ASTM A563

Scope
1.1 This specification covers chemical and mechanical requirements for eight grades of carbon and alloy steel nuts for general structural and mechanical uses on bolts, studs and other externally threaded parts.

1.3 Grades C3 and DH3 nuts have atmospheric corrosion resistance and weathering characteristics comparable to that of the steels covered in Specifications A242, A588 & A709. The atmospheric corrosion resistance of these steels is substantially better than that of carbon steel with or without copper addition. When properly exposed to the atmosphere, these steels can be used bare (uncoated) for many applications.

Table 1: Chemical Requirements for Grades O, A, B, C, D and DH Nuts

Table 2: Chemical Requirements for Grades C3 and DH3 Nuts

Table 3 Mechanical Requirements for Nuts with UNC & 8 UN Threads

A: To determine nut proof load in pounds, multiply the appropriate nut proof load stress by the tensile stress area of the thread. Stress areas for UNC  and 8 UN thread series are given in Table 4.
B: Non-zinc-coated nuts are nuts intended for use with externally threaded fasteners which have a plain (non-plated or non-coated) finish or have a plating or coating of insufficient thickness to necessitate overtapping the nut thread to provide assemblability. Zinc-coated nuts are nuts intended for use with externally threaded fasteners which are hot-dip zinc-coated, mechanically zinc-coated, or have a plating or coating of sufficient thickness to necessitate overtapping the nut thread to provide assemblability.
C: Nuts made in accordance to the requirements of Specification A194, Grade 2 or Grade 2H, and marked with their grade symbol are acceptable equivalents for Grades C and D nuts. When A194 zinc-coated inch series nuts are supplied, the zinc coating, overtapping, lubrication and rotational capacity testing shall be in accordance with Specification A563.
D: Nuts made in accordance with the requirements of Specification A194, Grade 2H, and marked with its grade symbol are an acceptable equivalent for Grade DH nuts. When A194 zinc-coated inch series nuts are supplied, the zinc coating, overtapping, lubrication and rotational capacity testing shall be in accordance with Specification A563.

Table 4 Tensile Stress Areas

As The stress area is calculated as follows: As = 0.7854 [D –0.9743/n]²
where:
As = stress area, in.²,
D = nominal size, in., and
n = threads per inch.

Table 5 Thread Dimensions and Overtapping Allowances for Nuts Hot Dip Zinc Coated per F2329

A – These allowances also apply to the minimum and maximum major and minor diameters.

Table X1.1 Nut Suitability Chart