Measurement of Surface Roughness
Measurement of Surface Roughness
(OP)
We have a part that requires a smooth surface finish on a sharp radius (.005 / .010) of a brass part. This radius is used as a sealing surface, so it must be very smooth to make the part bubble tight.
Our quality department has taken issue with the specifying of a 16 finish for this surface, because they don't have an objective method for measuring it (i.e. profilometer). I've suggested that a visual inspection could be performed instead, but they're of the opinion that this is bad practice, because it doesn't give an objective result.
I have two questions:
1. Is there a standard for visual inspection of surface finishes? I think if I can say, "inspect visually per ____", that would likely be sufficient.
2. Is there a good tool for measuring the smoothness of small, nonflat surfaces?
Thanks in advance.
Our quality department has taken issue with the specifying of a 16 finish for this surface, because they don't have an objective method for measuring it (i.e. profilometer). I've suggested that a visual inspection could be performed instead, but they're of the opinion that this is bad practice, because it doesn't give an objective result.
I have two questions:
1. Is there a standard for visual inspection of surface finishes? I think if I can say, "inspect visually per ____", that would likely be sufficient.
2. Is there a good tool for measuring the smoothness of small, nonflat surfaces?
Thanks in advance.





RE: Measurement of Surface Roughness
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Measurement of Surface Roughness
Isn't that a bit backwards, specifying a design constraint based upon a lack of tooling or experience in the QC dept.? How do they objectively measure any other finishes?
Make them buy one. Or trust the supplier, if they have one. A profilometer and a lathe head to sweep the indicator along a circular lay path, done. May need to change the callout to specify a circular lay.
RE: Measurement of Surface Roughness
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http://www.zygo.com/?/met/profilers/
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RE: Measurement of Surface Roughness
For sure, not specifying something because Quality can't verify it is a bit back asswards. Specify based on function.
However, maybe they can sub contract independent inspection, if they don't want to trust the vendor/the vendor can't inspect it either.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Measurement of Surface Roughness
We're looking into some of the tools specified, but haven't come to a good conclusion yet.