Composite tool insert

Abstract

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.

Description

technical field

[0001] The present invention relates to a tool insert. Background technique

[0002] The use of diamond compacts, also known as PCDs, as cutting elements is well known in the art and is widely used in various cutting, drilling, milling and other abrasive operations because diamond cutting The knives are highly wear-resistant. But diamond cutting knives are not always suitable for all substrates encountered. As is known, diamond tools cannot be used satisfactorily for milling or drilling through ferrous substrates, such as steel. The result is that the use of diamond cutters is unsuitable when it is necessary to mill through a steel sleeve used to line a vertical borehole or shaft in a downhole drilling operation.

[0003] Due to the interaction with ferrous materials, PCD is not suitable for drilling through steel casings, and a drill liner is required instead. Tungsten carbide cutters are therefore usually used in drills to mill through steel sleeves. O...

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