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What epoxy for this gear case repair?

tomjelly

Stainless
Joined
Aug 26, 2007
Location
GA
Out of production gear case, small approx 8mm od thin roller bearing broke out of the boss at the bottom. Small and hard to access, I'd like to fill the whole bottom with epoxy to support that side of the bearing. Low speed low temp application with grease, not oil. I need about 3 cubic inches of epoxy; wondering what type would be best and where to buy that small amount retail or should I just use some jb weld hardware store stuff. Its an aluminum case, I'd like to use aluminum or steel filled putty, roughen the area and press it in by hand after the bearing is in place, completely filling the area all the way to the case wall, 1/2" deep I could embed some steel struts radially between the bearing and case wall and/or make a crescent shaped piece to fit in there around the bearing too- should I?, but I'm not going to attempt to weld down in there, not enough room (for me anyway).
 

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I've done similar, with success. If you can, remove that roller bearing, and do an aggressive sand-blast down there.
Clean-clean-clean is what it needs to be if it is going to hold. How thick is the case wall? I would be tempted to make a support for the open side of the bearing.
Then drill/tap the case wall adjacent. And put a little preload on that support with a screw in the new tapped hole. Then fill around the whole shebang with epoxy.
You gotta do what you gotta do when you can't buy parts. I've been there.
But, I feel if it blew the side of that boss out, epoxy alone isn't gonna do the job.
 
Good idea screwing a support in from the side; but the bearing shell for the roller bearing is super thin, so thin that I would only be able to run it up to make contact as any pressure would distort it. I might be able to mill a radius matching the bearing od into the face of a nut (maybe the type of long nut used to connect threaded rod if they come that small) and unscrew a bolt from that nut to wedge into the case side. I'll have to think about that...
 
Wheelieking makes a good point, it did blow out the casting. Your idea of supporting it with rods or a crescent-shaped piece might work. I've used a lot of JB Weld, but recently I tried some West Systems epoxy and I have to say, that stuff is amazing and versatile. Used without filler, it's got the viscosity of vegetable oil. They sell microfiber reinforcement that can be mixed-in in any amount to go as thick as you want it. Pricey, but worth it. They have a lot of helpful documentation their website as well. If you decide epoxy is the way to go, use West Systems.

Jeff
 
Sounds like you have a drawn cup needle bearing.It is very important that you have a truly round bore with the correct press fit if you want it to last. The drawn cup depends upon the bore to maintain its round shape.
 
Yes, I'm sure that's the type of bearing it is. I guess I'll have to machine the curved nut and tension it against the side of the case. Not a perfect solution but should be ok for the amount of use it will get here.
 
I would drill and tap some studs in a circular pattern around the bearing. Clean and clean again, I like using spray oven cleaner, yah I know it’s toxic to aluminum but rinse it off good and it will be clean.
I would rough the outside of bearing so the epoxy can grip it.
I think the best epoxy is Devcon plastic steel.
Build a dam using putty around the studs and pour it full.
 
In a former life I was a machine repairman in a large forge. We used Belzona. It came in tubs large enough to fill the void. If I was doing the repair I would just get a new housing and save all that time and trouble.
 
Just because we are hashing solutions and not sticking to "what epoxy should I use". (DEVCON LS is Good stuff!)

But, If I were not wanting to go back in there to repair the repair, I would...

Mill the damage surfaces "mostly" flat and square. Minimum material removal! Just enough to give good geometry and support.

Drill and tap for a pair of screws as a logical eye might best locate. (Drill through if possible)

Make up a repair block from alu. that could be screwed down with the previously tapped holes. Trying for a tight fit across the newly milled surfaces.

Mount the repair block, locate center and bore for the bearing.

Disassemble and clean up.

Assemble bearing and repair block with screws WET with whatever epoxy. I like 3M 2216, Devcon is good, J-B weld has some impressive performance values as well. (Not the Quick set)

Barring that, I would turn up a sleeve stepped both in and out to suit the bearing and a bored out socket.

Made of steel, press it in.

Viola! Better than new!
 
In a former life I was a machine repairman in a large forge. We used Belzona. It came in tubs large enough to fill the void. If I was doing the repair I would just get a new housing and save all that time and trouble.

Belzona is very good stuff but expensive and not as easy to find as Devcon. I think Devcon is as good as Belzona.
 
no idea if such a repair makes sence.

but:

- activate the aluminum with some hot lye (oven cleaner?), dry with hot air and proceed immediately
- if you have some epoxy resin fill it with fine band saw swarf washed in solvent and add dryed silica flower/fine sand for consistency and
compressive strenghth.
- if using some common putty i would prewet the surface with resin or at least epoxy glue. you can let it cure a bit.
 
If you can machine it I would bore the hole bigger and flat with the broken out piece
Then bolt in a excentric steel ring
Bore a pilote hole centric with the broken out bore and turn a mating shoulder to the underside of the ring
Just to get the the ring in the right place

Peter
 
Use an adhesive with a methacrylate based chemistry for your aluminum case. Epoxides are old technology. Just recommending your favorite brands, you might as well recommend your favorite beer, for all the good that will do.

-Doozer
 
If I was going to use any epoxy, I would use Belzona.

That said, whatever happened broke out a significant piece of aluminum. No epoxy is going to hold up to that. You need a mechanical repair. At minimum, a steel sleeve, with epoxy for a support on the weak side. What is the bottom thickness? I would think about a threaded stud, screwed into the bottom of the case with locktite, with the bearing pocket bored into the stud.
 
Could you locate on the remains of the bore.
Then drill/bore out the hole, then thread it to accept a plug of of either aluminum or steel. Loctite in place the re-machine the bore ?
It depends on the wall thickness of the main case of course, but it seems you need to add some strength to the original bore.
Good luck,
Bob
 
I vote for JB Weld

Clean are well first

Apply the JB Weld

Let it cure 24 hours before you touch it
 
Use an adhesive with a methacrylate based chemistry for your aluminum case. Epoxides are old technology. Just recommending your favorite brands, you might as well recommend your favorite beer, for all the good that will do.

-Doozer

mma adhesives to my knowledge have no advantage on metal in this application. they excel in production environments and for plastics epoxy cant be used on without expensive prep.
 
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Fooled around with this for a bit and came up with a jack screw against the remaining part of the bore cup side. It holds well in place as I ground the case wall and outer part of the bore cup parallel and I can easily tension it against most of the bearing, and roughly in line with the shaft its gear will engage with, to the point where I could crush the bearing if I wanted to. The epoxy only needs to keep the screw from unscrewing or moving. I think I'll give this a try using jb weld. I like the idea of drilling and tapping the case for a stud bored for the bearing but I think this will work for the application and I can't put that much time into this repair.

SteelStik Epoxy Putty Stick | J-B Weld

versus

J-B Weld Twin Tube | J-B Weld

was going to use the putty but the twin tube stuff says 5020 psi, the putty says 900 psi, so I should use the twin tube I guess

Looks like the machine jammed while the previous owner had it; The teeth on the gear on the shaft were broken, probably before the case bore but then broken gear teeth must have gotten in between and broke the shaft out of there.
 

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