Robinson racing 48pitch pinions that are steel use a 5-40 imperial grub screw
Robinson racing 48pitch older alum purple pinions use a 4-40 imperial grub screw
Robinson Racing 48pitch new dark grey alum pinions use a 3mm metric grub screw.
(so there are some u.s. pinions that use metric grub screws now)
Hobby works use a imperial grub screw in there pinions which i think is even smaller than the above ones (not sure what it is but it uses a .05" imperial hex driver. It could be 4-40 but im not 100% sure
RW, Kawada, atlas and most other brands all use a 3mm metric grub screw.
if you have a metric 3mm tap its easy to tap out an imperial alum pinion to accept a 3mm grub screw.
Last edited by LOSI123; 05-12-2009 at 03:32 PM.