[Mr-Potato-Head]

Thanks for the add! I’m in the beginning phase of converting a 14/40 lathe to centroid cnc but not just cnc, full manual and cnc! Please save your criticism, I’ve heard it all! Here’s where I’m at, I’ve solved for most of this conversion but the cross slide has me stumped, if I replace the lead screw for a ball screw, it won’t hold position for manual operation ( will have a crank on one end and motor on the other) I want to be able to fire up the lathe and use all of its manual functions without powering on the computer but can only see a few options.

One I attach a ball screw beside the cross slide ( with a protective cover) and let it back drive or uncouple it for manual moves with the manual lead, problem is uncoupling the factory lead will be much harder than a semi exposed ball but for motorized moves.

Two, I mill a dove tail into the sides of my cross slide and make a second cross slide that will piggy back on it. When in manual I lock the two together and let the ball screw back drive (if it will freely, that question comes later) and when under cnc I uncouple and let the top slide float on the bottom one which will be locked in position with it’s gib.

Three, I swap out the lead for a ball screw and use a brake, this gets even trickier in my mind because from what I understand, ball screw brakes require current, so how do I apply the brake without constantly having to toggle a switch? Maybe I can make the crank touch sensitive so when my fingers are on it, it’s open but soon as I take my hand off, it’s locked, like the touch lamps I played with as a kid... (I think that’s more engineering than I’m capable of, but maybe it’s pretty simple of it can turn a $30 lamp on and off?)

Anybody else do anything similar or am I a ugly unicorn?

If I leave a ball screw coupled and try push it around with the lead screw, will it add significant resistance? ( motors will be powered off and directly connected so they should spin somewhat freely?)

Is there such a thing as a mechanical brake?

Should I just hold it with both hands and hope for the best?

I can make more room under the slide for what ever needs to be there, I planned actually to mill matching dovetail into a milling table to make gang tooling easier and increase range for aforementioned gang tooling.

Penny for your thoughts.

[Sterob]

I won't comment on your beauty, but my first thought was to just have the ballscrew and stepper,and use a MPG as a electronic handwheel?
I guess you won't have any 'feel' when your machining. That might be a deal-breaker.....

[Mr-Potato-Head]

It takes away all the manual functions, the goal here is to be able to use the machine in full manual mode when control is powered off.

[mactec54]

It takes away all the manual functions, the goal here is to be able to use the machine in full manual mode when control is powered off.

It is quite easy to add a simple drag brake pushing on the on screw or cross slide, just a spring loaded Nylon or Delrin block, just adjust the loading to stop any back movement of the screw when you want to use it in manual mode

It does not take very much pressure to do this, can even add it to the hand wheel with a thumb screw to adjust it, there are many way to do this just get creative and think about it