Feature of size

[Runz]

I am having a discussion with a fellow employee with regards to Feature of Size.
There is a flat part that has a hole in it and there is a dimension which is an edge distance from the edge of the hole to the edge of the plate (See attached). They claim this is a Feature of Size dimension, because they believe it has opposing elements and I believe this is not a fOS dimension, but simply locating the hole.

Who is correct and why?



Thanks,

 

[greenimi]

Please post a picture/ sketch.

 

[Runz]

For some reason I can't upload an attachment??? But think of a simple plate of steel that is 4in round x .06in thick with a Ø.250 thru hole randomly placed. There is a dimension locating the hole on the surface from the edge of the plate to the hole edge.

 

[pylfrm]

They claim this is a Feature of Size dimension, because they believe it has opposing elements and I believe this is not a fOS dimension, but simply locating the hole.

What is your counterargument?

What standard provides the definition you are arguing over?

Why does it matter whether this is or isn't a feature of size?


pylfrm

 

[Runz]

ASME Y14.5 and why so many questions? It either is or it isn't. We are simply trying to understand whether this is a feature of size or not and why. This is a forum to ask questions and gain knowledge, correct.

 

[greenimi]

is an edge distance from the edge of the hole to the edge of the plate

Okay. I agree. It is Y14.5.


The question for you is: where do you see this practice of dimensioning from the edge of the hole to be a practice encouraged or recommended by ASME Y14.5?
Could you, please, indicate a figure within the above mentioned standard?

If this kind of dimensioning scheme is not per the standard recommendations, how do you expect the people on this forum to give you an advice?

 

[Sem_D220]

Runz,
The questions you were asked were actually intended to get some background so that you can get a thorough answer for your specific case.

 

[3DDave]

It is an odd case.

Variation in that dimension does not add or remove material from the part in this particular case. For typical features of size the variation in the governing dimension does add or remove material.

OTOH variation in the dimension does restrict or release constraint on the part which tends to be the case for non-RMB evaluations of features subject to size tolerances.

Practically speaking, the standard deals with typical applications and doesn't deal with this one. To offset that, it recognizes that users can create whatever rules they like in the form on notes on the drawing. So, if the desired treatment is as if it's a feature of size, then write down what the fabricator, inspector, and user of the part should expect based on variation in that dimension.