Hex jam nuts are thinner than a standard hex nut but have the same dimension across the flats and corners. Hex jam nuts have two common applications. A jam nut can be threaded onto a bolt and run tight against the standard nut which will lock the nut in place and prevent it from backing off. Jam nuts are sometimes used for leveling purposes as well.

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

Stock

Diameters: 1/2″ – 2″
Origin: Import
Finish: Plain and hot-dip galvanized

Dimensions

Click table to show drawingHex Jam Nut
Nominal Size F C H Part Numbers
Width Across Flats Width Across Corners Thickness
Basic Max Min Max Min Basic Max Min Plain Galvanized
1⁄2 3⁄4 0.750 0.736 0.866 0.840 5⁄16 0.323 0.302 11827 11828
5⁄8 15⁄16 0.938 0.922 1.083 1.051 3⁄8 0.387 0.363 11829 11830
3⁄4 11⁄8 1.125 1.088 1.299 1.240 27⁄64 0.446 0.398 11831 11832
7⁄8 15⁄16 1.312 1.269 1.516 1.447 31⁄64 0.510 0.458 11833 18834
1 11⁄2 1.500 1.450 1.732 1.653 35⁄64 0.575 0.519 11835 11836
11⁄8 111⁄16 1.688 1.631 1.949 1.859 39⁄64 0.639 0.579 11837 11838
11⁄4 17⁄8 1.875 1.812 2.165 2.066 23⁄32 0.751 0.687 11839 11840
13⁄8 21⁄16 2.062 1.994 2.382 2.273 25⁄32 0.815 0.747 19678 19679
11⁄2 21⁄4 2.250 2.175 2.598 2.480 27⁄32 0.880 0.808 11841 11842

Dimensions per ASME B18.2.2 1987 (1999)