472 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. When the slot is wider than the cutter diameter, it is important to observe the proper direction of feed in relation to cutter rotation. Feed direction is against the cutter rotation when making the type of cut shown in Figure 26-78. 26.8.7 Machining Multilevel Surfaces Milling a multilevel surface is probably the easi- est of the milling operations, Figure 26-79. Lay out lines for the various levels on the work’s surface. Make the cuts until all the lines have been reached. For accuracy, check the depth of the cut with a micrometer. Make necessary table adjustments accordingly. 26.8.8 Drilling and Boring Holes may be located for drilling, reaming, and boring to very close tolerances on the vertical mill with a wiggler, Figure 26-80, a center scope, Figure 26-81, or an edge finder (either electronic or mechanical), Figure 26-82. After the first hole is located, it is possible to locate the remaining holes using the micrometer feed dials on the table move- ment screws. Mills with a digital readout display make it easier to locate the remaining holes and pro- vide more accuracy. Goodheart-Willcox Publisher Figure 26-78. When machining internal openings, remember that feed is always against cutter rotation. Goodheart-Willcox Publisher Figure 26-79. Machining a stepped (multilevel) surface. Goodheart-Willcox Publisher Figure 26-80. Aligning the center of a hole using a wiggler.