Lots of non-engineering types offering their "opinions" in them thar books and articles.
Lock washers are not useless. In the right application they do the job they are intended to do. They do nothing until the nut loosened enough to provide a gap for the split lock washers to expand, and then the knife-edges grab to keep the nut from falling off. But htey can "give" and move enuogh ot prevent proper torquing which causes more problems.
Nylock nuts on 911 valve covers can be re-used many times.
But they are a band-aid for a mis-application.
Bolts (and screws and studs etc) stretch like springs when tightened.
That spring tension should provide enough friction to keep the nut from loosening up.
If it doesn't then chances are the stud is inncorrectly sized or improperly torqued.
If under-torqued there is little or no stretch (as in a 911 valve cover) so a self-locking nut is used to make up for that lack of friction.
Most of the time a lock washer or self-locking nut is used as a compromise.
Example: in order to obtain say 35% of yield on a 911 valve cover without over-squeezing the gasket and warping the cover, the stud would have to be tiny. Really tiny. Like 1/16" diameter tiny. Like, snap off really easy tiny.
compromise.
Note that there is ALWAYS an exception.
Always.
PS how many of us have earned a paycheck with a pair of these band-aid application tools?
