Spray metal repair on FF axle housing.

[Eurasiaoverland]

I have a FF rear axle where the bearings have spun on the spindles, creating about 0.15 mm of wear on the bottom surface of the spindle. Currently the axle is at a machine shop and I have a quote for a spray metal repair (using an arc/wire spray welder, not flame/power).

Is anyone familiar with the technique? Is it suitable for an exle spindle? The bearing is not an interference fit on the spindle, but the spindle does support the weight of the rear part of the vehicle on those surfaces where the bearings sit.

Last thing I want to do is end up with something rapidly wearing into a state far worse than it is now.

Note: FF rears are expensive here when available and will invariably be worn as almost nobody maintains anything in this part of the world. Aside from the wear, the axle is in excellent condition with zero rust and appears not to have been used off road much, if at all.

 

[aztoyman]

We sent huge Caterpillar spindles and other parts off for metal spray and never had any failures. Our dealership main branch actually had the equipment on site. The process saved a lot of parts that in the past would have been unrepairable. I don't remember whether it was an Arc or Flame version of the process unfortunately.

 

[DrRock]

I’ll second @aztoyman s response. I am a mechanical engineer and this process is well understood and has excellent results with the electric method. Good luck and hope this works out for you.

Cheers, James

 

[Eurasiaoverland]

Thanks guys. I'm going to go ahead with it. Hopefully timing works and I can see the work being done.

 

[Kernal]

@Eurasiaoverland : What is the total cost per side? I'm sure that would vary greatly between countries/regions but still would be interesting to know.

If you have the spindle(s) repaired using this process could you try to get photos (or better video) of the complete process
and post it up here (or post it on youtube with a link??)

 

[Eurasiaoverland]

@Eurasiaoverland : What is the total cost per side? I'm sure that would vary greatly between countries/regions but still would be interesting to know.

If you have the spindle(s) repaired using this process could you try to get photos (or better video) of the complete process
and post it up here (or post it on youtube with a link??)

I went to the shop on Saturday and watched them start the work - it's a very time consuming process. Once the work is finished I'll update my build thread with pictures and maybe videos that I took. The method used an arc spray gun, where two 1/16" 13 % Chromium steel wires are melted simultaneously (with the arc between the two wires) and blasted out with compressed air.

In essence, the process is:
- machine away a 'channel' in the old spindle surface. There should not be an edge of spray metal material, it should be bound by parent material on each side.
- a masking compound is applied to areas where metal spray is not desired (e.g. the threads on the end of the spindle).
- a bond material is sprayed on the machined area.
- the wire spools are then changed to the filler metal and this is built up in roughly 10 second passes on the spindles. The operator never got the spindle aboive 90º C.
- Once the material has been built up to 2 mm oversize, an initial cut is made to smooth off the filler. Water is used to dissolve the masking compound and release the overspray.

That's as much as I saw. The machinist builds each of the three areas separately (two bearing surfaces and the grease seal surface) and will machine them all to spec in one session, then reverse the axle housing in the lathe and do the other side.

I've been quoted MYR 800 (just under USD190) per side, though that may have been for just the two bearing surfaces.. In Malaysia, that's quite expensive but it'll probably be a day and a half of work so would cost massively more in Europe or, I assume, the USA. But it's really the only solution (and I hope it's a good one) to worn spindles by my assessment, other than replacement (and they are long since out of production).

 

[Eurasiaoverland]

Yesterday I picked up the axle from the machine shop and I've spent the morning checking out the work. I've test fitted the hubs with new bearings, and checked the lock washer and locking nut alighment. Everything is correct. I only had to clean up one keyway with a grinding disc in the Dremel and run a thread file over the threads on one side, and I think it's perfect.

Here you can see the RH spindle. The areas of different colour are where the repairs have been done; so on the two bearing surfaces and the inner diameter where the grease seal rides. The bearings have that same tight but not interfering fit that they do on new front spindles and I'm very happy with the work. The new metal texture is not as smooth as the original, but the machine shop owner told me the new filler will be harder than substrate. And given that it could be machined to size without ripping chunks out, it seems to be good. Only time will tell if the work is strong enough, but I reckon it will be fine. I'll be keeping a close eye on rear wheel bearing pre-load. An added bonus to having done this is that I know the two spindles are dead straight along the axis of the housing.

Here's a picture of the arc spray:

 

[aztoyman]

I'm glad it worked out and that you are happy with the work. As far as it lasting, they hold up long term on pretty much the same part on massive Caterpillar haul trucks.