Z-axis huge slack / beginning a conversion

[black5f]

Hi. I have a Myford/Rodney mill mounted on a very nice base. This is always a problem with rack and pinion z axis. My Myford drives the rack thought a worm and wheel which is hinged so it can be diss engage. I tighten up the vertical and always approach in from the same direction (very normal on a lead screws). The hand wheels marked in thou, I reckon about 5 accuracy but its a challenge. But it drives the rack via a worm to gear everything down.

Tom

[Robin Hewitt]

I agree with John S. If you leave any springs or gears in the Z drive you will come to regret them.

Best to make the plate detatchable from the screw. That way you can still use the sensitive drill handle and you don't have to hammer against the screw when you dislodge taper tooling.

[diy-john]

Thanks, like this advice, this is what I wanted to hear. For a while thought this is it, need another mill, but now there is some light.

Had another look at the mill today.

1) Z-axis (the original question)
- Do you think it might be best to fit the ball -screw as in picture?
-- (and yes make attachment -plate detachable from screw)
- Or perhaps try to hide the screw inside the "tower"?
- Or attachment to the quill ?


2) The Z-axis screw is possible to disable. (picture)
- perhaps one could leave it there, then?
- or would you take that out altogether?


3) Noticed, actually there is slack in X/Y -axes,too.
- So while we are at it, maybe retrofit ball screws, there too?
- How to choose correct ball-screws?
-- Length: existing screws + a bit more?
-- Diameter: similar to existing screws? (does it matter if they are not quite the same?)
-- Where to go from here? Take the table apart, to measure existing screw? Make a mockup / sketch?
- View from underneath of my mill (X/Y -table)


4) X/Y -table drawing / plan of parts to change?



Would appreciate any comments (no need to answer all questions). Sorry for a long post . Thanks!