Minimum rotor thickness for Mk 2 spitfire

[Eric Straub <ericst@MICROSOFT.com>]

I took my 9 inch disc brake rotors into the machine shop to get them 
turned, but they won't do it until they know what the minimum thickness is 
(liability reasons).  I've looked in my workshop manual & my Haynes manual, 
but neither seems to have this.

Does anyone know what the minimum thickness for these is???

Eric.