Hi Col,

Thanks for the advice, I have been reading up on inserts, but I'm still a long way from having a clear handle on the different types.

This problem with getting consistent finish on mild steel, I've had before, but always skirted around it with extra polishing and so on.

This time, I had a chance to play around a bit and I wanted to try and understand what was happening, I think I can begin to see some of the issues a bit more clearly.

I'll start looking at uncoated inserts...........thanks for the tip... (pun intended)

PS I meant to provide link to this site, which I've found helpful for carbide insert identification. http://www.carbidedepot.com/formulas-insert-d.htm