Casting your own gear without making it oversize and machining it down to
size is unlikely to work very well or for very long.

Cutting gear teeth is not a basic diy operation.

You would be better off trying to buy a metal replacement of the same size
as you have in plastic.  You might be able to use plastic again if you coul=
d
provide some local cooling (heat sink, air flow, etc.)  You will have to do
a bit of research on gear design to get the proper replacement size.

You may have to bore out the hub or put a bushing in to make it fit your
current shaft.

Gordon Williams




----- Original Message -----=20
From: "veegee" <veegee@veegee.org>
To: "PICLIST" <piclist@mit.edu>
Sent: Monday, May 13, 2013 4:58 PM
Subject: [OT] Making a new spur gear


> Hi all,
>
> I modified a cheap laminator for the purpose of making PCBs via the
> toner transfer method. Simple enough: reverse engineer the PCB, figure
> out where to put the resistors/etc to increase temperature to ~170-180
> degrees C.
>
> It worked exceptionally well. Never before have I been able to get such
> perfect toner transfers. The clothes iron method doesn't even compare.
>
> I was able to push a few board through before one of the plastic spur
> gears driving the rollers melted due to the high temperature. Luckily,
> the other two gears, which are identical, are unharmed.
>
> I need to make a replacement gear for the rollers. I'm probably going to
> use plaster of Paris to make a mold using the other gears and cast some
> appropriate material to make the new one. Of course, the mold will first
> be properly set and baked before casting.
>
> I'm leaning towards using aluminum, which melts at 660.32 degrees C. The
> gears are small, less than 2cm in diameter. Melting a small piece of
> aluminum over the mold with a blowtorch should do the trick.
>
> Aluminum seems to be the best option. Low melting point, safe (no
> dangerous fumes) when melted, easy to cast, cheap, and everywhere*.
>
> Everywhere* but I can't seem to find anything around to melt. My unibody
> MacBook Pro is not an option. Soda cans will work if melted slowly, but
> they tend to produce a lot of slag, which I'd rather not deal with for
> such a small job. And I don't want to have to drink 10 cans of soda to
> do it.
>
> Can anyone name a few household/cheap easily acquired things made out of
> (preferably) pure aluminum that can be melted?
>
> Any tips?
> --=20
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