True position of sphere

[prdave00]

Is there a difference between the following feature control frames (FCF) to control the position of a sphere using the attached intentionally incomplete drawing to put it into context?

FCF A
|TP|SØ.1|A|B|
|TP|.05|B|

FCF B
|TP|Ø.1|A|B|
|TP|.05|B|

My instinct is that they are equivalent - the lower frame truncates the poles of the spherical tolerance zone in both.

 

[prdave00]

I need to correct the post...

Is there a difference between the following feature control frames (FCF) to control the position of a sphere using the attached intentionally incomplete drawing to put it into context?

FCF A
|TP|SØ.1|A|B|
|TP|.05|B|

FCF B
|TP|Ø.1|A|
|TP|.05|B|

My instinct is that they are equivalent - the lower frame truncates the poles of the spherical tolerance zone in both.

 

[Belanger]

Of the choices given, option "B" doesn't control the location of the sphere in and out of the picture. The Ø symbol in the upper FCF doesn't have an S for spherical, so the tolerance zone's shape is cylindrical (controlling north/south/east/west in the view shown, but not depth-wise).

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

http://www.gdtseminars.com

 

[prdave00]

Belanger:

I'm not sure I see your point. Re FCF B, doesn't the actual center of the sphere have to meet both conditions, i.e., lie within the a .1 diameter cylinder and within the planes separated by .05? In my head, I'm imagining a cylindrical tolerance zone that is .1 in diameter and .05 tall. Since the cylinder's axis is coaxial with datum axis A, doesn't that include in/out of page?

In FCF A, the resulting tolerance zone would be a sphere with its poles chopped off.

I drew the tolerance zones in the attachment. Let me know what I'm missing.

 

[prdave00]

Now the attachment....

 

[Belanger]

In your latest attachment showing the tolerance zones, you're assuming that the cylinder for B's upper FCF is vertically oriented. That's not necessarily the case; I was basing my assessment on having the FCFs placed as indicated on the original drawing, i.e., a circle extruded straight back into the computer screen. IOW, take the tolerance zone pic that you drew for Option A: I was seeing the effective tolerance zone for Option B as the exact same picture, but extending all the way into the picture.

I'm not totally comfortable with either option. I'm just saying that they don't seem to be the same, and B is probably ambiguous.

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

http://www.gdtseminars.com

 

[fsincox]

I am with JP, the top statement calls out a spherical zone to a framework and then adds some refinement to "B" although if "B" is so impotant I would have used B primary, A secondary and refine to B, similar to what might be done with a composite (note: I did not say use a composite).
Basically, In the second statement you expect A alone to esablish a zone it alone can not support as it is a circular zone in a veiw diretionally oriented in the plane of the paper since it is shown in that view. I suspect you think it is a zone controlling into the depth of the paper, like a spherical zone would automatically do.
I am not a fan of seperate incomplete frameworks unless now other way will gey the job done.

 

[fsincox]

Dave,
I have a lot of interest in this subject myself.
thread1103-314840
thread1103-322523