"B. Vibert" wrote:
> > This is quite true, but has more to do with hard spots, rather than high
> > spots. The cutting tool is more likely to deflect at points where the
> > rotor has work-hardened from heat (these areas are sometimes
> > 0.010-0.015" deep and must be undercut, which requires more tool
> > pressure). And, quite so, tool pressure on both sides of the rotor
> > ensures that the cut is true on both sides in the direction of rotation.
> >
>
> I've tried turning rotors in a lathe, it's rarely worth the time and trouble
>as
> the results are usually not very good for the reasons Doug mentioned above. If
> you cut one side and then rechuck it is quite difficult to get it parallel
>with
> the side you just faced. I've used very accurate dial indicators when
> rechucking, even tried facing both sides without rechucking, and still had
> pulsations.
> I think the problem is not so much with warpage as with minutely varying
> thickness in the rotor, probably from the harder spots in the rotors.
> While a warped rotor will shudder somewhat, a varying thickness one is very,
> very, much worse. This is why the real brake lathes face both sides at once.
> Usually it's not worth the trouble to turn them as new ones are not really
>that
> expensive.
The replacement rotor I bought was not turned, it was milled. Not being a
machinist, common sense (usually wrong) suggests that this would avoid the high
spots from hardening. However, the high spots would appear after the pads set
in
because brake pads themselves act as a tool on a lathe.
> I have no experience with drum brakes.
>
>
> 1997 Shetland Sheepdog
Peter Thomas
1966 Triumph TR4A IRS
1996 Ford Windstar GL
1991 Shetland Sheepdog
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