How do you handle a hole pattern relative to datums when evaluating position?

How do you handle a hole pattern relative to datums when evaluating position?

• A. The pattern’s centers must be exactly on the primary datum axis.
• B. The pattern’s centers must stay within the cylindrical tolerance zone relative to the DRF defined by the datums.
• C. The pattern's centers must be located at the minimum clearance distance from datums.
• D. The hole pattern is constrained by the datums only if the datums are parallel.

Answer: (B)

The concept being tested is how a hole pattern is evaluated for true position relative to a datum reference frame. When you apply a positional tolerance to a pattern, the centers of the holes must lie inside a cylindrical tolerance zone that is defined by the datums and oriented in relation to the datum reference frame. This means every hole center is allowed to deviate from its true position, but only within that cylinder, whose location and orientation are constrained by the datums that establish the DRF. That’s why the correct choice states that the pattern’s centers must stay within the cylindrical tolerance zone relative to the DRF defined by the datums—the standard way to control true position with respect to datums. The other ideas aren’t correct because true position isn’t enforced by forcing centers exactly onto a datum axis; tolerances allow deviation within the specified cylinder. Minimum clearance to datums isn’t how a positional tolerance is defined. And datums constrain the pattern regardless of whether they are parallel; the DRF is established by the datum features and governs how the tolerance zone is oriented and located.

The concept being tested is how a hole pattern is evaluated for true position relative to a datum reference frame. When you apply a positional tolerance to a pattern, the centers of the holes must lie inside a cylindrical tolerance zone that is defined by the datums and oriented in relation to the datum reference frame. This means every hole center is allowed to deviate from its true position, but only within that cylinder, whose location and orientation are constrained by the datums that establish the DRF. That’s why the correct choice states that the pattern’s centers must stay within the cylindrical tolerance zone relative to the DRF defined by the datums—the standard way to control true position with respect to datums.

The other ideas aren’t correct because true position isn’t enforced by forcing centers exactly onto a datum axis; tolerances allow deviation within the specified cylinder. Minimum clearance to datums isn’t how a positional tolerance is defined. And datums constrain the pattern regardless of whether they are parallel; the DRF is established by the datum features and governs how the tolerance zone is oriented and located.