This chapter is focused on the interaction between cutting medium and freshly formed surfaces with the aim of providing a new level of understanding on the mechanics of chip flow in orthogonal metal cutting and analyzing its influence on the cutting forces and tool life in conventional milling. The first part of the chapter presents experimental results from an investigation performed with a specially-designed orthogonal metal cutting apparatus and a model material under dry conditions, with the objective of analyzing the influence of active and inert gas shields in the kinematics of chip flow, the friction coefficient, the chip-compression factor and the cutting forces. In particular, authors provide a correlation between surrounding medium, tribological conditions, surface roughness, freshly cut surfaces and chip curling at the tool-chip contact interface. The second part of the chapter extends the investigation to conventional milling of an engineering material in order to study the influence of cutting in the presence of air or under an argon atmosphere in the overall cutting forces and tool wear. Results from the investigation based on orthogonal metal cutting show that cutting in the presence of oxygen leads to higher values of friction, chip compression factor and chip curl radius, and to lower values of the shear plane angle. The presence of oxygen is also responsible for increasing the cutting forces and tool wear in conventional milling.