"woodworker88" wrote: (clip) the low quality pinions
seem to be slightly over the correct pitch diameter, making proper
meshing difficult. (clip)
^^^^^^^^^^^^^^^^^^^^^^
The pitch diameter of a gear is not a fixed number. It is determined by the
center-to-center distance of the gears and the gear ratio. IOW, the two
pitch circles adjust so they roll on each other. If the pinion is slightly
too large, you might be able to solve the problem by just moving the drive
motor out a little. This will work, but it will depend on how the motor is
mounted whether it is practical.