Message 1 of 2
I've attached some pictures of the part in question...
Message 2 of 2
It is a bit difficult to work out the natural extract direction from your jpgs, but it looks as though the dark-blue region is basically cylinderical, with its top edge face cut at an angle to the body, such that you can't use the top face for the datum? If it is cylinderical and is native VX geometry, you can:
1) Pull two face iso curves from the cyliderical face (Wireframe tab, 8 along, 4 down);
2) Draw a 3 point circle on each iso curve;
3) Draw a line between the circle centers ( = direction of draw), then place a Plane normal to this line.
Or if you are not fussed about the whereabouts of the Plane origin, you only need one iso curve to define a 3-point plane.
If the situation is more complex, then FineView does come into play. Nudge the view until it appears that you are looking along the direction of draw. Place a Plane true to the screen view with FineView. You can now test your eyeballs (!):
Run the Extrude command (no endcaps), and select the edge of the feature for extrusion. Via the extrusion options panel, force the extrude direction to be along your Plane's Z axis. You now have a surface that can be compared to the original feature. If the test surface does not match the original:
1) Create a Sketch normal to your Plane, take intersection reference curves of the original feature and the test surface, measure the angular error.
2) Back in the model, restore the original nudged screen view via View/Align Plane.
3) Nudge the view with FineView by the angular error you measured in the Sketch.
4) You will probably need to repeat this with a Sketch at 90 degrees to the first, to ensure there is no compound angle error.
5) Create a new screen view Plane with FineView. That should be it :-)