TABLE OF CONTENTS All machining, whether heavy single-point planing or turning, form-tool turning or milling, grinding, honing, or lapping, involves essentially the same process at the point where the cutting tool meets the work. Figure 4.1.1 illustrates this process.
Material lying in front of the cutting tool is compressed as the tool advances and fail in shear in a narrow zone extending at an angle from the cutting edge to the surface of the workpiece ahead of the tool. For practical purposes in single-point cutting this shear zone can be considered a plane. As the cutting tool advances into the work, the shear plane also constantly moves forward. The material that passes through the shear plane is deformed. This material comprises the chip. In the case of ductile materials, it is apt to consist of a continuous ribbon of deformed and heated metal moving away from the workpiece along the face of the cutting tool. In the case of nonductile or brittle materials, the shear action periodically causes fracture, and the chips consist of discrete pieces rather than a continuous ribbon of material.
Since the energy expended in cutting is manifested as heat, the chip, the cutting tool, and even the workpiece experience a considerable rise in temperature. This temperature rise can be reduced when a fluid coolant is applied to the cutting tool. In addition to reducing temperature, the coolant lubricates the tool in its movement against the workpiece and, more...
