Using dimension with plus minus tolerance at intersection of basic dimension.

[Vladdo]

I have a small feature with an angled wall and want to locate its position. When using the corners of the feature it's difficult to get repeatable measurements due to the small size and variation in the radii. So instead, I have a basic dimension representing the contact point of the mating part and a dimension with plus/minus tolerance intersecting that point. See attached.

Is this acceptable per ASMY Y14.5-2018? The standard says this okay to do for conical tapers per section 5.14 and Figure 5-22, but can I use a similar approach for different types of features?

 

[3DDave]

The image button is right there.

They left the door open, but it may not be clear what the origin of the basic dimension is or what the orientation is; there isn't a standard way to reference a datum feature in a linear dimension.

 

[Burunduk]

Vladdo, what do the basic and toleranced dimensions originate from? This information is important for answering on "Is this acceptable per ASMY Y14.5-2018?".

 

[CheckerHater]

Vladdo,

You may also consider round pin leaning against surface in question, then take the measurement from the pin.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[jassco]

Hi, Vladdo:

That is acceptable as long as you establish datum. This BASIC dimension functions as "Gage Dimension".

Best regards,

Alex

 

[drawoh]

Vladdo,

Why not apply basic dimensions to the sharp corners and apply one or more profile tolerances? Does everything need to be accurate, or just the sloped face?

--
JHG

 

[Vladdo]

Thanks everyone for the input. I was also not seeing anything in ASMY Y14.5-2018 that restricts this method.

But you did bring up good points on the orientation concern by not having datums. Clarifying that this is a basic gage dimension is also a good idea, our inspectors got thrown off by not seeing a control frame linked to this basic.