In the process of metal cutting, whether the chips are easy to break is directly related to the deformation of the chips. Therefore, the study of the principle of chip breakage 

must start from studying the rules of chip deformation.

The hardness of the chips formed during the cutting process will increase due to relatively large plastic deformation, while the plasticity and toughness will be significantly 

reduced. This phenomenon is called cold work hardening. After cold work hardening, the chips become hard and brittle and are easily broken when subjected to alternating 

bending or impact loads. The greater the plastic deformation experienced by the chip, the more obvious the hard and brittle phenomenon will be, and the easier it will be to 

break. When cutting high-strength, high-plasticity, and high-toughness materials that are difficult to break chips, efforts should be made to increase the deformation of the 

chips to reduce their plasticity and toughness and facilitate chip breaking.

The deformation of chips can be composed of two parts:

The first part is formed during the cutting process, which we call basic deformation. The chip deformation measured during free cutting with a flat rake face turning tool is 

relatively close to the value of the basic deformation. The main factors that affect the basic deformation are tool rake angle, negative chamfer, and cutting speed. The smaller 

the rake angle, the wider the negative chamfer, and the lower the cutting speed, the greater the chip deformation, which is more conducive to chip breaking. Therefore, 

reducing the rake angle, widening the negative chamfer, and reducing the cutting speed can be used as measures to promote chip breaking.

The second part is the deformation of the chips during the flow and curling process, which we call additional deformation. Because in most cases, only the basic deformation 

during the cutting process cannot break the chips, and an additional deformation must be added to achieve the purpose of hardening and breaking. The simplest way to 

force the chips to undergo additional deformation is to grind (or press) a chip breaker of a certain shape on the rake face, forcing the chips to curl and deform when they 

flow into the chip breaker. After the chip undergoes additional recurling deformation, it is further hardened and brittle, and when it collides with the workpiece or flank 

surface, it is easily broken.