Especially , the idea of " datum dimension precision back " is being put forward , and this idea is being realized by backing composition composed by outer - diameter micrometer , airproof shafting , microwatch . at the same time , use " non - lock " to replace " lock " , this way make the system compact , eliminate many bigger error and resolve th 尤其是提出了基准尺调整后精确后退的思想，并通过外径百分尺、密珠轴系、千分表组成后退机构加以实现。同时以“无锁”代“锁” ，使系统结构紧凑，受力小，消除了多项较大误差从而解决了测试精度低的关键问题。
