直径大于200毫米、分度误差在±1′左右的圆分度用万能工具显微镜或投影仪都无法测量。我们用10″光学分度头,配制一个莫氏4号锥体的底盘5和一个瞄准装置6相结合进行测量(如左图),效果很好。瞄准装置借用工具显微镜的主显微镜及其支臂,安装在自制的底座8上,转动手轮,带动丝杆7,可使瞄准装置作前后位置的调节。测量前按一般方法校准被测件与回转中心 Circular indexing of diameters greater than 200 mm and indexing errors of ± 1 ’can not be measured with a universal tool microscope or projector. We use the 10 "optical sub-head, the preparation of a Morse No. 4 cone chassis 5 and a targeting device 6 combined with the measurement (left), the effect is good. Aiming device borrowed the microscope and its main tool microscope Arm, mounted on a self-made base 8, turn the hand wheel, drive screw 7, the sighting device can make the front and rear position adjustment.After the measurement according to the general method of calibration of the measured piece and the rotation center