Types of Chips

 The form and dimension of chips produced in machining indicate the nature and quality of a particular machining process. Different forms of chips formed during cutting processes are:

1.      The discontinuous or segment form

2.      The continuous or ribbon type

3.      The continuous with built up edge

Discontinuous chip

In some cutting conditions, chips will be fractured into fairly small pieces. This type of chip is obtained in machining fairly brittle materials such as cast iron and bronze. Reasonably good tool life, surface finish and less power consumption are the advantages of this type of chip form in brittle materials. But with ductile metals, the surface finish is bad and the tool life is short.

Conditions tending to promote its formation include: brittle material, greater depth of cut, low cutting speed and small rake angle.

Continuous chip

In some cutting conditions continuous ribbon of metal formed with no signs of shear or discontinuities. These types of chips are considered most desirable for low friction at the tool chip interface, lower power consumption and good surface finish.

The factors favorable for its formation are: ductile metals such as mild steel, copper etc. , fine feed, high cutting speed, large rake angle, keen cutting edge, smooth tool face and an efficient lubrication system.

Continuous chip with built up edge

In some cutting conditions, owing to the high heat and pressure generated on the cutting edge, a piled up metal is welded to the cutting tip and forms a false cutting edge called built up edge. When this built up become unstable, break down and some fragments leave with the chip and others adheres to the work surface forming rough surface.

Conditions tending to promote the formation of built up edges include: low cutting speed, low rake angle and high feed.