On Feb 11, 9:45 am, woodworker88 wrote:
On Feb 11, 5:10 am, Ecnerwal
wrote:



In article
,

woodworker88 wrote:
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.

First option - bite the bullet and order some good ones, even if it
means boring them out yourself.

Second - set up a sacrificial good gear and the 8 pinions in a dedicated
grinding setup, apply abrasive, and run for a while - but this requires
disassembly, reassembly, "cut and try" and building a new fixture, and
getting another good gear. If I understand grinding theory correctly, a
softer "good gear" material should embed the abrasive and grind the "bad
gears".

--
Cats, coffee, chocolate...vices to live by

Alright, I was thinking about doing that. I can bore out new ones,
but what would you suggest doing about the 2mm keyway? The new
pinions are a press fit onto the motor shafts (the old ones had
setscrews) and they seem to be holding, although those are still also
keyed as well.
Thanks, ww88

Depending on the torque being transmitted, you could file off the
keyway and produce a flat on the motor shaft. The pinion set screw
would press on the flat.

I have bought good quality gears from QTC in New Jersey; price was
quite reasonable: For M 1 module pinions (just a little smaller teeth
than 24 DP) the price was less than $10. Enlarging the pinion bore
without affecting the concentricity between PD and bore took some
thought but can be done if you have a lathe and face plate.

I bolted a piece of aluminum plate to the face plate and drilled/
bored a counterbore for a light press fit on the gear OD. Pressed the
pinion into the bore using the tailstock. Added 2 small finger clamps
to hold the pinion tight in the bore... Since I was curious about the
concentricity between the gear OD and its bore I checked with a dial
indicator: The indicator needle did not move perceptively and I was
happy. Then drilled to 7/16" and bored to 12 mm. Had to buy a 3 mm
broach for the keyway. Since these were change gears for a hobbing
machine the keyway was necessary.

You can lap the gears for improved running smoothness. But you should
use an appropriate non-embedding abrasive that breaks down after a
short period of use. Powdered turkey bone is one such material,
another is the old domestic cleaning powder named "BON AMI". I found
some at a flea market.

Trust this helps.

Wolfgang