Types of Chips
Types of chips:
Following
are the three common types of chip from a single point tool:
Continuous
chips are formed by the continual plastic deformation of metal without fracture
ahead of the leading edge of the tool and is made by the graceful flow of the
chip up the tool face. MS steel and copper are considered to be most desirable
materials for obtaining continuous chips. The chips obtained have same
thickness throughout. This type of chip is the most desirable. Since its stable
cutting, leading to generally good surface finish. On the opposite hand these
chips are difficult to handle and dispose off.
Continuous
chips tend to be formed when the subsequent condition exist:
•
Ductile material
•
High cutting speed
•
Small chip thickness
•
Large rack angle
2. Discontinuous or Segmental
chip:
This
type of chips are made by a series of rupture occurring approximately
perpendicular to the tool place face each chip element passing off along the
tool face the chip element in the form of small segment may adhere loosely to
every other and becomes slightly longer.
Since
the chips hack into small segments the friction between the tool and thus the
chips reduces’ resulting in better surface finishing. These chips are
convenient to collect handle and dispose off. Discontinuous chips tend to be
formed when one or more or the subsequent conditions exist:
•
Brittle material, such as cast iron and bronze.
•
Large chip thickness
• Low
cutting speed
•
Small rack angle
Discontinuous
chips also are produced when cutting more ductile material with the utilization
of a cutting fluid.
3. Continuous Chip with Built up
Edge:
This
type of chip is extremely almost like the continual chip. With the difference
that it's a built up edge adjacent to tool face and also it's not so smooth. It
is obtained by machining on ductile material, during this condition of high
local temperature and extreme pressure within the cutting and high friction
within the tool chip interference, may cause the work material to stick or weld
to the leading edge of the tool. Successive layers of labor material are then
added to the built up edge. When this edge becomes larger and unstable, it
breaks up and a part of it's carried up the face of the tool along side the
chip while the remaining is left over the surface being machined, which
contributes to the roughness of the surface. The built up edge changes its size
during the cutting operation. It first increases, then decreases, and then
again increases etc.
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