Cutting Tools Research: Report of Subcommittee on Carbide Tools: The Mechanism of Tool Vibration in the Cutting of Steel

Abstract

The report deals with some fundamental investigations of vibration in cutting tools. It is shown that this phenomenon may be the result of both self-induced and forced vibration. The former is a function of the cutting properties of the metal and the sharpness of the tool, while the latter depends on the interference of the tool with the surface cut during previous revolutions. Certain limitations of speed, tool frequency, and tool sharpness exist, vibration being rarely observed at low cutting speeds, at high tool frequencies, or with a freshly lapped tool. The amplitude of vibration appears to be independent of the depth of cut and seems to be limited to a value slightly in excess of that which makes the maximum vibrational velocity at the tool point equal to the speed of the work. It is governed to some extent, however, by the internal damping characteristics of the tool shank. The self-inductive influence originates from the decrease in the cutting force which occurs as speed is increased, and becomes more powerful as the wear of the tool progresses. Failure of carbide tools under vibratory cutting conditions occurs in the form of a fatigue crack which spreads inwards parallel to the top face of the tool. Photographs and profile records are given of surfaces cut under various conditions of vibration, together with a theoretical analysis of the manner in which the surfaces are formed. With small feeds, forced vibration occurs and phasing normally results. This is demonstrated by the resulting patterns on the surface, which show an orderly arrangement of the waves. A few practical examples are described.