Peg-in-Hole SmartMates
You can add mates automatically between features that have a "peg-in-hole"
relationship. The requirements are:
One of the features must be a base or boss, and
the other must be a hole or a cut.
The features must be extruded or revolved.
The faces that are used in the mate must both
be of the same type (either a cone or a cylinder, not one of each type).
A planar face must be adjacent to the conical/cylindrical
face of both features.
To create peg-in-hole SmartMates:
Do one of the following:
In the FeatureManager design tree of a part
document, select a feature with a cylindrical or conical face. Drag the
feature name into an assembly graphics window.
In the graphics area, select the circular
edge of the screw head and drag the component
into an assembly graphics window.
When the pointer is
over another cylindrical or conical face of a hole or cut (when you drag
the feature name), or a circular edge of a hole or cut (when you drag
the component), the pointer changes to 
.
A preview of the part
snaps into place. If the preview indicates that you need to change the
alignment condition, press the Tab
key to flip the alignment (aligned/anti-aligned).
Drop the part.
Two mates are applied:
a Concentric mate between the
cylindrical or conical faces, and a Coincident
mate between the planar faces that are adjacent to the conical faces.