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Lock Nuts

Lock Nuts

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
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)