Rotary tools or bits

Abstract

Rotary tools or bits carry cutter element including pointed contact structures and elements for chipping, cutting, and breaking non-ductile materials such as rock. The cutter elements directly contact and cut through rock and other materials and have tapered contact structure ends. Rotary tools or bits for carrying the cutter elements carry fixed cutter elements, or have sockets for removable threaded or rotatable cutter elements, arranged in straight or curved rows on the head opposite a drill-string-engaging base of the tool. The tools also have radially-extending buttresses which help to protect the cutter elements from damage as a drill string and bit are withdrawn from a bore.

Description

[0001] This invention relates to rotary tools used to drill, mill, or mine brittle formations, and it relates particularly to tools or bits using contact structures that are tapered and pointed and to cutting elements using such contact structures. Several new contact structures and cutting elements are disclosed for use in a family of earth-boring bits and of bodies for earth-boring bits.BACKGROUND OF THE ART[0002] The mining, construction, and drilling industries make extensive use of rotary tools. These tools apply intense loads to small areas to break brittle formation and structures into chips. Tapered cutting elements are commonly used for this purpose. Such elements are alternatively referred to as studs, buttons, cutters, cutting tools, and bits. A plurality of cutting elements may be attached to a holding tool. This tool may be a rotating drum, disc, or bit body. Such tools are used to mine minerals, cut trenches, mill pavement, drill holes, and the like.[0003] A cutting el...

AI Technical Summary

Problems solved by technology

In the drilling industry, the vast majority of cutting elements now in use are not replaceable.

Usually, however, the entire drilling tool is replaced when the contact structures, contact elements, or cutting elements are significantly worn or damaged.

The heat generated at the point is intense, and it may build up during times of continuous use.

The point may also itself fracture.

In harder formations, nonetheless, pointed and truncated contact structures can be damaged so rapidly that they are impractical to maintain.

This limitation has led to use of a radius or nose on the end of the contact element or structure, and the equipment employing such contact structures then applies higher forces.

Such designs have met with limited success, as the difference in hardness between the two grades of carbide used has not been great enough.

Such elements are limited to larger bit sizes, and their use is limited to shallow holes in relatively soft formations.

These bits use a relatively compact cutting element compared to the cutting elements commonly used in mining machinery because of the limited space available on a bit.

This design has not been well accepted in the drilling industry, likely because in this type of bit the bearings wear out before the tungsten carbide cutting elements do.

Polycrystalline diamond and cubic boron nitride are both substantially harder than impact grade of cemented tungsten carbide but are significantly less impact resistant.

The cost of polycrystalline diamond-coated contact structures is relatively high, and they are easily damaged and are generally not replaceable.

During use, polycrystalline diamond material has a tendency to delaminate from the tungsten carbide backing and to disintegrate.

Large numbers of diamonds are needed because the contact structures are small, they are irregular and the diamonds are brittle.

As a result the chips cut from the formation face are very small, and chip flushing is poor.

A second contact structure is adapted to cut deeper holes into soft and medium formations, and should cost more than the first design due to its increased complexity.

A third design is the most complex and is adapted to cut soft, medium, and medium hard formations, and will cost the most of the three.

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