On Mon, 29 Oct 2012 10:37:59 -0500, Jamie
t wrote:

N_Cook wrote:

isw wrote in message
]...

In article ,
Splork wrote:


My low tech pencil sharpener has a drive that uses a 2.2" gear to drive

the

mechanism from the motor. The gear broke into 3 pieces.

I can probably repair it but am unsure of the composition and what to
use for
cement/ strengthening.

Cut a groove around the perimeter, deep enough to get past the gear
teeth. Wrap a steel wire around the gear in the groove, and twist the
ends to make it tight. If cyanoacrylate will stick to the plastic, use
that to get the pieces assembled before you add the wire.

Isaac


Are you saying cut a slot through the middle of the teeth into the bulk
under the teeth?
I suspect a .4mm saw in a Dremmel would end up as a melted mess and not a
slot, perhaps a heated scalpel blade in a jig

Or perhaps use some nicrome wire with some silone sleeve at the overlap,
apply a weight and some adjustable current. Hope the wire melts into the
bulk of the plastic and perhaps ypu can ignore twisting off of the wire.
May need to recess 3 pins into the disc part , then swathe in hotmelt or
something, if the 3 sections have failed with smooth edges, before doing the
wire job


what is a waxy plastic gear? I can't picture any gears being made of wax
or material soft like wax?

Jamie


Thanks to all the replies!!

The unit is at least 20 years old.

The gear is brown Bakelite in color. I say waxy because it has a soapy feel and
I can scrape the material with my thumbnail and get some to come off. Like very
hard wax. Odd for a drive gear material so I suppose it changed in nature over
time. The exterior seems most changed so perhaps there is some material
strength remaining.

The teeth are about twice as wide as the body and none have broken off. A clean
3 way break. The body is too thin for making a groove around the perimeter.

Adhesive would be required in and around the breaks for adequate strength.

I cannot think of an adhesive for this material so I posted here hoping for
anyone familiar with it to chime in.

As an alternate to a lost wax reproduction, I thought of reassembling the gear
and wiring it to stay put, some holes could be drilled through the disc (several
on each segment) and a 2 operation repair then be undertaken. On one side a
layer of JB Weld between hub and teeth, then a repeat on the other side. Would
give a metal sandwich with the holes ensuring the teeth remain in roper position
and are driven. Will look over the unit to see if any special clearance need be
observed. Likely the best option in hand.

Just discovered someone who has cloned the gear and is selling them $12 or so.