To cut a long story short; I've revived my CNC mill, from being sat on my bench doing nothing for around 9 months because of a damaged spindle.
I got a new spindle custom made for the machine, just fitted it tonight; switched on, booted up, and put the thing into first gear...

However: The X-axis sounded VERY ODD.
Took a closer look, and it is missing steps BADLY + stalling very often.

If I jog X+ and it starts to stall, giving it a little nudge tweak on the ballscrew brings it back into movement.
It does stall/jitter in both directions, but more so in one that the other.
Turning the ballscrew by hand doesn't mechanically feel that sticky; which is what has confused me.

I removed all the bellows, gave it a good clean (not that it needed much) and oiled all the ways and ballscrews. Ran it back and too, to let it soak in. And still the same.

If I send single steps, then it just jitters back and to on either step.

At the highest feed rates (1320mm/min) it doesn't seem to have this problem. Just anything less than this causes the issues...

SO: Is this a "bad stepper" one on it's arse? Or a mechanical issue?
It would be a *MASSIVE* pain in the arse to fully remove the X-axis and investigate in detail, so I'm not jumping to that immediately.

Anyone any ideas?
Cheers,
Dan