Use an optical system to calibrate thread gauges

Calibration of external and internal thread gauges according to different standards is usually performed by contact measuring systems, but a laser/optical system could be more user-friendly.

Calibration of external and internal thread gauges according to different standards is usually performed by contact measuring systems, on single-axis length measuring machines.

The pitch diameter, although the most important single dimension of the screw threads, is only a conceptual parameter, therefore it's accurate measurement is difficult.

The pitch diameter of the screw thread represents the diameter of an imaginary cylinder with surface passing through the thread at points where the widths of ridges and grooves are equal.

To determine the pitch diameter of screw threads the most practical procedure is the use of three wires, placed in the thread groove, two on the one side and one on the opposite side of the screw.

That arrangement of the wires permits the opposite sensing elements of a length measuring instrument to be brought into simultaneous contact with all three wires, thus providing a dependable measurement of the over-wire distance.

Use of two wires instead of three wire leads to a lower accuracy.

Calibration of internal threads is performed with special T-probes.

Object of OPTIGEW project is to evaluate the application of laser and/or optical technology and develop an optical calibration device, in order to reduce the uncertainty of measurement and make calibration operation more user-friendly.

A special analysis software module would also be developed and integrated with the laser and/or optical measuring system.

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