If you have a decent parting tool, set your bar in 4jaw(can get it nice and tight)
put a small centre in the end.Turn the OD to 80mm, go in with your parting tool as far as you feel comfortable, leave a 30ish mm dia to support the bar and do the the same until you have all your discs(leave some green on the thickness) remove from lathe and cut through the 30mm section to leave you with your discs then chuck in 3 jaw and clean both faces to finished thickness.