Stainless Metric Socket Head Cap Screws

Metric Stainless Steel Socket Head Cap Screws — A2-70 and A4-70, DIN 912

Shop Metric Stainless Socket Head Cap Screws

Metric stainless socket head cap screws conform to DIN 912 in A2 or A4 stainless property classes. A2 is equivalent to 304/18-8 stainless (18% chromium, 8% nickel); A4 is equivalent to 316 stainless, adding molybdenum for superior chloride resistance. The 70 designation in A2-70 and A4-70 indicates a minimum tensile strength of 700 MPa (~101,500 PSI) — significantly lower than Class 12.9 alloy (1,220 MPa). Verify load requirements before substituting stainless for alloy in metric mechanical assemblies, particularly where high clamp load is critical.

A2-70 Stainless — Standard Corrosion Resistance

A2-70 (304/18-8) stainless metric SHCS provide excellent resistance to oxidation, atmospheric moisture, and most mild chemicals. They are the standard choice for food processing and commercial kitchen equipment, pharmaceutical and laboratory machinery, outdoor hardware not in direct marine or salt-water exposure, and washdown environments where 700 MPa tensile strength is sufficient for the joint. A2-80 (800 MPa) is available for higher-strength stainless requirements — contact us for availability.

A4-70 Stainless — Chloride and Marine Resistance

A4-70 (316) stainless adds approximately 2–3% molybdenum to the A2 base, significantly improving resistance to pitting corrosion from chlorides, salt water, and acidic solutions. A4 is the correct specification for marine hardware, coastal outdoor structures, swimming pool and water treatment equipment, chemical processing machinery, and medical-grade applications where the highest available corrosion resistance is required. A4-80 (800 MPa) is available for higher-strength requirements — contact us for availability in DIN 912 metric SHCS form.

Strength Comparison: Stainless vs. Alloy Metric SHCS

A2-70 and A4-70 stainless metric SHCS have a minimum tensile strength of 700 MPa (~101,500 PSI). Class 12.9 alloy metric SHCS provide 1,220 MPa (~177,000 PSI) — approximately 74% higher. Class 10.9 alloy provides 1,040 MPa (~151,000 PSI). If maximum clamping force is required in a metric assembly and the environment permits use of alloy steel, Class 12.9 is substantially stronger. Use stainless when corrosion resistance is the design driver and 700 MPa strength is sufficient.

Frequently Asked Questions

What is the difference between A2-70 and A4-70 metric stainless SHCS?
A2-70 uses 304/18-8 stainless alloy (18% chromium, 8% nickel) and provides good general corrosion resistance. A4-70 uses 316 stainless, adding approximately 2–3% molybdenum for significantly better resistance to chlorides, salt water, and acidic solutions. Both have the same 700 MPa minimum tensile strength. Use A4 for marine, coastal, or chemical environments; use A2 for general corrosion resistance where chloride exposure is not a primary concern.

Are metric stainless SHCS dimensionally the same as metric alloy SHCS?
Yes. A2-70 and A4-70 stainless DIN 912 metric SHCS are dimensionally identical to Class 12.9 and Class 10.9 alloy DIN 912. Same head dimensions, same counterbore dimensions, same hex key sizes. The only difference is material and tensile strength.

What tensile strength do metric stainless socket head cap screws have?
A2-70 and A4-70 stainless metric SHCS have a minimum tensile strength of 700 MPa, approximately 101,500 PSI. This is significantly lower than Class 12.9 alloy at 1,220 MPa. For maximum clamping force in metric applications, Class 12.9 alloy is the stronger choice.

Can metric stainless SHCS be used in food service equipment?
Yes. A2 stainless (304/18-8) is widely accepted for food service equipment fastening. It resists oxidation, moisture, and mild cleaning chemicals well. For applications with aggressive CIP (clean-in-place) chemistry or significant chloride exposure, A4 (316) stainless provides better long-term corrosion resistance.

Metric stainless socket head cap screws are typically used in assemblies where other components are also A2 or A4 stainless — mixing stainless and carbon steel fasteners in wet environments can accelerate galvanic corrosion. Pair with stainless metric flat washers and lock washers for a fully corrosion-resistant assembly. For maximum clamping strength in metric applications where corrosion is not a concern, metric alloy socket head cap screws (Class 12.9, DIN 912) are significantly stronger. For inch-series stainless socket head applications, see stainless steel socket head cap screws (ASME B18.3). The full socket head cap screw selection and all socket fastener types are available through the Socket Head Cap Screws and Sockets categories.