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A lesson in Datums and Geometric Tolerancing Please

tham

New member
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
 

especial

New member
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

New member
If I understand correctly,

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

Rajesh
 

especial

New member
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

New member
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

New member
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..
 

tham

New member
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

New member
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
 

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