I saw a study years ago that showed that nuts will come loose EASIER with a split lock washer than without. They simply don't work. I only use them as spacers or to add a little friction for a bolt that I don't want tight but don't want floppy loose either. If a lock washer is to be considered, a "nord-lock" is the only one i would ever consider for such an application. Nylocks are good for some applications but not all. Stover locknuts are great but there is no way to get a proper torque reading so are useless for any application that requires a specific torque rating. Nord-locks are awesome but if i was to use them for main/rod caps, I would still use a cotter pin because the provisions are there.
https://www.nord-lock.com/insights/v...k-washer-work/