Recovering thread on aluminium casting.

[Screwdriver]

I risk getting my head bitten off for this but have you investigated the possibility of an industrial "chemical metal" repair? I would imagine some of the modern heavy duty stuff could easily outperform aluminium alloy in terms of strength and durability etc.

 

[Kram]

I dont see that adding much extra time

 

[Dougal Thompson]

Certainly repairing the original has some appeal. I have considered a good clean up, solvent wipe, a layer of JB weld and a tidy up in a lathe. Just not sure that was a goer. However, as you say, some modern epoxies will be stronger than the alloy. The thread will still have strength as the deepest part of it is intact and I'm pretty sure the epoxy would just be steadying up any vibration of a loose fit thread. Same for the body repair.
Kram, thank you for a positive alternative if all else fails, although I can only see time and cost mounting on all the details this part requires.
I'll have a search around the Internet for epoxy advice.
Many thanks to all.

 

[Agroshield]

...I have considered a good clean up, solvent wipe, a layer of JB weld and a tidy up in a lathe.

Maybe view this video and consider if solvent wiping is the best preparation (I think it is about 12-14 minutes in if you are impatient):

 

[Dougal Thompson]

Thank you, very interesting. So Ajax it is!! And glue within the hour.

 

[Screwdriver]

I tried to be impatient but I found the whole thing quite fascinating!

 

[addjunkie]

The industrial bodge product would be either Devcon, or Belzona. Both are machinable

 

[winchman]

The industrial bodge product would be either Devcon, or Belzona. Both are machinable

I havd bodged a few things with this and I can't believe how good it is but not cheap

 

[Screwdriver]

I havd bodged a few things with this and I can't believe how good it is but not cheap

I've heard of them but no direct experience. I guess they must be a bit like the old Chemical Metal™ but an industrial strength version. Just how much is it?

 

[zzr1200]

Devon is my preferred choice.....

I once repaired/resized a stub axle pivot bush hole in steering axle beam of a 50ft Genie scissor lift that had worn 1/4" oval.

Lined up the top bush with a rod through the bottom bush and filled the gap with Devcon, 4 years later it was still holding up to the punishment of being on a National Hire Fleet of magic carpets....

https://www.cromwell.co.uk/shop/mat...-inchsfinch-plastic-steel-putty/p/DEV7112019K

https://www.cromwell.co.uk/shop/mat...cts/plastic-steel-putty-a/f/9025?query=Devcon

 

[addjunkie]

I've heard of them but no direct experience. I guess they must be a bit like the old Chemical Metal™ but an industrial strength version. Just how much is it?

Smallest kit of belzona is about 50 quid, plus vat

 

[Screwdriver]

Devon is my preferred choice.....

I once repaired/resized a stub axle pivot bush hole in steering axle beam of a 50ft Genie scissor lift that had worn 1/4" oval.

Lined up the top bush with a rod through the bottom bush and filled the gap with Devcon, 4 years later it was still holding up to the punishment of being on a National Hire Fleet of magic carpets....

My thought being since this is effectively a static carrier, it is not a wear component and may be an ideal candidate for a repair of this type. So long as the threads hold up and the correct application procedure is followed assuming that is even possible in a non commercial application without specialised equipment.

 

[Screwdriver]

Smallest kit of belzona is about 50 quid, plus vat

Sounds like "a lot" but if there's enough material in the smallest kit for this application, could be a relatively cheap option.

Plus if you have any left you can go around looking for other things to glue up...

 

[zzr1200]

I was made aware of Devcon by an old mechanic in his 70's.

He had been asked to repair an obsolete gearbox the input shaft bearing had seized and damaged the surface. He turned down the shaft and used Devcon the build the surface back up. Then he re-machined the bearing surface and retaining nut thread.

He said that the gearbox had been in use for about 5 years without a problem.

 

[Dougal Thompson]

Excellent info and I thought all my troubles were behind me.
That was until I spoke to the guy who does my machining jobs.
He has used Belzona for repairs to aluminium castings with success, including cutting coarse threads, but says it doesn't work well for cutting fine threads. It would work well for the body repair. He suggests that so long as the existing thread takes the preload torque, epoxy could be used at that stage on the threaded section. Unfortunately that would mean it could never come out again without destroying it.
What I thought might work would be to coat the housing threads with release agent before screwing it in. Once the release agent was dry it hopefully wouldn't contaminate the epoxy and would give some hope if it ever had to come out. (both carriers have to be withdrawn before the diff can be manoeuvred out of the housing making it more difficult to remove by destruction)
Sound like a plan?

 

[Screwdriver]

How about he sets it up on the lathe to tidy up the existing threads, leaves it set up and reinforces the thread with the epoxy then once cured run the threading tool along the existing path. Should act like a thread chase and leave any annoying voids. Threads might even clean up as they are. Of course once you're in the realms of cutting a thread on a lathe, might as well glue a sleeve on, thread that and be done with it.

 

[northwest]

Very soon you are going to get one of the lads who have actually done this sort of thing come along and give you their thoughts. It is a simple repair, not difficult at all.

I use Devcon regularly, it would not suit this application.

 

[Shox Dr]

If your ‘man’ can cut a thread. Then I would buy some billet and make a new one.

what happens if the epoxy breaks off while you are building it up, and locks it solid. What do you do then?

 

[brightspark]

I have used belzona to good use but not a good use for that application

 

[Dougal Thompson]

Ok, so a consensus against the epoxy.
I was worried about the ring idea thinking it might pull off, but of course although the preload is pulling on the threaded ring, the working load is pushing into it so a more attractive option and the glue will be working in shear which should be very strong.
I can see that turning down the part would be straightforward and a standard threading operation, but how would the ring be achieved (I'm a layman in lathe terms).