z axis ball screws

[mddolson]

Due to a lack of available $ (funds) I am now looking at a staged approach to converting my 3 in 1 to cnc.

I'm now considering converting to ball screws first , then to cnc.

Has any one done a ball screw conversion on the z-axis on a Smithy, HF or Craftex 3in1?

The x and y axes are pretty straight forward, but the z axis looks like a bit of a challenge. The quill has about 1/32" back lash in it.

There is a collar/ring at the base of the spindle bearing.
This could be replaced by a ring clamp plate, to mount the hardware.
Next comes the screw, nut/drive pulley.
I've considered mounting the screw solid into the plate, and rotating the nut, against thrust bearings.
The alternate would be to fix the nut against the milling head and rotate the screw in bearings secured to the ring clamp plate.

I'd be interested in hearing from anyone with experience on this.

Mike D

[philbur]

Have you looked into the potential problems, due to the increased pitch and also lack of friction, when manually operating a machine fitted with ballscrews.

Phil

Originally Posted by mddolson Due to a lack of available $ (funds) I am now looking at a staged approach to converting my 3 in 1 to cnc. I'm now considering converting to ball screws first , then to cnc. Has any one done a ball screw conversion on the z-axis on a Smithy, HF or Craftex 3in1? The x and y axes are pretty straight forward, but the z axis looks like a bit of a challenge. The quill has about 1/32" back lash in it. There is a collar/ring at the base of the spindle bearing. This could be replaced by a ring clamp plate, to mount the hardware. Next comes the screw, nut/drive pulley. I've considered mounting the screw solid into the plate, and rotating the nut, against thrust bearings. The alternate would be to fix the nut against the milling head and rotate the screw in bearings secured to the ring clamp plate. I'd be interested in hearing from anyone with experience on this. Mike D

[mddolson]

potential problems?

I believe I have. My intent is to use 0.20" pitch ball screws, with 10:1 pulley reduction between cranks and screws. This would reduce a single turn movement on the crank to 0.02" feed. If additional friction is needed I was considering putting a friction clutch on the crank.

Mike D