Important formulas
Conversion table Metric/Inch
Spindle speed
Length dimensions
1000 x V c D c x π
(min -1 )
n =
mm 25.4
mm to Inch =
Cutting speed
n
n x D c x π 1000
m 0.3048
V c =
(m/min)
m to feet =
V f
Feed per min.
Cutting speed
f n V x n f = (mm/min)
m/min to SFM = m/min x 3.28
f n
Feed per revolution
SFM x 3.82 D
f z x Z
f n =
(mm)
RPM =
Cross section of chip
n
Feed
ap x f n A = (mm 2 )
V f
mm/rev 25.4
mm/rev to Inch/rev =
Material removal rate (Boring)
f n
A x V c Q = (cm
3 /min)
IPM = RPM x IPR
Cutting performance (Boring)
Workpiece material
Workpiece material No. k c 1.1 (N/mm 2 )
m
ap x f n x V c x k c 1000 x 60
c
P =
(kW)
St 37-2 St 50-2
1.0037 1.0050 1.1191 1.2312 1.4301 1.4401
1780 1990 2220 1800 2350 2600 1020 1005 1130
0.17 0.26 0.14 0.27 0.21 0.19 0.25 0.25 0.44 0.23 0.23 0.21
CK 45
Torque (Boring)
40CrMnMo S 8 6
(D c
2 - D
i 2 ) x f
n x k c
X5CrNi 18 10
M c =
(Nm)
8000
X5CrNiMo17 12 2
GG 20
Specific cutting force
GGG 40 GGG 80
k c 1.1 h m c
k c =
(N/mm
2 )
AL Wrought alloys
3.3535 3.2581 3.7164
780 830
AL Cast alloys
TiAI 6V4
1370
Thickness of chip
f z x sin κ h = (mm)
A
Cross section of chip
mm 2 mm mm mm
ap D c
Depth of cut
With an entering angle of 90° the chip thickness is equal to the feed per tooth (f z ).
Cutting diameter
D i F f
Diameter of starting bore
Feed force
N
Material removal rate (Drilling)
f n f z h
Feed per revolution Feed per tooth Thickness of chip Specific cutting force
mm mm mm
V f x π x D c 2 4 x 1000
(cm 3 /min)
Q =
k c
N/mm
2
Cutting performance (Drilling)
k c 1.1
Specific cutting force for a chip cross section of 1mm 2 and chip thickness h = 1mm
M c x 2 x π x n 60 x 1000
P =
(kW)
N/mm 2
m c M c
Increase of the k c curve
Torque
Nm
Feed force (Drilling)
n P Q
Spindle speed
min -1
0.63 x f n x D c x k c 2
F f =
(N)
Cutting performance Material removal rate
kW
cm 3 /min
V c V f
Cutting speed Feed per min. Number of teeth
m/min
Torque (Drilling)
mm/min
D c
2 x k
c x f n
M c =
(Nm)
Z
8000
5
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