Lock nuts are available in numerous styles, grades and finishes. The term “lock nut” is not meant to imply that there is an indefinite permanency of fixity once used. Most locknuts can be removed and some can even be reused if removed correctly. Lock nuts are most commonly available in ASTM A563 Grades A and DH and ASTM A194 Grade 2H. They are manufactured with a standard hex or a heavy hex pattern. Two of the most common lock nut styles are Anco and Tri-Lok. The Anco style is a self-locking nut with a ratchet pin that is made from stainless steel. This ratchet pin slides along the threads as the nut is spun onto the bolt and prevents the nut from backing off. One benefit to using an Anco style lock nut is that the ratchet pin can be bent back so that the nut can be easily removed if needed. The Tri-Lok style is a “prevailing-torque” locknut which is frictionally resistant to rotation due to the thread distortion on the top thread of the nut. For various other types of lock nuts, please call one of our estimators!

Since hot-dip galvanizing typically adds 2.2 to 5 mils of thickness to the threaded portion of a fastener, galvanized lock nuts are tapped oversized to compensate for the corrosion resistant coating on the bolts.

Finished Hex Dimensions

Click table to show drawingDimensioned Anco Lock Nut
Nominal Size F C H Weight Each (lbs.)
Width Across Flats Width Across Corners Thickness
Basic Max Min Max Min Basic Max Min
12 34 0.750 0.736 0.866 0.840 716 0.448 0.427 0.04
58 1516 0.938 0.922 1.083 1.051 3564 0.559 0.535 0.07
34 118 1.125 1.088 1.299 1.240 4164 0.665 0.617 0.12
78 1516 1.312 1.269 1.516 1.447 34 0.776 0.724 0.19
1 112 1.500 1.450 1.732 1.653 5564 0.887 0.831 0.28
118 11116 1.688 1.631 1.949 1.859 3132 0.999 0.939 0.40
114 178 1.875 1.812 2.165 2.066 1116 1.094 1.030 0.54
138 2116 2.062 1.994 2.382 2.273 11164 1.206 1.138 0.73
112 214 2.250 2.175 2.598 2.480 1932 1.317 1.245 0.94
Dimensions per ASME B18.2.2 1987 (1999)

Heavy Hex Dimensions

Click table to show drawingDimensioned Anco Lock Nut
Nominal Size F C H Weight Each (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)