ASTM A563 Structural Nuts
A563 is the nut specification that pairs with most ASTM bolting, from A307 to structural A325 and A490. The grade letter on the nut sets its strength.
| Style | Hex or heavy hex; style is separate from grade |
|---|---|
| Galvanized | Nuts are overtapped after galvanizing and must be lubricated |
Common A563 grades and pairing
| Grade | Typical marking | Used with |
|---|---|---|
| A | None required | A307 |
| C | Grade mark per A563 | A325 plain |
| C3 | C3 (weathering) | A325 Type 3 |
| D | D | A325 |
| DH | DH | A325 galvanized, A490, A354 BD |
| DH3 | DH3 (weathering) | A490 / A325 Type 3 |
Structural pairing per ASTM F3125 and RCSC. A194 2H may be permitted in place of DH as specified.
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
ASTM A563 · carbon and alloy steel nuts
FIELD IDENTIFICATION
DH
What it is
A563 is the nut specification that pairs with most ASTM bolting, from A307 to structural A325 and
A490. The grade letter on the nut sets its strength.
Style
Hex or heavy hex; style is separate from grade
Galvanized
Nuts are overtapped after galvanizing and must be lubricated
Heavy hex nut, grade on face (DH shown)
Common A563 grades and pairing
Grade
Typical marking
Used with
A
None required
A307
C
Grade mark per A563
A325 plain
C3
C3 (weathering)
A325 Type 3
D
D
A325
DH
DH
A325 galvanized, A490, A354 BD
DH3
DH3 (weathering)
A490 / A325 Type 3
Structural pairing per ASTM F3125 and RCSC. A194 2H may be permitted in place of DH as specified.
Key points
A heavy hex nut is a shape, not a grade. Always check the grade mark.
Governing standards: ASTM A563/A563M-26; ASTM F3125/F3125M-26; RCSC Specification. Editions shown are the latest confirmed as of September 2026. The drawing and the
governing standard always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-9CC7CE · thefastenerapp.com/fastener-guide/technical-reference/astm-a563-structural-nuts · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
