Re: Anti-backlash on Taig mill

--- In CAD_CAM_EDM_DRO@y..., Steve Blackmore <steve@p...> wrote:

> On Mon, 13 May 2002 16:07:51, you wrote:
>
> >Even if the screw is tensioned, that has no effect on the lash at

the nut,

> >none!
>
> Not a screw - it's a nut????
>
> It preloads the thread against the nut - I admit it's not "true
> anti-backlash" but loosen it off and see what happens ;)
>

I suspect that the various contributors to this thread are talking
about (at least) two different things:

- The contribution of end-float in the leadscrew to backlash, and

- The contribution of wear in the axis feed nut & leadscrew to
backlash.

As far as I can tell, Steve has been describing how the first of
these is controlled - there is a nylock nut on the (motor) end of the
leadscrew that is adjusted to preload the leadscrew bearings &
thereby adjust out any end-float in the leadscrew. Crank this up too
tight & the bearings will run rough; too loose & there will be
measurable end float that will be visible as backlash for that axis.

The second source of backlash in the Taig mill setup is the feednuts
themselves. These are substantial brass (bronze?) nuts - about 1"
long, and slit axially along one side. A certain amount of adjustment
of backlash in these nuts is possible by removing the leadscrew &
nipping them up to decrease the size of this axial slit. Not terribly
controllable, however!

The third source of backlash on the Taig, which no-one has yet
mentioned in this thread, is that the motor couplings transmit power
via four Nylon quills - these are about 1/8" diameter & made from
stiff Nylon tubing, pressed into matching pairs of holes in each half
of the coupling. This arrangment has always seemed somewhat crude to
me (although it tramsmits the power just fine & is undeniably
cheap/easy to make) - it is an obvious point where wear will occur,
and poor fitting of the quills in their holes will contribute to the
backlash. I have it on my list to replace these couplings on my Taig
with something more sensible - perhaps an Oldham coupling with a zero
backlash torque disc, for example. This would also make it a simpler
job to remove & re-fit the motors - lining up the 4 quills with their
matching holes is not easy.

Regards,
Tony