Machinery's Handbook, 31st Edition
SHAFT ALIGNMENT
2737
6th Arrangement.— Place rim and face indicators as shown in Fig. 6a.
r
f
A f B A f C
A
2 2 ! ! # ! ! #
F r R r
= − + − = − + −
F
R
B
C
Fig. 6a. Dial Indicator Arrangement 6
+
-
o
+
+
+
+
o
-
o
o
o
+
-
o
-
-
-
Fig. 6b. Interpreting Dial Indicator Readings for Indicator Arrangement 6 Solid lines represent the desired location for the dashed lines (movable unit). The plus, minus, and zero readings on the indicators are represented by one of these nine scenarios. Depending on the magnitude of the variables, the generic graph gives a mental picture of what the formulas should yield. Example: Calculate the shims necessary for a pump and motor alignment where dimen sions are A = 4.75 inches, B = 6.25 inches, and C = 31.75 inches. The two indicator dials: r = minus ( − ) 0.024 inch and f = plus (+) 0.005 inch respectively. Solution: The top left block in Fig. 6b describes the situation of negative rim and positive face values. The generic graph suggests that both the front and rear feet need some shims to be removed, but the calculations below require that some positive movement of the front feet is required. If in doubt, follow the numbers; the graphs are not drawn to scale. The formulas call for 0.005 inch added under the front feet and the rear feet to be lowered by 0.021 inch:
A f B
A f C
! ! #
! ! #
F r
R r
. 2 0024 2 = − + − = − − = − =
. 2 0024 2 = − + − = − − = + − =− ^
. 475 0005 625 . . #
. 475 0005 3175 . . #
+ −
+ −
. . 0 012 0 006578 0005 . inch
. 0 012 0 03342 0021 . . inch
h
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