Here's a tip for those of you without a lathe.
Take the Tetrix wheel hub, remove the set screw and drill the center out to .248" Now the wheel hub will fit right over the pinion gear. Put the locating flange of the wheel hub on the motor side. Add a little Loctite and tighten down the set screw. Now take the axle hub and drill out two of the 6-32 threaded holes(opposite). now you can take two of the allen head screws in the kit and attach the axle hub to the wheel hub. Now you have a nice coupler to attach the axle. Look in the Grainger catalog at shoulder bolts and find one that will fit your specs.
Roy
