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[peteski]

Unfortunately CA already failed — that's why I'm using epoxy.

It's already curing, but if it fails again, I will try the "keying" option.

Thanks for all the excellent tips!

Apologies for the thread drift.

I'll mention it again; if there is even trace of oil/grease on the joint area, the adhesive will fail.  Even slightly sanding the metal shaft with some 400 grit sandpaper would greatly improve adhesion. Same with roughening the inside of the hole in the gear.

Hopefully the epoxy will work (I hope you didn't use the 5-minute type - it is rather weak). If not, you still have some other methods to try. 

[kiwi_bnsf]

The whole assembly was washed in iso and scrubbed with a toothbrush and dried.

The part of the shaft that where the gear should be seated was then rolled between two files repeatedly until it was visibly roughed.

Epoxy was then applied.

We’ll see how it lasts.

(This should not be required with a Kato mechanism)

[MK]

Epoxy is good too, in a sense it won't attack plastic.

[peteski]

The whole assembly was washed in iso and scrubbed with a toothbrush and dried.

The part of the shaft that where the gear should be seated was then rolled between two files repeatedly until it was visibly roughed.

Epoxy was then applied.

We’ll see how it lasts.

(This should not be required with a Kato mechanism)

Yes, that doesn't sound like it is up to Kato's quality.  I'm an big Kato fanboy, but I see that even they don't have perfect record. There are other examples, like the early GS-4 design causing shorts when converted to DCC< then later driver axle tubes cracking (both were addressed and redesigned).  I also see the universal couplings cracking on the motor shaft of the RDCs (and likely other models which use that coupling. But overall, Kato still does a great job, and produces mostly very high quality products.

As far as Isopropyl alcohol goes, even 99% strength does does not do as good of a job degreasing as acetone or naphtha.  Hopefully it will work for you.

[rrjim1]

If the gears are plastic or a plastic derivative, use CA and not Loctite.  Loctite will eventually weaken the plastic.

Loctite also makes products just for plastic, even epoxy. I have used 620 on nylon and Delrin and I haven't noticed any problems in 25-30 years. Keeps those old gears on a smooth axle, the only problem is you need a tool to remove them, yes it holds that well.  CA, even the black harden stuff just doesn't hold well on a smooth axle.

[MK]

Loctite also makes products just for plastic, even epoxy. I have used 620 on nylon and Delrin and I haven't noticed any problems in 25-30 years. Keeps those old gears on a smooth axle, the only problem is you need a tool to remove them, yes it holds that well.  CA, even the black harden stuff just doesn't hold well on a smooth axle.

True, but he specifically said thread locker, thus my cautionary comment on having it in contact with plastics.

[rrjim1]

True, but he specifically said thread locker, thus my cautionary comment on having it in contact with plastics.

Just saying "Loctite" made it sound like all Loctite products attack plastic. What he said really doesn't matter. I just wanted people to understand that Locitite make some great products that work on plastic.     

[peteski]

My fault - I should have been more specific than just saying "Loctite". Sorry!