hard spots on drums - the "why"

[dardal@xxxxxxxxxxxxxxx]

Quoting Kenyon Wills <imperialist1960@xxxxxxxxx>:

> 
> 
>  it is my understanding that if you run a car under hard braking and then
> park it with the pads still really hot, that they can create hardspots. 
> Hardened metal has been changed metallurgically and when the shop tries to
> turn the drum, the softer material gets trimmed away, but the blade that cuts
> the drum does not cut the hardspots well.

This is reversible.  You could put these drums to fernice and heat them up to
their anealing temperature, and then let them cool down real slow.  The
material will come back to its anealed state.  Then, it will machine nice.  If
we knew exactly what type of cast iron we are dealing with, the anealing
temperature can be looked up in metal handbooks.

D^2