Location tolerance exercises

[Ivan Silva]

Hello,

I'm solving some question about position tolerance from a book and there are two of them which I didn't understand what is wrong with my resolution. Could someone help me with it?

Picture for question 69 and 70:

69. The perpendicularity callout and this tolerance of position callout:
A. Have exactly the same meaning (official answer)
B. Have a different meaning

My resolution:
The perpendicularity tolerance tells that the cylidrical face must fit inside an 9.8 diameter cylinder which is perpendicular to datum A.
The position tolerance tells that the uAME axis must fit inside an variable diameter cylinder (it's variable because bonus tolerance is allowed

This said, I don't understand why both tolerance have the same meaning since one control a face inside a fixed diameter cylinder and another a axis inside a variable diameter cylinder.
-----------------------------------------------------------------------------------------------------------------------------------

70. It’s legal to use the tolerance of position callout solely to control perpendicularity:
A. True (official answer)
B. False

Is not the position tolerance knowed as a tolerance which controls position and orientation at the same time? Is there a way to cancel the position control of an position tolerance?

PS: I'm studying GD&T by myself trough the standard and some books. So I don't have any teacher guiding me who could solve the exercises.

 

[greenimi]

https://www.eng-tips.com/viewthread.cfm?qid=314972

https://www.eng-tips.com/viewthread.cfm?qid=468707

 

[Burunduk]

Ivan Silva,
Both the position and perp. tolerances in the study book example are applied at MMC, and therefore there are two interpretations that can apply to each of them. One is called the axis interpretation (or resolved geometry method) - the cylindrical tolerance zone for the axis, which can be enlarged per the bonus tolerance available. The other is known as the surface interpretation or method, and it is based on the virtual condition boundary - the surface of the feature is limited by the VC which you already know how to calculate.

The pin has only an orientation relationship with datum. Therefore the clearer way to communicate the requirement is the version with the perpendicularity symbol in the feature control frame. The position tolerance only becomes the right choice when the tolerance is applied to a pattern of features, not to a single one as shown. In the case of a pattern of features, the use of the position symbol locates the tolerance zones to each other according to any basic dimensions that are applicable between them, in addition setting them perpendicularly to datum A. This can't be achieved by the perpendicularity tolerance which doesn't control location generally and neither between features in a pattern.

 

[greenimi]

Ivan Silva,

Could you, please, let us know the book and the author?
Would be very helpful for all of us setting the stage for the discussion.

 

[Ivan Silva]

@greenimi

“ Everything I Needed to Know About Geometric Dimensioning and Tolerancing I Learned from My Dog”
By Dave Slopsema

 

[greenimi]

With all due respect for Dave S. and his training company (along with his over 25-30 years experience with GM) I do no agree with his assessment.
It IS his opinion and he has the right to have one.
I am talking specially about this statement "It’s legal to use the tolerance of position callout solely to control perpendicularity"

Every time when we are talking about legality, opinions differ.