2 questions

[greenimi]

1. A disc has the thickness of .100+.010/-.005 and associated with the thickness above a straightness callout with Diametric symbol and tolerance of .005 at MMC. The question is do we need the diametric symbol in this application?

What is the tolerance zone shape : two parallel planes or cylindrical?

2. A cone has an included angle of 90 degrees ( 45 degress to the centerline of the cone). The question is do we need the 90 degrees basic to define the cone or 90 degrees basic is implied?
The cone will be define with profile or maybe composite or even two single segments profile.
Thank you

 

[CheckerHater]

1. Straightness is used to control lines. Straightness with diameter symbol normally applies to derived median line. Straightness applied to flat surfaces usually used to control "every line element" of the surface. Does any of this describe your design requirement?

2. This was discussed before. Opinions differ. My personal approach is that when there is a possibility of misinterpretation, one should clearly state the angle on the drawing, even if it is 90 deg. angle.

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

 

[greenimi]

Q#1: It is a question from a GD&T test. The Q is what is the dimension of the gage to check the straightness of the disc. The straightness callout has the diametric symbol shown and I was not sure that this diametric symbol is needed (legal) in this application or not. The gage dimension won't change, but I am trying to learn the "proper" GD and T language.

Q#2: Fair enough! You could not be too explicit, only too ambiguous.

 

[Belanger]

1. The diameter symbol makes the shape of the tolerance zone a cylinder. And if it's applied to the thickness dim then it doesn't make any sense. (Without the diameter symbol it would make sense in a pre-2009 version of ASME.) There is no gage to make for the straightness callout because the GD&T needs to be corrected first (but I realize this is a test question).

2. Technically, the angle doesn't need to be dimensioned, because anything that looks like 90º is presumed to be 90º. Just because the 90º corner is rotated from how we normally think of a corner doesn't change the rule. However...in the real world it's OK to put the 90º on the print.

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