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Mon Jan 20, 2020 6:14 am

Shot peening
Cryo treating
Nitriding
Polishing

Any of these worth doing to stock axles to give them a better chance of surviving?

Just wondering what the typical failure of them is (Seen the spades crack off)

Mon Jan 20, 2020 8:07 am

Polishing is the best thing you can do. Stock axles have very sharp ridges at the spade/shank interface. These are where cracks start. Polishing this transition will extend axle life.

Shot peening may help, but no testing has been done that I know of.

The real problem is the level of hardness that stock axles have. They are so hard they are brittle.

Chromoly axles are way better for this reason.

Mon Jan 20, 2020 10:31 am

Too hard? Are you saying the chromoly axles are softer?
Interesting, makes me wonder what people have tried in the past wrt making them last.
Shot peening makes stuff harder, so I guess that's out.
Also, afaik cryogenic treatment also increases hardness too, can the spade b annealed to a degree?

Mon Jan 20, 2020 10:33 am

Ohio Tom wrote: Polishing is the best thing you can do. Stock axles have very sharp ridges at the spade/shank interface. These are where cracks start. Polishing this transition will extend axle life.

Shot peening may help, but no testing has been done that I know of.

The real problem is the level of hardness that stock axles have. They are so hard they are brittle.

Chromoly axles are way better for this reason.

Stock IRS type axles.....are as you noted....very hard on the outside at least.....but have some level of spring tension/wind up ability in their core. Pretty damn tough...but yes....brittle amd under stress on the outside layer. A lot like case hardening.

Several notes in factory manuals through the years.....point out specifically that grooving, denting, deep scratching or heavy sanding the outer surface of the axle can cause breakage.

I have actually seen this happen twice....once on an aircooled beetle and once on a rabbit. But....had something dragging on the shaft that put a small groove in it....very small. It snapped at the groove.

I'm not sure I would suot peen something made like that. Ray

Mon Jan 20, 2020 11:22 am

On a stock axle polish the spade end. If you are willing to spend the money on Cyro it would be cheaper and better to just go ahead and buy stronger aftermarket axles.

Mon Jan 20, 2020 11:34 am

X 2 on polishing the spade end and about 6 inches up the axle....I've broken my share to trans parts, but the axles held up through some extreme treatment.

Mon Jan 20, 2020 12:47 pm

vwracerdave wrote: On a stock axle polish the spade end. If you are willing to spend the money on Cyro it would be cheaper and better to just go ahead and buy stronger aftermarket axles.

Not that simple in the UK.
Shipping kills it with the empi axles.
The Finnish guys (kuplapaja? ) are making awesome axles but they're over a $1000. I can have stuff nitrided quite cheaply here, not had quotes on cryo or shot peening though.

Mon Jan 20, 2020 12:48 pm

rugblaster wrote: X 2 on polishing the spade end and about 6 inches up the axle....I've broken my share to trans parts, but the axles held up through some extreme treatment.

That's the thing, my trans is stock, so I have to baby it any how to a degree...

Mon Jan 20, 2020 12:49 pm

raygreenwood wrote: Ohio Tom wrote: Polishing is the best thing you can do. Stock axles have very sharp ridges at the spade/shank interface. These are where cracks start. Polishing this transition will extend axle life.

Shot peening may help, but no testing has been done that I know of.

The real problem is the level of hardness that stock axles have. They are so hard they are brittle.

Chromoly axles are way better for this reason.

Stock IRS type axles.....are as you noted....very hard on the outside at least.....but have some level of spring tension/wind up ability in their core. Pretty damn tough...but yes....brittle amd under stress on the outside layer. A lot like case hardening.

Several notes in factory manuals through the years.....point out specifically that grooving, denting, deep scratching or heavy sanding the outer surface of the axle can cause breakage.

I have actually seen this happen twice....once on an aircooled beetle and once on a rabbit. But....had something dragging on the shaft that put a small groove in it....very small. It snapped at the groove.

I'm not sure I would suot peen something made like that. Ray

It would seem HD axles are much thicker all the way up to the spade.
I wonder if stock axles could be spray welded app the way...

Mon Jan 20, 2020 2:31 pm

eye wood thunk new axles would be the best way to go and not much more than what all the suggestions are.

Mon Jan 20, 2020 4:15 pm

mark tucker wrote: eye wood thunk new axles would be the best way to go and not much more than what all the suggestions are.

UK Luke 72 wrote: vwracerdave wrote: On a stock axle polish the spade end. If you are willing to spend the money on Cyro it would be cheaper and better to just go ahead and buy stronger aftermarket axles.

Not that simple in the UK.
Shipping kills it with the empi axles.
The Finnish guys (kuplapaja? ) are making awesome axles but they're over a $1000. I can have stuff nitrided quite cheaply here, not had quotes on cryo or shot peening though.

Mon Jan 20, 2020 5:24 pm

Polishing, and shot peening would be about all I would do. I’ve known a few people that have added durability by doing those things. The bottom line in material, and diameter. The material doesn’t allow much twist, and is only so big in diameter at the spade. The race axles are softer, and allow a little twist to absorb the shock. I know a few instances where lines were painted on IRS axles so the twist in the axle could be monitored. I’ve seen some twisted 90 degrees that haven’t yet broken.

Mon Jan 20, 2020 6:22 pm

Cryo and temper, and/or shot preening would probably help.
I don't think nitriding is a good idea.

Mon Jan 20, 2020 8:17 pm

UK Luke 72 wrote: Too hard? Are you saying the chromoly axles are softer?
Interesting, makes me wonder what people have tried in the past wrt making them last.
Shot peening makes stuff harder, so I guess that's out.
Also, afaik cryogenic treatment also increases hardness too, can the spade b annealed to a degree?

As a hobby blacksmith, I can tell you that if you dont know the source material and the current hardness then tempering it down further is a shot in the dark.

If you know those two variables it would be pretty simple. In my area there are a few ceramics kilns that dont mind tempering large items in their precisely controlled ovens. The part has to be immaculately clean though.

Tue Jan 21, 2020 7:58 am

Here is a pic i took of a stock axle next to a heavy duty axle. General knowledge is that the stock axle is brittle and it tapers skinny to towards the spade. YIKES!

Tue Jan 21, 2020 8:16 am

the reason stock axles are skinnier at the spade end is to increase the angle they can operate at...so you may lose some travel with the larger ones

Tue Jan 21, 2020 8:59 am

Does anyone have any pics of the polished ends? To what degree is necessary?

I can chuck them up in the lathe.

Tue Jan 21, 2020 6:07 pm

This is the only pic of polished spades I could find, but it’s not the best. Radius all the edges of the spade. Spinning it in a lathe would help on the shaft part. See if you can get the majority of the forging stamping surface irregularities smoothed out, and literally polish it with wet fine sandpaper/metal polish.

http://img2169.imagevenue.com/img.php?image=33714_DSC00075_122_236lo.JPG

Tue Jan 21, 2020 9:35 pm

UK Luke 72 wrote: Does anyone have any pics of the polished ends? To what degree is necessary?

I can chuck them up in the lathe.

I couldn't find a whole lot of info on polishing axles when I did mine, so I just did the best I could - polished on the left, not polished on the right.

Sun Jan 26, 2020 7:23 am

So this is how far I went with polishing

60/120/240 grit, did about 6" or so.
The specks on the spade are dirt and crap, I just coated them in light oil to stop any corrosion.

These came out of a LHD car (mine's RHD)
They are marked driver side and passenger side... I take it they need to go back in the same way?