A563

The ASTM A563 specification covers the chemical and mechanical requirements for carbon and alloy steel nuts used on bolts, studs, and externally threaded fasteners. The charts below address over tapping allowances for hot-dip galvanized nuts, grade marking requirements, and mechanical requirements. For information on suitable nuts for various grades of bolts, visit the Nut Compatibility Chart.

According the A563 specification, “The requirements for any grade of nut may, at the supplier’s option, and with notice to the purchaser, be fulfilled by furnishing nuts of one of the stronger grades specified herein unless such a substitution is barred in the inquiry and purchase order”. This is important because some nut grades are not readily available in certain sizes and finishes. Additionally, the specification allows for the substitution of ASTM A194 grade 2H nuts in lieu of A563 grade DH nuts due to the lack of availability of grade DH nuts in nominal sizes 3/4″ and larger.

Hot-dip galvanized nuts must be tapped oversize to allow for the added thickness of the zinc on the threads of the externally threaded fastener. These allowances are addressed in the chart below and a more detailed explanation of this issue can be found in the Frequently Asked Questions section of this site.

Various nut styles exist and to some degree are determined by their grade. These styles include hex, heavy hex, square, jam, coupling, and sleeve.

Scope

Standard specification for carbon and alloy steel nuts.

A563 Grades

A

B

C

D

DH

C3

DH3

Carbon steel, hex or heavy hex

Carbon steel, hex or heavy hex

Carbon steel, quenched and tempered, heavy hex

Carbon steel, quenched and tempered, heavy hex

Carbon steel, quenched and tempered, heavy hex

Weathering steel, quenched and tempered, heavy hex

Weathering steel, quenched and tempered, heavy hex

A563 Mechanical Properties

Grade

Style

Size, in.

Proof Load, ksi

Hardness, HBN

Black

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

For UNC, 8UN, 6UN, and Coarse Pitch Threads

A563 Chemical Properties

Element

Grades O, A, B, C

D**

DH**

Carbon

0.55% max

0.55% max

0.20 – 0.55%

Manganese, min

0.30%

0.60%

Phosphorus, max

0.12%

0.04%

0.04%

Sulfur, max

0.15%*

0.05%

0.05%

* For grades O, A and B a sulfur content of 0.23% max is acceptable with the purchasers approval

** For grades D and DH a sulfur content of 0.05 – 0.15% is acceptable provided the manganese is 1.35% min

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

* Selection of a class shall be at the option of the manufacturer

** Nickel or Molybdenum may be used.

A563 Grade Identification Markings

Grade Identification Marking

Specification

Material

Nominal Size, In.

Proof Load Stress, ksi

Hardness Rockwell

See Note

Min

Max

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

>1 – 1-1/2

120

105

B69

C32

2,3

ASTM A563 Grade C

Carbon Steel, may be Quenched and Tempered

1/4 – 4

144

B78

C38

4

ASTM A563 Grade C3

Atmospheric Corrosion Resistant Steel, may be Quenched and Tempered

1/4 – 4

144

B78

38

4,6

ASTM A563 Grade D

Carbon Steel, may be Quenched and Tempered

1/4 – 4

150

B84

C38

5

ASTM A563 Grade DH

Carbon Steel, Quenched and Tempered

1/4 – 4

175

C24

C38

5

ASTM A563 Grade DH3

Atmospheric Corrosion Resistant Steel, Quenched and Tempered

1/4 – 4

175

C24

C38

4,6

NOTES: 

  • In addition to the indicated grade marking, all grades, except A563 grades O, A, and B, must be marked for manufacturer identification.

  • 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.

  • Properties shown are those of nonplated or noncoated coarse thread nuts.

  • New List IProperties shown are those of coarse thread heavy hex nuts.

  • Properties shown are those of coarse thread heavy hex nuts. Other nuts styles and fine threads may apply.

  • New List ItemThe nut manufacturer, at his option, may add other markings to indicate the use of atmospheric corrosion resistant steel.

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

Thread Dimensions and Oversizing Allowances

For Nuts: Hot Dipped Galvanized per Specification A153, C1.C

Nominal Nut Size, in. and Pitch

Diametral Allowance, in.

Pitch Diameter

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

0.0562 – 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

Inch Fastener Standards. 7th ed. Cleveland: Industrial Fasteners Institute, 2003. B-173.