Envelope Requirement

[Wakkadder]

I have started to get drawings with "Envelope Requirement" added to certain Diameters, I am aware that it is a feature of the Size Dimension but do not understand the Significance of the Two Lines in the Report.

Could somebody explain the difference between the Upper Line and the Lower.

https://www.pcdmisforum.com/image/pn...AAAElFTkSuQmCC

[JEFMAN]

Are you talking about a e in a circle ?
In this case, you have to contruct a max inscribed or a min circunscribed circle / cylinder.

[AndersI]

Actually, you don't have to construct it yourself, as it is re-calculated under the hood in the "Size" dimension by the method the standard requires, irrespective of what you did when measuring it.

And (E) is not maxins/mincirc only, but also an LP (two-point diameter) for the other end of the tolerance range. But you know that :-)

[AndersI]

I have started to get drawings with "Envelope Requirement" added to certain Diameters, I am aware that it is a feature of the Size Dimension but do not understand the Significance of the Two Lines in the Report.

Could somebody explain the difference between the Upper Line and the Lower.

The upper line is the [largest] two-point diameter (upper tolerance limit) (LP)
The lower line is the max inscribed diameter (lower tolerance limit) (GX)

Edit - Addendum

...assuming we're talking about holes. For shafts it's the other way around:

The upper line is the min circumscribed diameter (upper tolerance limit) (GN)
The lower line is the [smallest] two-point diameter (lower tolerance limit) (LP)

[vpt.se]

So... Had some weird experiences with SIZE in 2018, has anything been done in order to correct the SIZE command? Running 2019 R1 SP1 at the moment, but have stayed away from SIZE due to the 2018 conundrums.

[Wakkadder]

Thanks for the responses, I think I get it now but not 100% sure. It does however give me a direction to research further

[Roberto]

Not familiar with this "Envelope requirement". Is this ISO 8015 standard?

[JEFMAN]

Not familiar with this "Envelope requirement". Is this ISO 8015 standard?

ISO 14405-1 :

3.8
envelope requirement
combination of the two-point size (3.6.1) applied for the least material limit of the size (3.4) and either the minimum circumscribed size (3.7.1.3) or the maximum inscribed size (3.7.1.2) applied for the maximum material limit of the size
Note 1 to entry: The “envelope requirement” was previously referred to as the “Taylor principle”.

Here :

https://www.iso.org/obp/ui/#iso:std:iso:14405:-1:ed-2:v1:en

[Roberto]

JEFMAN Thank you for posting this!

[Entey]

This issue still exists in 2018 version, are latter versions fixed?

E modifier should be LP / GX or GN, but in 2018 and 2017 its giving GX and GN and no LP.