Understanding Cutting Speed, Feed Rate, and Depth of Cut in Machining

SPINDLE SPEED [N] :  Spindle speed plays a very important role in calculating cutting speed. Spindle speed is also called RPM. This means how much revolution the spindle does in a minute is called RPM or spindle speed.

Suppose 2000 spindle speed. If you want to show spindle speed in a  CNC program, it should be called S2000.


CUTTING SPEED: It is the speed at which material remove in one minute by cutting tool from a linear distance of workpiece. It is express as mm/min or m/min.

            Formula ;                             Cutting speed (Vc)= (π D1 N)/1000  mm/min

        Where D1 = Uncut diameter of the workpiece                      N = Spindle speed


Sometimes tool have cutting speed limitation . Consider limitation of tool for cutting speed Vc 200 to 250 and diameter D is 50. That time we need to calculate spindle speed Let’s see the calculation  ;

                                   200 = (3.14 ×50×N)/1000 

                                    N = 1274 RPM
FEED: It is simply defined as a movement of cutting tool each cut . It is express as mm/rev.


DEPTH OF CUT : Thickness of metal removed in each cut of the tool . It is a perpendicular distance measure from the machined surface to the uncut surface of a workpiece . Depth of cut calculation while performing turning 
                 
                                      d = (D1-D2)/2