You can position a datum axis by selecting a plane and a point that is not on the plane. ABAQUS/CAE creates a datum axis thta is normal to the plane and passes through the point.
To create a datum axis normal to a plane and passing through a point:
From the main menu bar, select Tools
Datum.
The Create Datum dialog box appears. The dialog box outlines the types of datum geometry you can create.
ABAQUS/CAE displays prompts in the prompt area to guide you through the procedure.
Tip:
You can also create a datum axis using the 
tool, located in the module toolbox. For a diagram of the datum tools in the toolbox, see “Using the Datum toolset,” Section 40.2.
From the list of types at the top of the dialog box, choose Axis.
The Method list indicates the methods you can use to create a datum axis.
From the Method list, select Normal to plane, thru point and click OK.
From the part or assembly in the current viewport, select a planar face.
From the part or assembly in the current viewport, select a point.
The datum axis appears. You cannot modify a datum axis created with this method; you must delete the old axis and create a new one.
