Steel Nylon insert Lock Nuts with Black Oxide coating.
Especially useful for situations that involve vibrations. A prevailing torque type of locking nut that uses a a nylon collar to increase friction on the screw thread. The nylon collar insert is placed at the end of the nut, with an inner diameter slightly smaller than the major diameter of the screw. The screw thread does not cut into the nylon insert, however, the insert deforms elastically over the threads as tightening pressure is applied.
*NOTE: Sizes 1/4-20 and 1/4-28 nuts have Black Phosphate and Oil finish