Smithy GN1300 - Manual (Page 95)

Half nut to screw backlash
Worn threads on the half nut can cause excessive backlash in the longitudinal direction.
Half nuts are made of brass and do wear out over a period of time. The only fix for a
worn half nut is to replace the worn nut with a new one.
Crossfeed Backlash Adjustment
Excessive backlash in the crossfeed can be coming from three different places:
1. The fit of the crossfeed screw to the front screw mount.
2. The fit of the crossfeed screw into the brass crossfeed nut.
3. The fit of the brass crossfeed nut into the carriage casting.
There are adjustments for each of the above areas. Before making any adjustments to
the crossfeed screw system, it is recommended that all the gibbs on the table and
carriage system be checked and adjusted as per the owners’ manual.
Crossfeed Screw To Front Mount
Slowly turn the crossfeed handle clockwise and watch the gap between the dial and the
front screw support mount. Change directions and note if the gap increases slightly. If so
this is a sign that there is some play in the mounting. To reduce this play, follow the
procedure below.
1. Loosen the two nuts that hold the crossfeed handle on the end of the screw.
2. Tighten the inner nut slowly while checking the ease of movement of the crossfeed
Lead Screw & Dial Mounting Trestle
Spanner Nut
Handwheel
Retaining Bolt &
Washer
Figure 12.4 Parts of the Handwheel
Granite 1300 Series Operator’s Manual
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