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JBC 520
Principles of operation
The JBC 520 aligns the axis of the lathe to the hub’s axis. Instead of using a pair of
runout screws to eliminate compensate for runout, it uses one screw. By precisely
positioning that screw by spinning the ring, you can adjust for runout by only applying
correction exactly where it is needed. This eliminates trying to get two screws in
combination to eliminate the runout.
Background on Lateral Runout
Low Point
-0.015
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Lateral Position
Lateral run-out is caused by an angular misalignment between the vehicle hub and the
lathe spindle. The motion this misalignment causes happens once per revolution of the
lathe. This is the steady end to
0.015
end sweep you see on a dial
Source
High Point
indicator. As the lathe and hub
0.01
Lateral position of
turn, the lateral runout starts at
the lathe (inches)
zero, goes up to its high point,
0.005
Source
back through zero, through its
0
low point and back up to zero.
This happens each time the
-0.005
spindle
completes
one
revolution (360 degrees). This
-0.01
is shown in Figure 1.
©1998 Pro-Cut International LLC
INTERNAL DISTRIBUTION ONLY
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360
345
330
315
300
285
270
255
240
225
210
195
180
165
150
135
120
105
90
75
60
45
30
0
15
Lateral Position
In order to eliminate lateral
Degrees Rotation
runout, we need to introduce a
second source of lateral
Figure 1: Lathe runout over 1 revolution
runout. We need to introduce
lateral runout exactly equal to and opposite of the lateral runout that is present in the
original hookup.
With the
0.015
standard runout screws we
Original Runout
adjust
two
screws
in
0.01
combination until they exactly
0.005
equal and opposite of the
Equal Zero
original lateral runout.
A
Source
0
Device
perfectly
adjusted
system
Adj. LRO
would look like Figure 2. With
-0.005
the ring device, we place the
-0.01
single screw so that it is
Adjustment Runout
exactly opposite the high point
-0.015
of the original runout then turn
Degrees Rotation
the screw until the added
runout exactly equals the
Figure 2: Corrected Lateral Runout
original runout. This makes
the total motion zero.