co-axial features

[waltryan1]

Re: Fig. 4-24 in ASME Y14.5-2009, and Fig. 4-19 in ASME Y14.5M-1994. Did they put positional tolerancing without a datum back in the standard when I wasn't looking?

 

[KENAT]

? I'm looking at fig 4-19 of -94 std and I don't understand what you're asking. Datums are clearly identified and referenced in that figure.

Posting guidelines faq731-376

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

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

 

[Belanger]

You mean on the right-hand side of the drawing...
If two coaxial features are the same size and called out together, then it's legal to use the position symbol without a datum. In a sense, each end of the part creates a datum for the other, ensuring coaxial alignment.

I think this has always been OK, but it's a special case of two or more features that are the same size and are to be coaxial.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[SeasonLee]

Position may be used on coaxial diameters without a datum reference, this is revised in 2009 standard, please ref to 7.6.2.3 and Fig.7-59 for details.

Season

 

[Tarator]

2 coaxial feaures of size don't have to be same size.. you still can use a Position control with no datum. Only difference is that you would call the sizes DIA separately.

 

[Belanger]

Good point, Tarator. That's specifically mentioned in paragraph 7.6.2.3 of the Y14.5 standard (and shown in Fig. 7-51).

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems