By studying some boring machining families, standard time datum for unit operation was set up. Some methods of shortening operation changing time were also presented.
通过对钻孔加工族的时间研究，初步建立不同工步单件加工时间的标准资料，并探讨节省作业转换时间的方法。
2
The datum chemical reagents must be used in the preparations of standard solutions;
标准贮备液的配制要使用基准级试剂；
3
Gearboxes shall be taken as the standard unit. To adjust bottom base by referring to horizontal subdivision section of gear box, box body processing datum plane or support of bottom base;