The Hardlock Nut can be made of a single material and can be used repeatedly as the preload does not degrade.
A repeat Junker test was conducted 50 times, and the change in the preload is shown in the graphs below. The experimental results (lower graph) from a 51st Junker test confirm no large change in the preload.
Bolt: M12 × body 70 mm, strength classification: 4.8, surface treatment: trivalent chromate
Nut: Hardlock Nut, strength classification: 4, surface treatment: trivalent chromate
Tighten the convex nut to 70% of the yield point.
Tighten the concave nut until firm one-sided contact is made with the convex nut.
Results of the Junker test after the first tightening
Results of the Junker test after the 51st tightening