surface finish call out.
surface finish call out.
(OP)
Howdy!
So I have a customers print sitting in front of me with a general surface finish symbol on a face, and it relates to a note. The note states: "surface marked to have 125"
Everyone at the shop says that it implies 125 or better... and they also say nobody will have an issue if we make it better than they asked.
My argument is that it says "to have". not "or better" or some other ambiguous verbiage. It may need increased friction on one surface...but I don't know what it does. I just have a print.
on the flip side to that my mind then wonders... whats the tolerance on a 125 surface finish!? I have a surface finish tester and the comparison plates... if comparison plates used... better than 250, but rougher than 63?
Whats the word... is our 8 micro inch finish going to get rejected?
So I have a customers print sitting in front of me with a general surface finish symbol on a face, and it relates to a note. The note states: "surface marked to have 125"
Everyone at the shop says that it implies 125 or better... and they also say nobody will have an issue if we make it better than they asked.
My argument is that it says "to have". not "or better" or some other ambiguous verbiage. It may need increased friction on one surface...but I don't know what it does. I just have a print.
on the flip side to that my mind then wonders... whats the tolerance on a 125 surface finish!? I have a surface finish tester and the comparison plates... if comparison plates used... better than 250, but rougher than 63?
Whats the word... is our 8 micro inch finish going to get rejected?





RE: surface finish call out.
When used with a symbol single value is always max average.
When not used with a symbol I (and most I've worked with/met/asked...) tend to infer the same thing, but someone might be able to argue that its use without the symbol is ambiguous.
Giving a single value without it being max then lands you in a situation where as you point out you don't have a 'tolerance' on the value.
If I want deliberately rough surface - as is sometimes the case on optical components I usually use the roughness symbol on the print with max & min given.
So, if it was my part no I wouldn't reject your 8 micro inch finish - I'd just wonder why you went to the effort of making it so smooth when I don't need it and wonder how much extra $ that cost me.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: surface finish call out.
Thanks! I will read up on that thread this evening.
RE: surface finish call out.
Wisecracks aside, KENAT's answer is 1:1 what I would have said.
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: surface finish call out.
Chris, CSWA
SolidWorks '15
SolidWorks Legion
RE: surface finish call out.
Sure you are legally protected as it complies with drawing, and if everyone at the customer is competent in the related fields it should never reach you or at least be resolved very quickly - but that's not always the case.
So remember, since no good deed goes unpunished, creating parts much better than spec can come back to bite you at least indirectly.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: surface finish call out.
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: surface finish call out.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: surface finish call out.
I personally prefer the term "surface texture" as opposed to "surface roughness" or "surface finish". "Surface finish" would describe processes like anodizing, electroplating or painting. And "surface roughness" would not include characteristics like waviness or lay. Surface texture callouts can be very complex or very simple, depending on what is required in the finished product. For some situations having a surface that is too smooth is not acceptable. So in this case an upper and lower limit would be shown for the surface roughness.
In regards to the question asked in the OP about a single value shown for surface roughness, it is commonly interpreted to describe a maximum limit. Below is an excerpt from a legacy surface roughness standard (MIL-STD-10) describing how to interpret this type of callout.
RE: surface finish call out.
Chris, CSWA
SolidWorks '15
SolidWorks Legion