waxy plastic gear repair

G11 is better, stronger! FR5

Jamie

Here are 2 scans. One lighter to show some detail, the other both sides, one which easily reassembles.

I think JB weld must might do a good job after each piece has a couple of holes to the other side to form a clamp.

On Tue, 06 Nov 2012 22:57:02 -0500, Splork wrote as underneath my scribble :

Crack on the left is the original, the gear has been running eccentric some time, wear on the right teeth is considerable, if you do a repair pay considerable attention to concentric-icity(!!) to the centre. Is the equipment worth it? A dirty repair might be to use hot glue for thin metal or fibre washers in the rebates... try first to see if hot glue will stick to the soft gear material, might have to abrade.

That's the word I was looking for yesterday. Concentric.

This is a pencil sharpener. When I reach to use it and it is gone . . . Yeah, worth it.

The only repair that I think worthwhile, which is potentially long lasting, is on each piece, to place 2 holes halfway between hub and teeth, 3 holes on the largest, to allow jb weld (Strong metal bearing epoxy) to join obverse and reverse of the gear (2 operations). Once sandwiched between the "weld", being restrained and driven by the pins that form through the holes, I can place the gear on the drive shaft and greasing the gear end to prevent adhesion, make a third gluing operation for a strong tight fit around the shaft end.

So the cracks will not be repaired, but the pins/vias that form in the holes will keep it together, sandwiched between plates which prevent it from divergence in any axis. The 3 segments held and driven separately.

Now if laziness prevails........ :-)

On Wed, 07 Nov 2012 20:49:51 -0500, Splork wrote as underneath my scribble :

Good luck with it, hot glue has some 'give' in it which would provide the required flexibility.

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What I call hotmelt string is more convenient in this sort of operation. With the gun hot, squeeze out a long run of hotmelt over clean metal sheet. When cold , use like soldering operation with an old soldering iron, melding original material and the string.

Thanks for the suggestions. Sounds interesting to me. Never used hot glue so I find the use of it like solder intriguing, and I like cleverness.

Perhaps I am over estimating my need for strength. Rarely successful at repairing plastic gears and one of this size seems an unlikely candidate for glue. I do have a glue gun here somewhere.

There is a lot of force applied to the shaft via the hub. Lots of torque needed to turn the sharpener blades. Manually un-movable.

Will probably use the idea I had using JBWeld to create the least amount of give, but will experiment with hot glue to experience it's usefulness, and use it when I attempt small plastic gear replacement.

Good stuff!

Thanks again

Splork udtrykte præcist:

Perhaps you can find somebody with a 3D-printer who will print a new gear?

Somebody who has made their own 3D-printer might be looking for interesting stuff to print.

But then again, get a new one, unless you have lot of free time and no money.

Leif