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Copyright © 2020 Quality Machine Tools, LLC
PM-835S v3 2020-10
Figure 4-13
Saddle gib (Y axis), front
Figure 4-14
Saddle gib (Y axis), rear
Figure 4-15
Knee gib (Z axis), topside
Figure 4-16
Knee gib (Z axis), underside
LEADSCREW BACKLASH CORRECTION
When alternating between clockwise and counter clockwise
rotation of the X or Y leadscrews, the handwheel moves freely
a few degrees but the table stays put. This is backlash, a fea-
ture of all standard leadscrews. 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.
Each leadscrew nut comprises two internally-threaded com-
ponents, one fixed, the other adjustable. Backlash is corrected
by rotating the adjustable nut shown in Figures 4-17 and 4-18.
Clockwise or counter-clockwise rotation of the nut has a simi-
lar effect in reducing backlash. Adjust backlash by rotating the
nut finger tight, then re-tighten the two socket head screws.
Figure 4-17
Table (X axis) backlash adjuster
Figure 4-18
Saddle (Y axis) backlash adjuster
Figure 4-12
Table (X axis) gib screw, right side
