Pitch diameter (PD) on an API R or RX ring groove cannot be directly measured. However, the PD can be easily obtained with a simple calculation.
Find the specified pitch diameter (per the design print or API/ANSI spec), add the BX-1000 deviation of the major diameter, and then subtract the BXG-1000 deviation of the groove width.
Like this: Actual PD = (Print or API 6A Spec PD) + (BX-1000 deviation) – (BXG-1000 deviation)
Example:
R53 spec PD: 12.750″
Deviation Measurements: BX-1000= 0.004″, BXG-1000= -0.001″
Part’s PD =12.750″ + (0.004″) – (-0.001″) = 12.755″