Question about Independency Principle 1

[pmarc]

Imagine that fig. 2-7 from Y14.5-2009 shows a pin instead of the rectangular block, and the flatness callout has been replaced by straightness FCF. Everything else stays the same (of course the diameter symbol is added to 10.7-10.8 dimension).

Knowing this, what is the minimum possible diameter of a perfect cylindrical boundary that the pin would never violate?

Thanks.

 

[pmarc]

Para. 3.5.
LOCAL SIZE OF AN EXTRACTED CYLINDER, LOCAL DIAMETER OF AN EXTRACTED CYLINDER
distance between two opposite points on the feature, where
— the connection line between the points includes the associated circle centre; and
— the cross-sections are perpendicular to the axis of the associated cylinder obtained from the extracted surface

IOW, is a local diameter one consistent number or can a local diameter vary as we rotate around the circle?

Well, the lower picture shows two local diameters, so I would not interpret it as one consistent number in a single cross-section.

 

[Belanger]

Thanks -- that helps a lot. Unlike ASME's definition, this one states that "the connection line between the points includes the associated circle centre."

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

That is right. Of course there are other issues with this definition, but if we are solely talking about the connection line between two points, I think there is way less ambiguity in ISO in comparison to what has been defined in ASME.