SURFACE ROUGHNESS

The machined surface and tolerances achieved on components are directly affected by both the insert nose radius and the feed rate. From a strictly theoretical perspective, surface roughness can be calculated from the following formula:

2

6

f n

x 10

f n

R t =

8 x r

R t

Where

R t = Theoretical Profile Depth, m inches f n = feed / rev, inches r = insert nose radius, inches

The following table presents feed values for common insert nose radius sizes and surface roughness requirements:

feed f n , inches / rev

R t , minch

r = 1/64”

r = 1/32”

r = 3/64”

r = 1/16”

r = 3/32”

16

.0015

.002

.0025

.003

.0035

32

.002

.003

.0035

.004

.005

63

.003

.004

.005

.0055

.007

125

.004

.0055

.007

.008

.010

250

.0055

.008

.010

.011

.014

500

.008

.011

.014

.016

.019

The maximum feed per rev can be determined from the table by selecting the nose radius and speci- fied surface roughness requirement. For example, Surface roughness requirement R t = 63 m inches Insert nose radius r = 1/32” Theoretical starting point for feed f n => .004 inches / rev When selecting the feed for finishing to a specified level of surface roughness, the feed values provided in the table should not be exceeded. In general the feed in a finishing operation should be kept low in order to produce an acceptable component finish.

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