ASME B18.2.

2-2022

Table 1.1.1-1
Dimensions of Square and Hex Machine Screw Nuts

IHI

<
Gv chamfer
optional

Width Across Corners

Basic Major
Nominal Diameter of Width Across Flats, F Square, G Hex, G1 Thickness, H Bearing Surface Runout to
Size Thread Basic Min. Max. Min. Max. Min. Max. Min. Max. Thread Axis, FlM
0 0.060 %z 0.150 0.156 0.206 0.221 0.171 0.180 0.043 0.050 0.005
1 0.073 %z 0.150 0.156 0.206 0.221 0.171 0.180 0.043 0.050 0.005
2 0.086 3/16 0.180 0.188 0.247 0.265 0.205 0.217 0.057 0.066 0.006
3 0.099 3/ 6 0.180 0.188 0.247 0.265 0.205 0.217 0.057 0.066 0.006
1

4 0.112 % 0.241 0.250 0.331 0.354 0.275 0.289 0.087 0.098 0.009
5 0.125 %6 0.302 0.312 0.415 0.442 0.344 0.361 0.102 0.114 0.011
6 0.138 5/16 0.302 0.312 0.415 0.442 0.344 0.361 0.102 0.114 0.011
8 0.164 1%z 0.332 0.344 0.456 0.486 0.378 0.397 0.117 0.130 0.012

10 0.190 % 0.362 0.375 0.497 0.530 0.413 0.433 0.117 0.130 0.013
12 0.216 7/16 0.423 0.438 0.581 0.619 0.482 0.505 0.148 0.161 O.D15
1;4 0.250 7/16 0.423 0.438 0.581 0.619 0.482 0.505 0.178 0.193 O.D15
5/16 0.312 9/16 0.545 0.562 0.748 0.795 0.621 0.650 0.208 0.225 0.020
% 0.375 % 0.607 0.625 0.833 0.884 0.692 0.722 0.239 0.257 0.021
GENERAL NOTES:
(a) For additional requirements, refer to section 3.
(b) As shown in the figure, no countersink is required.
(c) Material. Unless otherwise specified, machine screw nuts shall be made of carbon steel.
(d) Mechanical Property Requirements. Unless the purchaser specifies otherwise in the inquiry and purchase documents, machine screw nuts
have no mechanical requirements.

5
 ASME B18.2.2-2022

Table 1.1.1-2
Dimensions of Small Pattern Hex Machine Screw Nuts

Botto m
chamfer
optional

Width Across
Basic Major Width Across Flats, F Corners, Hex,
Nominal Diameter of [Note (1)] G1 Thickness, H Bearing Surface Runout to
Size Thread Basic Min. Max. Min. Max. Min. Max. Thread Axis, FIM
0 0.060 % 0.121 0.125 0.134 0.140 0.043 0.050 0.005
1 0.073 % 0.121 0.125 0.134 0.140 0.043 0.050 0.005
2 0.086 %z 0.150 0.156 0.171 0.180 0.057 0.066 0.006
3 0.099 %z 0.150 0.156 0.171 0.180 0.057 0.066 0.006

4 0.112 3/16 0.180 0.188 0.205 0.217 0.057 0.066 0.009

0.125 1; 0.241 0.289 0.011
5 4 0.250 0.275 0.087 0.098
6 0.138 1; 0.241 0.250 0.275 0.289 0.087 0.098 0.011
4
8 0.164 1; 0.241 0.250 0.275 0.289 0.087 0.098 0.012
4

8 0.164 5/16 0.302 0.312 0.344 0.361 0.102 0.114 0.012

10 0.190 1; 0.241 0.250 0.275 0.289 0.087 0.098 0.013
4
10 0.190 %6 0.302 0.312 0.344 0.361 0.102 0.114 0.013
11;32
10 0.190 0.332 0.344 0.378 0.397 0.117 0.130 0.013
GENERAL NOTES:
(a) For additional requirements, refer to section 3.
(b) As shown in the figure, no countersink is required.
(c) Material. Unless otherwise specified, machine screw nuts shall be made of carbon steel.
(d) Mechanical Property Requirements. Unless the purchaser specifies otherwise in the inquiry and purchase documents, machine screw nuts
have no mechanical requirements.
NOTE: (1) The purchaser shall specify the desired basic width across flats for those sizes with multiple options listed (see para. 3.13).

6
 [�FN Table 1.1.1-15
Dimensions of Hex Castle Nuts

. JJ
1- H ­
I�T-.
�� +0.016 i n .
approx.

- l, � tI
I
\

�
R R

Unslotted Thickness Dia. of

and Height of Cylindrical Maximum Runout
Basic Major Width Across Width Across Flats, T Width of Radius of Part, U of Bearing Surface
Nominal OiamPtPr nf Flats, F Corners, G Thickness, H [Note (1)) Slot, S Fillet, R [Note (2)) tn ThrP"tl AYi�. FIM
Size Thread Basic Min. Max. Min. Max. Basic Min. Max. Nom. Min. Max. Min. Max. Max. Min. [Note (3)) >
"'

%6 ::
% 0.2500 7/16 0.428 0.438 0.488 0.505 %2 0.274 0.288 0.18 0.20 0.07 0.10 0.094 0.371 0.015 �

5/16 0.3125 1;2 0.489 0.500 0.557 0.577 2 %4 0.320 0.336 1 %4 0.22 0.24 0.09 0.12 0.094 0.425 0.016 Cll
.....
N
...... 0.3750 0.551 0.562 0.628 0.650 1 3/ 0.398 0.415 0.27 0.29 0.12 0.15 0.094 0.478 0.017
o:>
N
% 9116 32 %2 N
7/1 6 0.4375 1 1116 0.675 0.688 0.768 0.794 2%
4 0.444 0.463 1%
4 0.29 0.31 0.12 0.15 0.094 0.582 0.018 N
0
1; 0.5000 % 0.736 0.750 0.840 0.866 9116 0.552 0.573 1% 0.40 0.42 0.15 0.18 0.125 0.637 0.019 N
2 2 N

0.5625 7/a 0.861 0.875 0.982 1.010 3%4 0.598 0.621 2 7; 0.41 0.43 0.15 0.18 0.156 0.744 0.020
%6 64
1 5/16 2 3/
% 0.6250 0.92 2 0.938 1.051 1.083 32 0.706 0.731 % 0.49 0.51 0.18 0.24 0.156 0.797 0.021
% 0.7500 1% 1.088 1.125 1.240 1.299 1 %6 0.798 0.827 %6 0.55 0.57 0.18 0.24 0.188 0.941 0.023
7/a 0.8750 1 %6 1.269 1.312 1.447 1.516 29; 0.890 0.92 2 2% 0.64 0.67 0.18 0.24 0.188 1.097 0.025
32 2
1 1.0000 1 1/2 1.450 1.500 1.653 1.732 1 0.982 1.018 2 3/ 0.70 0.73 0.24 0.30 0.188 1.254 0.027
32

1% 1.1250 1 1 1/16 1.631 1.688 1.859 1.949 1 %2 1.136 1.176 1%6 0.80 0.83 0.24 0.33 0.250 1.411 0.030
1% 1.2500 17/a 1.812 1.875 2.066 2.165 1% 1.228 1.272 7/a 0.86 0.89 0.31 0.40 0.250 1.570 0.033
1% 1.3750 2 1/1 6 1.994 2.062 2.273 2.382 1% 1.351 1.399 1 0.98 1.02 0.31 0.40 0.250 1.726 0.036
1 1/2 1.5000 2 1/4 2.175 2.250 2.480 2.598 1% 1.474 1.526 1 %6 1.04 1.08 0.37 0.46 0.250 1.881 0.039
GENERAL NOTE: For additional requirements, refer to section 3.
NOTES:
(1) Height of Hex. Height of the hex is measured from the bearing surface to the top of the arc.
(2) Cylindrical Part. Maximum diameter of cylindrical part shall not exceed maximum width across flats.
(3) Bearing Surface. Bearing surface of nuts of nominal size % in. and smaller shall have chamfered corners. Bearing surface of larger size nuts shall be washer faced or have chamfered corners.
 ASME 818.2.2-2022

MANDATORY APPENDIX I
SLOT GAGES AND GAGING FOR SLOTTED NUTS

The gages specified in Table 1-1 shall be used to determine the acceptability of the alignment and bottom contours of the
slots in slotted nuts in accordance with the following procedure.
The gaging for slot alignment provides for equal variations in the location of the cotter pinhole in the bolt and the
location of the slots in the nut.
To inspect the nut, the slotted end of the gage shall be inserted through the threaded hole from the bearing surface of the
nut. The gage pin shall then be inserted into both the gage slot and the nut slots through three adjacent faces of the nut,
consecutively. Slot alignment shall be considered satisfactory if the gage pin fits into the slots without interference at all
three gaging positions. The bottom contour shall be acceptable if the gage pin contacts the bottom surfaces of opposite
slots during the alignment gaging at all three positions.
Some deviations from the specified gage plug diameters, D, may be necessary to compensate for variations in the nut
thread minor diameter due to differences in manufacturing practices. To ensure adequate service life, gages and gage pins
shall be suitably hardened.

22
 ASME 818.2.2-2022

Table 1-1
Dimensions of SLot Gages and Gage Pins

optional

Gage Gage Pin

Gage Plug
Diameter, D
N_
__,[� te
o_ (1
-')_,_
__,_ ] __ Gage Pilot
_ Gage Gage Pin
Basic Coarse Fine Diameter, Slot Diameter,
Major Minimum Maximum Minimum Thread Thread E Width, F G Minimum
Nominal Diameter Gage Pilot Gage Plug Gage Face +0.000 +0.000 +0.002 +0.000 Gage Pin
Size of Thread Length, A Length, B Diameter, C -0.001 -0.001 ±0.005 -0.000 -0.002 Length, H
0.2500 0.288 0.110 0.375 0.196 0.2 1 1 0.181 0.065 0.065 1.00
0.3125 0.316 0.150 0.406 0.252 0.267 0.237 0.085 0.085 1.06
0.3750 0.415 0.180 0.500 0.307 0.330 0.292 0. 115 0.115 1.19
0.4375 0.463 0.200 0.562 0.360 0.383 0.345 0. 115 0.115 1.25
0.5000 0.573 0.260 0.625 0.417 0.446 0.402 0.145 0.145 1.38

0.5625 0.621 0.280 0.703 0.472 0.502 0.457 0.145 0.145 1.44
0.6250 0.731 0.310 0.781 0.527 0.565 0.512 0.175 0.175 1.56
0.7500 0.827 0.370 0.938 0.642 0.682 0.627 0.175 0.175 1.75
0.8750 0.922 0.480 1.109 0.755 0.798 0.740 0.175 0.175 1.94
1.0000 1.018 0.550 1.250 0.865 0.910 0.850 0.235 0.235 2.12

1.1250 1.176 0.600 1.406 0.970 1.035 0.955 0.235 0.235 2.31
1.2500 1.272 0.660 1.562 1.095 1.160 1.080 0.305 0.305 2.50
1.3750 1.399 0.770 1.718 1.195 1.285 1.180 0.305 0.305 2.69
1.5000 1.526 0.810 1.875 1.320 1.410 1.305 0.365 0.365 2.88
1.7500 1.759 1.190 2.188 1.534 1.519 0.425 0.425 3.25

2.0000 2.013 1.370 2.500 1.759 1.744 0.425 0.425 3.62

2.2500 2.251 1.610 2.818 2.009 1.994 0.425 0.425 4.00
2.5000 2.505 1.730 3.125 2.229 2.214 0.545 0.545 4.38
2.7500 2.759 1.980 3.438 2.479 2.464 0.545 0.545 4.75
3.0000 3.013 2.160 3.750 2.729 2.714 0.615 0.615 5.12

3.2500 3.252 2.400 4.062 2.979 2.964 0.615 0.615 5.50

3.5000 3.506 2.640 4.375 3.229 3.214 0.615 0.615 5.88
3.7500 3.760 2.890 4.688 3.479 3.464 0.615 0.615 6.25
4.0000 4.0 14 3.140 5.000 3.729 3.714 0.615 0.615 6.62
NOTE: (1) Diameters tabulated are equivalent to the minimum minor diameters of Class 28 threads. If the nuts are not threaded with unified
coarse (UNC) or fine (UNF) threads, the diameter of gage shall be the same as the diameter of the GO thread plug gage for the bore.

23
 ASME 818.2.2-2022

NONMANDATORV APPENDIX A
FORMULAS FOR NUT DIMENSIONS

Table A- 1 specifies formulas for various nut dimensions.

24
 Table A-1
Formulas for Nut Dimensions

Width Across Flats I Nut Thickness I Limits for Width Across Corners, G
Tolerance Tolerance
Nut Type Nut Size Basic [Note (1)] (Minus) Basic [Note (2)] (Plus or Minus) Min. Max.
Square % to % F = 1.500D + 0.062 0.050D H = 0.875D 0.016D + 0.01 2 1.373 x (Min. F ) - 0.030 1.4142 x (Max. F )
% to 1l;z F = 1.500D 0.050D H = 0.875D 0.016D + 0.01 2 1.373 x (Min. F ) - 0.030 1.4142 x (Max. F )

Hex flat 1 % to 1 1/2 F = 1.500D 0.050D H = 0.875D 0.016D + 0.01 2 1.14 x (Min. F ) 1.1547 x (Max. F )

Hex flat jam 1% F = 1.500D 0.050D H = 0.500D + 0.062 0.016D + 0.01 2 1.14 x (Min. F ) 1.1 547 x (Max. F )
1 % to 1 1/2 F = 1.500D 0.050D H = 0.500D + 0.125 0.016D + 0.01 2 1.14 x (Min. F ) 1.1547 x (Max. F )

Hex and hex slotted % F= 1.500D + 0.062 0.015D + 0.006 H= 0.875D 0.015D + 0.003 1.14 x (Min. F ) 1.1547 x (Max. F)
5/16 to % F= 1.500D 0.015D + 0.006 H= 0.875D 0.015D + 0.003 1.14 x (Min. F ) 1.1547 x (Max. F)
% to 1 % F= 1.500D 0.050D H= 0.875D - 0.016 0.016D + 0.01 2 1.14 x (Min. F ) 1.1547 x (Max. F)
1 % to 1 1/2 F= 1.500D 0.050D H= 0.875D - 0.031 0.016D + 0.01 2 1.14 x (Min. F ) 1.1547 x (Max. F) >
"'
::
�
Hex jam % F= 1.500D + 0.062 0.015D + 0.006 H= See Table 1.1.1-5 0.015D + 0.003 1.14 x (Min. F) 1.1547 x (Max. F) Cll
.....
N o:>
U'1 5/16 to % F= 1.500D 0.015D + 0.006 H= See Table 1.1.1-5 0.015D + 0.003 1.14 x (Min. F) 1.1547 x (Max. F) N
N
% to 1 % F= 1.500D 0.050D H= 0.500D + 0.04 7 0.016D + 0.012 1.14 x (Min. F) 1.1 547 x (Max. F) N
1 1/4 to 1 1/2
0
F= 1.500D 0.050D H= 0.500D + 0.094 0.016D + 0.01 2 1.14 x (Min. F) 1.1547 x (Max. F) N
N

Hex thick and hex thick % F = 1.500D + 0.062 0.015D + 0.006 H = See Table 1.1.1-7 or 0.015D + 0.003 1.14 x (Min. F ) 1.1547 x (Max. F )
slotted Table 1.1.1-8
5/ 6 to % F = 1.500D 0.015D 0.006 H = See Table 1.1.1-7 or 0.015D 0.003 1.14 (Min. F ) 1.1 547 (Max. F )
1 + + x x

Table 1.1.1-8
% to 1l;z F = 1.500D 0.050D H = See Table 1.1.1-7 or 0.015D + 0.003 1.14 x (Min. F ) 1.1547 x (Max. F )
Table 1.1.1-8

Heavy square % to 1Y2 F = 1.500D + 0.125 0.050D H = l.OOOD 0.016D + 0.01 2 1.373 x (Min. F ) - 0.030 1.4142 x (Max. F )
[Note (3)]

Heavy hex flat 1 % to 4 F = 1.500D + 0.125 0.050D H = l.OOOD 0.016D + 0.01 2 1.14 x (Min. F ) 1.1547 x (Max. F )
[Note (3)]