ASME B18.2.3.3M Metric Heavy Hex Structural Bolts

ASME B18.2.3.3M Heavy Hex Structural Screw (Metric) Dimensions

Metric Dimensions for Heavy Hex Structural Bolts

ASME B18.2.3.3M Standard specifies the dimensions and requirements for metric heavy hex structural bolts, commonly used in structural steel connections and high-strength applications. It includes details on bolt geometry, thread specifications, and tolerance limits to ensure structural integrity and reliability. This page provides comprehensive ASME B18.2.3.3M Dimensions, including metric size charts and engineering data.

Metric heavy hex structural bolts per ASME B18.2.3.3M are differentiated from standard hex bolts by a thicker head (greater bearing surface) and shorter thread length — engineered for high-tensile pretension in steel-erection, large-pressure-vessel, and offshore-platform applications. The dimensional envelope spans M12 through M36. In ASTM A193 Grade B8 material, the Class 1D condition is the typical specification because limited cold straightening is permitted for the heavier bar stock required.

ASME B18.2.3.3M Heavy Hex Structural Screw Dimensions

Nominal Dia., D , and Thread Pitch	Body Diameter.,D _s	Width Across Flats,S	Width Across Corners, E	Head Height, K	Wrenching Height, K ₁	Washer Face Thickness,C	Washer FaceDia.,D _w
M12 × 1.75	12	11.73	21	20.67	24.25	23.35	7.76	7.24	5.2	0.6	0.3	19.6
M14 × 2	14	13.73	24	23.67	27.71	26.75	9.09	8.51	6.2	0.6	0.3	22.5
M16 × 2	16	15.73	27	26.67	31.18	30.14	10.32	9.68	7	0.8	0.4	25.3
M20 × 2.5	20	19.67	34	33	39.26	37.29	12.88	12.12	8.8	0.8	0.4	31.4
M24 × 3	24	23.67	41	40	47.34	45.2	15.44	14.56	10.5	0.8	0.4	38
M30 × 3.5	30	29.67	50	49	57.74	55.37	19.48	17.92	13.1	0.8	0.4	46.6
M36 × 4	36	35.61	60	58.8	69.28	66.44	23.38	21.72	15.8	0.8	0.4	55.9
All dimensions are in millimeters. Basic thread lengths, B, are the same as given in . Transition thread length, X, includes the length of incomplete threads and tolerances on grip gaging length and body length. It is intended for calculation purposes. For additional manufacturing and acceptance specifications, reference should be made to the Standard.

Nominal Dia., D , and Thread Pitch

Body Diameter.,D _s

Width Across Flats,S

Width Across Corners, E

Head Height, K

Wrenching Height, K ₁

Washer Face Thickness,C

Washer FaceDia.,D _w

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

M12 × 1.75

11.73

20.67

24.25

23.35

7.76

7.24

5.2

0.6

0.3

19.6

M14 × 2

13.73

23.67

27.71

26.75

9.09

8.51

6.2

0.6

0.3

22.5

M16 × 2

15.73

26.67

31.18

30.14

10.32

9.68

0.8

0.4

25.3

M20 × 2.5

19.67

39.26

37.29

12.88

12.12

8.8

0.8

0.4

31.4

M24 × 3

23.67

47.34

45.2

15.44

14.56

10.5

0.8

0.4

M30 × 3.5

29.67

57.74

55.37

19.48

17.92

13.1

0.8

0.4

46.6

M36 × 4

35.61

58.8

69.28

66.44

23.38

21.72

15.8

0.8

0.4

55.9

All dimensions are in millimeters.
Basic thread lengths, B, are the same as given in .
Transition thread length, X, includes the length of incomplete threads and tolerances on grip gaging
length and body length. It is intended for calculation purposes.
For additional manufacturing and acceptance specifications, reference should be made to the Standard.

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Certifications

ISO 9001 - 2015 Certified
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NACE MR0175/ISO 15156-2
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DFAR
MERKBLATT AD 2000 W2/W7/W10

ASME B18.2.3.3M Heavy Hex Structural Screw (Metric) Dimensions

ASME B18.2.3.3M Heavy Hex Structural Screw Dimensions

Related Specifications

Surface Treatments

Certifications

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