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Gib Adjustment
The goal of adjusting the cross slide, tailstock, saddle,
and compound gib screws is to remove sloppiness
in the ways without over-adjusting them to the point
where the slides become stiff and dif
fi
cult to move.
In general, loose gibs cause poor
fi
nishes and
tool chatter; however, over-tightened gibs cause
premature wear on the slide, leadscrew, and half nut,
and are dif
fi
cult to operate.
The gibs have a tapered shape and are held in
position by screws at opposing ends of the slide.
When the opposing screws are turned in the opposite
directions from each other, the taper
fi
lls the void
between the sliding components.
The gib adjustment process usually requires some
trial-and-error. Typically, you make a slight adjustment
to the gib screw, then check the feel of the adjustment
by turning the handwheel.
You then repeat this process as necessary until you
fi
nd
the best balance between loose and stiff movement.
Most machinists
fi
nd that the ideal gib adjustment is
where a small amount of drag or resistance is present
yet the handwheels are still easy to move.
Figures 88–91 show the location of the screws for
each gib on this machine.
Half Nut Adjustment
The half nut mechanism can be tightened if it becomes
loose from wear. The pressure exerted by the half nut
is controlled by a gib similar to the one in the saddle.
The half nut gib is adjusted with two set screws.
To adjust the half nut :
1. Open the half nut.
2. Remove the thread dial.
3. Turn the two half-nut adjustment set screws,
shown in Figure 92, clockwise about an 1
⁄
8th of
a turn.
4. Open/close the half nut several times and notice
Figure 90. One of two front saddle gib screws.
Left Gib Screw
Figure 91. One of two tailstock gib screws.
Left Gib Screw
how it feels (you may need to move the carriage
handwheel slightly to get the half nut to close).
Figure 92. Half nut gib adjustment.
Half Nut
Adjustment
Set Screws
Leadscrew
Half Nut
Figure 89. One of two rear saddle gib screws.
Gib Screw
Figure 88. One of two cross slide and
ompound gib screws.
Compoung
Front Gib
Screw
Cross Slide
Front Gib
Screw
