Functional Design Using Design Accelerators - Autodesk Inventor 2010: No Experience Required - page 330

FIGURE 7.20 Adding a sketch to the V-belt pulley
FIGURE 7.21 Cutting most of the weight out of the pulley
9. Click OK to make the cut.
Doing so creates a gap in the pulley. This is sometimes referred to
as a disjointed feature . Although this used to prove troublesome to
other CAD systems, Inventor has always used conditions like this to
offer creative ways for you to defi ne geometry.
You need a plane that bisects the thickness of the pulley. On this
plane, you'll create the shape of a spoke to reinforce the pulley. Let's
create a work plane to do the job.