The problem of chip disposal has become more acute with the invention of high speed carbide and ceramic tools. An intruding protrusion in the normal flow path of the chip has been found to be an effective method for chip-control. A study of the variables of the mechanics of chip formation, viz. an analysis of cutting forces, chip thickness and dynamic shear strain in relation to the size and location of the intruding protrusion reveals some interesting characteristics. This paper attempts to present a physical explanation of such behaviours of the cutting variables.