[kaliken]

We have typically run 6061 hex on our drive train with fairly little issue. Again as people have mentioned before, understanding the loading is of the up most importance. Our drive shafts are doubly supported (we do not cantilever) which puts the loads well within 6061's range. So bottom line "do the math"

Only issues we have had was a some galling issues between the alum. shaft and the alum. wheel. Usually only occurs when the hex was too tight of a fit to begin with.