Y14.5M-1994 Feature Control Frames & Datums 2

[macduff]

Is tagging a feature control frame to a datum correct when the datum has no size? I'm aware tagging a datum to a feature control frame (sec 3.4.6) is correct, but only see examples when size is involved. Thank You!

Colin Fitzpatrick CSWP(aka Macduff)

 

[Belanger]

What you show in the attachment is not correct, according to the Y14.5 standard, so the red markups are correct. Now, we would know what you mean (I see that quite often) but if you want to follow the fine points of the rules then the answer is no.

And it doesn't really have anything to do with whether it's a sizable thing (a "feature of size"). A datum symbol can be attached to a feature control frame, but a FCF shouldn't be attached to the datum.

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

 

[macduff]

Hey John-Paul,
I was in error when mentioning size, thank you for the correction. Question, where in Y14.5-1994 states where I'm correct with my markup?

Also, I don't understand your one part of the sentence "Now, we would know what you mean (I see that quite often) but if you want to follow the fine points of the rules then the answer is no." Are you seeing being done elsewhere?

Thank you sir!

Colin Fitzpatrick CSWP(aka Macduff)

 

[Belanger]

I'm not sure offhand of the exact paragraph in the 1994 edition, but in 2009 it is paragraph 3.5, called "Feature Control Frame Placement." Look for similar words in Section 3 of the 1994 standard.

What I meant by my comment is that if you showed me a drawing with the perpendicularity tolerance attached to the datum feature symbol (the version that was crossed out), we would still interpret it as controlling the perpendicularity of the surface known as datum feature C.

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

 

[powerhound]

Figure 3-6 in the 1994 standard shows how this is supposed to look. As JP said, while your attachment is not technically correct, it's not profoundly confusing either. I know what the intent is. So while I can't cite where the standard says your markup is correct, I can show you where the correct way to do it is shown. If your colleague's next question is "Show me where it says I can't do it." just throw up your hands and walk away.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[macduff]

John,
That was hilarious, and I thank you for the laugh this afternoon! Question, are you sure Fig 3-6 is correct? I'm seeing a datum target example.

Jon-Paul,
Section 3.5 is correct, and no mention of tagging to a attaching/datum

3.5 FEATURE CONTROL FRAME
PLACEMENT
The feature control frame is related to the considered
feature by one of the following methods and as
depicted in Fig. 3-25:
(a) locating the frame below or attached to a
leader-directed callout or dimension pertaining to the
feature;
(b) running a leader from the frame to the feature;
(c) attaching a side or an end of the frame to an
extension line from the feature, provided it is a plane
surface;
(d) attaching a side or an end of the frame to an
extension of the dimension line pertaining to a feature
of size.

Colin Fitzpatrick CSWP(aka Macduff)

 

[powerhound]

Figure 3-5...sorry

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[macduff]

Prefect, more ammo!

Colin Fitzpatrick CSWP(aka Macduff)