N_Cook wrote:

Jamie t wrote in message
...

Splork wrote:


On Mon, 29 Oct 2012 10:37:59 -0500, Jamie
et 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.


They call it micarta
http://en.wikipedia.org/wiki/Micarta

Jamie



In that case, known as Tufnol in the UK . But as those are cloth reinforced
I would not have expected the material to split , has it got fibrous mat
reinforcement?


Micarta is the trade name for the company that created the process. I
guess you can use a wide range of material to make it, you need to be
specific in its use, which dictates the composites better suited for the
jobs.

People that make knife handles could use micarta composite and what
they mostly do is use layers to clothe soaked in a resin and compressed
in a bundle until hardened...

I've seen them use all sorts of different materials over the years,
including hemp.

Jamie