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what is difference between positional tolerance& perpendicular tolerance

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amolpagdal

Automotive
Mar 15, 2013
9
what is difference between positional tolerance (considering primary datum) & perpendicular tolerance
 
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perpendicular means a feature is at right angles to some datum but does not have a specific position in the XYZ direction.
A positional tolerance positions a feature from datums or specific feature in the XYZ planes but does not always control perpendicularity.
 
Also note that position involves a distance.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
amolpagdal,
Are you, by any chance, thinking about quite common situation where a single secodary datum feature of size is nominally perpendicular to primary datum plane A, and this feature is controlled either by perpendicularity or position callout relative to A?

If that is the case, geometrically there is no difference between both controls, although it is worth to remember that perpendicularity is more in line with the letter of Y14.5 standard, mainly because in this very situation position tolerance adds no extra value to geometric definition of considered feature.
 
It appears the ISO confused this issue more, if you are working with that!
Otherwise if not ISO forget it!
Frank
 
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