The universal 3D sensor is a very precise and versatile measuring instrument for milling and EDM machines(insulated probe).The 3D sensor is clamped into a tool holder and inserted into a milling spindle. Once clamped into the machine spindle, the run-out(T.I.R) is fully adjustable to zero. Then you are able to find exact positioning of the spindle axis on the deges of the workpiece.This allows for zeros to be set and the length to be measured quickly and esaily. You may approach in any direction (X/Y/Z axis hence the name"3D Sensor"). When the dial gage shows zero, the spindle axis is exactly on the workpiece edge.The 3D sensor allows for the edge to be found on the first attempt. No calculating of the probe's ball diameter is necessary-just Zero it out! Problems with mathematics...