
57Mechanics of Orthogonal Cutting
It follows that
r
c
==
−
The shear angle φ can be calculated from the following equation:
ϕ
γ
γ
=
−
−
tan
cos
sin
1
1
r
r
c
c
The shear angle φ depends on the chip thickness ratio r
c
and the normal rake
angle γ. The shear angle increases with increasing the ratio r
c
and the rake
angle γ. Greater shear angles are preferred because they reduce the area of
shear plane and, therefore, the cutting force.
The chip thickness ratio r
c
depends upon the workpiece material, cutting
speed V, feed rate f, and the tool rake angle γ. As the rake angle increases,
r
c
also increases. Also r
c
increases with an increase of the ...