Re: [CAD_CAM_EDM_DRO] Ball-screws

Hi All,

Bill and I have, for a few weeks, been looking into the possibility of
fitting Ball-screws to my Bridgeport like machine, him in the States and me
in the Britain.

The machine will be retro-fit with CNC using DC servos.

I know there are those of the opinion that what is being done is a waste of
time and money and that a CNC machine should be bought and mine shipped to
the scrap heap. This is not an option for the simple reason of where it is
and the amount of time it took me to install it. I really don't want to do
it again.

If I fit Ball-screws manufactured in this country the cost is something in
the order of £500 an axis, $750 in your money, and they would be metric 25mm
with a 5mm lead. The dials would all have to be changed.

The travel on the X axis is 29" and the Y is 12". The lead-screw fitted at
the moment is 1" with a lead of 0.200" and 0.035" of backlash in the centre
and almost none at the ends.

Between us we have come up with just two possible companies that have
answered email and the phone.

1) McMaster-Carr

1" dia. 48" ball-screw in the two lengths, 0.004" error/foot and a lead of
0.250" including Qty. 2 ball-nuts = $166.00.

2) Rockford

3/4" dia. 48" ball-screw in the two lengths, 0.003" error/foot and a lead of
0.200" including Qty. 2 ball-nuts = $423.00.

1.150" dia. all the rest the same as above = $511.00

All are ex-stock and I believe have 50um repeatability.

Why such a difference in cost? If it is quality does the difference add up
to $257 worth on an elderly machine.

Regards,

Terry