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
12 78 0.875 0.850 1.010 0.969 3164 0.504 0.464 0.07
58 1116 1.062 1.031 1.227 1.175 3964 0.631 0.587 0.12
34 114 1.250 1.212 1.443 1.382 4764 0.758 0.710 0.20
78 1716 1.438 1.394 1.660 1.589 5564 0.885 0.833 0.30
1 158 1.625 1.575 1.876 1.796 6364 1.012 0.956 0.43
118 11316 1.812 1.756 2.093 2.002 1764 1.139 1.079 0.59
114 2 2.000 1.938 2.309 2.209 1732 1.251 1.187 0.79
138 2316 2.188 2.119 2.526 2.416 11132 1.378 1.310 1.02
112 238 2.375 2.300 2.742 2.622 11532 1.505 1.433 1.31
158 2916 2.562 2.481 2.959 2.828 11932 1.632 1.556 1.62
134 234 2.750 2.662 3.175 3.035 12332 1.759 1.679 2.04
178 21516 2.938 2.844 3.392 3.242 12732 1.886 1.802 2.41
2 318 3.125 3.025 3.608 3.449 13132 2.013 1.925 2.99
214 312 3.500 3.388 4.041 3.862 21364 2.251 2.155 4.19
212 378 3.875 3.750 4.474 4.275 22964 2.505 2.401 5.64
234 414 4.250 4.112 4.907 4.688 24564 2.759 2.647 7.38
3 458 4.625 4.475 5.340 5.102 26164 3.013 2.893 9.50
314 5 5.000 4.838 5.774 5.515 3316 3.252 3.124 11.94
312 538 5.375 5.200 6.207 5.928 3716 3.506 3.370 15.26
334 534 5.750 5.562 6.640 6.341 31116 3.760 3.616 18.12
4 618 6.125 5.925 7.073 6.755 31516 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
12 1116 1732 0.097 0.177 18 16440 16441
58 1516 1116 0.122 0.177 33 16442 16443
34 11532 1316 0.122 0.177 41 16444 16445
78 134 1516 0.136 0.177 64 16446 16447
1 2 1116 0.136 0.177 82 16448 16449
118 214 1316 0.136 0.177 105 16450 16451
114 212 138 0.136 0.177 133 16452 16453
138 234 112 0.136 0.177 163 16454 16455
112 3 158 0.136 0.177 200 16456 16457
158 314 134 0.178 0.28 320 19481* 19482*
134 338 178 0.178 0.28 307 16458 16459
178 312 2 0.178 0.28 360 16471* 16472
2 334 218 0.178 0.28 380 16460 16461
214 4 238 0.24 0.34 560 16462 16463
212 412 258 0.24 0.34 720 16464 16465
234 5 278 0.24 0.34 920 16611 16612
3 512 318 0.24 0.34 1040 16613 16614
314 6 338 0.24 0.34 1350 - -
312 612 358 0.24 0.34 1633 18490 18460
334 7 378 0.24 0.34 1880 - -
4 712 418 0.24 0.34 2200 18461 18462
Dimensions per ASTM F436
*Usually domestic