Go to Tools -> Options -> Mechanical Design -> Drafting
-> General and
check Display in the current view to display the view
axis.
1. Click the Dimensions icon
from the Dimensioning toolbar.
2. Click a first element in the view (highlighted
when selected).
3. Select one of the two view axes or
the origin.
4. Click anywhere in the drawing window to
confirm the dimension creation.
Extension lines cannot
be applied onto axes because axes are infinite lines. However, if you wish
to obtain extension lines, select the original point instead of the
vertical axis.