Test Data on Hard Lock Nuts

Hard Lock Nuts are classified as return rotation prevention-use countermeasures. They are evaluated as looseness stopping nuts that exhibit a performance superior to that of ordinary double nuts. A variety of tests have yielded data on the performance of Hard Luck Nuts, as follows:

1）Axis perpendicular vibration tests

These tests, of which the Junker vibration test developed in Germany is a famous example, are a representative method of evaluating screw loosening. Junker test data on the Hard Lock Nut’s performance gathered by the Shonan Institute of Technology is available. 

 

2) Axial rotation vibration tests

No test data is available at present. 

 

3) Axial direction load increase/decrease tests

These tests form a method of measuring the axial force reduction due to bolt fatigue with repeated loading. No Hard Lock Nut-related axial direction load increase/decrease test data is available at present. However, test data is available on friction joint-use high-tensile bolts employed in structures such as pylons.
Application example: Hard Lock Nuts are employed in pylons and other structures (NTT pylons, etc.) as a replacement for high-tensile bolts. 

 

4) Impact tests

a) The US NAS 3350 and 3354 standard vibration tests are well known internationally, Hard Lock Industry has adopted these test standards as in-house standards as well.
b) Regarding dropping tests, in-house comparison test data from a certain ironworks is available.
c) Regarding hammer tests, no test data is available but there are extensive actual application records. 

 

5）The Hard Lock Nut’s major features apart from its loosening stopping function

a) Sufficient fastening is possible regardless of the axial force (pre-set axial force control is possible).
b) Effectiveness is maintained even in the case of repeated use (repeated re-use is possible until nut metal fatigue occurs).
c) Compatible with a wide range of environmental conditions (flexible combinations of shape, material and surface processing).