Martyfrom your photo's it appears that you are cutting 90* (angle of lathe bit), and cutting from the headstock to tailstock.You are using just the very tip of the insert, to cut, you should have a rounded end on the bit,(you don't want a sharp/pointy tip on the insert), makes for a rough finish.you can get better finish by angling the tool/insert towards the tailstock, approximately 45*,so you are using a more slicing angle when cutting on the inserts side,when cutting from the headstock to tailstock, make sure you have the clearance at the at the center,for finishing the cut.I am cutting at 350 rpm on Delron/Teflon and getting glass smooth finishes, by using a slicing angle cut on the lathe bits with a rounded cutting tip etc. Do some experimenting on changing the angles and tip designs of the lathe bits, if using carbide bits, you'll need a green cutting wheel to sharpen them......... I use 90* HS steel bits, carbide does cut as fine for me.HTH's,Don