Slot with True position and Boundary call-out

[[Ky...]]

The attached drawing shows slots with MMC and true position. But there is a boundary call-out under the DRF. I did a search in forum, Brett Krienke and Aaron Gerber commented on it and quoted some things out of Y14.5M - 2018. I tried to look it up in the Spec but could not find it. I tried to read the answers from the forum but it is just kinda like I'm reading stereo instructions.
What does the bounday call-out do to affect the true position. 😕

Thanks
Kyle

Boundary.png

[[Br...]]

The 1994 revision of the standard required you to include the "Boundary" under the feature control frames for a position tolerance applied to an elongated feature or slot when the MMC symbol was present. In 2009-2018 it became default and it is unnecessary to put the word Boundary under the FCF.

What it means is that there is a theoretical boundary of identical shape that no element of the surface may violate. The size of the boundary is equal to the MMC size of the feature plus its positional tolerance. If you have a copy of the standard, it breaks down the math of this pretty well to help you understand.

Your drawing is a little messed up in that they chose dimensions from the centerpoints of the radii and applied a position tolerance to them instead of using the full length of the feature. Those are not features of size. That is just wrong and makes it difficult to calculate the boundary.

[[An...]]

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Well,I think the term "boundary" makes clear that this tolerance is related
to the surface and not the center points.

[[Br...]]

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But now its weird to calculate because instead of having a length with a tolerance to the ends, you have some non feature of size(which is completely illegal in Y14.5) with a position tolerance applied to it. Whats the MMC size of a feature that isn't real, and is neither external or internal? Where it really gets weird is now the boundary has to be dynamic or something, because as the with expands or contracts, the radii on the end change location, while that center width stays the same. In this regard, it isn't clear at all.