ASME B18.2.1

ASME B18.2.1 - Bolt Dimension

Nominal or basic product diameter

Unit

Body diameter
( E )

Width across flats (F)

Width across corner (G)

Head Height (H)

Full threading length (LT)

da (max)

dw (min)

D (major) 2A

D1(pitch) 2A

D2 (minor) MIN. 2A

R

c

b

inch

inch

UNC

 

Min.

Max.

Min.

Max.

Min.

Max.

Min.

Max.

<6"(s)

>6"(L)

Max.

Min.

Min.

Max.

Min.

Max.

Min.

Min.

Max.

Min.

Max.

Min.

Max.

1/2"

0.500

13

Inch

0.493

0.500

0.736

0.750

0.840

0.866

0.302

0.323

1.250

1.500

0.550

0.675

0.488

0.499

0.444

0.449

0.404

0.015

0.025

0.015

0.025

0.000

0.157

mm

12.52

12.70

18.69

19.05

21.34

22.00

7.67

8.20

31.75

38.10

13.97

17.15

12.39

12.66

11.26

11.39

10.26

0.38

0.64

0.38

0.64

0.00

4.00

9/16"

0.563

12

Inch

0.555

0.563

0.798

0.812

0.910

0.938

0.348

0.371

1.375

1.625

0.652

0.731

0.550

0.561

0.502

0.507

0.459

0.020

0.045

0.015

0.025

0.000

0.197

mm

14.08

14.29

20.27

20.62

23.11

23.83

8.84

9.42

34.93

41.28

16.56

18.56

13.96

14.25

12.74

12.87

11.65

0.51

1.14

0.38

0.64

0.00

5.00

5/8"

0.625

11

Inch

0.617

0.625

0.922

0.938

1.051

1.083

0.378

0.403

1.500

1.750

0.715

0.844

0.611

0.623

0.559

0.564

0.512

0.020

0.045

0.015

0.025

0.000

0.197

mm

15.67

15.88

23.42

23.83

26.70

27.51

9.60

10.24

38.10

44.45

18.16

21.44

15.53

15.83

14.20

14.34

13.00

0.51

1.14

0.38

0.64

0.00

5.00

3/4"

0.750

10

Inch

0.741

0.750

1.100

1.125

1.254

1.299

0.455

0.483

1.750

2.000

0.840

1.012

0.735

0.748

0.677

0.683

0.626

0.020

0.045

0.015

0.025

0.000

0.197

mm

18.82

19.05

27.94

28.58

31.85

32.99

11.56

12.27

44.45

50.80

21.34

25.71

18.68

19.00

17.20

17.35

15.89

0.51

1.14

0.38

0.64

0.00

5.00

7/8"

0.875

9

Inch

0.866

0.875

1.285

1.312

1.465

1.516

0.531

0.563

2.000

2.250

1.005

1.181

0.859

0.873

0.795

0.801

0.737

0.040

0.065

0.015

0.035

0.000

0.197

mm

22.00

22.23

32.64

33.32

37.21

38.51

13.49

14.30

50.80

57.15

25.53

29.99

21.82

22.18

20.18

20.34

18.71

1.02

1.65

0.38

0.89

0.00

5.00

1"

1.000

8

Inch

0.990

1.000

1.469

1.500

1.675

1.732

0.591

0.627

2.250

2.500

1.190

1.350

0.983

0.998

0.910

0.917

0.845

0.060

0.095

0.015

0.035

0.000

0.236

mm

25.15

25.40

37.31

38.10

42.55

43.99

15.01

15.93

57.15

63.50

30.23

34.29

24.97

25.35

23.11

23.29

21.45

1.52

2.41

0.38

0.89

0.00

6.00

1-1/8"

1.125

8

Inch

1.114

1.125

1.631

1.688

1.859

1.949

0.658

0.718

2.500

2.750

1.315

1.519

1.079

1.123

1.035

1.042

0.970

0.060

0.095

0.015

0.035

0.000

0.236

mm

28.30

28.58

41.43

42.88

47.22

49.50

16.71

18.24

63.50

69.85

33.40

38.59

27.41

28.52

26.28

26.46

24.63

1.52

2.41

0.38

0.89

0.00

6.00

1-1/4"

1.250

8

Inch

1.239

1.250

1.812

1.875

2.066

2.165

0.749

0.813

2.750

3.000

1.440

1.687

1.233

1.248

1.160

1.167

1.095

0.060

0.095

0.015

0.035

0.000

0.276

mm

31.47

31.75

46.02

47.63

52.48

54.99

19.02

20.65

69.85

76.20

36.58

42.86

31.32

31.70

29.46

29.63

27.80

1.52

2.41

0.38

0.89

0.00

7.00

1-3/8"

1.375

8

Inch

1.363

1.375

1.994

2.062

2.273

2.382

0.810

0.878

3.000

3.250

1.565

1.856

1.358

1.373

1.284

1.292

1.219

0.060

0.095

0.015

0.035

0.000

0.276

mm

34.62

34.93

50.65

52.37

57.73

60.50

20.57

22.30

76.20

82.55

39.75

47.13

34.49

34.87

32.62

32.81

30.97

1.52

2.41

0.38

0.89

0.00

7.00

1-1/2"

1.500

8

Inch

1.488

1.500

2.175

2.250

2.480

2.598

0.902

0.974

3.250

3.500

1.690

2.025

1.483

1.498

1.409

1.417

1.344

0.060

0.095

0.015

0.035

0.000

0.315

mm

37.80

38.10

55.25

57.15

62.99

65.99

22.91

24.74

82.55

88.90

42.93

51.44

37.66

38.04

35.80

35.98

34.15

1.52

2.41

0.38

0.89

0.00

8.00

1-5/8"

1.625

8

Inch

1.613

1.625

2.356

2.438

2.686

2.815

0.962

1.038

3.500

3.750

1.795

2.194

1.608

1.623

1.534

1.542

1.469

0.060

0.095

0.015

0.035

0.000

0.354

mm

40.97

41.28

59.84

61.93

68.22

71.50

24.43

26.37

88.90

95.25

45.60

55.73

40.84

41.22

38.97

39.16

37.32

1.52

2.41

0.38

0.89

0.00

9.00

1-3/4"

1.750

8

Inch

1.738

1.750

2.538

2.625

2.893

3.031

1.054

1.134

3.750

4.000

1.940

2.362

1.733

1.748

1.659

1.667

1.594

0.060

0.095

0.015

0.035

0.000

0.354

mm

44.15

44.45

64.47

66.68

73.48

76.99

26.77

28.80

95.25

101.60

49.28

60.00

44.01

44.39

42.14

42.33

40.50

1.52

2.41

0.38

0.89

0.00

9.00

1-7/8"

1.875

8

Inch

1.863

1.875

2.719

2.812

3.099

3.248

1.114

1.198

4.000

4.250

2.071

2.531

1.858

1.873

1.784

1.792

1.719

0.060

0.095

0.015

0.035

0.000

0.394

mm

47.32

47.63

69.06

71.42

78.71

82.50

28.30

30.43

101.60

107.95

52.60

64.28

47.19

47.57

45.31

45.50

43.67

1.52

2.41

0.38

0.89

0.00

10.00

2"

2.000

8

Inch

1.988

2.000

2.900

3.000

3.306

3.464

1.175

1.263

4.250

4.500

2.190

2.688

1.983

1.998

1.909

1.917

1.844

0.060

0.095

0.015

0.035

0.000

0.394

mm

50.50

50.80

73.66

76.20

83.97

87.99

29.85

32.08

107.95

114.30

55.63

68.28

50.36

50.74

48.48

48.68

46.85

1.52

2.41

0.38

0.89

0.00

10.00

2-1/4"

2.250

8

Inch

2.238

2.250

3.262

3.375

3.719

3.897

1.327

1.423

-

5.000

2.440

3.037

2.233

2.248

2.158

2.166

2.094

0.060

0.095

0.015

0.035

0.000

0.433

mm

56.85

57.15

82.85

85.73

94.46

98.98

33.71

36.14

-

127.00

61.98

77.15

56.71

57.09

54.82

55.03

53.19

1.52

2.41

0.38

0.89

0.00

11.00

2-1/2"

2.500

8

Inch

2.488

2.500

3.625

3.750

4.133

4.330

1.479

1.583

-

5.500

2.690

3.375

2.483

2.498

2.408

2.416

2.344

0.060

0.095

0.015

0.035

0.000

0.472

mm

63.20

63.50

92.08

95.25

104.98

109.98

37.57

40.21

-

139.70

68.33

85.73

63.06

63.44

61.17

61.37

59.54

1.52

2.41

0.38

0.89

0.00

12.00

2-3/4"

2.750

8

Inch

2.738

2.750

3.988

4.125

4.546

4.763

1.632

1.744

-

6.000

2.940

3.712

2.733

2.748

2.658

2.666

2.594

0.060

0.095

0.015

0.035

0.000

0.512

mm

69.55

69.85

101.30

104.78

115.47

120.98

41.45

44.30

-

152.40

74.68

94.28

69.41

69.79

67.51

67.72

65.89

1.52

2.41

0.38

0.89

0.00

13.00

3"

3.000

8

Inch

2.988

3.000

4.350

4.500

4.959

5.196

1.815

1.935

-

6.500

3.190

3.712

2.982

2.997

2.908

2.916

2.844

0.060

0.095

0.015

0.035

0.000

0.591

mm

75.90

76.20

110.49

114.30

125.96

131.98

46.10

49.15

-

165.10

81.03

94.29

75.75

76.13

73.86

74.07

72.24

1.52

2.41

0.38

0.89

0.00

15.00