Cutting under active and inert gas shields: A contribution to the mechanics of chip flow

Abstract

This paper is focused on the interaction between cutting medium and freshly formed surfaces with the aim at providing a new level of understanding on the mechanics of chip flow in metal cutting. The methodology draws from specially designed orthogonal metal cutting experiments performed in dry conditions under active and inert gas shields for observation of chip flow and measurement of friction, chip-compression factor and forces acting on the cutting tools. The presentation is a step towards clarification of common belief among researchers and practitioners that active gases influence metal cutting by showing that oxygen acting on the freshly cut surfaces of lead may change friction, chip compression factor, chip curling and forces to a level that goes significantly beyond what has been said and written in the context of metal cutting fundamentals. The overall content of the paper is original and discloses new experimental results and explanations about the influence of the surrounding medium on tribological conditions at the tool–chip contact interface and about the correlation between surrounding medium, surface roughness, freshly cut surfaces and chip curling.