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Purpose:
This document defines glass surface quality on optical components per MIL-O-13830.
Definitions:
SCRATCH: Any marking or tearing of the glass surface.
SLEEK SCRATCH: A hairline scratch.
CRUSH or RUB SCRATCH: A surface scratch or a series of small scratches.
DIG: A small rough spot on the glass surface similar to pits in appearance. A bubble is considered a dig.
Procedure:
Surface quality is to be specified by a number such as 60/40. The first digits relate to the maximum width allowance of a scratch as measured in microns. The next digits indicate to maximum diameter allowance for a dig in hundredths of a millimeter. Thus, as can be seen from the table below, a surface quality callout of 60/40 would permit a scratch width of .0024 inches and a dig diameter of .0158 inches. The size of a defect is to be measured through the use of an optical comparator.
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Scratch or
Dig Number
|
Maximum
Scratch Width
|
Maximum Dig
or Bubble Diameter
|
Dig or Bubble
Separation Distance
|
|
|
mm
|
inch
|
mm
|
inch
|
mm
|
inch
|
|
120
|
0.12
|
0.0047
|
1.20
|
0.0473
|
20
|
0.787
|
|
80
|
0.08
|
0.0031
|
0.80
|
0.0315
|
20
|
0.787
|
|
60
|
0.06
|
0.0024
|
0.60
|
0.0236
|
20
|
0.787
|
|
50
|
0.05
|
0.0020
|
0.50
|
0.0196
|
20
|
0.787
|
|
40
|
0.04
|
0.0016
|
0.40
|
0.0158
|
20
|
0.787
|
|
30
|
0.03
|
0.0012
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0.30
|
0.0118
|
20
|
0.787
|
|
20
|
0.02
|
0.0008
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0.20
|
0.0079
|
20
|
0.787
|
|
15
|
0.015
|
0.0006
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0.15
|
0.0059
|
20
|
0.787
|
|
10
|
0.010
|
0.0004
|
0.10
|
0.0039
|
1
|
0.040
|
|
05
|
0.005
|
0.0002
|
0.05
|
0.0020
|
1
|
0.040
|
|
03
|
0.003
|
0.00012
|
0.03
|
0.0012
|
1
|
0.040
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