If a hole feature has a position callout with a diameter symbol and datums A and B, what does the corresponding tolerance zone look like?

If a hole feature has a position callout with a diameter symbol and datums A and B, what does the corresponding tolerance zone look like?

• A. A cylindrical zone coaxial with the true position and bounded by the DRF
• B. A rectangular plate around the hole
• C. A cubic zone
• D. A spherical zone around the hole

Answer: (A)

The main idea is that a position tolerance using the diameter symbol defines a cylindrical tolerance zone around the hole’s true position. The true position is the exact centerline the hole should have in the datum reference frame, and because the tolerance is specified with a diameter, the allowable deviation is radial in all directions around that axis, forming a cylinder. This cylinder is oriented and bounded by the datum reference frame defined by the included datums (A and B), so its axis is aligned with the hole’s true position and its ends are constrained by the DRF. Thus, the tolerance zone is a cylindrical region coaxial with the true position and bounded by the DRF. The other shapes (rectangular, cubic, spherical) don’t describe this radial, axis-centric cylindrical zone.

The main idea is that a position tolerance using the diameter symbol defines a cylindrical tolerance zone around the hole’s true position. The true position is the exact centerline the hole should have in the datum reference frame, and because the tolerance is specified with a diameter, the allowable deviation is radial in all directions around that axis, forming a cylinder. This cylinder is oriented and bounded by the datum reference frame defined by the included datums (A and B), so its axis is aligned with the hole’s true position and its ends are constrained by the DRF. Thus, the tolerance zone is a cylindrical region coaxial with the true position and bounded by the DRF. The other shapes (rectangular, cubic, spherical) don’t describe this radial, axis-centric cylindrical zone.