You could get a knurling tool from Micro Mark but expensive for one shot. Not sure how to do this in home workshop. There are some videos on you tube about knurling. I did this a few times when I was a machine mechanic but on a larger scale.
I would rough up the shaft and each side of the gear near the shaft location and use five minute epoxy.
Red loctite might work between the shaft and inside the gear hole as I believe it expands a little when setting. I remember pulling a couple bolts many years ago that red was used in.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
To put in some potentially helpful material that was only partially addressed in the ‘old’ thread:
”Real” Loctite is an anaerobic-curing material, meaning it will only set up if the joint is not exposed to oxygen. An upset shaft may only produce this if it cuts corresponding ‘keyways’ in the gear, which may facilitate splitting, but the advantage is that it will not set up before the gear is actually pressed into the equivalent of perfect or interference fit.
Cyanoacrylate cures by exposure to moisture. That may be difficult to ensure in a tight joint. As noted the basic crosslinked ‘result’ is brittle and may not bond effectively to some materials (and I do think some of the Delrins are in that category) ... more on that in a moment.
Epoxies are time-delay chemical cure, so are ideal for mechanical joining ... but depend on a relatively thick layer of bond for full strength, very different from the situation with regular CA. For a shaft with gear you might want to open up some of the joint while keeping enough of the shaft OD and gear ID intact to preserve alignment in both ‘wobble’ and runout.
For shock loading, you want more of an elastic bond than an initially strong but brittle one. Epoxies inherently provide this; I believe it is a characteristic of at least some Loctite. I think the CA formulation that is loaded with tiny elastomer (rubber) particles is intended to provide elastic bond, and some of you with firsthand experience with it might comment. Notably, the stretched-latex-membrane technique that reanimated this thread is inherently both self-locking and highly elastic without ‘bond failure’ at all in torque loading.
There are surface-activating techniques other than mechanical roughing that can be used for better bond strength; perhaps the most applicable here would be to use an ‘activator’ in the hole of an otherwise-slippery gear to enhance “bondability” there. Has anyone here experimented with etching ‘primer’ for plastic pipe, or the ‘activator’ in one of those rear-view-mirror reattachment kits?
Now, the next fun thread will be about how to fix the situation when a gear does split...
PiobondWhat about this rubber based adhesive piobond??
Brian
My Layout Plan
Interesting new Plan Consideration
It's "Pliobond", and it's too soft for that application. Tim Warris, of Fasttracks fame, recommends it for affixing his laser-cut tie templates under his style of turnouts.
Think of Pliobond as industrial-strength rubber cement. It does not have the right characteristics for gear-on-shaft even if you get a reliable thin film on the two mating faces and press them together without twisting ... which you can’t.
Note that the ‘balloon trick’ referenced above is the equivalent of putting much better structured rubber molecules in the joint with the proper geometry to load them in compression without tensile separation on any part of the ‘bond line’ that finds itself loaded in tension...
I was just always a fan of the rubber based adhesives due to their basic 'elasticity'
When I was young, Pliobond was the best adhesive for strong resilient bond, or when some vibration damping was needed. The only real drawback was the stink, and if you spilled it on anything stainable that was pretty much it. But my grandfather loved it for general repairs and so did I.
It’s just not good for smooth metal shaft slip-fit into a slick plastic gear, at least not without thinning and very extensive ‘drying’ time as it can’t be applied as contact adhesive for that fit.
Just joined the forum only to say "thank you everyone." I stumbled across this thread today and learned so, so much!! I'm happy it wasn't closed. I enjoyed reading and learned from ALL the posts, 2011 or not.
to the forum.
We don't close nuthin' around here unless it goes off topic or political.
However, there is no charge for you to start a totally new thread as old threads often have dead links and comments by people who have moved on.
Your first handful of post are moderated which means we never get spam. Don't just sit back and lurk, step up to the plate. Sometimes that means you find out that you knew less than you thought you did. That's a good thing.
Henry
COB Potomac & Northern
Shenandoah Valley
I just read back over this excellant subject thread, and remembered some things I had forgotten,....ah, memory recall these days
I hear a lot of suggestions to use Loctite.
.
When most people talk "Loctite", they are referring to one of three products, 271 "red", 242 "blue", or 290 "green". None of these are plastic compatible. I would never use one in a model. Also, they are intended to lock the threads of fasteners to prevent screw walk out. Not gears on shafts.
The correct LocTite product to use would be RC-609 which is specifically made for cylindrically fitting parts, but again, is not intended for plastics.
I have fixed this problem like this:
Just outside the gear seat area, make a hole, or file a shallow slot in the shaft. On the side of the gear, make a hole or file a slot. Put the gear into position. Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes.
Allow the epoxy putty to cure overnight, and you will have a firm mechanical connection between the shaft and gear.
-Kevin
Living the dream.
SeeYou190 Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes. -Kevin
Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes.
Why this particular epoxy, and why this partcular color of their epoxies??
railandsailWhy this particular epoxy, and why this partcular color of their epoxies??
I use Blue/Green Kneadatite for all kinds of modeling work, so I always have it around.
This product has lots of positive atributes. It has an incredible amount of adhesiveness, and it has a long working time. It can be worked with normal sculpting or dental tools easily, it is fully non-toxic, and it does not attack any plastic I have ever used it on. When fully cured it is 100% inert, and it does not change dimension when curing.
Loctite "Plastic Weld" two part epoxy would probably work as well, but it had a shorter working time and it is more difficult to shape.