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PM 25MV v9 2020-10
Copyright © 2020 Quality Machine Tools, LLC
LEADSCREW BACKLASH CORRECTION
When alternating between clockwise and counter clock-
wise rotation of the X or Y leadscrews, the handwheel
moves freely a few degrees but the table stays put. This
is backlash, a feature of all leadscrews other than the
precision type found on CNC machines. The acceptable
amount of lost motion depends on the user, but 0.005”
is generally a good compromise. Smaller numbers are
possible, but overdoing it can lead to premature wear of
leadscrew and nut.
Excessive backlash can be corrected by compressing
the leadscrew split nut. For the X-axis this is done by
tightening the socket head screw in Figure 4-3. A long-
handled 4 mm hex wrench is required, ideally one with
an extra-thick shank to minimize flexing. The corre
-
sponding adjustment for the Y-axis is difficult because
the split nut and leadscrew are concealed by castings,
Figure 4-4. Access to the adjusting screw is possible
Figure 4-2
Z-axis gib adjustment, upper screw
The lower screw is under the pleated way cover.
Figure 4-3
X-axis backlash adjustment
Figure 4-4
Y-axis backlash adjustment
Both options are two-man procedures
DOWNFEED RETURN SPRING
The quill should automatically retract when the coarse
downfeed levers are released following a drilling opera-
tion. If it does not, check for binding in the quill lock. The
return spring, Figure 4-5, is held by a spring cup which
is locked to the spindle by a special C-clip beneath the
drawbar cap, Figure 3-2. Spring force is not adjustable.
only if the entire machine is unbolted from the bench or
stand, then: 1.
Lifted
by sling and engine hoist (see In-
stallation, Section 1), or; 2.
Tilted
backward by pivoting
on the back edge of the base casting.
Figure 4-5
Quill return spring
