3-Wire Measurement

Calculate the expected micrometer reading over three precision wires to verify the pitch diameter of 60° threads.

"Best Wire" contacts the thread exactly at the pitch line.
Target Measurement Over Wires (M)
0.0000
in
Pitch Diameter
--
Wire Constant (C)
--
Measurement Geometry
Micrometer Spindle
The Formula (60° UN/Metric)
M = PD + 3W - (0.866025 × Pitch)

Measurement M is what you read on your micrometer. PD is the Pitch Diameter, and W is the wire diameter.

Why 3 Wires?

Using three wires (two on one side, one on the other) allows the micrometer to stay parallel to the thread axis, providing the most accurate measurement of the pitch line without specialized thread mics.