Which statement about applying true position to a bolt hole pattern is accurate?

Which statement about applying true position to a bolt hole pattern is accurate?

• A. The true position tolerance is applied to the axes of the holes, referencing the DRF and the bolt circle diameter.
• B. The true position tolerance is applied to the pattern’s outer boundary only.
• C. The true position tolerance replaces the need for any datum references.
• D. The true position tolerance is defined by a circular runout around the bolt circle.

Answer: (A)

Understanding how true position works for a bolt hole pattern means focusing on where the holes’ axes must be, not the outer boundary of the pattern. When you apply a true position tolerance to a bolt hole pattern, you’re specifying how far each hole’s axis can deviate from its nominal location, relative to a defined datum reference frame. The centers of the holes lie on the bolt circle, so the bolt circle diameter sets the locus for those centers. The datum reference frame fixes the orientation and location of the pattern in relation to the rest of the part, and the true position tolerance is projected to the axes of the holes within that frame. This approach uses the DRF to establish a precise, repeatable reference, and the bolt circle diameter to define the circular path along which the hole centers should lie. The tolerance zone is typically cylindrical around each hole axis, aligned with the true position, and it’s constrained by the datums. It isn’t about the pattern’s outer boundary, and it doesn’t replace datum references. Circular runout is a different tolerance concept, used to control rotation about an axis for a surface or features, not the true position of hole axes relative to a datum frame. So, the statement that true position is applied to the axes of the holes, referencing the DRF and the bolt circle diameter, is the correct description.

Understanding how true position works for a bolt hole pattern means focusing on where the holes’ axes must be, not the outer boundary of the pattern. When you apply a true position tolerance to a bolt hole pattern, you’re specifying how far each hole’s axis can deviate from its nominal location, relative to a defined datum reference frame. The centers of the holes lie on the bolt circle, so the bolt circle diameter sets the locus for those centers. The datum reference frame fixes the orientation and location of the pattern in relation to the rest of the part, and the true position tolerance is projected to the axes of the holes within that frame.

This approach uses the DRF to establish a precise, repeatable reference, and the bolt circle diameter to define the circular path along which the hole centers should lie. The tolerance zone is typically cylindrical around each hole axis, aligned with the true position, and it’s constrained by the datums.

It isn’t about the pattern’s outer boundary, and it doesn’t replace datum references. Circular runout is a different tolerance concept, used to control rotation about an axis for a surface or features, not the true position of hole axes relative to a datum frame.

So, the statement that true position is applied to the axes of the holes, referencing the DRF and the bolt circle diameter, is the correct description.