CHESTER Craftsman, Instruction Manual, Page: 21 / 53

Cutting Speed & Feed
As you proceed to the process of metal cutting, the relative `speed' of work piece rotation and `feed' rates
of the cutting tool coupled to the material to be cut must be given your serious attention. This relationship
is of paramount importance if items are to be manufactured in a cost­effective way in the minimum time,
in accordance with the laid down specifications for quality of surface finish and accuracy. You, as a
potential supervisory / management level engineer, must take particular note of these important
parameters and ensure that you gain a fundamental understanding of factors involved.
Cutting Speed
All materials have an optimum Cutting Speed and it is defined as the speed at which a point on the
surface of the work passes the cutting edge or point of the tool and is normally given in meters/min. To
calculate the spindle Speed required,
Where:
N = Spindle Speed (RPM)
CS = Cutting Speed of Metal (m/min)
d = Diameter of Work piece
Table 2 shows the cutting speed recommended for some common metals. It may be possible to exceed
these speeds for light finishing cuts. For heavy cuts they should be reduced.
Metal meters /min
Cast Iron 20­28
Mild Steel 18­25
High Speed Steel 12­18
Brass 45­90
Bronze 15­21
Aluminium up to 300
Table 2. Cutting Speed
Feed
The term `feed' is used to describe the distance the tool moves per revolution of the work piece and
depends largely on the surface finish required. For roughing out a soft material a feed of up to 0.25 mm
per revolution may be used. With tougher materials this should be reduced to a maximum of 0.10
mm/rev. Finishing requires a finer feed then what is recommended.
Chester UK Craftsman Lathe
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