Indications of how the milling tool engages with the material, and its affects on the cutting process and the result
A. Conventional milling
The tool rotate against the relative direction of movement of the workpiece.
The advantages are smooth cut engagement and no pulling force on the workpiece.
B. Climb milling
The tool rotate with the relative movement direction of the workpiece.
The advantages are lower cutting forces, thicker chips when engaged capturing more of the heat, downward force means easier mounting, chip moves away from the working direction, good surface smoothness and longer tool life.
Climb milling is usually better, but there are times when conventional milling has advantages for example when milling cast or forged parts and the processing work hardened work pieces.
C. The combination of counter and climb milling
If material to be removed exceeds the centerline of the milling tool, a combination of A and B will arise.
An advantage of this compared to climb milling is that the cut is not initiated by the tip of the cutting edge, which is the most sensitive part of the insert. Instead, the cut is initiated a bit into the rake face of the tool and gives the tip a better engagement.