Part Modeling > Datum Features > Datum Axes > To Create a Datum Axis and Adjust Its Size
  
To Create a Datum Axis and Adjust Its Size
1. Click Model > Axis. The Datum Axis dialog box opens.
2. Click the References collector, and in the graphics window, select up to two placement references for the new datum axis. You can select planes, surfaces, edges, vertices, curves, and datum points.
 
* To add multiple references, hold down the CTRL key while you select references.
3. Select the required constraint option from the constraint list in the References collector. The constraints are Through, Normal, and Tangent.
4. Repeat steps 2 and 3 until you have selected enough constraints. You might have to select additional references to make the datum fully constrained.
5. Click the Display tab to adjust the size of the datum axis.
6. Select the Adjust outline check box.
7. Select one of the following options:
Size—Type a value in the Length value box. The length of the datum axis is the distance between the two ends of the previewed datum axis.
Reference—Select an edge, surface, datum axis, feature in Part mode, or Part in Assembly mode as the reference.
8. Click OK.