The instrument are designed with adjustable centerholes at both ends that make its fitting and measuring rapidly and easy.
该仪器两端设计有可调心式中心孔，安装测量迅速方便。
2
The machine drills the "centerholes" for the hands as well as the "pilot holes" which will guarantee the positioning of the strip during blanking operations.
用机器钻出安装指针的中心孔及导向孔，以确保铜条在冲切工序固定位置。
3
They stacked rocks with centerholes (tube or doughnut shaped) from the surface to the deep stone layer as a guide for their drills (similar to today's guide tubes).