钻通孔时提高钻头寿命的装置是在原介绍装置(见《机床》1980.No6)的基础上改进的。两装置的工作原理相同,结构上所不同的仅是用一组摆杆5、活动垫圈3和调整螺钉6代替原装置的活动垫圈。当钻头即将钻通工件时,为自动减小钻头进给量,可通过予先调整螺钉6来改变摆杆5和本装置中心 The means to increase the life of a drill bit when drilling a through hole is based on the original introduction of the device (see “Machine Tool” 1980. No.6). The two devices work the same principle, the structural difference is only a set of swing lever 5, movable washer 3 and adjusting screw 6 instead of the original device activities washers. When the drill is about to drill through the workpiece, in order to automatically reduce the drill feed, you can adjust the screw 6 to change the swing lever 5 and the center of the device