Originally Posted by
fietsbob
"Fits 3/8" x 26tpi ". is your axle that size?
No it's not. It's 13/32"
http://www.sturmey-archer.com/produc.../id/57/specs/1
Besides, those axle extenders require 14 mm dropouts and there would be no provision for anti rotation washers.
To the OP, don't forget to allow for those anti rotation washers in your calculations. They are vital.