Basic Dimensions 1

[litensguy]

I know the basic dimension issue has been discussed at length in the past, however I have to bring it up again. See the example below. It has been explained to me that basic dimensions can be used to define measurement or inspection planes as shown here, (Plane 1 & Plane 2). Can these be basic dimensions be applied without a FCF? Would the FCF for the roundness apply somehow?

 

[Belanger]

Those basic dimensions simply identify the locations where the circularity tolerance will be checked. This is to ensure some semblance of repeatability in the inspection process. So those basic dimensions themselves have no tolerance ("established tooling or gaging tolerances apply"--Y14.5) but they are linked to the feature control frame for circularity because of the notes that mention Plane 1 and Plane 2.

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