Astm f436 type 1 is a standard material and dimensional specification for hardened steel washers intended for general purpose mechanical and structural use with bolts nuts studs and other internally and externally threaded fasteners of nominal thread diameter 1 4 through 4 inch. Care should be taken to specify 5 16 thick washers when 5 16 thick washers are required per aisc. Astm f436 covers the chemical mechanical and dimensional requirements for hardened steel washers to use with bolts from 1 2 through 4 inches in diameter.