Nuts and Washers

A320 bolts will use A194 heavy hex nuts. There are multiple grades within the A194 specification. The appropriate grade of A194 nut will be determined by the chemistry and strength of the fastener grade.  The chart below matches the compatible grade of nut with the specific grade of bolt. Nuts are heavy hex pattern, matching the width across the flats of the bolt head. Carbon steel nuts can undergo an impact test and will need to marked with an “L” to show it has been tested. However, impact testing is not required if the bar stock or nut is smaller than 5/8″ diameter.

All washers used with alloy steel versions of the A320 specification comply with ASTM F436. There are no ASTM specifications covering stainless steel washers. Washers are provided in their respective stainless steel grade. It is also important to note that stainless steel washer dimensions can vary between manufacturers.

Grade of Bolt A194 Heavy Hex Nut Grade
A320 Grade L7 4 or 7
A320 Grade L7M 7M
A320 Grade B8 (Class 1 and 2) 8
A320 Grade B8M (Class 1 and 2) 8M
A320 Grade B8C 8C
A320 Grade B8T 8T
A320 Grade B8LN 8LN
A320 Grade B8MLN 8MLN
For Class 2 stainless steel grades, strain hardened nuts available as a supplementary requirement

Heavy Hex Nut Dimensions

Click table to show drawingHeavy Hex Nut
Bolt Diam. F C H Weight
(lbs.)
Width Across Flats Width Across Corners Thickness
Basic Max Min Max Min Basic Max Min
1⁄2 7⁄8 0.875 0.850 1.010 0.969 31⁄64 0.504 0.464 0.07
5⁄8 11⁄16 1.062 1.031 1.227 1.175 39⁄64 0.631 0.587 0.12
3⁄4 11⁄4 1.250 1.212 1.443 1.382 47⁄64 0.758 0.710 0.20
7⁄8 17⁄16 1.438 1.394 1.660 1.589 55⁄64 0.885 0.833 0.30
1 15⁄8 1.625 1.575 1.876 1.796 63⁄64 1.012 0.956 0.43
11⁄8 113⁄16 1.812 1.756 2.093 2.002 17⁄64 1.139 1.079 0.59
11⁄4 2 2.000 1.938 2.309 2.209 17⁄32 1.251 1.187 0.79
13⁄8 23⁄16 2.188 2.119 2.526 2.416 111⁄32 1.378 1.310 1.02
11⁄2 23⁄8 2.375 2.300 2.742 2.622 115⁄32 1.505 1.433 1.31
15⁄8 29⁄16 2.562 2.481 2.959 2.828 119⁄32 1.632 1.556 1.62
13⁄4 23⁄4 2.750 2.662 3.175 3.035 123⁄32 1.759 1.679 2.04
17⁄8 215⁄16 2.938 2.844 3.392 3.242 127⁄32 1.886 1.802 2.41
2 31⁄8 3.125 3.025 3.608 3.449 131⁄32 2.013 1.925 2.99
21⁄4 31⁄2 3.500 3.388 4.041 3.862 213⁄64 2.251 2.155 4.19
21⁄2 37⁄8 3.875 3.750 4.474 4.275 229⁄64 2.505 2.401 5.64
23⁄4 41⁄4 4.250 4.112 4.907 4.688 245⁄64 2.759 2.647 7.38
3 45⁄8 4.625 4.475 5.340 5.102 261⁄64 3.013 2.893 9.50
31⁄4 5 5.000 4.838 5.774 5.515 33⁄16 3.252 3.124 11.94
31⁄2 53⁄8 5.375 5.200 6.207 5.928 37⁄16 3.506 3.370 15.26
33⁄4 53⁄4 5.750 5.562 6.640 6.341 311⁄16 3.760 3.616 18.12
4 61⁄8 6.125 5.925 7.073 6.755 315⁄16 4.014 3.862 21.80

Dimensions per ASME B18.2.2 1987 (1999)

Hardened Washer Dimensions

Click table to show drawingWasher
Bolt Size B A C Weight (lbs.) Per 1000 Pieces Part Numbers
Outside Diameter Inside Diameter Thickness Domestic
Min Max Plain Galvanized
1⁄2 11⁄16 17⁄32 0.097 0.177 18 16440 16441
5⁄8 15⁄16 11⁄16 0.122 0.177 33 16442 16443
3⁄4 115⁄32 13⁄16 0.122 0.177 41 16444 16445
7⁄8 13⁄4 15⁄16 0.136 0.177 64 16446 16447
1 2 11⁄16 0.136 0.177 82 16448 16449
11⁄8 21⁄4 13⁄16 0.136 0.177 105 16450 16451
11⁄4 21⁄2 13⁄8 0.136 0.177 133 16452 16453
13⁄8 23⁄4 11⁄2 0.136 0.177 163 16454 16455
11⁄2 3 15⁄8 0.136 0.177 200 16456 16457
15⁄8 31⁄4 13⁄4 0.178 0.28 320 19481* 19482*
13⁄4 33⁄8 17⁄8 0.178 0.28 307 16458 16459
17⁄8 31⁄2 2 0.178 0.28 360 16471* 16472
2 33⁄4 21⁄8 0.178 0.28 380 16460 16461
21⁄4 4 23⁄8 0.24 0.34 560 16462 16463
21⁄2 41⁄2 25⁄8 0.24 0.34 720 16464 16465
23⁄4 5 27⁄8 0.24 0.34 920 16611 16612
3 51⁄2 31⁄8 0.24 0.34 1040 16613 16614
31⁄4 6 33⁄8 0.24 0.34 1350 - -
31⁄2 61⁄2 35⁄8 0.24 0.34 1633 18490 18460
33⁄4 7 37⁄8 0.24 0.34 1880 - -
4 71⁄2 41⁄8 0.24 0.34 2200 18461 18462
Dimensions per ASTM F436
*Usually domestic