Development of a laser-guided deep-hole evaluating system

The probe with a 110-millimeter diameter is fabricated for measuring accuracies of extremely deep holes. It consists of a measurement unit, skid unit and a laser diode, which are used to detect the position and inclination of the probe. Measurement unit, which is mounted on the forward part of the probe, is equipped with a pentaprism and a stylus with a corner cube prism. The hole shape is detected by measuring movement of a stylus perpendicular to the hole wall using a laser interferometer. The laser interferometer is set in front of the probe. Its laser beam is radiated toward the pentaprism of the measurement unit and deflected toward the corner cube prism. The beam reflected from the corner cube prism reaches the interferometer via the pentaprism. In the present study, a probe is fabricated using skids instead of piezoelectric actuators and its performance is examined. The use of skids reduces the production cost because they are less expensive as compared to piezoelectric actuators. The results show that roundness and straightness of a deep hole measured by the probe correspond well with those by an electric micrometer and a roundness tester when measuring the gradually changing hole wall.