Applying datums in the order A-B-C affects what aspect of the part?

Applying datums in the order A-B-C affects what aspect of the part?

• A. It reduces the part's degrees of freedom.
• B. It increases the part's degrees of freedom
• C. It has no effect on degrees of freedom
• D. It only affects the material condition of the part

Answer: (A)

Datums create a fixed reference frame that locates and orients a part in space. When three datums are defined in a specific order, they progressively constrain the part’s position and orientation, reducing its degrees of freedom. A rigid body has six degrees of freedom: three translations (x, y, z) and three rotations (about x, y, z). The primary datum constrains the most movement by fixing two translations and one rotation, the secondary datum adds constraints that reduce the remaining degrees of freedom, and the tertiary datum completes the frame to lock the last remaining freedom. With a complete datum reference frame, the part’s position and orientation are defined relative to those datums, so its mobility within the tolerancing context is reduced accordingly. This effect is about constraining motion, not about increasing it, and it isn’t about material condition. Three datums establish a stable reference for measuring and tolerancing, effectively fixing the part in space within that frame.

Datums create a fixed reference frame that locates and orients a part in space. When three datums are defined in a specific order, they progressively constrain the part’s position and orientation, reducing its degrees of freedom.

A rigid body has six degrees of freedom: three translations (x, y, z) and three rotations (about x, y, z). The primary datum constrains the most movement by fixing two translations and one rotation, the secondary datum adds constraints that reduce the remaining degrees of freedom, and the tertiary datum completes the frame to lock the last remaining freedom. With a complete datum reference frame, the part’s position and orientation are defined relative to those datums, so its mobility within the tolerancing context is reduced accordingly.

This effect is about constraining motion, not about increasing it, and it isn’t about material condition. Three datums establish a stable reference for measuring and tolerancing, effectively fixing the part in space within that frame.