Work needed

I found that the X axis bearings were knackered. Even with the naked eye you could see nasty pitting on the bearing surfaces. I managed to find some decent quality SKF bearings of the same size from The Bearing Boys and this fixed the problem on the X axis. Then I looked at the Y axis bearings. They were fine but I cleaned and regreased them.

The spindle sounded a bit noisy when I spun it up (see Youtube video in previous post) and I noticed when I first got the machine home that it was difficult to turn. So I removed the quill assembly, disassembled the spindle and bearings and replaced them with Nachi and SKF equivalents. I didn't bother to post mortem the bearings once they were out but they were noisy and gritty so changing them was the right thing to do. 

While the quill and spindle were out, I ran the motor to see how noisy it was - as I was in the bearing changing groove, it seemed a good time to check. With the VFD running, the motor was pretty noisy but once the VFD was killed, the motor was almost silent while still spinning. So most of the noise was due to the ancient Hitachi VFD. Turning the spindle speed override up and down while running demonstrated that quite clearly. Good result.