Machinery's Handbook, 31st Edition
AXIS NOMENCLATURE 1387 rule also holds with a horizontal-spindle machine and a vertical table, or angle plate, as shown in Fig. 3. Here, spindle movement back and away from the angle plate, or work piece, is a positive Z -motion, and movement toward the angle plate is a negative Z -motion.
Table movement to the left in effect moves the cutter to the right, relative to the workpiece, or in the + direction
+Y +Z Z
+X
Workpiece
X
Y
X Table Motion
Fig. 1. Fig. 2. Rotary motions also are governed by a right-hand rule, but the fingers are joined and the thumb is pointed in the positive direction of the axis. Fig. 4 shows the designations of the rotary motions about the three linear axes, X , Y , and Z . Rotary motion about the X -axis is designated as A ; rotary motion about the Y -axis is B ; and rotary motion about the Z -axis is C . The fingers point in the positive rotary directions. Movement of the rotary table around the Y -axis shown in Fig. 4 is a B motion and is common with horizontal machining centers. Here, the view is from the spindle face looking toward the rotary table. Referring, again, to linear motions, if the spindle is withdrawn axially from the work, the motion is a positive Z . A move toward the work is a negative Z . When a second linear motion is parallel to another linear motion, as with the horizontal boring mill seen in Fig. 5, the horizontal motion of the spindle, or quill, is designated as Z and a parallel motion of the angle plate is W . A movement parallel to the X -axis is U and a movement parallel to the Y -axis is V . Corresponding motions are summarized as follows: Linear Rotary Linear and Parallel X A U Y B V Z C W
+Y
B
+Y
A
+Z
+X
+X
C
+Z
Fig. 3. Fig. 4. Axis designations for a lathe are shown in Fig. 6. Movement of the cross-slide away from the workpiece, or the centerline of the spindle, is noted as a plus X . Movement toward the workpiece is a minus X . The middle finger points in the positive Z -direction; therefore,
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