Re: How to make a datum tag on a diameter

If you haven't already, set your GTOL standard to ASME or ISO, etc. in the detail options.    If you don't have the right standard set you won't be able to create it.  File-->Prepare-->Drawing Properties-->Detail Options.  Go to "gtol_datums".    (Creo 2.0)

1. Create a model datum.  In drawing: Annotate tab-->Model Datum pulldown-->model datum axis...follow the prompts to create it on a cylinder.  If you already have a datum, select it then right click --> properties.  I usually create mine in the model and not the drawing.
2. In the new window, give it a name, select the display button on the right then select "In Dim", hit the button to the right and select your diameter dimension. 
3. Now you can move your datum to where you want it.  If you do the above in the model, don't forget to show the datums in your drawing.

I've never had a problem with datum tags but I skipped Creo 1.0