From: <cfisher@borgwarner.com>
> I checked my hubs because of the shimmy problem and found the right
> front to have over .055" runout. My question is how best to true it.
>
> I asked a machinist at work about chucking on the inside of the hub bore
> where the inside bearing presses in. He didn't think it would work
I believe he is correct. You need more support and a longer axis for location.
If I had a large lathe and lots of time, I'd machine a fixture that would
locate/hold the hub by the counterbores for both inner and outer bearings. A
couple of light facing cuts and you are done.
If I had only a small lathe and a milling machine, I'd make on the lathe a
cylinder matching the inner bearing counterbore and bolt it to the mill table.
Walk it with an indicator. Plunk on the hub and hold it down with clamps. Walk
the outer bearing counterbore to make sure all was straight, then make very
light end-mill cuts on the hub face.
If you could mount a spare axle stub vertically on a surface grinder (lock the
table travel), you might be able to grind the face. Don't try this without
knowing what you are doing. Since you are by-definition going to grind a total
of .055" from the high spot it is imperative that you take a thousandth off the
high spot first. Accidently making your first touch anywhere else could make
for entirely too much excitement in the shop!
There may be some sort of dedicated method to do this on brake machine. There
are lots of cars that have brake drums with integral bearing counterbores. How
do automotive machinists locate them?
>and
> suggested I mount it on the car and use a die grinder to even it out.
Either he was joking or that was the most astonishingly-bad advice I can
imagine coming from a machinist.
> If I go to an automotive machine shop, will they know how to tackle
> this?
Maybe.
> Can someone tell me how to tell them to do it?
You could tell them of my suggestions, but I have to believe that if they don't
have a system in place for this, following my methods could be expensive at
shop rates.
Outfits that do brake disks on the car (I have never seen this done, but I am
told that it sometimes is done) may be able to adapt their setup to face your
hub.
> Should I just try the die grinder with the hub on the car?
No. Unless the spindle is immobilized and you have a precision method of
keeping the grinder on a straight path in a plane perpendicular to the axle
axis, you have little hope of success. Rotating the hub 180 degrees from the
indicator to a spot where you could grind a little and then back to check might
take you ten years. It would take me a hundred years.
--
Phil Ethier West Side Saint Paul Minnesota USA
1962 Triumph TR4 CT2846L, 1992 Saturn SL2, 1993 Suburban,
1994 Miata C package
pethier [at] comcast [dot] net http://forum.mnautox.com/forums/
http://www.flickr.com/photos/pethier
I decry the textmessagization of the American-English language.
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