Ahmad K Elshennawy, George F Schrader
Small and medium-size work pieces usually are turned around a horizontal axis. Turning operations may be divided into two classes: those done with the work piece between centers and those done with the work piece chucked or gripped at one end with or without support at the outer end. There are many kinds of lathes, ranging from manual one-tool-at-a-time lathes, to semi-automatic, automatic, and CNC production-type lathes. Lathe accessories and attachments include chucks, collets, centers, drivers, and digital read out systems. Under average conditions, reasonable tolerances for rough turning and boring range from 0.15 mm (˜ .005 in.) for diameters under 15 mm (˜ .5 in.) to 0.40 mm (˜. 015 in.) for diameters over 50 mm (˜ 2 in.). For finishing operations, tolerances from 50 µm (.002 in.) for diameters below 15 mm (˜ .5 in.) to 0.180 mm (˜ .007 in.) for diameters above 50 mm (˜ 2 in.) are usually achievable. For hole finishing, a properly used fluted reamer will produce holes to within 25 µ m (.001 in.) of nominal size. For purposes such as manufacturing planning, setup, scheduling, and costing, it is often necessary to calculate the machining time and metal removal rate for a lathe operation.
By Gary Conner
By George N Bullen FSME