How is flatness tolerance inspected?

How is flatness tolerance inspected?

• A. By checking the maximum deviation of the surface from an ideal plane using a flatness gauge, surface plate, or CMM.
• B. By measuring the average roughness of the surface.
• C. By checking color variation of the surface.
• D. By counting texture.

Answer: (A)

Flatness tolerance is a form control that specifies how far a surface may deviate from a perfect plane over its entire area. To inspect it, you compare the surface to a true plane using a reference such as a surface plate and measurement tools like a flatness gauge, a CMM, or a dial-indicator setup. The key idea is the maximum deviation—the greatest distance between the surface and the reference plane across the whole surface. If that maximum distance is within the specified tolerance, the surface passes. This differs from surface roughness tests, which measure microscopic texture (average roughness) rather than how the surface lies relative to a plane. Checking color variation or counting texture does not inform flatness, since those relate to appearance or texture, not form.

Flatness tolerance is a form control that specifies how far a surface may deviate from a perfect plane over its entire area. To inspect it, you compare the surface to a true plane using a reference such as a surface plate and measurement tools like a flatness gauge, a CMM, or a dial-indicator setup. The key idea is the maximum deviation—the greatest distance between the surface and the reference plane across the whole surface. If that maximum distance is within the specified tolerance, the surface passes. This differs from surface roughness tests, which measure microscopic texture (average roughness) rather than how the surface lies relative to a plane. Checking color variation or counting texture does not inform flatness, since those relate to appearance or texture, not form.