- [Instructor] The first symbol category form
constrains how much a shape is allowed to deviate
from its perfect geometric form.
These form controls are used to control individual features
independent from any geometry or dimensions of a part.
The straightness control constrains how much an edge
or axis can deviate from a perfectly straight line.
The flatness control defines virtual planes
above and below the surface to be constrained.
As long as every point on the surface
lies between those virtual planes,
the surface is within the desired tolerance.
The flatness control determines how rough a surface can be
before it must be rejected.
The circularity control describes
how much a given cross-section of a round feature
can deviate from a perfect circle.
Circularity controls can be applied
to control the shape of any round feature
including cylinders, cones, or spheres.
Cylindricity constrains both the straightness
of a cylindrical feature's axis
as well as the roundness of every cross-section
through that cylindrical feature.
It controls how much a cylindrical feature
is allowed to deviate from a perfect cylinder.