Stainless steel hex cap screw markings

Tips index

Inch

• 18-8 , which can be 302, 303 or 304 stainless, refers to 18% chromium and 8% nickel content.
• 316 is more corrosion resistant than 18-8 because it contains molybdenum, but in inch fasteners both have the same tensile strength.

Metric

• A2 refers to metric 18-8.
• A4 refers to metric 316.
• Class 50, 70 and 80 designate increasingly higher metric strength levels.
• A manufacturer's mark is required on metric M5 or larger diameters.