Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 313)

Introduction to Programming
Chapter 10
10-39
Cutting Speed
The term “cutting speed” refers to the velocity of the surface of the
revolving cutting tool relative to the workpiece. Cutting speeds are
determined by the spindle speed in revolutions per minute (rpm) and the
diameter of the cutting tool in the following equation:
Metric Units English Units
3.14159 x D x N 3.14159 x D x N
V = --------------- V = -----------------
1000 12
Where : Is :
V cutting speed in meters or feet per minute
D diameter of the tool in millimeters or inches
N rpm of the spindle
Or, stating the equations in terms of required spindle rpm:
Metric Units English Units
V V
N = 318.30989 --- N = 3.81972 ---
D D
From the metric equation, if a desired cutting speed is known, for example
V = 100 surface meters per minute using a cutting tool with a diameter, D
= 100 millimeters, the spindle speed, N is equal to approximately 318 rpm.
Spindle speed is programmed with an S--word. In this above example the
S--word would be S318.