. For structural joints requiring maximum clamping force, alloy is the correct choice. Use stainless when corrosion resistance is the priority and load requirements allow it.

Do stainless flat head socket cap screws use the same countersink angle as alloy?
Yes — inch-series stainless flat head socket cap screws conform to ASME B18.3 with the same 82° included countersink angle as alloy inch-series. They are dimensionally interchangeable; the difference is material properties only.

Stainless steel flat head socket cap screws are frequently used alongside stainless flat washers and lock washers to maintain a consistent material in corrosive environments, as mixing carbon steel and stainless fasteners in wet conditions can accelerate galvanic corrosion. For maximum clamping force in countersunk applications, see alloy steel flat head socket cap screws. For metric countersunk stainless applications, see metric stainless flat head socket cap screws. The full flat head socket cap screw selection is available through the Flat Head Socket Cap Screw category.

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