Z-axis mill drive

[Nzoldun]

Newbie to the site. Has anyone tried using the fine down-feed on a mill-drill as the Z-axis CNC? My mill spindle is heavily spring biased upwards - it requires about 750 oz-ins on the main lever to start to move down, but only about 60 on the fine feed. Because it's hobby only, speed will not be an issue, but I wouldn't want it to 'bounce.

[chich2]

Welcome Nzoldun,
I have seen 1 bloke do it but I would suspect it would not be very acurate due to the backlash found in the gear reduction of the fine feed and also the backlash from the rack and pinion on the quill.

Chich

[Torsten]

There are two methodes I am aware of to convert the Z-Axes drives.

1. disregard the downfeed mechanism and implement a Ballscrew.
The benefit of this Methode is very little Backlash and very fine controll of the Axes movements Ideal for fine work and Engraving.
The drawback is the offcenter location off the Ballscrew on the Quill.
This will create some sideway forces that will increase with load aplied and
when the quill is extended out.

2. Using the Finefeed handle to Drive the Z-Axes.
This will be a more sturdy way of driving because it uses the Mechanism
the way the Machine whas designed to be used.
The Mayor Problems with this approch is the elimination of Backlash in both
the Rack and Pinion and the Wormgear.
Even with the best approch on this you will probably not be able to match the same Backlash free behavior of the 1st Methode.
My personal oppinion if you can live with 0.002 Backlash and want a sturdy
Design this may be the better way to get there.
Do not underestimate the difficulty in removing the Backlash, if done right this way it will not be a easier implementation by compareson.

Good Luck