JIS B 1181 Hexagon Nuts

Table 2 — Unified hexagon ordinary nuts, thick ordinary nuts and lock nuts — Normal series

1 2 3 4 5 6 7 8 9 10 11 12 13
Nominal size
D		 Width across flats
A		 Width across corners
C		 Diameter of washer face
B		 Thickness Tolerance on squareness of thread to face of nut
Ordinary nuts
E		 Thick ordinary nuts
P		 Lock nuts
F
Max. Min. Max. Max. Min. Max. Min. Max. Min. Max. Min. Max.
in in in in in in in in in in in in in
1/4 0.4375 0.4305 0.505 0.421 0.411 0.224 0.214 0.286 0.276 0.161 0.151 0.007
5/16 0.5000 0.4930 0.577 0.483 0.473 0.271 0.261 0.333 0.323 0.192 0.182 0.009
3/8 0.5625 0.5545 0.650 0.545 0.535 0.333 0.323 0.411 0.401 0.224 0.214 0.010
7/16 0.6875 0.6795 0.794 0.668 0.658 0.380 0.370 0.458 0.448 0.255 0.245 0.011
1/2 0.7500 0.7420 0.866 0.730 0.720 0.442 0.432 0.567 0.557 0.317 0.307 0.013
a 9/16 0.8750 0.8670 1.010 0.855 0.845 0.489 0.479 0.614 0.604 0.349 0.339 0.013
5/8 0.9375 0.9295 1.083 0.918 0.908 0.552 0.542 0.724 0.714 0.380 0.370 0.014
3/4 1.1250 1.1150 1.300 1.100 1.090 0.651 0.631 0.822 0.802 0.432 0.412 0.017
7/8 1.3125 1.3005 1.515 1.285 1.275 0.760 0.740 0.916 0.896 0.494 0.474 0.020
1 1.5000 1.4880 1.732 1.473 1.463 0.874 0.844 1.015 0.985 0.562 0.532 0.020
1 1/8 1.6875 1.6575 1.948 1.641 1.625 0.989 0.949 1.176 1.136 0.629 0.589 0.024
1 1/4 1.8750 1.8300 2.165 1.813 1.797 1.087 1.037 1.275 1.225 0.744 0.694 0.024
a1 3/8 2.0625 2.0175 2.382 2.001 1.985 1.197 1.147 1.400 1.350 0.806 0.756 0.026
1 1/2 2.2500 2.2050 2.598 2.188 2.172 1.311 1.251 1.530 1.470 0.874 0.814 0.026
1 3/4 2.6250 2.5650 3.031 2.543 2.527 1.530 1.470 — — 0.999 0.939 0.030
2 3.0000 2.9400 3.464 2.918 2.902 1.754 1.684 — — 1.129 1.059 0.030

NOTE: In the case of the 7/16 in and 9/16 in nuts, the width across flats is 1/16 in larger than that of the corresponding bolt heads. This is in accordance with the American Standards from which these sizes are derived.

a To be dispensed with wherever possible.

b When nuts from 1/4 in to 1 in nominal size are hot forged, the tolerance on width across flats shall be two and a half times the tolerance shown in the table.