128 CNC Machining
Figure 6-10. This metal finish chart predicts the smoothness that will result from different insert nose
radius and feed rate combinations. For example, a 1/8″ radius and .010″ feed results in 25 rms finish,
while a 1/32″ radius and .008″ feed results in 60 rms finish. (Kennametal)
1110 1000
600
400
300
200
150
100
90
80
70
60
50
40
30
20
10
1/64 1/32 3/64 1/16 1/8 3/16 1/4 3/8 1/2 5/8
nose radius
theoretical
surface
finish
—
RMS
microinches
theoretical
surface
finish
—
AA
microinches
666
444
333
222
166.5
111
66.6
55.5
44.4
33.3
22.2
11.1
77.7
88.8
99.9
.100
.090
.080
.070
.060
.050
.040
.030
.025
.020
.015
.010
.009
.008
.007
.006
.005
.004
.003
.002
feed rate (ipr)