True Position of an intersection question

[[Je...]]

Per the attached ...If I Use an intersection for the projected datum C do I use a diametral or rectangle set up ? Is this My best method to report this ? Thanks in advance for any suggestions.

projection.PNG

[[Ma...]]

I don't think you need to create an intersection, unless I'm missing something. The projection of -C- can be done in the True Position dialog box. Just click on the P, in a circle, this will allow you to change the projection of the feature -C-. You can even create a theoretical plane at the projected height and select the plane as the projection termination.

Mark

[[Je...]]

Thanks Mark, The problem with this is the projection height is actually zero to datum E.

[[Aa...]]

There's obviously a lot to this we're not seeing, but from what we can see, I would say there are problems with this print on multiple levels.

First, your question about the shape of the tolerance zone is a very good one. Position FCFs applied to cylindrical features in the standard have cylindrical tolerance zones with two kinds of exceptions:
- Bidirectional tolerancing (7.4.4 of 2009) - this would have to be more clearly indicated than in your case, Jerry.
- When the DRF consists of only a plane that is parallel to the controlled cylinder - (e.g. Fig. 6-7 - IMO, this is a terrible and confusing example, and the same effect could have been achieved using a cylindrical tolerance zone for the position FCF, since the DRF has so much mobility)

Specifying a projected tolerance zone for zero length is very strange.

I would assume that C and D are nominally coaxial. Controlling the position of C to C-D seems really strange, too.

E doesn't add anything.

I'm not sure what "REF" after the 0.01 cylindricity FCF signifies...

[[Aa...]]

Jerry, I get what you're saying. Projection height of 0 means they're only trying to control the location at the one end. I guess that should have been obvious to me. 🙄

[[Je...]]

I very much agree this print is wrong... I have requested it change many times that We could actually do something useful with the projection. I tried the datum D feature with a projection and it defaulted to a 52mm height...Changing the height to zero didn't work.