Square Symbol and Position Tolerance Application

[Kelly_Bramble]

So, there is a discussion on another forum regarding application of the Square symbol per. ASME Y14.5-2009. I have worked out a solution to the op’s question and posted below.

References per. ASME Y14.5-2009 standard.

Definitions Paragraphs: 1.3.22, 1.3.23, 1.3.60

Paragraphs: 7.4.6, 7.4.4.1,
Figures: 7-28, 7-29, 7-34

Paragraphs: 3.3.16
Figures: 3-11, 3-18

Figures: 8.24
Paragraph: 8.8

Just for the record, I’m not recommending this in practice as I think the square symbol application is obscure and not understood by many - grey. Ultimately, we in engineering, design, manufacturing and quality should not be working with unnecessary complex and obscure drawing specifications. Moreover, the suggested application is NOT explicitly supported with an illustration or other within the ASME Y14.5-2009 standard.

Be aware that the tolerance boundary orientation is datum feature defined and that different datum features could result in a different shaped tolerance boundary.

Enjoy

Given:



Proof and Interpretation:



An alternative design using square symbol and locating square feature with a cylindrical tolerance boundary.

Note:

The immediately above example does NOT have an orientation control for the square feature. One would need a parallelism or other geometric specification specified to control the rotation.

[Cragyon]

What would be a real world application for either of these? I mean an existing part?

[Kelly_Bramble]

What would be a real world application for either of these? I mean an existing part?

Good question, I'll think about it. The original op was just exploring the square symbol and use within a FCF. The ASME Y14.5-2009 standard does not allow such use.

[Belanger]

I think if the MMC modifier were included in the first sketch, then everything would be fine. This is because the 2009 standard says that the boundary concept applies even if the word "boundary" isn't included. Ref. paragraph 7.4.5.1(c).

[Kelly_Bramble]

I think if the MMC modifier were included in the first sketch, then everything would be fine.

This would allow a functional gage to verify virtual condition of both surfaces simultaneously. Also, MMC would likely loosen the tolerances up a bit.

RFS is a legitimate specification – if this is what the design requires.