I have tried many kinds of inserts and different cutting speed but still unable to get a good finish on mild steel. Achieving it on stainless steel , brass and aluminium is super easy. I can get a better finish on mild steel by using sharper inserts designed for fine cutting but the result is still poorer than that obtained on other metals. May I know if there are things that I have missed ? The picture below shows the typical finish I get . With the same insert, the finish on stainless steel is close to mirror like.