GB2138864A

GB2138864A - Roller drill bits

Info

Publication number: GB2138864A
Application number: GB08311595A
Authority: GB
Inventors: Sho Takano
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 1983-04-28
Filing date: 1983-04-28
Publication date: 1984-10-31
Also published as: GB2138864B; DE3318100C1; FR2545530A1; AU559652B2; FR2545530B1; GB8311595D0; AU1407083A

Abstract

An insert 6 for a roller drill bit includes a body 10 made of a hard metal, and a diamond compact 11 embedded in the body 10 and having an exposed portion extending across the end face of the body 10. <IMAGE>

Description

SPECIFICATION Tips for bits in a boring device BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to tips for bits or cutters in a boring device which is used for drilling a deep hole such as an oil well, in the ground, or obtaining a geological sample of the soil for a survey of the strata under the ground.

2. Description of the Prior Art: Bits of the type to which this invention relates are shown by way of example in Fig.

1, the bits of which having been in the commercial market by Smith Tools Company, Hughes Tool Company or Varel Manufacturing Company. The bits 1 are attached rotatably by bearings 4 to the lower ends of two or three cutter branches 3 projecting from a cutter body 2 symmetrically relative to its longitudinal axis. The cutter body 2 is adapted for connection with a drill pipe. The bits 1 are forced through a well to carry out the drilling work. As a strong impact and a heavy friction are applied to tip blades on the bits, the heat of friction is accumulated in the bits. Therefore, water is supplied to the bits through the drill pipe to remove the heat therefrom. The borings are discharged through the space between the outer surface of the drill pipe and the bore wall.

Fig. 2 shows a tip 6 secured to the shank 5 of a bit 1, and having a blade 7 which cuts the wall of a bore or its bottom 8. The blade 7 has a ridge 9 which is subjected to a heavy friction as it is urged against the bottom 8 of the bore by the pressure transmitted from a source on the ground.

The conventional tips are made of a hard metal obtained by sintering a mixture of a powder of hard particles such as of tungsten or titanium carbide with a powder of a metal of the iron group such as nickel or cobalt, or such an alloy in which diamond particles are dispersed, or diamond particles per se. The hard metal is tough, since it has a structure in which the hard particles are bonded together by the binder metal such as nickel or cobalt, but it is inferior to diamond in hardness.

Diamond is hard, but low in impact resistance. The harder the material, the higher it is in wear resistance. The wear of the hard metal starts to occur in the binder metal, whether it may contain diamond particles or not, and its chipping becomes serious with the separation of hard particles. The application of an impact to diamond gives rise to its gradual chipping.

SUMMARY OF THE INVENTION It is an object of this invention to eliminate the drawbacks of the prior art and provide an improved tip for a bit in a boring device. This object is attained by a tip which comprises a body made of a hard metal, and a man-made diamond compact embedded in the body so that it may be exposed along the top of a ridge and along the entire length of the ridge.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal sectional view of a conventional bit for a boring device; Figure 2 is an enlarged view taken in the direction of an arrow in Fig. 1, and showing the relationship of the bit, tip and bore wall; Figures 3 to 5 show a tip embodying this invention in front elevation, side elevation and bottom plan, respectively; Figures 6 to 8 show another tip embodying this invention in front elevation, side elevation and bottom plan, respectively; Figure 9 is a side elevational view of the diamond compact employed in the tip shown in Figs. 6 to 8; Figure 10 is a bottom plan view of still another tip embodying this invention; Figure 11 is a side elevational view of the diamond compact employed in the tip shown in Fig. 10; and Figures 12 and 13 are bottom plan views of further embodiments of this invention.

DETAILED DESCRIPTION OF THE PRE FERRED EMBODIMENTS Referring first to Figs. 3 to 5 of the drawings, a tip 6 embodying this invention comprises a generally cylindrical body 10 formed from a hard metal, and having a symmetrical roof-shaped end which defines a ridge 9 in its center. The hard metal is of the type which has hereinbefore been described. A generally T-shaped diamond compact 11 is embedded in the roof-shaped end of the body 10, and exposed in a blade 7 and along the entire length of the ridge 9.

Referring to Figs. 6 to 9, a tip 6 according to another embodiment of this invention comprises a generally cylindrical body 10 formed from a hard metal, and having a spherical end surface. A diamond compact 11 is embedded diametrically in the spherical end of the body 10, and exposed in such a way that it may form a straight line when viewed in bottom plan, as shown in Fig. 8. The diamond compact 11 is a part-circular member as shown in Fig. 9, and has a radius which is equal to that of the spherical surface of the body 10, so that it may not project therefrom.

In practice, a plurality of these tips are attached to the shank of a bit in such a manner that their diamond compacts 11 may lie in parallel to the direction of rotation of the bit.

Different forms of tips embodying this invention are shown in Figs. 10 to 1 3. The bore drilled by the bit does not always have a flat bottom surface. If the bore has a stepped bottom surface, some of the tips are required to cut a vertical surface of a stepped portion.

In such a case, the body 10 of the tip is likely to get worn by friction if the diamond compact 11 js provided only along the ridge 9.

This problem is solved by the tips shown in Figs. 10 to 13. The tip 6 shown in Fig. 10 has additional diamond compacts 1 2 embedded in the hard metal at right angles to the diamond compact 11. The diamond compacts 1 2 are shown in side elevation in Fig.

11. Figs. 1 2 and 1 3 show a greater number of additional diamond compacts 1 2 which are radially disposed.

According to this invention, a diamond compact or compacts are embedded when the body is made of the powder of the hard metal, and the assembly is sintered in a customary way.

According to the tip of this invention, the heavy friction to which the blade 7 and the ridge 9 are subjected as a result of the pressure being applied therethrough to the bottom of the bore being drilled is borne by the diamond compact 11, or compacts 11 and 1 2 so that the hard metal body 10 may be protected against any substantial wear. The hard metal body 10 is sufficiently tough to absorb any impact arising during the drilling operation to protect the diamond compact or compacts 11 and 12. The tip of this invention, therefore, has a longer life than any conventional tip. The tip of this invention is particularly beneficial for use in a bit area having a relatively small radius of rotation where the tip is subjected to a friction rather than an impact.

Claims

1. A tip for a bit in a boring device, comprising a body made of a hard metal, and a diamond compact embedded in said body and having an exposed portion extending from a blade along the entire length of a ridge defined adjacent to said blade at one end of said body.

2. A tip as set forth in claim 1, wherein said diamond compact forms a straight line along said ridge when viewed from below said end of said body.

3. A tip as set forth in claim 2, further including a pair of additional diamond compacts disposed at right angles to said first mentioned diamond compact.

4. A tip as set forth in claim 2, further including a plurality of additional diamond compacts disposed radially relative to said first mentioned diamond compact.

5. A tip as set forth in claim 1, wherein said diamond compact is generally T-shaped when viewed from below said end of said body.

6. A tip as set forth in claim 1, wherein said diamond compact is embedded in said body when said body is made of the powder of said metal, the assembly of said body and said compact being thereafter sintered in a customary manner.