Retrofiting an old big milling machine

It has leadscrews also if i put the motors in the position of handwheels
it will have backlash from reduction gears plus backlash from leadscrew nuts.
I have read somewhere what you can pure inside leadscrew some material
like moglice and fix the backlash plus this material has lower friction than bronze nut.

I have read somewhere what you can pure inside leadscrew some material
like moglice and fix the backlash plus this material has lower friction than bronze nut.

I have done moglice nuts and they work surprisingly well if the screw is not worn too much. Ball screw is a better option in general.
If you want to go the moglice route, I would check with your supplier on pricing. It's not cheap. It's a system (type for nut/bearing FLP, I think it was) and you need to get the release wax they recommend and lapping compound that does not imbed. Timesaver yellow is what I used.
The process in a nutshell is to bore out the old nut, place it on the least worn section of prepared/waxed screw, fix it radially concentric to screw, seal and cap the openings and fill with moglice through a low point fill port. You'll need a vent and dam at the high point to capture excess resin. You want to fill it with minimal chance of trapping air. Make sure there are no leaks as the resin takes some time to gel and it can run out of the nut housing if you're not careful. When set, you have to break it free from the threads which should work okay if screw was waxed. Final lapping in place will get it to the feel you want.

I have made (many years ago) a new lead screw nut but the backlash is still there in the worn section.
A new lead screw and nut fort he lathe reduced almost all the backlash.
The ball bearing nut block and ball shaft have very little friction an almost nil backlash. The time required to try and repair the lead screw / nut,if it is possible to fit a ball screw system, is not worth the effort .
Cheers john

Interesting link there Andy. I'll have to try that sometime just for experimentation.

The leadscrews for x/y are 32mm and for z 65mm so are thick
ballscrews of this diammeter will have a serious cost also the ballnut is more bulky.
If put thinner ballscrews than leadscrews for example 25mm for x/y and 50mm for z
to have space for ballnut mounting and reduced cost will be ok?
Because it is knee mill the table up/down is z axis and table is about 1000+ kg
the weight force eliminates the z axis backlash ballnut automatically?

@OT-CNC which was your moglice supplier? What is the price?
I have not found a moglice supplier yet.

@OT-CNC which was your moglice supplier? What is the price?
I have not found a moglice supplier yet.

In the US, I get it from Devitt.
It's a German product if I recall correctly. Diamant polymer in Germany or maybe others in Europe sell it??
You'll have to check with them on cost.

Before you go that route inspect your screws carefully. Stone and polish any high spots/ nicks on the od and threads. When you cast the material it basically locks in. Any irregular high spot will bind during lapping. The wax layer is critical. It controls to some extent how much play the nut will have prior to lapping and allows you to brake it free. If you over apply, you have play, under apply and the nut is very difficult to brake free. If you need more details, I can dig into it deeper...