scope:

This standard provides a method for evaluating certain performance characteristics of all-metal prevailing torque type nuts, employing a hand torque wrench or other slow speed drive technique. It is intended primarily for product qualification testing.

Prevailing torque type nuts are those which are frictionally resistant to rotation due to a self-contained prevailing torque feature within the threads.

The test consists of 5 installations and removals of the nut in a tension measuring device using a hand torque wrench or a slow speed mechanical drive unit. The nut is assembled on a phosphate coated test bolt of a strength a zinc plated hardened test washer. During the first installation and removal 3 measurements are recorded: (1) maximum prevailing torque on. (2) torque at a specified tension, and (3) maximum prevailing torque off in the first revolution. (See NOTE 1) During the fifth removal the maximum prevailing torque off value is recorded.

NOTE 1: Minimum prevailing torque off in the first revolution is measured under specified conditions. See Paragraphs 3.7 and 3.8.