| 摘要 |
PURPOSE:To improve measurement precision and to shorten a measurement time by magnetizing a screw plug gauge or three styli. CONSTITUTION:A permanent magnet 5 is brought into contact with a holder 2 holding a plug gauge 1 for several seconds to obtain enough residual magnetic force to attract three styli 3. The three styli 3 when put close to the screw groove of the magnetized plug gauge 1 are attracted, so the three styli 3 are set in the screw groove symmetrically and accurately in a short time by using a pair of tweezers. Then, external distance M between the styli is measured to determine an effective diameter. Thus, measurement precision is improved and a measurement time is shortened. |
