An Account of Some Experiments on the Action of Cutting Tools

Abstract

Ilztroductiim.-The mode of action of cutting tools has been the subject of much investigation on account of its great importance t o mechanical engineers, who carry out a very large proportion of their work by aid of machinery designed to provide the most efficient action of various tools for shaping metals and other materials, but so far it has apparently not been studied by photoelastic methods.As a preliminary to the description of some experiments which have been made by aid of polarized light at the suggestion of the Cutting Tools Research Committee, it may be of interest to recall, very briefly, the principles upon which such experiments are based.Nearly all transparent bodies when loaded become doubly refractive, and a ray of ordinary light passing through the material in a state of stress is subjected to a selective retardation whereby its transverse vibrations lag one behind the other.No effect is visible to the eye, since ordinarylight consists of such a complex system of transverse vibrations that the eye is unable to detect what is going on, but if ordinary light is, as it were, strained through some kind of sieve whereby a homogeneous character of a particular kind is imparted to it, the effect of stress in the material becomes apparent.The most convenient apparatus for obtaining the homogeneous light mentioned above is a crystal of transparent calcium carbonate, cut in a special way, invented by an Edinburgh r h I E I.MEcH.E.