MACHINING Copyright Goodheart-Willcox Co., Inc. Chapter 26 Milling Machines 473 Using a Mechanical Edge Finder The mechanical edge finder is a precision positioning tool that makes it possible to locate the edge of a work- piece in relation to the center of the spindle with a tol- erance as close as .0002″ (0.005 mm). ″ Finding the Center of a Hole using a Mechanical Edge Finder 1. With the spindle rotating at a moderate speed, and with the tip of the edge finder as shown in Figure 26-82A, slowly feed the tip of the tool against the work. 2. The tip of the edge finder will gradually become centered with the shank, Figure 26-82B. 3. When the tip becomes exactly centered, the tip will abruptly jump sideways about 1/32″ (.8 mm), ″ Figure 26-82C. Stop the table immediately when this occurs. The center of the spindle will be exactly one-half the tip diameter away from the edge of the work. 4. Set the micrometer dial to 0 and, with the edge finder clear of the work, move the table longitudinally the required distance plus one-half the tip diameter. Follow the same procedure to get the traverse measurement. Goodheart-Willcox Publisher Figure 26-81. Aligning the center of a hole with a centering scope. or Fits in chuck collet Hole center line e Edge finder rotation Feed A B C Tip Shank Goodheart-Willcox Publisher Figure 26-82. A mechanical edge finder is a precision positioning tool for locating the edge of a workpiece in relation to the center of the spindle. It can achieve tolerances as close as .0002″ (0.005 mm). A—Feed the tip of the edge finder against ″ the work. B—As the edge finder rotates, the tip becomes centered with the shank. C—When the tip is exactly centered, it will sideways (away from the edge of the work).