Valbrona wrote: By the time you have a frame that needs the threading in the BB shell re-tapped, the threads are already knackered and quite often beyond repair. So, I have never really seen the point of having a BB shell tap in a bicycle workshop....
Lots of frames need the threads cleaning out when a new BB is fitted, some need tapping out from 26tpi to 24tpi, some are bad from new (filled with paint etc) and some get damaged in service, and then there are proper repairs i.e. ones which allow any BB to be fitted later on. Plenty of uses.
Valbrona wrote: Better just to fit one of those threadless ones.
Au Contraire... They are mostly dreadful things... In point of fact you are probably worse off with one of those than if you simply (say) glue a decent sealed unit in place.
cheers