Civil Engineering Reference
In-Depth Information
Fig. 11.21. Spot the rest of the holes.
Eliminating backlash
You have now drilled all 12 holes in the correct position without any errors from back-
lash in the feed screws. You can always eliminate backlash by going back a couple of
turns and then moving to the starting point again. As long as you only drill holes when
you are moving the same way, the holes should always be in the correct position. If
you did accidentally wind past the required hole position, just wind back a turn or two
and then move up to the hole again. By going back a couple of turns, and then moving
forward again, you are taking the backlash out of the equation and ensuring you are
drilling the holes accurately.
Review the method
If this is not all clear, read it through again doing the moves in your mind using the
drawing. The principle will work for any component you care to machine. Yes, you
might have to redraw the component out differently or redo the dimensions from the
datum rather than from an existing datum or centre point, but it will save you time and
stop you from scrapping work. Do make sure you double check your dimensions care-
fully if redrawing the component's co-ordinates.
As well as being relevant to machines without a readout, I have used the same prin-
ciple of reducing backlash on a worn-out CNC machine and reduced errors to within
drawing limits.
