Perp vs TP

[[Ca...]]

I don't have a problem, just a question.

I have a print with Datum A being a flat surface, and Datum B being a 5mm thru hole. Datum B has a 0.025 location to Datum A. Why would an engineer choose Location over Perpendicularity? Calypso SEEMS to evaluate them the same.

It's very probably just a personal choice thing, but I've got to know, is there mathematically a difference??

[[Me...]]

It's basically the same thing.

[[An...]]

_

[[Ca...]]

There's no MMC on this specific callout.

[[Da...]]

Just went through another GD&T training to bring the newbies into the fold last week.

the trainer repeatedly said
1. Define Datums
2. Qualify or Control Datums with Perpendicularity, Flatness etc.
3. Locate Your features

[[An...]]

_

[[Da...]]

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It’s not very good practice to use position tolerance when only constraining the perpendicularity, but it is totally permissible. In this instance, it is the very same thing. The DRF defines the orientation and location of the tolerance zone with the position tolerance and just the orientation of the tolerance zone with the perpendicularity tolerance, but here we have a position tolerance without any locational information, effectively resulting in the position tolerance constraining only the orientation. In both cases the tolerance zone is perpendicular to datum A.

Differences are in ASME the centerline of the UAME is evaluated, and in ISO it’s the not necessarily straight centerline made of the derived median points.