Question

 

Identify the kind of chips – continuous, discontinuous, segmented or built-up edge, that the following workpieces will tend to form under typical cutting (turning) conditions (i.e. not severely high cutting speeds, depths of cut or feeds). Also, state the reason for why that would be the case.

a) Grey Cast Iron

b) Titanium

c) 4140 Alloy steel

d) stainless steel 316

Answer 1

a) Grey Cast Iron - Discontinuous chips

These kind of chips are formed when machining hard and brittle materials like cast iron. During machining, the compressive force reaches the fracture limit of the material and thus fragments it.

b) Titanium - Segmented chips.

Segmented chips are semi continuous chips. These chips are formed due to areas of high and low strain and uneven temperatures on the material. That happens when the thermal conductivity of material is low such as that of titanium.

c) 4140 Alloy steel - Continuous chips

Continuous chips are formed when machining ductile materials such as alloy steels. They are long strands as the material does not get fractured.

d) Stainless steel 316 - Built up edge

The chips are similar to continuous chips but have a built up edge. These are formed in metals which are easily work hardened such as stainless steel. The chip material sticks to the tool face ( called as cold welding ). When they break, it results in a built up edge.