How would you annotate a bolt hole pattern with a true position tolerance?

How would you annotate a bolt hole pattern with a true position tolerance?

• A. Apply a true position tolerance to the axes of the holes, referencing the DRF and the bolt circle diameter.
• B. Apply a positional tolerance to the bolt circle circumference only.
• C. Apply a diameter tolerance to each hole without referencing a pattern datum.
• D. Use a runout tolerance around the outer boundary of the pattern.

Answer: (A)

When controlling a bolt hole pattern, the hole axes are placed with a true position tolerance defined in a datum reference frame and anchored to the bolt circle diameter. The true position defines where each hole’s axis should lie relative to the datums, and the bolt circle diameter specifies the circular locus around which those axes should be located. The tolerance zone is cylindrical around the true position of each hole axis, ensuring both radial and angular accuracy within the specified tolerance once the part is oriented to the DRF. If you tried to constrain only the circumference of the bolt circle, you wouldn’t force the individual hole centers to sit on that circle with the required precision. If you only applied a diameter tolerance to each hole without referencing the pattern datums, you’d be sizing the holes but not controlling their pattern location. A runout around the outer boundary governs how the feature moves as the part rotates, not the precise placement of multiple hole centers within a pattern. Using the true position relative to the DRF and the bolt circle diameter provides the correct, complete control of the pattern’s location.

When controlling a bolt hole pattern, the hole axes are placed with a true position tolerance defined in a datum reference frame and anchored to the bolt circle diameter. The true position defines where each hole’s axis should lie relative to the datums, and the bolt circle diameter specifies the circular locus around which those axes should be located. The tolerance zone is cylindrical around the true position of each hole axis, ensuring both radial and angular accuracy within the specified tolerance once the part is oriented to the DRF.

If you tried to constrain only the circumference of the bolt circle, you wouldn’t force the individual hole centers to sit on that circle with the required precision. If you only applied a diameter tolerance to each hole without referencing the pattern datums, you’d be sizing the holes but not controlling their pattern location. A runout around the outer boundary governs how the feature moves as the part rotates, not the precise placement of multiple hole centers within a pattern. Using the true position relative to the DRF and the bolt circle diameter provides the correct, complete control of the pattern’s location.