What to do with this TP callout?

[[Pe...]]

 

 

Hello, I have a part and callout that is this.  It has 5 holes that go through both walls.  The top TP is easy, I have a fully constrained datum frame.  But, I'm not 100% what to do with the bottom.  Should this just be a best fit of all 10 diameters to .015 allowing all degrees and translation and rotation?  I've never seen it with no datum reference at all.

 

[[Cl...]]

"Should this just be a best fit of all 10 diameters to .015 allowing all degrees and translation and rotation?  I've never seen it with no datum reference at all".

 

I believe you are correct.

 

[[Ra...]]

I don't believe you should use all 10 diameters for one best fit. Since the Position callout has a 2x Ø above it, and the 5x individually below, I would interpret that as 5 separate composite positions. Each composite position would consist of one hole, and its opposite.

That's just me though, would be interested in other opinions.

[[Cl...]]

I foud this on-line

True position is a geometric dimensioning and tolerancing (GD&T) concept that defines the exact location of a feature in relation to a datum reference frame. It is used to ensure that parts fit together correctly and function as intended. However, specifying true position without any datums is generally not allowed per ASME Y14.5 standards.

Thoughts?

[[Ma...]]

There is a difference between 1 TP image and 2 separate TP images. So second row is not without a datum.

 

[[Dr...]]

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This was my first thought as well, and if I saw just the feature control frame without knowing more about the part, I’d agree completely.

I’ll present an unlikely but plausible counterpoint: the print author meant for the "5X INDIVIDUALLY" to be interpreted as "each pattern of 5X should be evaluated individually", rather than your interpretation of "5X patterns [each consisting of two coaxial holes] evaluated individually."

I don’t think that’s what’s going on here, mostly because of the 2X Ø.25 callout implying that each pattern is two Ø.25 coaxial holes. The application of simultaneous/separate requirement language here isn’t standard (as far as I know), but based on what we have, I agree with the 5 separation positions approach.

[[Th...]]

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Y14.5-2009, 7.5.1 (b) (1): "Where datum references are not specified in a lower segment of the composite feature control frame, the FRTZF is free to rotate and translate within the boundaries established and governed by the PLTZF." Should be allowed in this scenario.

 

The 2x and 5x stuff I would be asking the person responsible for the print what they meant.

Edited July 9

[[Da...]]

Here's what it is:

All 5 of the holes on this side have to be within .025 locational tolerance @MMC.

Then, each All 5 of the holes on that side have to be within .025 locational tolerance @MMC.

AND, all 5 pairs of holes have to be within .015 locational tolerance @MMC to the matching hole on the other side.