The right hand(chain side) axle nut on my Dutch Gazelle/Shimano Nexus 8 cycle has split down one side. It's a plain nut rather than a cap nut because of the chain guard. It's a stainless steel, thin wall nut (could really be thicker) and by my measurement is 3/8". The Shimano leaflet bears this out. However, I can't tell what thread form it is. It looks as if it could be UNF or perhaps metric fine-given that it's Japanese. Does anyone know what it is?