Folks-
I'm still trying to gather data on this. Does any one have test data or references showing how conventional (helical-split, internal tooth, and external tooth) lock washers hold up under vibration and/or shock?
Look at pages 11 & 12 of following site. Their take are that lock waskers are useless, while some locking for internal/external locks but can damage material.
The purpose of any threaded fastener "locking" method is not to "maintain torque". After you stop twisting the nut or head of the screw the torque goes essentially to zero.
The goal is to maintain a desired level of tension in the fastener.
Far too many engineers use "torque" when they should use "preload".