removing backlash from rack/pinion drives wasRe: Shoptask Z-axis - quadralift?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@y...>
wrote:

>
> Never seen that approach. But...
>
> What is typically done is similar. The GEAR is split (or two
> narrow gears are used if you prefer<G>) and these two "halves"
> are sping loaded (rotationally) against each other.
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, ccq@x wrote:
> >
> > It might require a wider than usual gear/rack, but what if
> > you took a slitting saw, and slit the rack right down the
> > middle. lock one half down as usual, and then slide the
> > other half lengthwise, one direction or the other, until
> > all the slop is taken out. Would this be workable, or
> > just engender extreme wear, or sosmething?
> >

Splitting the rack will not work here - the "rack" in question
is actually the quill of the machine! Splitting the gear is
a possibility, however the backlash will return whenever the
cutting force overcomes the spring force. You'd need a very
strong preload spring.

IMHO, the right way to solve the problem is to eliminate
the rack and pinion drive completely, and use a ballscrew.
I've got my Z-axis ballscrew mount designed and half built,
hope to have it done in another week or so. Tonight I start
the "banjo" (the part that attaches the ballscrew to the
nose of the quill).

John Kasunich