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VC_GB
.f
m
OPTIMUM
M A S C H I N E N - G E R M A N Y
®
5
Cutting speeds
5.1
Selecting the cutting speed
The variety of factors makes it impossible to present universal indications about the
"correct“ cutting speed.
Tables with reference values about cutting speeds to be set must be evaluated with utmost
caution since they only apply for very particular cases. The reference values without cooling (no
best values) which are indicated in AWF documents are highly recommended. Furthermore, the
tables of reference values of the manufacturers of cutting materials should be evaluated e.g. for
hard metal cutting materials the indications of the company Friedrich Krupp Widia-Fabrik,
Essen applies.
V
c60
is the cutting speed at 60 min. service life, V
c240
according for 240 min. service life. Select
V
c60
for simple, easily replaceable lathe tools; V
c240
for simple tool sets depending on one
another; V
c480
for complicated tool sets where the tool change requires more time due to the
dependencies on one another and the accuracies of the cutting insert. The same
considerations apply with regard to maintenance of the tools.
It generally applies: High cutting speeds result in low-time chipping, little cutting speeds result in
cost-efficient chipping.
5.2
Influences on the cutting speed
v
c
= Cutting speed in [ m/min]
t
= Service life in [min]
The service life
t
is the period of time in minutes during which the cutting insert performs cutting
tasks until it is necessary to re-sharpen it. It is of utmost commercial importance. For the same
material
t
is smaller the higher you select the value
v
c
e.g. only a few minutes at
v
c
= 2000 m/
min. Different materials require different
v
c
for the same
t
. All considerations of this type
require that the other cutting conditions are maintained constant
(material, tool and setting conditions). If only one of these condition changes it is also neces-
sary to change
v
c
in order to obtain the same
t
. Therefore, only cutting speed tables are rea-
sonable which show all relevant cutting conditions.
5.3
Example for the determination of the required speed on your lathe
The necessary speed is depending on the diameter of the workpiece, of the material to be
machined, of the turning tool, as well as of the setting of the turning tool (cutting material) to the
workpiece.
Material to be turned: St37
Cutting material (turning tool): Hard metal
Setting angle [k
r
] of the turning tool to the workpiece: 90°
selected infeed [f]: about 0.16mm/rev
Target value of the cutting speed [
v
c
] according to the table: 180 meters per minute
Diameter [d] of your workpiece: 60mm = 0.06m [meters]
Speed
Set the speed on you lathe below the calculated speed.
n =
V
c
π
x d
=
180m
min x 3,14 x 0,06m
= 955 min
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