MACHINING Copyright Goodheart-Willcox Co., Inc. Chapter 26 Milling Machines 465 A sheet of paper between the work and the table will prevent the metal from slipping during the slitting opera- tion. The cutter is set to a depth equal to the thickness of the material plus 1/16″ 6 6 (1.6 mm). ″ Always use a sharp cutter! Cutting a Keyway in Round Stock In many situations, keyways for a standard square key must be cut in round stock. The keyway must be exactly on center if it is to be in alignment with the keyway in the mating part. After the machine has been set up and the workpiece is mounted (in a vise, between centers, in a V-block, or in a fixture), precise centering of the cutter may be accomplished by one of the following methods: • After making sure the machine is turned off, center the cutter visually on the work. With a steel square and a rule, adjust the table until both sides measure the same, Figure 26-58. A depth micrometer may be used instead of a rule for more accurate positioning. • For short pieces that cannot be centered by the above method, position the work under the rotat- ing cutter and bring it lightly into contact with the cutter. Use a traverse feed to pass the work under the cutter. A perfectly centered oval cut will result. Position the cutter on the oval, Figure 26-59. Lock the saddle to prevent table movement after the cutter has been centered. Goodheart-Willcox Publisher Figure 26-56. A worktable clamp made from a section of angle iron. Paper sheet Position of cut Angle iron clamp clamp Goodheart-Willcox Publisher Figure 26-57. Position the work so the cut is made over a T-slot. Table T-slot Work Slitting saw Arbor r n Angle ir on clamp 26.7.7 Drilling and Boring The toolmaker often finds it necessary to produce pre- cision holes in jigs, fixtures, and machine parts. The horizontal milling machine offers a convenient way to drill and bore holes in precise alignment with one another. Goodheart-Willcox Publisher Figure 26-58. Centering a cutter on round stock with a steel rule and machinist’s square. Arbor Rule 2nd position 1st position Square Square Cutter Work Rule Goodheart-Willcox Publisher Figure 26-59. Positioning the cutter on center using an oval made in the work with the cutter as a guide.