What is the main difference between true position and profile tolerances?

What is the main difference between true position and profile tolerances?

• A. True position controls where a feature lies; Profile controls the boundary shape of a surface.
• B. True position controls flatness; Profile controls runout.
• C. They are identical tolerances.
• D. True position applies only to lines.

Answer: (A)

The key idea is what each tolerance controls. True position fixes where a feature sits in relation to datums—its location in space. It constrains the axis or center of a feature of size so that the part places itself correctly with respect to the defined datums, but it does not dictate the exact shape of the surface around that feature. Profile tolerance, on the other hand, governs the boundary shape of a surface. It defines how far the actual surface is allowed to deviate from the intended contour, so it controls the surface’s boundary rather than where the feature lies in the part. So true position is about locating features, while profile is about the contour or boundary shape of a surface. For example, you’d use true position to ensure holes or holes in a pattern are in the right spots, and you’d use profile to ensure a curved surface follows a specified outline.

The key idea is what each tolerance controls. True position fixes where a feature sits in relation to datums—its location in space. It constrains the axis or center of a feature of size so that the part places itself correctly with respect to the defined datums, but it does not dictate the exact shape of the surface around that feature. Profile tolerance, on the other hand, governs the boundary shape of a surface. It defines how far the actual surface is allowed to deviate from the intended contour, so it controls the surface’s boundary rather than where the feature lies in the part. So true position is about locating features, while profile is about the contour or boundary shape of a surface. For example, you’d use true position to ensure holes or holes in a pattern are in the right spots, and you’d use profile to ensure a curved surface follows a specified outline.