Creating Contoured and Plastic Parts - Autodesk Inventor 2010: No Experience Required - page 403

FIGURE 8.47 Creating a new sketch offset from a face
16. Pick the check mark in the dialog to create the work plane and start
the new sketch.
17. In the sketch, draw a horizontal line in the space between the boss in
the middle and the edge of the hub.
18. Add a Coincident constraint between the line and the sketch center-
point. See Figure 8.48.
19. Finish the sketch, and save your work.
FIGURE 8.48 The sketch for the rib doesn't have to meet the edges of
the model.