Having read the above article I thought I'd check my bearings as described. The initial measurements taken at the nose showed pulling the chuck upwards gave a deflection of at least 3 thou while pulling down was less than a thou and backwards and forwards less than a thou as well.

Removing the bearing caps and the shaft for inspection showed the shaft to have very little wear. Likewise, although the bearing shells showed some wear marks they weren't in bad condition considering the age of the machine.

However, applying blue showed that the top of the front bearing was barely in contact with the shaft at all – that would explain the play only in the upwards direction. The blue had been applied with the shims removed and the bearings tightened until the shaft would not rotate and then slackened off until rotation was possible.

Here are a couple of pictures:

Here you can see the lack of contact.

This picture shows blue showing that the white metal bearings are touching, just, and not the bearing caps themselves when assembled without shims. It is also visible on the right side of the shell on the bottom of the picture that a recess has been milled along the edge of the shell. There is a corresponding milled edge on the other half of the bearing. (not by me)

Before I try to fix this, I'd thought I'd ask for your opinions of what to do and of any other things to test for. Thanks in advance.

Thanks for the words of advice. I was very reluctant to start cutting away at metal, given that this is the first time I've played with white metal bearings. I do have a small scraper that I inherited but have never wielded it in anger before. I'll go and have another try this afternoon and let you know how I get on.

Having reassembled the lathe I now have less than a thou movement on the nose in all directions. However, I ended up not adjusting anything! All I can think is that the front bearing housing just needed tightening up a little rather than re-shimming or scraping. Still I'm not complaining as:

a) The shaft is now in spec for bearing play;

b) I got to learn more about my machine long the way.

Thanks Pete B for another interesting and useful article