Greetings.

I'm the owner of some very cheap chinese C7 (so they say) rolled ballscrew. Diameter 20mm/pitch 5mm.
Obviously backlash is present and in a reasonable amount for the price but yet too big for my purpose. I was thinking about putting a double ballnut without replacing the screw but it is hard to find dealers that sell only the nut and also I'm not sure if I want to spend money on upgrading something that is not good in the first place (accuracy of the pitch isn't great too).
So I was wondering if it is possible to just replace manually the balls inside the nut and replace them with slightly bigger ones so to give preload to the screw.
Did someone ever tried to do this? Any suggestion on how much each ball bearing should be bigger (I have plenty of torque with the motors and I don't care too much about the life of the ballscrew)?

Thanks.