Describe the process of properly setting up and using an edge finder to establish a work coordinate system on a CNC mill.

Establishing a work coordinate system (WCS) using an edge finder on a CNC mill involves accurately determining the location of the workpiece edges relative to the machine's coordinate system. First, securely mount the edge finder in the machine's spindle. Ensure the edge finder is clean and free from damage. There are two main types of edge finders: mechanical and electronic. Next, select the appropriate spindle speed. For mechanical edge finders, the spindle should be set to a low RPM, typically between 500 and 1000 RPM. For electronic edge finders, consult the manufacturer's instructions for the recommended speed. Then, bring the edge finder close to the workpiece edge. Using the machine's jog mode, carefully move the edge finder close to the edge of the workpiece, leaving a small gap (approximately 0.020" to 0.050"). Approach the edge slowly to avoid collisions. After that, "indicate" the edge. For a mechanical edge finder, slowly move the edge finder in the X or Y axis until the edge finder's stylus 'breaks over,' indicating contact with the workpiece edge. For an electronic edge finder, slowly move the edge finder until the indicator light illuminates or the buzzer sounds, indicating contact. Record the machine coordinate. Record the machine coordinate at the point of contact. Then, account for the edge finder radius. Because the edge finder contacts the workpiece edge at its radius, the recorded machine coordinate needs to be adjusted by the edge finder's radius to determine the true location of the workpiece edge. The adjustment is added or subtracted depending on the direction of approach. Calculate the WCS offset. The WCS offset is the distance between the machine's coordinate system and the desired WCS origin. This is calculated by subtracting the adjusted machine coordinate from the desired WCS origin coordinate. Enter the WCS offset into the CNC control's work offset table (e.g., G54, G55). Repeat the process for the other axes. To fully establish the WCS, repeat the process for the other axes (X and Y) and for the Z-axis (if necessary). Finally, verify the WCS. After setting the WCS, verify its accuracy by running a simple test program to machine a feature at a known location on the workpiece.