Single Point Diamond Turning can produce adequate accuracy in figure and roundness for most x-ray grazing incidence optics. It cannot produce adequate smoothness, necessitating the subsequent polishing operation discussed here.
N J Brown,
B A Fuchs,
"Finishing Tubular Diamond Turned Optics", Proc. SPIE 0676, Ultraprecision Machining and Automated Fabrication of Optics, (13 February 1987); doi: 10.1117/12.939511; https://doi.org/10.1117/12.939511