When reusing Hardlock products

When reusing an HLN or HLB, first screw on the convex (tightening) nut, then screw on the concave (lock) nut by hand until it no longer turns. The gap between the nuts should be about one thread pitch. If not, refrain from reusing these nuts.

When no axial (fastening) force or extremely low torque (stress) is required

When tightening the concave (lock) nut, hold the convex (tightening) nut in position with a wrench to prevent simultaneous rotation.

If the concave and convex nuts come into close contact at lower than the specified torque

The thread tolerance class of Hardlock Nuts and Hardlock Bearing Nuts is 6H. If the target bolt/shaft has threads narrower than 6g (such as 8g), the tolerance between the bolt and nut will increase, which may result in the concave (lock) nut coming into close contact with the convex nut at a lower torque than specified. If this happens, the self-locking effect will be inadequate. We recommend using 6g bolts/shafts compatible with 6H internal fasteners. If using 6g class is not feasible (such as due to a custom product being used), please contact us for further assistance.

Hot-dip galvanizing

Because of the thick galvanizing layer that results, hot-dip galvanized Hardlock nuts are overtapped. These may not fit well with electroplated and other products having a thin coating. Before using a hot-dip galvanized Hardlock nut, check to make sure the bolt has a compatible surface treatment.

If a Hardlock product does not fit well with a bolt/shaft

The thread tolerance class of Hardlock Nuts and Hardlock Bearing Nuts is 6H, which is compatible with bolts/shafts having a thread tolerance class of 6g. Bolts/shafts fabricated from general hex nut measurements may not have a good fit because general hex nuts sometimes deviate from standard values. If the fit is poor, use a ring gauge or other instrument to check the size of the target bolt/shaft.

Surface Treatment Coloration Variation

The surface treatment process involves variables such as temperature, solution concentration and immersion time. While these variables may result in a difference in plating color, there is no effect on the corrosion resistance of the plating.

Phosphate coating (Parkerization) corrosion resistance

Parkerizing, also known as phosphating, is used as a foundation for other coatings and does not provide corrosion resistance on its own because it is penetrable. In some environments, a Parkerized surface may rust in a week or sooner.

Hardlock specification changes

At Hardlock, we work day in and day out to make sure the Hardlock Nut and our other products live up to customer expectations. In our pursuit of perfection, we may change basic dimensions, the engraved dimension tolerance and other specifications as needed. In cases where there is no major change in functionality, we strive to provide customers with advance notification about minor modifications, but due to restrictions on resources, we recommend checking the website from time to time. Thank you for your understanding.