ASME B18.3.1M Metric Socket Head Cap Screws

ASME B18.3.1M Metric Socket Head Cap Screws

Dimensions of ASME B18.3.1M Metric Socket Head Cap Screws

Nominal Size and Thread Pitch D A H S J M T G B E F K
Underhead Fillet
Body Diameter Head Diameter Head Height Cham
fer or Radius		 Hexagon
Socket
Size		 Spline
Socket
Size		 Key Engage
ment		 Wall
Thick-ness		 Transition Diameter Transi
tion
Length		 Junc
ture
Radius		 Charm-
far or Radius
Max Min Max Min Max Min Max Nom. Nom. Min. Min. Max. Min. Max. Min. Max.
M1.6 x 0.35 1.60 1.46 3.00 2.87 1.60 1.52 0.16 1.5 1.829 0.80 0.54 2.0 1.8 0.34 0.10 0.08
M2 0.4 2.00 1.86 3.80 3.65 2.00 1.91 0.20 1.5 1.829 1.00 0.68 2.6 2.2 0.51 0.10 0.08
M2.5 x 0.45 2.50 2.36 4.50 4.33 2.50 2.40 0.25 2.0 2.438 1.25 0.85 3.1 2.7 0.51 0.10 0.08
M3 x 0.5 3.00 2.86 5.50 5.32 3.00 2.89 0.30 2.5 2.819 1.50 1.02 3.6 3.2 0.51 0.10 0.13
M4 x 0.7 4.00 3.82 7.00 6.80 4.00 3.88 0.40 3.0 3.378 2.00 1.52 4.7 4.4 0.60 0.20 0.13
M5 x 0.8 5.00 4.82 8.50 8.27 5.00 4.86 0.50 4.0 4.648 2.50 1.90 5.7 5.4 0.60 0.20 0.13
M6 x 1 6.00 5.82 10.00 9.74 6.00 5.85 0.60 5.0 5.486 3.00 2.28 6.8 6.5 0.68 0.25 0.20
M8 x 1.25 8.00 7.78 13.00 12.70 8.00 7.83 0.80 6.0 7.391 4.00 3.20 9.2 8.8 1.02 0.40 0.20
M10 x 1.5 10.00 9.78 16.00 15.67 10.00 9.81 1.00 8.0 -- 5.00 4.00 11.2 10.8 1.02 0.40 0.20
M12 x 1.75 12.00 11.73 18.00 17.63 12.00 11.79 1.20 10.0 -- 6.00 4.80 14.2 13.2 1.87 0.60 0.25
M14 x 2(1) 14.00 13.73 21.00 20.60 14.00 13.77 1.40 12.0 -- 7.00 5.60 16.2 15.2 1.87 0.60 0.25
M16 x 2 16.00 15.73 24.00 23.58 16.00 15.76 1.60 14.0 -- 8.00 6.40 18.2 17.2 1.87 0.60 0.25
M20 x 2.5 20.00 19.67 30.00 29.53 20.00 19.73 2.00 17.0 -- 10.00 8.00 22.4 21.6 2.04 0.80 0.40
M24 x 3 24.00 23.67 36.00 35.48 24.00 23.70 2.40 19.0 -- 12.00 9.60 26.4 25.6 2.04 0.80 0.40
M30 x 3.5 30.00 29.67 45.00 44.42 30.00 29.67 3.00 22.0 -- 15.00 12.00 33.4 32.0 2.89 1.00 0.40
M36 x 4 36.00 35.61 54.00 43.37 36.00 35.64 3.60 27.0 -- 18.00 14.40 39.4 38.0 2.89 1.00 0.40
M42 x 4.5 42.00 41.61 63.00 62.31 42.00 41.61 4.20 32.0 -- 21.00 16.80 45.6 44.4 3.06 1.20 0.40
M48 x 5 48.00 47.61 72.00 71.27 48.00 47.58 4.80 36.0 -- 24.00 19.20 52.6 51.2 3.91 1.60 0.40
See para. 2.4.2 2.1.1 2.1.2 2.2.2 2.2.2 2.2.3 2.2.3 2.1.6 2.1.3
    Note:
  • The 14 x 2 mm size is not recommended for use in new designs.
ASME B18.3.1M Metric Socket Head Cap Screws ASME B18.3.1M Metric Socket Head Cap Screws

Dimensions of Metric hexagon sockets

Nominal Hexagon Socket Size J C
Socket Width Across Flats Socket Width Across Corners
Max. Min. Min.
1.5 1.545 1.520 1.73
2 2.045 2.020 2.30
2.5 2.560 2.520 2.87
3 3.071 3.020 3.44
4 4.084 4.020 4.58
5 5.084 5.020 5.72
6 6.095 6.020 6.86
8 8.115 8.025 9.15
10 10.127 10.025 11.50
12 12.146 12.032 13.80
14 14.159 14.032 16.09
17 17.216 17.050 19.56
19 19.243 19.065 21.87
22 22.319 22.065 25.31
24 24.319 24.065 27.60
27 27.319 27.065 31.04
32 32.461 32.080 36.80
36 36.461 36.080 41.38

Tolerance on Length. The tolerance on length shall be bilateral as tabulated below.

Nominal Screw Size M1.6 Through M10 M12 Through M20 Over M20
Nominal Screw Length Tolerance on Length, mm
Upt to 16 mm, incl.
Over 16mm to 50mm, incl.
Over 50 mm to 120 mm, incl.
Over 120 mm to 200 mm, incl.
Over 200 mm		 ±0.3
±0.4
±0.7
±1.0
±2.0		 ±0.3
±0.4
±1.0
±1.5
±2.5		 ...
±0.7
±1.5
±2.0
±3.0

Bosy and Grip Lenth Dimensions For Metric Socket Head Cap Screws

Nominal
Size		 M2 M1.6 M2.5 M3 M4 M5 M6 M8 M10 M12 M14 M16 M20 M24
Nominal
Length		 LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB
20 4.8 3.0 4.0 2.0
25 9.8 8.0 9.0 7.0 8.0 5.0 7.0 4.5
30 14.8 13.0 14.0 12.0 13.0 10.7 12.0 9.5 10.0 6.5
35 ... ... 19.0 17.0 18.0 15.7 17.0 14.5 15.0 11.5 13.0 9.0 11.0 6.0
40 ... ... 24.0 22.0 23.0 20.7 22.0 19.5 20.0 16.5 18.0 14.0 16.0 11.0
45 ... ... ... ... 28.0 25.7 27.0 24.5 25.0 21.5 23.0 19.0 21.0 16.0 17.0 10.7
50 ... ... ... ... 33.0 30.7 32.0 29.5 30.0 26.5 28.0 24.0 26.0 21.0 22.0 15.7 18.0 10.5
55 ... ... ... ... ... ... 37.0 34.5 35.0 31.5 33.0 29.0 31.0 26.0 27.0 20.7 23.0 15.5
60 ... ... ... ... ... ... 42.0 39.5 40.0 36.5 38.0 34.0 36.0 31.0 32.0 25.7 28.0 20.5 24.0 15.2
65 ... ... ... ... ... ... 47.0 44.5 45.0 41.5 43.0 39.0 41.0 36.0 37.0 30.7 33.5 25.0 29.0 20.2 25.0 15.0
70 ... ... ... ... ... ... ... ... 50.0 46.5 48.0 44.0 46.0 41.0 42.0 35.7 38.0 30.5 34.0 25.2 30.0 20.0 26.0 16.0
80 ... ... ... ... ... ... ... ... 60.0 56.5 58.0 54.0 56.0 51.0 52.0 45.7 48.0 40.5 44.0 35.2 40.0 30.0 36.0 26.0
90 ... ... ... ... ... ... ... ... ... ... 68.0 64.0 66.0 61.0 62.0 55.7 58.0 50.5 54.0 45.2 50.0 40.0 46.0 36.0 38.0 25.5
100 ... ... ... ... ... ... ... ... ... ... 78.0 74.0 76.0 71.0 72.0 65.7 68.0 60.5 64.0 55.2 60.0 50.0 56.0 46.0 48.0 35.5 40.0 25.0
110 ... ... ... ... ... ... ... ... ... ... ... ... 86.0 81.0 82.0 75.7 78.0 70.5 74.0 65.2 70.0 60.0 66.0 56.0 58.0 45.5 50.0 35.0
120 ... ... ... ... ... ... ... ... ... ... ... ... 96.0 91.0 92.0 85.7 88.0 80.5 84.0 75.2 80.0 70.0 76.0 66.0 68.0 55.5 60.0 45.0
130 ... ... ... ... ... ... ... ... ... ... ... ... ... ... 102.0 95.7 98.0 90.5 94.0 85.2 90.0 80.0 86.0 76.0 78.0 65.5 70.0 55.5
140 ... ... ... ... ... ... ... ... ... ... ... ... ... ... 112.0 105.7 108.0 100.5 104.0 95.2 100.0 90.0 96.0 86.0 88.0 75.0 80.0 65.5
150 ... ... ... ... ... ... ... ... ... ... ... ... ... ... 122.0 115.7 118.0 110.5 114.0 105.2 110.0 100.0 106.0 96.0 98.0 85.0 90.0 75.5
160 ... ... ... ... ... ... ... ... ... ... ... ... ... ... 132.0 125.7 128.0 120.5 124.0 115.2 120.0 110.0 116.0 106.0 108.0 95.0 100.0 85.0
180 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 148.0 140.5 144.0 135.2 140.0 130.0 136.0 126.0 128.0 115.0 120.0 105.0
200 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 168.0 160.5 164.0 155.2 180.0 150.0 156.0 146.0 148.0 135.0 140.0 125.0
220 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 184.0 175.2 180.0 170.0 176.0 166.0 168.0 155.0 160.0 145.0
240 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 204.0 195.0 200.0 190.0 196.0 186.0 188.0 175.0 180.0 165.0
260 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 220.0 210.0 216.0 206.0 208.0 195.0 200.0 185.0
300 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 256.0 246.0 248.0 235.0 240.0 225.0

ASME B18.3.1M Metric Socket Head Cap Screws

Thread Lengths For Determining Body And Grip Lengths On Screws Beyond Diameters And Lengths Tabulated

Nominal Size or Basic Screw Diameter LT LTT
Thread Length Total Thread Length [Note (1)]
Min. Max.
M1.6 15.2 17.0
M2 16.0 18.0
M2.5 17.0 19.3
M3 18.0 20.5
M4 20.0 23.5
M5 22.0 26.0
M6 24.0 29.0
M8 28.0 34.3
M10 32.0 39.5
M12 36.0 44.8
M14 40.0 50.0
M16 44.0 54.0
M20 52.0 64.5
M24 60.0 75.0
M30 72.0 89.5
M36 84.0 104.0
M42 96.0 118.5
M48 108.0 133.0

Note: (1) Tabulated values are equal to LT plus 5 times the pitch of the coarse thread for the respective screw sizes.