Re: Z axis conversion

stratton@... wrote:

> From: stratton@...
>
> > >
> > > Can someone point me in the right direction for info on
> converting
> > >
> > > the "Z" axis of a Bridgeport-Type mill. I'm reffering to the
> > > mechanicals of getting a backlash free mechanism. Is there a worm
>
> > > gear
> > > in there or what?
> >
> > The hardware in the Bridgeport M and J heads is hopeless for CNC.
> > There is a worm drive from the fine feed handle to the quill pinion.
>
> > Then, the quill rack and pinion drive adds even more backlash.
> > I pulled the quill pinion completely out, and drive the quill by a
> heavy
> >
> > coupling that attaches where the depth stop ring used to attach,
> > through the slot in the front.
>
> I recently got to play with an Ez-Trak CNC Bridgeport. They drive the
>
> quill through a bracket that clamps around the end of it like a shaft
> collar, reducing travel by 3/4" or so. The odd part is that this
> bracket is moved by a ballscrew actuater located a huge distance (>8")
>
> off the side of the spindle axis to the side of the head. I can't
> image how it manages to move without binding, but it does fairly well.

Whaat? When was this machine built? We just got a Bridgeport Series-I
EZ-Track about
2 months ago, and I felt very smug to see that it is actually VERY
similar to my setup.
The ballscrew is mounted from the bosses that the depth stop rod
attaches to, and the
quill is driven from the place where the depth stop ring attaches to the
quill on a manual
machine. The framework is just a little different, and they have fancy
parts that practically
make it hermetic to the side of the head (to keep chips out of the
screw) but functionally
it is really similar to what I did. The center of the ballscrew is
about 2.5" directly in front
of the surface of the quill. That makes it about 4" from center to
spindle center.

Hmm, on second thought, that sounds familiar. I wonder if Bridgeport
bought
a few Z drives from Anilam some years ago, before coming up with their
own
design?

Jon