1975 年 41 巻 486 号 p. 708-712
In gun drilling, the motion and attitude of the drill tip in a hole are indispensable to know the fundamental phenomenon and the accuracy of the hole is dominated by them. They can be obtained from the oil film thickness between the wear surface of drill and the hole wall. In our study, the variation of oil film thickness is transformed into the variation of the effective resistance, by means of inductance type of four small pickups and universal type of strain meter. As the output obtained shows the reciprocal of oil film thickness, linearizing circuit is designed by operational amplifier divider. Within the measuring range of 100 μm, the linearized output is 0.03 V/μm and the maximum noise is 30 mVp-p. The error of linearity is within ± 0.7 μm. The measuring error of pickup due to temperature depends on a conductivity change of the coil wire. By balancing the DC activated bridge circuit, the errors can be reduced within 1.0, 2.0 and 3.9 μm respectively at oil film thickness of 10, 50 and 100 μm. An example of practical measurements is shown.