[TR] brake hub bolts

[Randall]

> Are British fine thread bolts different in thread form or 
> pitch from  AN or SAE bolts?

Yes, both pitch and thread form are different for BSF vs UNF.  3/8" BSF is
20 tpi, while 3/8" UNF is 24 tpi.

BSW typically has the same pitch as UNC (except for 1/2"), but still
different thread form.

My guess is that there is a slight difference between the AN and SAE
hardware, perhaps in the class of thread fit or something like that.

Randall