Use of Milling Cutter

The milling cutter

Lead angle (ψr) or entering angle (kr)

The major cutting edge angle of the cutter is the dominant factor affecting the cutting force direction and the chip thickness.
It is named lead angle (ψr) for inch alternatively entering angle (kr) for metric cutters and measured in degrees.


Cutter diameter – Dc (inch)

The cutter diameter (Dc) is measured over the point PK, where the main cutting edge meets the parallel land.

Dc is the diameter that in most cases appears in the ordering code, with the exception of the CoroMill 300 and CoroMill 200, for which D3 is used.

The most important diameter to consider is (Dcap) – the effective cutting diameter at the actual depth of cut (ap) – used for calculation of the true cutting speed.

D3 is the largest diameter of the cutter; for some cutters it is equal toDc.


Cutting depth – ap (inch)

The cutting depth (ap) is the difference between the uncut and the cut surface in axial direction. Maximum ap is primarily limited by the insert size and machine power.

Another critical factor in roughing operations is torque, and in finishing operations, it is vibration.


Cutting width – ae (inch)

The radial width of the cutter (ae) engaged in cut. Especially critical in plunging step over, and for vibration in corner milling, where maximumae is especially critical.



Radial immersion – ae / Dc

Radial immersion (ae / Dc) is the width of the cut in relation to the diameter of the cutter.

Number of effective cutting edges on the tool – zc

For determining the table feed (vf) and the productivity. This often has a critical influence on chip evacuation and operational stability.



The total number of cutting edges on the tool – zn




Pitch – u (inch)

Distance between the effective cutting edges (u).


For a specific Sandvik Coromant cutter diameter, you can choose between different pitches: coarse (-L), close (-M), extra close (- H). An X added to the code, denotes a cutter version whose pitch is slightly closer than its basic design.


Differential pitch

Indicates an unequal space between the teeth on a cutter. This is a very effective way to minimize vibration tendencies.


The text is excerpted from SANDVIK website.