"Bob La Londe" wrote in message
...
"Karl Townsend" wrote in message
...
On Fri, 2 Mar 2012 20:13:56 -0700, "Bob La Londe"
wrote:

You might read "Gear and gear cutting" by Ivan Law to get a good
grasp
of the subject. You'll need machinery handbook to calculate your
depths and blank and rotation values, etc.

To replace a plastic gear, I'd use AL.

I could certainly cut aluminum. You wouldn't worry about galling in
this application? I don't really think of aluminum usually when I
think of an interacting mechanical part. As a static or linking
part sure, but aluminum to steel with mechanical interaction and
friction?


The gears on the 6" Sears/AA lathe are white metal. On mine the ways
were seriously worn from use but the gears are still fine.

This aluminum gear has held up well to heavy loading:
https://picasaweb.google.com/KB1DAL/...10370886636434
I ground the cutter bit with straight sides and rounded the teeth
afterwards with a file. Law's book gives a more accurate way to shape
the cutter.

This is my fixture to shape a cutter bit more closely to the tooth
gap, in this case a 30 degree involute spline on a hydraulic pump
shaft. The brass-tipped screw centers the pump shaft tooth space on
the slot the bit slides in.
https://picasaweb.google.com/KB1DAL/...96150338607922

I ground the bit freehand after marking the face beside the contact
areas with a fine-tipped felt pen. For the close fitting I pulled
strips of plastic-film sandpaper from the hobby store between the
splined shaft and the bit.

Bluing didn't stain the smooth surface very well. I think smoke from a
candle flame would work better.

jsw