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A563 Grade Identification Markings

Grade Identification Marking Specification Material Nominal Size, In. Proof Load Stress, ksi Hardness Rockwell See Note
Min Max
no_mark ASTM A563 Grade O** Carbon Steel 1/4 – 1-1/2 69 B55 C32 2,3
ASTM A563 Grade A Carbon Steel 1/4 – 1-1/2 90 B68 C32 2,3
ASTM A563 Grade B Carbon Steel 1/4 – 1 120 B69 C32 2,3
>1 – 1-1/2 105
C ASTM A563 Grade C Carbon Steel, may be Quenched and Tempered 1/4 – 4 144 B78 C38 4
C3 ASTM A563 Grade C3 Atmospheric Corrosion Resistant Steel, may be Quenched and Tempered 1/4 – 4 144 B78 38 4,6
D ASTM A563 Grade D Carbon Steel, may be Quenched and Tempered 1/4 – 4 150 B84 C38 5
DH ASTM A563 Grade DH Carbon Steel, Quenched and Tempered 1/4 – 4 175 C24 C38 5
DH3 ASTM A563 Grade DH3 Atmospheric Corrosion Resistant Steel, Quenched and Tempered 1/4 – 4 175 C24 C38 4,6
  1. In addition to the indicated grade marking, all grades, except A563 grades O, A, and B, must be marked for manufacturer identification.
  2. Nuts are not required to be marked unless specified by the purchaser. When marked, the identification marking shall be the grade letter O, A, or B.
  3. Properties shown are those of nonplated or noncoated coarse thread nuts.
  4. Properties shown are those of coarse thread heavy hex nuts.
  5. Properties shown are those of coarse thread heavy hex nuts. Other nuts styles and fine threads may apply.
  6. The nut manufacturer, at his option, may add other markings to indicate the use of atmospheric corrosion resistant steel.
  7. **ASTM A563 Grade O has been discontinued.

Inch Fastener Standards. 7th ed. Cleveland: Industrial Fasteners Institute, 2003. n-80-n-81.