
107Tool Wear, Tool Life, and Economics of Metal Cutting
war, emergencies, and whenever delay penalties are imminent. If S
pr
is the
amount of money the company receives for each component, the prot per
component is given by S
pr
– C
pr
, and the rate of prot P
r
is given by
P
r
=
t
pr pr
pr
Substituting by C
pr
and t
pr
and differentiating with respect to the cutting
speed V and equating by zero, the tool life for maximum prot rate (efciency)
is obtained. The line of maximum prot rate is plotted (dotted line) in Figure
4.14. It is clear that if a prot is to be made, the cutting speed for maximum
efciency, V
pr
, lies between that for the minimum cost, ...