An Investigation of some Shear Angle Theories

Summary In most shear angle theories in metal cutting, the relation between shear angle and other parameters, such as the mean angle of friction on tool face and the contact length between chip and tool, has been usually pursued on a steady state deformation process. But, it is difficult to make clear the reason why the steady state deformation of chip can be derived from each set of cutting conditions. In this study, an orthogonal dry cutting test was carried out using a carbide tool (P20) and diamond tool with the purpose of studying the compatibility of a machining equation. Intermittent cutting tests were also performed to study a transient chip formation. From an experimental result obtained in the cutting with a diamond tool, it was clear that the equation including the relation between shear angle and two machining parameters (rake angle and the product of cutting speed and depth of cut) is most adaptive as a machining equation. The reason why the shear angle depends on the product of cutting speed and depth of cut is as follows; the cutting temperature affects largely the chip material seizure on the tool face, and also, the thickness of secondary deformation zone. The chip material seizure and the thickness of secondary deformation zone are thought to be main causes of the variation in shear angle. As a result, it is concluded that, as temperature is approximately proportional to the product of cutting speed and depth of cut, the shear angle depends on the product of cutting speed and depth of cut.