Job completed and bike back in action. I had never taken a freehub apart before so had no idea what to expect. As this is the beginners section, forgive me while I ask some dumb or obvious questions.
1. What I undid the locknut with Shimano spline tool from a Shimano 6-speed freewheel (surprise) it made a sort of clicking whirring noise. This was caused by two radially serrated friction faces rubbing together as it undid. Is this normal? It made the same noise being done up again.
2. The hub spline is a complex thing with many different "keys" which ensure the many and various bits of the cassette can only go on in one place. is this an industry standard or are Campagnolo ones different from Shimano and others?
3. The splined shaft of the freehub shows some "hammering" fromthe sprockets, resulting in some catchy grooves on the shaft. This reminds me of the clutch centre of a Norton Commando which I had ages ago - a dreadful bit of British engineering. On the Norton this caused the clutch to not be a clutch anymore. Well, it would clutch, but not unclutch, if you see what I mean. Will this be a problem on the bike?
4. I was surprised to find the cassette was a budle of bits assemebled onto a plastic slider. Is there a way of buying individual sprockets? After all, the tiny ones are hardly used. It is the big ones that are worn out. (I am old.)
Thanks again for help and advice.