I am assembling some complex drive gearboxes for a 150 lb competition
robot. The gearboxes use 24 DP gears from Martin Sprocket, Boston
Gear, and Stock Drive, all high quality components. The one part that
I did not supply myself is the drive pinion from the 12 volt motor,
which is an 8mm shaft with a 2mm keyway. Prior to this year, I have
always used supplied pinions from Martin Sprocket (reamed and broached
by a third party supplier), which have been the same high quality as
the rest of the gears . However, this year, due to availability, I am
using pinions from a different supplier, which are of much lower
quality, most likely machined from gear bar stock.

The main problem is manifesting itself in that the low quality pinions
seem to be slightly over the correct pitch diameter, making proper
meshing difficult. Furthermore, the pitch diameter seems to vary
along their length, which makes it difficult to be consistent across
the 8 different gearbox parts.

My question is what is the best way to reduce the size of just one
gear. If the poor meshing was due to an undersize center-to-center
distance, I would simply apply some fine abrasive compound and run in
the gearbox, dissasemble, clean, and lubricate. However, in this
situation, I want to target only the low quality gear, and not the
high quality gear with which it meshes. Additionally, two pinions
actually drive this gear (two motors feed into a single gearbox), and
I need to target them individually to get the least binding with as
little backlash and slop as possible. I could individually locate the
high spots on each gear and attend to them with needle files and
scrapers, but this is extremely labor intensive for all 8 pinions, not
to mention the time and labor to disassemble and reassemble the
gearboxes several times.

Any suggestions would be much appreciated
Thanks
ww88