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Hexagon Socket Head Cap Bolts (Excerpt from JIS B 1176 2014)

Last updated:18 June 2019

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・The opening of the hexagon socket can be slightly round or chamfered.
・Screw tips are chamfered tips as stipulated with JIS B 1003. However, M4 or lower can have plain-sheared ends.
・Corners on the top of the head are round or chamfered, and can be selected freely by the manufacturer.
・Corners on the head seat surface are round or chamfered to dw, and cannot have burrs, etc.

Unit [mm]

d Nominal screw diameter M1.6 M2 M2.5 M3 M4 M5 M6 M8 M10 M12 (M14) M16 M20
p 0.35 0.4 0.45 0.5 0.7 0.8 1 1.25 1.5 1.75 2 2 2.5
b Reference 15 16 17 18 20 22 24 28 32 36 40 44 52
dk Max. c） 3.00 3.80 4.50 5.50 7.00 8.50 10.00 13.00 16.00 18.00 21.00 24.00 30.00
Max. d） 3.14 3.98 4.68 5.68 7.22 8.72 10.22 13.27 16.27 18.27 21.33 24.33 30.33
Min. 2.86 3.62 4.32 5.32 6.78 8.28 9.78 12.73 15.73 17.73 20.67 23.67 29.67
da Max. 2 2.6 3.1 3.6 4.7 5.7 6.8 9.2 11.2 13.7 15.7 17.7 22.4
ds Max. 1.60 2.00 2.50 3.00 4.00 5.00 6.00 8.00 10.00 12.00 14.00 16.00 20.00
Min. 1.46 1.86 2.36 2.86 3.82 4.82 5.82 7.78 9.78 11.73 13.73 15.73 19.67
e Min. 1.733 1.733 2.303 2.873 3.443 4.583 5.723 6.863 9.149 11.429 13.716 15.996 19.437
f Max. 0.34 0.51 0.51 0.51 0.6 0.6 0.68 1.02 1.02 1.45 1.45 1.45 2.04
k Max. 1.60 2.00 2.50 3.00 4.00 5.00 6.0 8.00 10.00 12.00 14.00 16.00 20.00
Min. 1.46 1.86 2.36 2.86 3.82 4.82 5.7 7.64 9.64 11.57 13.57 15.57 19.48
r Min. 0.1 0.1 0.1 0.1 0.2 0.2 0.25 0.4 0.4 0.6 0.6 0.6 0.8
s Nominal dia. 1.5 1.5 2 2.5 3 4 5 6 8 10 12 14 17
Max. 1.58 1.58 2.08 2.58 3.08 4.095 5.14 6.14 8.175 10.175 12.212 14.212 17.23
Min. 1.52 1.52 2.02 2.52 3.02 4.020 5.02 6.02 8.025 10.025 12.032 14.032 17.05
t Min. 0.7 1 1.1 1.3 2 2.5 3 4 5 6 7 8 10
v Max. 0.16 0.2 0.25 0.3 0.4 0.5 0.6 0.8 1 1.2 1.4 1.6 2
dw Min. 2.72 3.48 4.18 5.07 6.53 8.03 9.38 12.33 15.33 17.23 20.17 23.17 28.87
w Min. 0.55 0.55 0.85 1.15 1.4 1.9 2.3 3.3 4 4.8 5.8 6.8 8.6

Unit [mm]

Nominal screw diameter　d M1.6 M2 M2.5 M3 M4 M5 M6 M8 M10 M12 (M14) M16 M20
Nominal diameter length　ℓ ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg ℓs ℓg
Nominal diameter length Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max.
2.5 2.3 2.7 * *
3 2.8 3.2 * * * *
4 3.76 4.24 * * * * * *
5 4.76 5.24 * * * * * * * *
6 5.76 6.24 * * * * * * * * * *
8 7.71 8.29 * * * * * * * * * * * *
10 9.71 10.29 * * * * * * * * * * * * * *
12 11.65 12.35 * * * * * * * * * * * * * *
16 15.65 16.35 * * * * * * * * * * * * * * * *
20 19.58 20.42 2 4 * * * * * * * * * * * * * *
25 24.58 25.42 5.75 8 4.5 7 * * * * * * * * * * * *
30 29.58 30.42 9.5 12 6.5 10 4 8 * * * * * * * * * * * *
35 34.5 35.5 11.5 15 9 13 6 11 * * * * * * * * * *
40 39.5 40.5 16.5 20 14 18 11 16 5.75 12 * * * * * * * * * *
45 44.5 45.5 19 23 16 21 10.75 17 5.5 13 * * * * * * * *
50 49.5 50.5 24 28 21 26 15.75 22 10.5 18 * * * * * * * *
55 54.4 55.6 26 31 20.75 27 15.5 23 10.25 19 * * * * * *
60 59.4 60.6 31 36 25.75 32 20.5 28 15.25 24 10 20 * * * *
65 64.4 65.6 30.75 37 25.5 33 20.25 29 15 25 11 21 * *
70 69.4 70.6 35.75 42 30.5 38 25.25 34 20 30 16 26 * *
80 79.4 80.6 45.75 52 40.5 48 35.25 44 30 40 26 36 15.5 28
90 89.3 90.7 50.5 58 45.25 54 40 50 36 46 25.5 38
100 99.3 100.7 60.5 68 55.25 64 50 60 46 56 35.5 48
110 109.3 110.7 62.25 74 60 70 56 66 45.5 58
120 119.3 120.7 75.25 84 70 80 66 76 55.5 68
130 129.2 130.8 80 90 76 86 65.5 78
140 139.2 140.8 90 100 86 96 75.5 88
150 149.2 150.8 96 106 85.5 98
160 159.2 160.8 106 116 95.5 108
180 179.2 180.8 115.5 128
200 199.1 200.9 135.5 148
・P is the screw pitch.
・b applies where there is no shading between the thick stepped lines.
・c) Applies to head portion with no knurling.
・d) Applies to head portion with knurling.
・The minimum value of e is 1.14 times the minimum value of s.
・For gauge inspection of hexagon socket dimensions s and e, see JIS B 1016.
・The range of nominal lengths in general circulation is within the thick stepped lines.
   Shaded areas are with complete screw parts. Lengths of incomplete screw parts under neck are within 3P.
   Values in nonshaded areas indicate values for ℓ g and ℓ s, and are found with the following formulas. ℓ g max = ℓ nom − b, ℓ s min = ℓ g max − 5P
・It is best to avoid using bolts where nominal diameters are in parentheses.

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