Coupling error model for the contact probe of a three-dimensional screw thread-measuring machine

Coupling error is an important factor that affects the measurement accuracy of the contact scanning probe of a three-dimensional thread-measuring machine. To address this issue, this paper proposes a coupling error model for contact scanning probes. First, the mechanical structure of the contact scanning probe was introduced, and the main source of its coupling error was analyzed. Second, material mechanics was used to conduct a geometry–force analysis on the guiding mechanism of the probe, thereby establishing a coupling error model. Finally, the experiments were carried out to verify the accuracy of the coupling error model. From the experimental verification, the movement of the measuring head by 10 μm increased the deviation of the probe displacement by 2 μm, indicating the probe deflection. Moreover, the calculated probe deflection angle was consistent with the theoretical value, validating the proposed coupling error model. This method provides an important theoretical basis for the decoupling of measuring probe, thereby improving the accuracy of the probe guiding mechanism.