An edge finder is a common tool used in metalworking and machining to precisely locate the edges of a workpiece. It consists of a cylindrical body with a spring-loaded probe on one end and a shank on the other end that can be mounted in the spindle of a milling machine or other machine tool.

To use an edge finder, the machine operator places the shank into the spindle and positions the probe near the workpiece. The machine is then turned on, and the operator moves the workpiece until the probe makes contact with the edge. As the probe makes contact, it pushes into the body of the edge finder, compressing the spring inside. This causes a slight deflection of the probe, which the operator can observe as a visual or audible signal. Once the operator has located the edge, they can then use this information to make precise adjustments to the machine's position or cutting tool.

Edge finders are commonly used in machining applications such as milling, drilling, and grinding to accurately locate the edges of a workpiece for subsequent operations. They are available in a variety of sizes and styles to suit different types of machines and applications.