Making a GD&T dimension a criticla to function dimension 2

[TwentyBucks]

Hi,

I have a GD&T dimension (straightness .010") on a part drawing and I need to make this a critical to funtion dimension. I am using SolidWorks and for critical to function dimesions we oval them. What is the correct way to make a GD&T dimension a CTF dimension? Should I oval the entire feature frame of the GD&T dimension?

Thanks

 

[pmarc]

I would recommend reading following post:

http://www.eng-tips.com/viewthread.cfm?qid=324647

 

[KENAT]

See thread1103-322065 & other threads about the idea of critical dimensions.

What do you mean by critical dimension?

Except for allowing indication of dimensions/tolerances that are to be statistically controlled (which isn't the same thing), drawing standards don't really allow for indicating critical dimensions or even level of QA required etc. as such.

Simplistically, from a drawing standards point of view all tolerances are critical if you've assigned them properly.

Certainly I know of no formal industry standard that uses the 'oval' around a dimension to indicated 'critical'.

For safety critical features (which may in some cases might be related to dimensional limits) there are standards (especially automotive & aerospace) which apply and can be referenced on the drawing with note/flag note and indication of what grade etc.

If what you really mean is you want 100% inspection of that dimension/tolerance then I'd argue that should be in the quality plan or similar, not on the drawing.

However, if you insist on putting process information on the drawing arguably in contravention of ASME Y14.5-1994 1.4e then I'd flag the tolerance, and have a note saying something about '100% INSPECTION REQUIRED ON INDICATED DIMENSIONS. COPY OF INSPECTION REPORT TO BE SUPPLIED WITH PART.' or similar.

Or you could maybe write your own company spec and reference that, but I'd think twice about it as it means ensuring a copy of the spec goes to the vendor each time an order is placed.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[dgallup]

Guys, you need to get over your hangups about critical charateristic symbols. Entire industries have written quality standards around them. ISO TS-16949 for instance. The bad thing about them is the symbols have not been standardized. TS-16949 says to use the end customers symbols & definitions. Lacking that, create your own.

I don't think putting an oval around a dimension is a good practice to indicate critical characteristics. There are too many things besides dimensions that may need a critical characteristic symbol, surface roughness, a note, GD&T, etc.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[swertel]

You could also read DOD-STD-2101 for Classification of Characteristics: Criticals, Majors, and listed Minors.

--Scott
www.wertel.pro

 

[KENAT]

dgallup, what hangup, I referenced the concept of those standards in my post. I've even invoked at least one of those standards before.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[fsincox]

Guys, I thought there was a "KEY" symbol for this type of thing too?