simi off topic nylon gear with broken tooth in paper shredder

I tried repairing the missing tooth on the nylon gear by welding some nylon
in place and then filed it to shape. It broke at the weld possibly due to a
lack of skill on my part as I've never welded plastic before and used a
piece of metal heated by my mapp gas torch to melt it. I'm considering
making a metal tooth screwed to a backing plate inside the gear rim. The
nylon gear is acting against a steel gear so I doubt it will cause too much
damage if it's a little off. The shredder was free because it was broken so
no great loss if I can't fix it. You can't buy a repair part from the maker.
My friend already tried.
Thanks
Karl
Reply to
Karl Vorwerk
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Regardless of your skill, most plastics loose considerable strength each cycle of melting and cooling. The best weld in the world wouldn't be nearly as strong as the original intact part. Don't feel bad.
and used a
Reply to
Jim Stewart
Only a thought........What if you drilled a hole in the gear, cut a little slot from this hole to the outer edge of the gear where the tooth broke off and then make up a piece in a O=> shape. Surely this would have some mechanical strength to it.
Best of luck
Reply to
Skip
Why not just drill a couple of holes where the tooth was and insert a couple of brass pins, shape to fit. One brass 'tooth' against a steel gear should work.
Reply to
Nick Hull
Somewhat similar problem with a nylon gear mounted on a 7/16 hex shaft, any loading and the gear would jump a flat. Solution: I took a cheap stamped hex wrench and trimmed it to fit within the rim of the gear, then drilled and countersunk the gear and drilled and tapped the wrench and bolted them together with 8-32 FH bolts well secured with loctite. Works great now! Everybody thinks I'm cheap. Gerry :-)} London, Canada
Reply to
Gerald Miller
I would go here and see if I could find a stock gear and modify it as necessary to replace your broken gear.
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Reply to
Roger Shoaf
Thanks for the ideas. I'll try some sort of metal insert, pins or something. There's not enough meat on the gear to just insert pins. Nice to know that about plastic welding. The gear is on the first shredder bar. It's very proprietary looking: hex hole, acts as the shaft in the bearing and is stacked with the gear to drive the second bar. Sorry I don't know what 2 stacked gears molded together are called. It's like a step pulley. Thanks Karl
Reply to
Karl Vorwerk
Is there a chance that you can find the diametrical pitch of the gear and get some gear tooth cutters to fit? You may need to get two, as each cutter covers a limited range of tooth counts, and unless both fall within the same range you'll need two.
And -- you'll need a dividing head as well, to index the gear for tooth milling.
Then -- turn two blanks from brass or aluminum -- one with the bearing features needed, and a boss on which the other can be made a shrink fit. After the shrink fit, drill and ream on the joining line and drive in a dowel pin or tap and run in a screw to keep that shrink fit from slipping under load.
I think that brass (or even better bronze) would probably be the better choice of material, though if nylon almost did it, aluminum will probably hold for a while at least.
Good Luck, DoN.
Reply to
DoN. Nichols
I wish I had the hardware to do it. MY main metalworking tools are a drill press and an angle grinder. The angle grinder is getting more and more tempting as I try to fix it and fail. Karl
Reply to
Karl Vorwerk
Good luck with that.
At least you have a realistic outlook for the results. Best bet would be to find a pair of metal gears that you can graft in, in place of the metal-plastic set.
I have spent time in a dumpster that was literally full of shredders (and some other stuff, to be truthful) and there was not one shredder there that was not because of a stripped plastic gear. At that time, it would have helped if the yobbo's I was working with had not been feeding the GD shredder pizza boxes and rubber gloves, but that's cause, effect was the same.
Cheers Trevor Jones
Reply to
Trevor Jones
Of course, the traditional answer here is "But that gives you the excuse to buy the tools. :-)"
The necessary tools *can* be bought cheaply -- but not quickly, and you have to *want* to be able to do this sort of thing yourself.
I'm interested in what kind of paper shredder would use a Nylon gear in the first place. I've worked on two (I own one of them), and both used a heavy-duty chain drive with all metal gears. No use of Nylon anywere in there. And there are serious amounts of force involved, especially in a high-security shredder such as the one which I fixed at work -- not the one which I have. :-) The high-security one cuts paper to strips about 1/32" wide, and cuts the strips into 1/4" long segments.
Of course, one of them I was not able to fix without external supplies. Someone fed it a bundle of papers with a binder clasp on it. The binder clasp messed up quite a few of the cutters on both (meshing) cutter bars. (It also made a *lot* of noise when it failed, as the chain drive snapped at one link. It was powered by about a 3HP 3-phase motor.
My own came from a surplus sale, and was producing continuous strips about 1/4" wide. But examination of it showed that the cutter bars could be re-stacked to produce cuts 1/3 as wide, or about 1/12". I did that, and one side effect was to reduce the number of pages which could be cut at once without stalling the motor. :-)
Good Luck, DoN.
Reply to
DoN. Nichols
If only I had the cash and space. It's a Fellowes DM65C. I'm glad I didn't pay for it. I know what brand I won't be buying too. Karl
Reply to
Karl Vorwerk
Are you sure that's not a DM-6C Fellowes?
Mine's chopped up a lot of junk mail into confetti with a rather satisfying crunching noise and never given me a lick of trouble, save for the thermal cutout stopping it when I have a very tall pile to shred. It's only rated for intermittent duty, not the ENRON accounting offices...
But then again I'm careful not to feed it more than it can chew, including paperclips or small tree branches. Or as in the warning pictograms on the top, no left hands or neckties either. ;-)
Anything will break if abused.
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Reply to
Bruce L. Bergman
Mine, with the nylon gear jumping on the hex shaft is a General Binding 55X. It bogs down on more than a couple sheets of copy paper, but considering I paid a quarter for it, I'm not too disappointed. Gerry :-)} London, Canada
Reply to
Gerald Miller
It's a dm65c. It says so on top. I will say I don't actually know what was being shoved through it at the time. I think I'll email my friend and ask. Do you know what it's rated for? My friend said staples, credit cards and 6 or 7 sheets of paper. Karl
Reply to
Karl Vorwerk

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