THROWAWAY CUTTER AND THROWAWAY TIP

摘要

This invention relates to a negative type throwaway tip in a square flat plate form in which each of ridges at which the upper and lower surfaces intersect four side surfaces thereof at right angles respectively is adapted to work as a primary cutter and, at one longitudinal end of each primary cutter, a secondary relief surface is formed in such manner that it increasingly largely recedes from an imaginary extended line of a primary cutter as it advances from a midpoint of a cutter toward the corner of the upper or lower surface. The ridge at which the end on the corner side of a secondary relief surface intersects a side surface works as a secondary cutter. When said throwaway tip is fixed to the tool proper so that either upper or lower surface thereof is adapted to work as an outer peripheral relief surface directed toward the outer periphery of the tool and to gradually sharply incline to the outer periphery of the tool in the radial direction as it extends from the forward end of the tool along the axial direction toward the rear end, and so that a rake angle in the axial direction of a primary cutter directed toward the rotational direction of the tool at the outer peripheral side of the tool is made negative, a front relief angle is provided to a secondary cutter continuing to the forward end of the primary cutter.