A lesson in Datums and Geometric Tolerancing Please

[tham]

I understand how to select datum planes and axis to make them datums to use with my Geometric Tolerancing.



Can you select surfaces of a feature? I have a plate that is round, I need the outside round surface to be a datum for geometric tolerancing. How can I select this round surface? What am I supposed to use in place of the surface?



Help!!



Thanks

 

[tham]

No, that's not what I'm after. its not the thickness, its the outside diameter.

 

[especial]

hammer without seeing your round part and assuming you have datum A, B, C, D, ... . Datum A being the flat side , Datum B and C Being hole on the flat surface and Datum D being the round. Dia .XXX with a Plus minus and gd&t perpendicular within dia .005 max material condition to Datum A. This is just my guess and hope it helps you.



Thanks

AS

 

[Rajesh]

If I understand correctly,

Create a datum parallel to a datum(that passes through the axis) and tangrnt to the outside diameter.

Rajesh

 

[especial]

Attatch Datum to diameter (dimension) and move Datum only (not dimension) to the extension line . I left this little tip bit out .



Thanks

AS

 

[ProFishent]

Like especial says you can set the datum in a dimension. In the SETUP/GEOM TOL/SET DATUM menu under Placement, change to In Dim. Then pick the diameter dimension of the surface you want to reference. Select a datum tangent to the surface. In the drawing the datum will show with the dimension.

 

[dougr]

It's been a while since I did some serious detailing but can't you rename the internal axis from your feature and set that ??



After all it's really the feature axis that's the datum..

 

[ProFishent]

Yes, you can select a tangent plane or an axis.

 

[tham]

Thanks everyone. I did as especial and Profishent said and created a datum plain tangent to the circle, then attached the datum to the circle Diameter Dimension.



This looks a little strange in the model, but I think that is how PTC intends us to do it, so what can you do but follow it.



Thanks again.

 

[mekaneck]

wow, I'm responding to a really old post, but I'll put this here anyway:


If you want the round surface as the datum, you create an axis (by referencing that round surface), then go to properties on that new axis and make it a datum. You can also make the internal axis (from the original feature) as the datum (as dougr suggested) but I wouldn't recommend that.


In GD&T (ASME Y14.5), if you are calling out a round feature as a datum, the datum is the feature's axis. Therefore, in Pro/E, you want to create an axis as your datum, not a plane.
Edited by: mekaneck