TR6 Brake drum turning

[John Middlesworth <jape@email.unc.edu>]

I actually have a TR4A but since the specs are the same I thought I'd get
the quickest response by asking about TR6 drums (which are the same size).
I took the drum to have a shop turn it, but the machinist didn't have the
maximum diameter in any of his books.  One book in fact advised him to
look under "Standard Motor Company" for more info!  What's the minimum
thickness when he cuts down this drum?  (I don't have my shop manual in
town.)

John Middlesworth
1966 TR4A