Continuous feature distinction between similar features (Y14.5-2009)

[cbrf23]

Hi,
I have a question with regards to clarifying intent using <CF> when there are multiple surfaces of the same size.
I've marked up what I want to say, and was looking for help on what would be the best (clearest, least ambiguous, lowest chance for misinterpretation) way to specify this.



Essentially, what I'm looking to call out is:
[ul]
[li]Blue surfaces - 2X, not continuous[/li]
[li]Green surfaces - 2X, continuous feature, but not continuous to yellow surfaces[/li]
[li]Yellow surfaces - 2X, continuous feature, but not continuous to green surfaces[/li]
[/ul]

I realized even with adding the instance count, there is still ambiguity as to which surfaces are continuous to each other.
For example, I could interpret that dimensioning scheme in the following way, which would not give me the desired result.

I was thinking of adding a label to each CF dimension and using a balloon to make it clear which is which.
Something like this:

Before committing to this idea, I wanted to run this by some of the experts on this forum and see how you would handle this requirement.


For what its worth, the overall runout between all features is controlled by a note, and I really don't expect there to ever be any runout issues with these features from the normal machining process (single setup turned part) but, having spent enough years on the production floor as a manufacturing engineer, I know what can happen with rework, etc. and I just want to make sure that all requirements are crystal clear.

Thanks!

 

[CheckerHater]

I am not sure <CF> is the best way to control the features shown.

The way <CF> is (poorly) defined in Y14.5-2009, the features, forming <CF> must have common envelope embracing them, as if they must be checked with one single functional gage at once.

Your 623/621 Diameter fits this requirement, but groove diameters - not so much.

So if your goal is "crystal clear" least ambiguous requirements, would you consider different way of tolerancing?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cbrf23]

@CheckerHater - I'm always open to a better way of doing something! What do you suggest?
Profile of a surface? True pos of 0 at MMC?

 

[CheckerHater]

OK, let start with the function.

Your "green" and "yellow" grooves seem to accommodate O-rings - one per groove, individually.

Critical requirement will be not having "too deep" and "too shallow" groove due to a) size variation, b) eccentricity, which may be described in terms of Runout, Total Runout, Concentricity, Position (MMC or RFC) with some variations.

The good solution will be "compound" control, where one tolerance controls more than one condition, like runout or zero position at MMC.

Since I don't know for sure how your part works, I will stop for now.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cbrf23]

Runout or true pos would be the obvious choices. Just clutters up the drawing having multiple callouts like that.
C'est la vie!

I'll probably go with true-pos @ 0 for this part.
That tends to lend itself well to functional attribute gaging, which would be adequate for this part.

Runout would require a datum feature to be defined, and thus some way of simulating that datum, which would be difficult to (reliably) do off one of those ID surfaces.

Thanks CheckerHater!

 

[mkcski]

cbrf23:

You might want to investigate Simultaneous Requirement in Section 4.19. Use postion to same datums and add a note to segregate the turns using ID letters

 

[mkcski]

cbrf23:

Woops. I forgot to refer you to para 7.5.4 page 146 for the position interpretation of S.R

 

[pylfrm]

cbrf23,

If you do still want to use continuous features, something like the method shown in Fig. 1-16 of ASME Y14.5-2009 might be a good approach. Place "INDICATED A" below the left callout, "A" near the left two surfaces, "INDICATED B" below the right callout, "B" near the right two surfaces, and remove the "2X" from both callouts. This is similar to what you showed in your third image, but perhaps a bit more clear.


pylfrm