Re: [CAD_CAM_EDM_DRO] Backlash

Blue wrote:

>Hi Group,
>
>It has been a long time since I posted or read anything from this group, and
>then it was under another email address. I've been doing other things.
>
>I have a problem with my CNC lathe in that the adjustment of backlash on the
>cross-slide is impossible to get right and I'm looking for a cheap working
>solution that doesn't require a complete redesign.
>
>The leadscrew is Acme and the nuts, there are two of them, are bronze. The
>front nut is fixed and the rear one can be unlocked and allowed to move to
>take up the backlash. The nuts appear to be forced apart by a ball under
>pressure from dished washers acting like a spring.
>
>I do not want to fit ballscrews at this stage and the leadscrew has no wear.
>Does anyone know or have a design of anti-backlash device that would make
>adjustment much easier and predictable.
>
>

The problem is your existing screw has differential wear. That means
the thread
in the most used part of the screw is thinner than at the ends. It is
impossible
to make a fixed anti-backlash nut for a worn screw. The only way to make it
work is by making one of the nuts spring loaded. This will greatly
accelerate the
wear on the screw and nut. If you replace the screw with a hand-made one or
one made from commercial screw stock, then you will at least eliminate the
variation in the thread. (Note that crossslide screws are usually
LEFT-hand thread!)

Otherwise, a small ballscrew sounds like a good idea.

Jon