CNC mills remove material by moving a spinning tool through the raw material, physically displacing the material. However, there are multiple cutting strategies and tools that can be employed to produce a part; some of the most popular are listed below: 

Plain Milling

This is the most basic operation possible on a CNC mill, that’s used to produce flat faces parallel to the bed of the CNC mill.

Face Milling

Face milling is similar to plain milling, however, a much larger diameter tool is used and the depth of cut is only a fraction of plain milling and produces a large, flat surface.

Contour Milling

Contour milling refers to the process of producing curved or contoured surfaces. In most cases, the rough shape is first machined, then a final contour pass is performed using a tool like a ball end mill to get the desired shape.

Angular Milling

Angular milling refers to the process of milling a flat surface that is not parallel to the bed or the spindle axis. An example would be a chamfer on the corner of the part.

Side Milling

This refers to the process of milling a flat, vertical surface on the side of the part.

Groove or Slot Milling

Slotting refers to the process of cutting a groove inside the raw material. This slot can either pass through the material or, alternatively, only extend a fraction of the way through the material.

Hole Drilling

Holes are typically machined using a drill. However, larger holes can be machined with an end mill that cuts the hole by spiraling down into the workpiece.


After drilling, the hole can be reamed to achieve a precise diameter. Reamed holes are often used to accurately position items with locating pins.

Hole Tapping

Hole tapping is performed on a pre-drilled hole. The tap is introduced into the hole and either cuts or forms the thread at the required pitch to be able to accept a fastening element like a bolt.

Gang Milling

Gang milling is when multiple milling cutters engage the workpiece at the same time.

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