Sep 2025
ASTM A563
ASTM A563 is the standard specification that defines the chemical and mechanical requirements for carbon steel and alloy steel nuts used with bolts, studs, and other externally threaded fasteners. This specification ensures that nuts meet the required strength, performance, and compatibility for industrial applications.
Key Highlights of ASTM A563:
Nut Compatibility: The specification outlines which nut grades are suitable for different grades of bolts. (See Nut Compatibility Chart for reference).
Flexibility in Supply: In cases where a particular nut grade is not readily available in certain sizes or finishes, the supplier may provide nuts from a stronger grade—provided the purchaser is notified and has not restricted such substitution in the purchase order.
Substitution Option: ASTM A194 Grade 2H nuts can be supplied in place of A563 Grade DH nuts for sizes 3/4? and larger, since Grade DH nuts are often unavailable in those dimensions.
Hot-Dip Galvanized Nuts: These nuts must be tapped oversize to account for the added zinc coating on the threads. The standard provides detailed oversize tapping allowances, ensuring proper fit and function.
Nut Styles Covered:
Depending on the grade, various nut styles fall under ASTM A563, including:
• Hex nuts
• Heavy hex nuts
• Square nuts
• Jam nuts
• Coupling nuts
• Sleeve nuts
This standard plays a critical role in maintaining consistency, safety, and reliability in fastener assemblies used across industries.
A563 Grades:
| Grade |
Description |
| A |
Carbon steel, hex or heavy hex |
| B |
Carbon steel, hex or heavy hex |
| C |
Carbon steel, quenched and tempered, heavy hex |
| D |
Carbon steel, quenched and tempered, heavy hex |
| DH |
Carbon steel, quenched and tempered, heavy hex |
| C3 |
Weathering steel, quenched and tempered, heavy hex |
| DH3 |
Weathering steel, quenched and tempered, heavy hex |
A563 Mechanical Properties:
| Grade |
Style |
Size, in. |
Proof Load, ksi |
Hardness, HBN |
| Plain |
Galvanized |
| A |
Hex |
1/4" - 1-1/2" |
90 |
68 |
116 - 302 |
| Heavy Hex |
1/4" - 4" |
100 |
75 |
116 - 302 |
| B |
Heavy Hex |
1/4" - 1" |
133 |
100 |
121 - 302 |
| Heavy Hex |
1-1/8" - 1-1/2" |
116 |
87 |
121 - 302 |
| C / C3 |
Heavy Hex |
1/4" - 4" |
144 |
144 |
143 - 352 |
| D |
Heavy Hex |
1/4" - 4" |
150 |
150 |
248 - 352 |
| DH / DH3 |
Heavy Hex |
1/4" - 4" |
175 |
150 |
248 - 352 |
|
A563 Chemical Properties:
| Element |
Grades 1 & 2 |
Grade 3 |
Grade 4 |
| Carbon |
0.40% max. |
0.25 – 0.50% |
0.45 – 0.60% |
| Manganese |
0.50% min. |
0.70% min. |
0.80% min. |
| Phosphorus |
0.05% max. |
0.04% max. |
0.04% max. |
| Sulfur |
0.06% max. |
0.04 – 0.08% |
0.05 – 0.10% |
|
Classes for Grade C3*
| Element |
Classes for Grade C3* |
DH3 |
| A |
B |
C |
D |
E |
F |
N |
| Carbon |
0.33 - 0.40% |
0.38 - 0.48% |
0.15 - 0.25% |
0.15 - 0.25% |
0.20 - 0.25% |
0.20 - 0.25% |
|
0.20 - 0.53% |
| Manganese |
0.90 - 1.20% |
0.70 - 0.90% |
0.80 - 1.35% |
0.40 - 1.20% |
0.60 - 1.00% |
0.90 - 1.20% |
|
0.40% min |
| Phosphorus |
0.040% max |
0.06 - 0.12% |
0.035% max |
0.040% max |
0.040% max |
0.040% max |
0.07 - 0.15% |
0.046% max |
| Sulfur, max |
0.050% |
0.050% |
0.040% |
0.050% |
0.040% |
0.040% |
0.050% |
0.050% |
| Silicon |
0.15 - 0.35% |
0.30 - 0.50% |
0.15 - 0.35% |
0.25 - 0.50% |
0.15 - 0.35% |
0.15 - 0.35% |
0.20 - 0.90% |
|
| Copper |
0.25 - 0.45% |
0.20 - 0.40% |
0.20 - 0.50% |
0.30 - 0.50% |
0.30 - 0.60% |
0.20 - 0.40% |
0.25 - 0.55% |
0.20% min |
| Nickel |
0.25 - 0.45% |
0.50 - 0.80% |
0.25 - 0.50% |
0.50 - 0.80% |
0.30 - 0.60% |
0.20 - 0.40% |
1.00% max |
0.20% min** |
| Chromium |
0.45 - 0.65% |
0.50 - 0.75% |
0.30 - 0.50% |
0.50 - 1.00% |
0.60 - 0.90% |
0.45 - 0.65% |
0.30 - 1.25% |
0.45% min |
| Vanadium |
|
|
0.020% min |
|
|
|
|
|
| Molybdenum |
|
0.06% max |
|
0.10% max |
|
|
|
0.15% min** |
| Titanium |
|
|
|
0.05% max |
|
|
|
|
|
A563 Grade Identification Markings:
| Grade Identification |
Specification |
Material |
Nominal Size (In.) |
Proof Load Stress (ksi) |
Hardness Rockwell |
Notes |
| Min |
Max |
| Grade O** |
Carbon Steel |
1/4" – 1-1/2" |
69 |
B55 |
C32 |
2,3 |
| Grade A |
Carbon Steel |
1/4" – 1-1/2" |
90 |
B68 |
C32 |
2,3 |
| Grade B |
Carbon Steel |
1/4" – 1" |
120 |
B69 |
C32 |
2,3 |
|
Grade C |
Carbon Steel (Quenched & Tempered) |
1/4" – 4" |
144 |
B78 |
C38 |
4 |
|
Grade C3 |
Corrosion Resistant Steel (Q&T) |
1/4" – 4" |
144 |
B78 |
C38 |
4,6 |
|
Grade D |
Carbon Steel (Quenched & Tempered) |
1/4" – 4" |
150 |
B84 |
C38 |
5 |
|
Grade DH |
Carbon Steel (Quenched & Tempered) |
1/4" – 4" |
175 |
C24 |
C38 |
5 |
| Grade DH3 |
Corrosion Resistant Steel (Q&T) |
1/4" – 4" |
175 |
C24 |
C38 |
4,6 |
|
|
Thread Dimensions and Oversizing Allowances:
| Nominal Nut Size, in. and Pitch |
Diametral Allowance, in. |
Pitch Diameter (in.) |
| Min |
Max |
| 0.250" - 20" | 0.016" | 0.2335" | 0.2384" |
| 0.312" - 18" | 0.017" | 0.2934" | 0.2987" |
| 0.375" - 16" | 0.017" | 0.3514" | 0.3571" |
| 0.437" - 14" | 0.018" | 0.4091" | 0.4152" |
| 0.500" - 13" | 0.018" | 0.4680" | 0.4745" |
| 0.562" - 12" | 0.020" | 0.5284" | 0.5352" |
| 0.625" - 11" | 0.020" | 0.5860" | 0.5932" |
| 0.750" - 10" | 0.020" | 0.7050" | 0.7127" |
| 0.875" - 9" | 0.022" | 0.8248" | 0.8330" |
| 1.000" - 8" | 0.024" | 0.9428" | 0.9516" |
| 1.125" - 8" | 0.024" | 1.0678" | 1.0768" |
| 1.125" - 7" | 0.024" | 1.0562" | 1.0656" |
| 1.250" - 8" | 0.024" | 1.1928" | 1.2020" |
| 1.250" - 7" | 0.024" | 1.1812" | 1.1908" |
| 1.375" - 8" | 0.027" | 1.3208" | 1.3301" |
| 1.375" - 6" | 0.027" | 1.2937" | 1.3041" |
| 1.500" - 8" | 0.027" | 1.4458" | 1.4553" |
| 1.500" - 6" | 0.027" | 1.4187" | 1.4292" |
| 1.750" - 5" | 0.050" | 1.6701" | 1.6817" |
| 2.000" - 4.5" | 0.050" | 1.9057" | 1.9181" |
| 2.250" - 4.5" | 0.050" | 2.1557" | 2.1683" |
| 2.500" - 4" | 0.050" | 2.3876" | 2.4011" |
| 2.750" - 4" | 0.050" | 2.6376" | 2.6513" |
| 3.000" - 4" | 0.050" | 2.8876" | 2.9015" |
| 3.250" - 4" | 0.050" | 3.1376" | 3.1517" |
| 3.500" - 4" | 0.050" | 3.3876" | 3.4019" |
| 3.750" - 4" | 0.050" | 3.6376" | 3.6521" |
| 4.000" - 4" | 0.050" | 3.8876" | 3.9023" |
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