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I've had better luck using sharp, positive rake inserts intended for aluminum, even on steel. I've not found the negative rake or brazed carbide to be useful on a light lathe.
On Wed, Jul 13, 2022, 10:46 PM Mike Poore <mpoore10@...
I am sure this is not the first time for this topic, but I'd like to know what setup, if any, anyone has found that provides a good surface finish using carbide on 1018?
I have acquired a lot of carbide inserts and holders along with my QCTP. I have negative rake and no rake holders. I have chipbreakers and flat carbide. I turned some aluminum after rebuilding the lathe and the surface finish was as good as one could expect so far as it was nearly a mirror finish using the slowest feed. Then I tried 1018 with the same tooling and ended up with a fairly rough finish. It looked and felt like the metal was tearing rather than cutting. I have tried other combos and nothing yet is satisfactory. I have a diamond disc sharpener, but I think the carbide is sharp enough to do better than it is. There is plenty of HSS laying around that could be used, but the idea of indexable carbide would be preferred if I can make it work.
There is plenty of experimenting left to do. I was hoping someone could give me a starting point as far as insert shape, rake, speeds (I am guessing it might be a little different than what the book says for an old WWII cast iron bearing lathe.), and tool angle. Thanks for any help.