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Dual Dimensioning Secondary Tolerance Rounding

Dual Dimensioning Secondary Tolerance Rounding

Provide a config option or change  the standard to round the secondary unit tolerance before.pngafter.pngrather than truncating.

3 Comments
Peridot

You can vote for your own idea.

I will suggest that this was once discussed and PTC weighed in on the discussion.

If my take-away was correct, the idea that the metric equivalent would represent a value larger than the primary dimension tolerance value, this was not allowed.  So they err on the side of caution by reducing (always) the tolerance by truncating rather than rounding.

I am sure ASME has also discussed this and from what I remember, the implementation is in compliance with ASME recommendations.

Regular Member

Yes, that description of the background is correct, and the truncating is intentional.  The idea is a valid proposal, with a detail setup option as the user-configurable setting; it may be contrary to standard, but if enough people want it that way for their company, it could be done.

I agree that this should be a "configurable" option to ease/speed drawing preparation.

Regarding the dimensioning practice, so long as it follows ASME Y14.5 section 1.5

About rounding, this is also covered in section 1.6.4 acknowledging (1994) ANSI/IEEE 268 / (2009) IEEE/ASTM SI 10 rounding of US Customary linear units.

As I would make the understanding of the dimension shown, making the assumption that units are disclosed on the drawing (metric [inch]), that the secondary units are treated as reference and should not be used in the qualification for the feature and are provided as "information only"

my thoughts, for what they are worth