Pitch Diameter Gage Operation Manual
Models MRP 1500/2500/3500
Copyright © 2018 Gagemaker. All rights reserved
54
Inspection Criteria
Determining Pitch Diameter and Ovality Measurements with the MRP Gage
The MRP gage measures dimensional changes across the face of connectors called pitch diameter and
ovality. Since pipe is not perfectly round, these measurements are critical in determining the proper fit of
the connector.
Pitch Diameter
Pitch diameter is the distance across the face of the pipe or coupling. Determining the “round” diameter
of a connector requires locating the largest and the smallest diameter readings on the part and taking the
average of the two readings, as shown in the following formula:
(Largest Di Smallest Diameter) = Pitch Diameter
2
Example:
Largest Diameter
Reading
Smallest Diameter
Reading
Averaged Diameter
+.005
-.010
-.0025
Largest and Smallest Indicator Readings for Diameter and Ovality
Ovality
Ovality is the amount of out-of-roundness in a piece of pipe or a coupling. Determining ovality requires
locating the largest and the smallest diameter readings on the part and subtracting the smallest reading
from the largest reading, as shown in the following formula. Ovality readings are always positive (no sign
attached).
Largest Diameter - Smallest Diameter = Ovality
Example:
Largest Diameter
Reading
Smallest Diameter
Reading
Ovality
+.005
-.010
.015
LARGE
READING
SMALL
READING
+
÷
2
-
=