Bonding Nylon and Other Plastics?

Putting together a drive train with a 3/16" axle. The Nylon gears had a center hole of 3/8". So I got some 3/8" O.D., 0.191" I.D. nylon spacers and some
6-32 x 3/16" set screws.
The idea was to tap the spacer for a set screw and then mount the gear onto the spacer for a nice tight fit with the axle while keeping the gear square to the spacer.
I didn't think friction would hold, and it didn't. Superglue failed immediately. 5 minute Expoxy and silicone glue only worked marginally.
Things would start out OK, but after a few hours, the "collar" around the nylon would lose it's bond and start to slip. This surprised me. I expected a failure mode of pulling off the gear since the shear force would be pretty strong, but expermimentation is a great thing and experience a great teacher.
Does anybody know how to bond Nylon to Nylon? Ideally some solvent similar to PVC cement for PVC exists?
On the broader topic, I haven't found good ways to bond a number of common plastics. Epoxy and silicon glues are the best I've found overall but they both will fail eventually.
One article I've found said that arcylic is soluble in MethylEthylKetone or MEK. Don't know if this is true or if MEK is available.
And what kind of plastic is superglue good for anyway?
So anybody have any suggestions or links so I can fill out the following chart?
Nylon UHMW Acetal PVC Styrene ABS Acrylic
Nylon ? ? ? ? ? ? ?
UHMW ? Epoxy ? ? ? ? ?
Acetal ? ? ? ? ? ? ?
PVC ? ? ? PVC Cement ? ? ?
Styrene ? ? ? ? Acetone ? ? Model Cement
ABS ? ? ? ? ? ? ?
Acrylic ? ? ? ? ? ? MEK/?
Thanks,
Kevin
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"Nylon" is usually not pure nylon, and is often blended with additives and even lubricants, making it difficult or impossible to bond. Websites like masterbond.com offer technical tips on how to bond different materials. You might want to poke around there for a while.
You might also try a hot glue. The "high temp" rather than low or all-purpose temp glues might work better.
Super Glue should work okay for acrylic, but it dries out, or otherwise becomes very weak. I've used it for some peopjects and the immediate bond is quite good, but a year or two later the joint just falls apart.
-- Gordon Author: Constructing Robot Bases, Robot Builder's Sourcebook, Robot Builder's Bonanza
Kevin C. wrote:

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Kevin C. wrote:

For acrylic and lexan I use a product by Craftics Inc. called "Plastick Acrylic Solvent Cement" (its spelled with a k). The label states (right next to the warning about it causing cancer in the state of California) that it contains "methylene chlordide and diacetone alchol". You apply it with a plastic squeeze bottle with a dull needle on the end. Place two pieces of acrylic together and run the needle along the seem. The capilary action sucks the solvent in between the two pieces and forms a bond by melting the two pieces together.
You could try the Yellow Pages looking under "Plastics". If you find a dealer they could most likely answer your other questions.
James
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Some of the polyurethane glues work pretty well on many plastics. Two in particular come to mind: PL Premium construction adhesive, and Sika or 3M Deck sealant. We use them both to glue PET bottles together to make pressure vessels in water rocketry. PET is notoriously hard to glue, and with appropriate handling these joined bottles can withstand 120PSI or more - very impressive.
The deck sealants go off quickly in the tube after opening (under one week) and are somewhat flexible (rubbery) when cured; they have an absoutely evil grip however. You can get them at boating shops, and they're kinda expensive.
PLP is thinner, foams a bit as it cures (how much depends on the humidity), and can be kept in an re-sealed cartridge for months. You can get it at many big hardware stores, near the Liquid Nails, but unfortunately not here in Australia. It's dirt cheap.
Clifford Heath.
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I'm assuming that the gear doesn't have a collar or you would of put a set screw in the collar of the gear itself. You need to mechanically mount nylon to steel. You need one spacer to center the gear on the shaft. Do you have room to mount something on the shaft next to the gear, like a larger OD spacer or collar, so that you can attach the gear to it by using screws or pins thru the side of the gear?
Good Luck, Mike

center
onto
chart?
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I've had some experience trying to bond nylon to ANYTHING in some military applications. Nylon doesn't bond well with anything really, although there are some special surface treatments (involving some sort of electronic etching or something) that will make the surface capable of decent bonding. Usually we either fastened it on with countersunk screws or used polyethylene instead.
One possible solution to your problem is to torque the fastener down and drill a dang small (1/32 maybe?) hole through the screw and parent material, and put a cotter pin through it.
Yet another solution (if I understand your problem correctly) is to cut a couple vertical cuts/channels in the screw (and the threads of the other nylon nut) and then use the epoxy. It won't bond to the nylon, but will fill in the gaps and act like a machine key.
Dave
snipped-for-privacy@glenevin.com (Kevin C.) wrote in message

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