【转帖】deviation calculation signed

yang686526

deviation calculation signed?
does anyone know wheter or not deviation is supposed to be signed? to explain:
if i evaluate a surface with a single point the nominal is defined as 0.0000, and the point measurement is .001" toward the inside material of nominal. how is deviation calculated? does it have sign (ie negative or positive value)? please indicate a iso or asme standard if possible.
thanks
scott
a you talking about section 6.5 "profile control" per asme y14.5m-1994?
heckler
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(in reference to david beckham) "he can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. apart from that, he's all right."  -- george best
yes. given a profile tolerance and its application how should the deviation be reported? if it is .001 toward the inside of material direction, how should the deviation be reported: +.001" or -.001"?
thanks,
scott
if you have more material than what you spec'd as nominal on the print, the deviation is "+". if you have less material than what you spec'd as nominal on the print, the deviation is "-".
that being said, you can say that there is a .xxx deviation without specifying which direction. i wouldn't think that direction really matters. either the part is within the spec'd tolerance or it isn't. however if you have to specify, i would use the above example. sorry i can't quote a standard for you.
david
david,
thanks for your reply. i agree with you, though im trying to find information in a standard that defines "deviation" and how or if it should be summarized with a sign when referencing the reporting of a profile tolerance.
for the application of such a tolerance i believe it is required to know the direction of deviation not only to report it but to actually use the information to possibly correct the problem.
i just need some documentation that supports this "school of thought".
scott
asme y14.5.1m-1994 6.5(c) actual value.
"for both unilateral and bilateral
profile tolerances two actual values are necessarily
calculated: one for surface variations in the positive
direction, the actual value of profile is the smallest
intermediate tolerance to which the surface con-
forms. note that no single actual value may be calcu-
lated for comparison to the tolerance value in the
feature control frame , except in the case of unilateral
profile tolerances."
this is what i was able to find. read all of section 6.5 profile control if you need something else.
david
david,
thank you! i couldnt find the section 6.5(c), then after carefully reading i noticed that you referenced asme y14.5.1m not simply y14.5m. i am embarassed to say i did not know of the exsistance of this document. i found it on the asme website and promptly purchased it and downloaded it.
thank you again for pointing it out. this will most likely suffice in my quest to put this issue to rest.
scott
no worries!
david