Re: [CAD_CAM_EDM_DRO] Help Needed, Ballscrews

wanliker@... wrote:

> <<You could do some enquiries for me, as I have got no-where on the
> net.
> I am looking for Ball leadscrews for my miller. It is a Bridgeport
> look-alike. The X axis needs a 3/4" to 1" x 32" Ball-screw, plus
> flanged Ball-nut 2/10" lead. The Y axis is 15" long. I just require
> the threaded part as I'll make up my own ends. I would prefer the
> diameter nearer 3/4" than 1" as the ball-nut is larger than the acme
> nuts on the machine and it may be difficult to get them in. >>

Gee, there are guys selling 34" ballscrews on eBay all the time. I've
seen
at least 20 of them go by. Most of them go below $100. There are some
people
who must have a basement full of these, as the same types keep showing
up.
I also occasionally see the Y axis screws show up, too. Although, at
something like
$79 for a 34" screw, I wouldn't hesitate to buy 2 and cut one down for
the Y axis.

What the trick is, (I wish I'd thought of this before doing it the hard
way) is they
make a sleeve which fits in place of the bronze nut in the Bridgeport
"yoke".
The nut sits outside the yoke, attached to the sleeve. So, you just
slide the
whole assembly into the big hole (about 1.75", I think) in the yoke, and
fasten
it with the screw that Bridgeport uses to hold the bronze nut in. This
will
probably take a long-handled, screw-holding screwdriver, but it probably

means you can make the swap without even taking the machine apart.

I do not recommend small-diameter screws, as bowing under compressive
load
could be a major problem. I'm using .975" screws, and it is a small
problem
on my machine. Bowing (and torsion) of the screw shows up like
backlash.

Jon