How do I improve the accuracy of a 2418 mini CNC mill?

I’m pretty happy with my 2418 mini CNC mill, it worked well and didn’t need any calibrating. It seems to be within about 0.5mm straight out of the box, impressive for something that only costs a few hundies. However, the most obvious improvement is reducing the amount of backlash or ‘webble wobbles’ out of the leadscrew. The ball-nut had a very loose fit and wriggles around before transferring power and moving the sliding components.

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