New subject: Coming up dry for Alps/Radio Shack/Atari/Commodore plotter gears

22 Apr 2003

Hi
 As long as the load is not that great, one can whack
out the center with a drill and then notch it with a file.
The drill needs to be larger than the OD of the inner splins.
You then fill the voids with a mixture of epoxie and
fiber glass wool. Using something like JB Weld will
make the material as hard as most plastics. To keep
things aligned while the epoxie is setting, make a
jig to hold things by drilling some concentric holes
in layers of plywood that are bolted together, for alignment.
You need to put a wax surface on the plywood where
the epoxie will be so it doesn't stick.
 It isn't real clean looking but should be functional.
Dwight

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Hello Ethan,

Internal splines, which is basically what that extrusion die would be are
much harder to do than cutting gear teeth on the OD of a gear blank.
The internal splines would have to be done on a slotter ( or possibly
a shaper with the right set up, i.e. some cutting machine with a linear
reciprocating cutting motion ) or cut into the die with EDM or wire
EDM processes. Much more difficult, and therefore more expensive
manufacturing processes. Original gears probably were shot in a
plastic injection mold, but the mold making is very expensive too, and
not something to do for very small production runs. Too bad you couldn't
find someone with a broach, because broaching internal splines might
not be as expensive a manufacturing process as long as you found
someone with the broach already made up. To have a tool and die maker
have to make a broach would also be expensive. Also extrusion die blank
material would have too not be too hard to broach. But then you have to
have the extrusion process set up and run. All in all, if you can't find them
already made up, milling the teeth into blanks or slotting on a lathe are
probably going to be your only really feasible options.

Best Regards

At 08:13 AM 4/22/03 -0700, you wrote:
>Having worked out the pitch of the broken drive gears (120), and
>having looked on a couple of web sites _and_ contacted someone
>at Boston Gear, it's looking grim.
>
>According to the e-mail I got back, Boston Gear doesn't carry anything
>finer than a pitch of 64.  When I asked who did carry such gears, the
>answer was: "I am not familiar with any company that makes miniature
>gearing." :-(
>
>My goal all along has been to find a company that has a bag of these
>on the shelf.  I had no idea it was such an unusual item.  I don't
>relish the idea of fabrication, but maybe that's what we're facing.
>
>Rather than machining each gear, I wonder how hard it would be to
>make an extrusion die to pump out a long gear and cut it into 5/32"
>slices?
>
>-ethan
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