Axminster SIEG Super X1 Micro Mill Ballscrew Upgrade and Modifications. ... Underside view of the X axis showing the ball nut and stepper motor mountings. New thrust bearings ordered from Simply Bearings in the UK, a pair of 19mm outer, 6mm inner thrust bearings and a single 8x3x4 bearing for support. ... Y axis ballnut and screw fitted to the ...