How does the 3-2-1 locating principle constrain degrees of freedom in workholding?

The 3-2-1 locating principle positions a workpiece using six contact points arranged on three reference planes.

• Primary plane: Three widely spaced points support the base, controlling movement along Z and tilting around X and Y.
• Secondary plane: Two points on a perpendicular side control movement along Y and rotation around Z.
• Tertiary plane: One point on a third perpendicular face controls movement along X.

Clamps keep the workpiece seated against these locating points during machining.