(note: holding stub axle by the splines was an error duly pointed out by David in the comments. Axle re-measured and post updated.)
I was complaining to Phil Z. about my wheel bearing failure and he suggested I have a look at the stub axle. So I chucked it up on the lathe, holding it by the splined outboard end (was careful to have the chuck jaws positioned correctly on the splines) and then I measured a couple of things.
Where the outboard bearing seats had 0.009″ runout.
At the inboard bearing seat I measured 0.015″ runout (sorry, fuzzy pic slipped past me).
Where the seal rides, 0.020″.
The face where the CV joint mates had 0.010″ runout.
I did not measure that outer edge of the CV mounting flange as I thought eccentricity there was not important as the cv is aligned by the bolts.
And here is a quick vid of the assembly spinning.
What does all this mean? How does a new stub axle measure up? Was this runout the cause of my bearing failure?
Addendum: Crow eating time. David’s points about where I was grabbing the axle (splines) was correct. I re-measured runout with axle held by outer bearing seat.
Runout at inner bearing about 0.005″.
At seal, 0.007″.
Flange face, 0.002″.
Looks a lot better in motion.
So there, no smoking gun after all.
shooftie 
#1 by oldfussbudget on April 22, 2012 - 6:39 pm
Showing off your new clock, eh? 😉
Non-expert here, so don’t believe me.
If you take a look at the video you can clearly see that the shaft is canted in the chuck jaws. Watch it wobble inside the jaws. Aside from that, I don’t think measuring relative to the tops of the splines will give you good info. The axle (42.4) is supported and held in alignment by the bearings so ISTM any meaningful runout measurement must be relative to the bearing seats. Also since you’ve got a CV joint on one end of the thing and a rubber tire on the other end, I’d think that the only places you might be concerned about runout would be the grease seals and the brakes.
More on the bearing post…
#2 by albell on April 22, 2012 - 6:49 pm
I’m sure, and I just checked (was still chucked up) that the axle was held true. But when I have time I’ll hold it by the outboard seat and measure the runout on the inner seat. You hit the nail on the head when mentioning grease seals, I think my inner bearing failure was due to moisture rather than heat (after looking at the bearing some more).
I’ll measure the axle some more later.
cheers
ab
#3 by oldfussbudget on April 22, 2012 - 6:53 pm
OK, maybe I’m wrong. But run the video, cover up everything but the chuck jaws and watch the upper line of the splines during the slow-motion section.
#4 by albell on April 22, 2012 - 10:17 pm
I see what you mean now. Yup, I screwed up 🙂
ab
#5 by oldfussbudget on April 22, 2012 - 6:56 pm
Just for info, what’s the runout on the chuck, and is it bell-mouthed?
#6 by albell on April 22, 2012 - 10:13 pm
Dunno about the bellmouthed chuck, how do you measure that? Chuck runout greater than 0.001″ but less than 0.002″.
ab
#7 by oldfussbudget on April 22, 2012 - 11:50 pm
Hmmm….without going to the books, how about make a couple of equal diameter disks, chuck one in the bottom of the jaws gently but enough to take out the slack in everything, and then offer the other one up to the jaws and see what if any clearances you get. Bell-mouthing happens from holding work in the tips of the jaws, either by simple wear or by straining them.