Surface roughness comparisons (profileometer)
Surface roughness comparisons (profileometer)
(OP)
I was recently told that when using a surface roughness tester that as long as the results are within +/- 4, the results are acceptable. For instance, on the same sample one machine gets a reading of 32 and another gets a reading of 29 both are accurate/acceptable, or, when checking a "known" if the machine is within +/- 4 of the "known" the machine is giving accurate/acceptable readings. Will someone please:
1) validate this or
2) list the proper +/- variation
ps: We know that when a drawing requires a certain finish (i.e., 32) the finish has to be at least that good (i.e., 32 or lower).
Thanks in advance for your time.
1) validate this or
2) list the proper +/- variation
ps: We know that when a drawing requires a certain finish (i.e., 32) the finish has to be at least that good (i.e., 32 or lower).
Thanks in advance for your time.





RE: Surface roughness comparisons (profileometer)
On the face of it, your test procedure is non-compliant, but that is really dependent on the exact wording of the requirement, and other information that only your company has.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Surface roughness comparisons (profileometer)
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Surface roughness comparisons (profileometer)
From a strict constructionist perspective, your upper test limit should actually be 28, but what that would mean is that you potentially throw out gobs of product, which is bad for the bottomline.
The correct answer to your specific problem is that your processing limits need improvement. Your process should be designed to result in no more than 28, which allows for the +4 error in the testing.
Alternately, you need a tester with better accuracy.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Surface roughness comparisons (profileometer)
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Plymouth Tube
RE: Surface roughness comparisons (profileometer)