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ASME B18.3 TABLE 2A Standard Dimensions for Hexagon and spline flat countersunk head cap screws, inch series

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Socket Flat Countersunk Head Cap Screws. The flat countersunk head shall have a flat top sur-face and a conical bearing surface with included angle of approximately 82 deg.

Dimensional Drawing and Technical Diagrams

1775_tmkL8c_b18_3table2a.jpg

Key Dimensions and Technical Parameters

Dimensions in inches - ASME b18.3Table 2A - 2008- Socket Flat Countersunk Head Cap Screws
d thread size Nr. of threads x inch d1 min b basic thread length dk max theo.Sharp k max t min S nom M nom
inches mm UNC UNF
0 (0.06) 1.52 - 80 0.568 0.5 0.138 0.044 0.025 0.035 0.048
1 (0.073) 1.85 64 72 0.07 0.62 0.168 0.054 0.031 0.05 0.06
2 (0.086) 2.18 56 64 0.082 0.62 0.197 0.064 0.038 0.05 0.06
3 0.099) 2.51 48 56 0.095 0.62 0.226 0.073 0.044 0.062 0.072
4 (0.112) 2.84 40 48 0.108 0.75 0.255 0.083 0.055 0.062 0.072
5 (0.125) 3.18 40 44 0.12 0.75 0.281 0.90 0.061 0.078 0.096
6 (0.138) 3.51 32 40 0.133 0.75 0.307 0.097 0.066 0.078 0.096
8 (0.164) 4.17 32 36 0.159 0.875 0.359 0.112 0.076 0.094 0.111
10 (0.19) 4.83 24 32 0.184 0.875 0.411 0.127 0.087 0.125 0.145
1/4 6.35 20 28 0.244 1 0.531 0.161 0.111 0.156 0.183
5/16 7.94 18 24 0.305 1.125 0.656 0.198 0.135 0.188 0.216
3/8 9.53 16 24 0.368 1.25 0.781 0.234 0.159 0.219 0.251
7/16 11.11 14 20 0.429 1.375 0.844 0.234 0.159 0.25 0.291
1/2 12.70 13 20 0.492 1.5 0.938 0.251 0.172 0.312 0.372
5/8 15.88 11 18 0.616 1.75 1.188 0.324 0.220 0.375 0.454
3/4 19.05 10 16 0.741 2 1.438 0.396 0.220 0.5 0.454
7/8 22.23 9 14 0.865 2.25 1.688 0.468 0.248 0.562 -
1 25.40 8 12 0.989 2.5 1.938 0.540 0.297 0.625 -
1-1/8 28.58 7 12 1.108 2.81 2.188 0.611 0.325 0.75 -
1-1/4 31.75 7 12 1.233 3.12 2.438 0.683 0.358 0.875 -
1-3/8 34.93 6 12 1.357 3.44 2.688 0.755 0.402 0.875 -
1-1/2 38.10 6 12 1.482 3.75 2.938 0.827 0.435 1 -

Reproduced by permission of DIN Deutsches Institut für Normung e. V. The definitive version for the implementation of this standard is the edition bearing the most recent date of issue, obtainable from Beuth Verlag GmbH, Burggrafenstraße 6, 10787 Berlin, Germany.
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