The pitch diameter (E) of a 60-degree Unified Thread is a critical dimension used to verify the accuracy of a thread’s fit. It represents the effective diameter where the thread thickness is equal to the space between threads.
Use this calculator to find the ideal size wire to use in measuring pitch diameter on 60° threads.
This calculation is performed using a three-wire measurement method, where precision wires of known diameter (G) are placed in the thread grooves, and a micrometer measures the dimension across the wires (M). The formula used to determine the pitch diameter is:
E = M – (3G – 0.86603/n)
Wire Diameter (G): inches
Measured Value (M): inches
Threads Per Inch (n): TPI
Pitch Diameter (E): inches
