Authorized Distributor of Parker O-Rings, Parker Seals and Parker Products
Authorized Distributor of Parker O-Rings, Parker Seals and Parker Products
The quality of the surface of an O-ring has a great influence over its sealing and contamination performance. Several industry standards exist for the identification of surface quality. Visual inspection standards are written for imperfection detection with the unaided eye. Magnification is used for reference purposes only.
The Rubber Manufacturers Association (RMA) OR-1 O-ring Inspection Guide— Surface Imperfections Control is intended to provide manufacturers and users with seals that have a surface quality adequate for intended use. The Military Standard MIL STD 413 C is the most common surface standard for O-rings and contains standard imperfection classifications.
Imperfections are typically classified into eight categories. In addition, different surface quality specifications may be necessary for non-O- ring parts. Common specifications for non-standard parts include surface roughness (measured by profilometer), external and internal voids and color.
Backrind
A longitudinal recess oriented circumferentially and located only at the parting lines. Edges are irregular and can be present on the full circumference on the OD and/or ID within the specified limits
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MIL-STD 413 C |
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AS 568 |
O-Ring CS (in) |
O-Ring CS (mm) |
Depth (in) |
Depth (mm) |
Width (in) |
Width (mm) |
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< 0.100 |
< 2.54 |
0.000 |
0.00 |
0.000 |
0.00 |
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0.100-0.134 |
2.54-3.42 |
0.003 |
0.08 |
0.005 |
0.13 |
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0.135-0.204 |
3.43-5.20 |
0.004 |
0.10 |
0.006 |
0.15 |
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0.205-0.268 |
5.21-6.83 |
0.004 |
0.10 |
0.006 |
0.15 |
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>0.268 |
> 6.84 |
0.005 |
0.13 |
0.010 |
0.25 |
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Parting Line Indentation
A shallow recess located on the parting line at the ID of OD.
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MIL-STD 413 C |
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AS 568 |
O-Ring CS (in) |
O-Ring CS (mm) |
Depth (in) |
Depth (mm) |
Width (in) |
Width (mm) |
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< 0.100 |
< 2.54 |
0.003 |
0.08 |
0.010 |
0.25 |
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0.100-0.134 |
2.54-3.42 |
0.003 |
0.08 |
0.015 |
0.38 |
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0.135-0.204 |
3.43-5.20 |
0.004 |
0.10 |
0.020 |
0.51 |
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0.205-0.268 |
5.21-6.83 |
0.005 |
0.13 |
0.025 |
0.63 |
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>0.268 |
> 6.84 |
0.006 |
0.15 |
0.030 |
0.76 |
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Foreign Material
Any contamination or depression formed by its removal.
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MIL-STD 413 C |
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AS 568 |
O-Ring CS (in) |
O-Ring CS (mm) |
Depth (in) |
Depth (mm) |
Width (in) |
Width (mm) |
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< 0.100 |
< 2.54 |
0.000 |
0.00 |
0.000 |
0.00 |
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0.100-0.134 |
2.54-3.42 |
0.003 |
0.08 |
0.005 |
0.13 |
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0.135-0.204 |
3.43-5.20 |
0.004 |
0.10 |
0.007 |
0.18 |
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0.205-0.268 |
5.21-6.83 |
0.005 |
0.13 |
0.010 |
0.25 |
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>0.268 |
> 6.84 |
0.006 |
0.15 |
0.015 |
0.38 |
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Parting Line Projection and Excessive Flash
A continuous ridge of material on the parting line at the OD and/or ID within specified limits.
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MIL-STD 413 C |
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AS 568 |
O-Ring CS (in) |
O-Ring CS (mm) |
Height (in) |
Height (mm) |
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< 0.100 |
< 2.54 |
0.003 |
0.08 |
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0.100-0.134 |
2.54-3.42 |
0.003 |
0.08 |
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0.135-0.204 |
3.43-5.20 |
0.004 |
0.10 |
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0.205-0.268 |
5.21-6.83 |
0.005 |
0.13 |
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>0.268 |
> 6.84 |
0.006 |
0.15 |
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Non-Fill
A randomly spaced indentation having coarser than the O-ring surface.
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MIL-STD 413 C |
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AS 568 |
O-Ring CS (in) |
O-Ring CS (mm) |
Depth (in) |
Depth (mm) |
Width (in) |
Width (mm) |
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< 0.100 |
< 2.54 |
0.000 |
0.00 |
0.000 |
0.00 |
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0.100-0.134 |
2.54-3.42 |
0.002 |
0.05 |
0.010 |
0.25 |
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0.135-0.204 |
3.43-5.20 |
0.003 |
0.08 |
0.015 |
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