Lock nuts come in many different grades, styles, and finishes. As the name signifies, lock nuts are not irremovable once they are fixed. On the contrary, it is possible to remove most of the locknuts and perhaps some can be reused provided they are removed correctly. These nuts are commonly available in ASTM A194 Grade 2H and ASTM A563 Grades A & DH.

Lock nuts are manufactured using a heavy hex or standard hex pattern. Tri-Lok and Anco are the most common style of lock nuts. Anco style happens to be a self-locking nut provided with a ratchet pin made of stainless steel. When the nut is spun right onto the bolt, this pin slides all along the threads and prevents the nut from pulling back. The major benefit of using an Anco style nut is that it is possible to bend the ratchet pin back so that the nut could be removed easily if necessary. Tri-Lok style appears to be a “prevailing-torque” lock nut that is frictionally resistant to rotation owing to the thread distortion found on the nut’s top thread. For more information on the other kinds of lock nuts, contact us today to discuss with our expert estimators!

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
1⁄2 3⁄4 0.750 0.736 0.866 0.840 7⁄16 0.448 0.427 0.04
5⁄8 15⁄16 0.938 0.922 1.083 1.051 35⁄64 0.559 0.535 0.07
3⁄4 11⁄8 1.125 1.088 1.299 1.240 41⁄64 0.665 0.617 0.12
7⁄8 15⁄16 1.312 1.269 1.516 1.447 3⁄4 0.776 0.724 0.19
1 11⁄2 1.500 1.450 1.732 1.653 55⁄64 0.887 0.831 0.28
11⁄8 111⁄16 1.688 1.631 1.949 1.859 31⁄32 0.999 0.939 0.40
11⁄4 17⁄8 1.875 1.812 2.165 2.066 11⁄16 1.094 1.030 0.54
13⁄8 21⁄16 2.062 1.994 2.382 2.273 111⁄64 1.206 1.138 0.73
11⁄2 21⁄4 2.250 2.175 2.598 2.480 19⁄32 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
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)