Rule #1 of Y14.5 1

[OmarEn07]

Hi Guys,
I have a question, I hope you could help me:
Rule #1 of Y14.5 states that the limits of size of a FOS also control its form (UOS). But what happens when a FOS has only one limit of size? For example, a pin diameter that is called out at 10.00mm Max.

Thanks in advance for your help.
Best Regards.

 

[3DDave]

Point-to-point measurement cannot determine straightness. It can determine the allowable deviation from perfect form at that location, but determining if the feature is still within tolerance requires other measurements.

The rules-writers for the standard took a short cut and also failed to note that the deviation only applies along the vector between the points being measured. The way it's phrased is a distraction.

To be compliant the feature has to fit the envelope and equal or exceed the smallest measurement along every vector which is normal to the center point, axis, or center plane (as applies) of the envelope.

 

[greenimi]

To be compliant the feature has to fit the envelope and equal or exceed the smallest measurement along every vector which is normal to the center point, axis, or center plane (as applies) of the envelope.

Is this requirement coming from the math standard: Y14.5.1?
I am talking about the "normality" aspect.

 

[Sem_D220]

greenimi,
Maybe you will find this explanation too simplistc, but:
When you examine a cylindrical feature, deviations in the radial direction between adjacent points on the surface, will be read as a straightness error, when straightness is measured along the axial direction of the feature. Hence the relationship between "cross sectional" form to "longtidual" form.

semiond.

Edited to identify myself

 

[djhurayt]

If a picture really is worth a thousand words . . .