Y14.5-2009, figure 5-13 & 5-14

[AndrewTT]

In figure 5-13, the circularity (free state) FCF is associated with the size dimension. Is this an error in the standard or is there something about the free state modifier that allows this? I cannot find any wording in the text showing that circularity is anything other than a surface control, which means the FCF should not be associated with the size dimension, but should have a leader or extension line going to the surface to be controlled.

Also, figure 5-14 has the circularity FCF (free state) aligned with the size dimension. This is consistent with figure 5-13.

Figure 5-13 & 5-14 are consistent with how flatness DMP and straightness DML are denoted (FCF associated with the size dimension). All three of these form controls (free state, FDMP, SDML) do not have rule #1 apply to them. Is this why the circularity FCF is associated with the size dimension in figures 5-13 & 5-14?

Would it be wrong to have the circularity FCF, in figure 5-13 & 5-14, shown independent of the size dimension, with a leader going to the surface to be controlled?

 

[Belanger]

I don't think the text of the standard addresses that point -- but you bring up a valuable concern!

Since circularity has only one meaning (it tolerances the surface), then the thinking is that it doesn't matter if the FCF is tagged to the surface or the size dimension. For some other symbols, such as straightness or parallelism, it would be very important where the FCF is tagged.

Also check out Figs. 9-6 vs. 9-7... your same question also applies to runout tolerances. But again, since there's no confusion about what total runout means, then either method seems to be acceptable.

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

 

[powerhound]

To add to this point, I've been in a position where I had said that placing the FCF under the size dimension is how you associate it to it. I had also said that extensions of principle are a real thing. He wanted to apply circularity at MMC and extend the principle of straightness and flatness at MMC to circularity. Since the standard shows a circularity FCF associated with a size dimension it must be okay to do. Man, I was in a real pickle.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[AndrewTT]

Saw the attached in Y14.41 (digital product definition data practices). More evidence that circularity and cylindricity can be associated with the size dimension.

 

[aniiben]

Fig 5-13 is missing the restraining note: so either add the restraining note (a note similar with the one shown on fig 5-14) either remove the F symbol from the circularity callout in fig 5-13.

 

[powerhound]

Circularity and cylindricity ARE associated with the size dimension through rule #1. This does not mean you can call out cylindricity or circularity at MMC though.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech