Originally Posted by
chuckybb
I'm working on an old (early '70's) Sunshine front hub and these are the lock nuts being used. The concave side is toward the dropout. I'm not sure if these are proper for use as a lock nut or if they are from another use.
I had those on a late 1970s bike, nice large flange hubs with cutouts like Campy of that era. The concave side is the one that grips the dropout - rather than using a toothed face that grips well but can chew the frame ends, these just reduce the contact area to increase grip pressure.