So if like me you try turning it in your four jaw chuck or on the face plate to get cheap flat plate don't be surprised if you start to hit rather hard patches at the change of direction points in the metal .
Tonight it took me five resharpens of the facing tool before I realised that it was these hard & stressed points that were taking the cutting edges off the HSS hand ground cutters in a matter of a few seconds .
I spent ages resetting all the gibs , checking the flatness of the tool post mount , security of the tools in the tool post etc, etc . & run out of the lathe , for I couldn't understand why the flat piece I was turning kept measuring up like a section of round cheese some 0.08 mm out towards one corner .
It was the hard zones allowing the tool & tool post to be forced to the tail stock fraction every time it passed the hard zone area . I should have worked it out after the third resharpening session .
In the end I dug out some old heavy 3/4 inch TCT tools , put on a different tool post on that would take it and got cracking .. even then the TCT had to be resharpened once & there is still a slight hill 0.06 mm in the worst corner .