ASME 14.5 (2009) allow true position control on theoretical point of intersection?

[QAetc]

Hello,
I am wondering if there is anything stating directly or indirectly whether or not it is allowed under ASME Y14.5 (2009) applying a true position control to a theoretical point of intersection.

In order to measure a theoretical sharp corner for the location of a feature we are extracting two planes which intersect to form a line, then we measure a point on that line some exact distance from the part's centerline. Is it possible to simply apply a true position tolerance to this point, or is that not allowed because the point itself is not a physical feature? I have received conflicting opinions on this and have been digging through the text of 14.5 to no avail.

Thanks!

 

[chez311]

or is that not allowed because the point itself is not a physical feature?

Position cannot be applied to theoretical points/lines/planes, only physical features. Additionally per Y14.5-2009 position tolerancing must be applied to a FOS - you mentioned two planes at some inclination to each other, these could not be controlled for position individually either since they are not FOS.

Is utilizing profile an option? I don't know about applying it to theoretical features, but at least you would have two tolerance zones which you could extrapolate their intersection to determine the indirect control of this theoretical feature. Each planar feature could also be refined with flatness/orientation controls in a similar manner.

 

[QAetc]

Chez, thanks for the quick reply. That (Position cannot be applied to theoretical points/lines/planes, only physical features) is what I feared would be the case. Unfortunately, in this case, we are unable to control the intersection point as closely as we'd like by using solely surface profiles due to the planes themselves being rough/warped from the manufacturing process (allowing a profile tolerance of say 0.020" would make the effective tolerance zone for the intersection point much larger than we need). I believe we can use a combination of profile and an angle tolerance between planes to get the desired effect, however.

Thanks again!

 

[chez311]

QAetc,

No problem, glad to help. Multiple Single Segment and Composite profile may also be worth considering to refine the original larger .020" profile tolerance.