COMPOSITE TOOL INSERT

摘要

A tool insert comprises a substrate (10) having a support surface and a support ring extending laterally from the support surface. The support ring is sized to define a recess (14) within the confines thereof and a shelf about the periphery thereof. A layer (12) of ultra-hard abrasive material is located within the recess and bonded to the substrate and the support ring (16), and presents a primary cutting edge (22) for the tool insert. A protective layer (18) is bonded to the shelf about the support ring so as to protect the primary cutting edge. The protective layer provides a secondary cutting edge (20) for the tool insert, the depth of the protective layer being selected so as to be sufficient to protect the primary cutting edge whilst cutting, milling or drilling through a first substance but to expose the primary cutting edge upon encountering a second substance.