Screw options for small knee mill

[cncuser1]

I have an old knee mill, made from castings.
It is table top, so about half or 2/3 the size of the commonly known Sieg X2.

It will be used for manual milling only, no CNC.
It is fairly accurate but the 5/8" acme screws and nuts should be replaced. (Could use a good scraping too.)

My question is are ballscrews an option?
I know double nut ballscrews are great for reducing backlash.
Also backdriving the screws from cutting forces may be an issue.
I have 1/8" pitch Amce now so I'd be looking for something in that range.

I'm wondering if there are any great benefits to manual milling with ballscrews or should I KISS ( and stay with Acme)?

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[awerby]

You could use a ball screw for this. There's enough loading from the weight of the bed that backlash won't be an issue, even if you were using it in CNC mode to drive Z, Since it's a manual mill, the only advantage to the ball screw would be less work for the motor to do; you shouldn't use dual nuts as that will just add friction. And you don't need an expensive precision ball screw either; the window-closer type would work fine.

[cncuser1]

You could use a ball screw for this. There's enough loading from the weight of the bed that backlash won't be an issue, even if you were using it in CNC mode to drive Z, Since it's a manual mill, the only advantage to the ball screw would be less work for the motor to do; you shouldn't use dual nuts as that will just add friction. And you don't need an expensive precision ball screw either; the window-closer type would work fine.

I was questioning about all 3 axis.....Are ballscrews advantageous for light, small, manual milling? In what way?

[awerby]

Ball screws are easier to back-drive, so you'd need to lock down any axes you weren't using at the time. They'd be more expensive than regular acme leadscrews, and unless you bought ball screws with great precision, probably less accurate.