Cutting speed formula – turning and milling
The cutting speed formula is the same for both milling and turning.
In milling, where the tool is rotation, the cutting speed depends on:
1. Rotation speed of the tool
2. Diameter of the tool.
On lathes, where the part is rotating, the cutting speed depends on:
1. Rotation speed of the part
2. Diameter at which the tool is doing the cutting.
Metric mode
S in m/min, D in mm, N in RPM.
The 1000 in the denominator is to convert the D in mm to meters.
Inch mode
S in ft/min, D in inch, N in RPM.
The 12 in the denominator is to convert the D in inch to feet.
