Hi, Thanks for the quick replys. I realise I'm running the tool backwards, it's not something I usually do but I was just trying to see if the same problem occured whilst the tool was working in that direction.
I remade a slug with a tight fitting shoulder, made no difference at all. I am also using new inserts, the CCGT are very sharp. I've tried taking light cuts of 0.1mm so not to load the live center end and it makes no difference I still get the banding along the length.
Logically trying to work out the problem, it's worse at the tailstock end so I would expect there's movement there somewhere although I have the live center well tight against the stock.
As i'm using new inserts there may be rubbing going on so I have reset the tool height several times above and below as well as on center.
As I have found that by running the tool backwards I get a very nice finish I am trying to think why, If the problem was with movement of the material I would have expected a poor finish in any direction.