CA1235112A - Drill bit - Google Patents
Drill bitInfo
- Publication number
- CA1235112A CA1235112A CA000478795A CA478795A CA1235112A CA 1235112 A CA1235112 A CA 1235112A CA 000478795 A CA000478795 A CA 000478795A CA 478795 A CA478795 A CA 478795A CA 1235112 A CA1235112 A CA 1235112A
- Authority
- CA
- Canada
- Prior art keywords
- axis
- drill bit
- face
- spigot
- drilling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
DRILL BIT
A drill bit for drilling bore holes in underground formations comprising a bit body with a connecting spigot for connecting to a drill string or the like, and a cutt-ing head which comprises a circumferential face extending parallel to its longitudinal axis and an end face having a drilling axis which is aligned with the axis of the connecting spigot. The drilling axis is parallel to and is offset relative to the axis of the cutting head. It is preferred that the end face is, at least in part, con-ical in shape.
DRILL BIT
A drill bit for drilling bore holes in underground formations comprising a bit body with a connecting spigot for connecting to a drill string or the like, and a cutt-ing head which comprises a circumferential face extending parallel to its longitudinal axis and an end face having a drilling axis which is aligned with the axis of the connecting spigot. The drilling axis is parallel to and is offset relative to the axis of the cutting head. It is preferred that the end face is, at least in part, con-ical in shape.
Description
51~Z
DRILL BIT
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to drill bits and more part-ocularly concerns drill bits for use in drilling bore holes in underground formations.
5 Description of Prior Art U.S. Patent No. 2,953,3S4 describes a drill bit for drilling bore holes into earth formations. The drill bit includes a cutting head which has a circumferential cult-in face and an end cutting face both having an axis 10 which is spaced from the axis of rotation of the drill bit during drilling. This arrangement produces an eccen-trig rotation of the cutting head so that the bore-hole produced is larger in diameter than the diameter of the cutting head.
This arrangement has the advantage that it can be withdrawn from a bore-hole without damaging the cutting faces and can also be used for increasing the depth of an existing bore-hole or for reaming an existing bore-hole without damaging the cutting faces.
The application of this type of drill bit is limited however because it requires a drill core to centre and guide it during drilling operations. If the drill core breaks, if there is a pilot hole or if the underground formation being drilled is not sufficiently firm the 25 drill bit will tend to rotate about its own axis so that the bore-hole will be the same diameter as the cutting head of the drill bit.
It is an object of the present invention to provide an improved drill bit for drilling bore holes in under-30 ground formations. It is a further object of the invent lion to provide a drill bit which is capable of drilling a bore hole of a diameter larger than the diameter of the drill bit and which has improved centering reliability.
SUMMARY OF THE INVENTION
According to the present invention we provide a drill bit for drilling bore holes comprising a connecting spigot for connecting to a drill string, said spigot having a longitudinal axis of no-station, a cutting head having a longitudinal axis, said cutting head comprising a circumferential face having an axis which is substantially coincident with the cutting head axis and an end face projecting away from lo said spigot and having a drilling axis, said drilling axis of the end face of the cutting head being substantially aligned with the axis of no-station of the spigot and said cutting head axis being spaced from and substantially parallel to the axis of rotation of the spigot.
Preferably the end face of the cutting head is at least partially conical in shape.
Advantageously the circumferential face has a first surface portion radially more remote from the axis of rotation of the spigot and a second surface portion fad-tally nearer said axis, the first surface being relative-lye more wear-resistant than the second surface.
The drill bit of the invention has an end face pro-jetting away from the spigot and has a drilling axis which is aligned with the axis of rotation of the spigot.
Thus the drill bit tends to centre itself relative to the drilling axis, especially when the end face is conical in shape. The positioning of the cutting head axis spaced from the axis of rotation provides an eccentric drilling action whereby a bore hole having a diameter larger than that of the cutting head is achieved.
The drill bit is effective in soft or frangible underground formations and can also be used in pilot holes provided that the pilot hole radius is shorter than the shortest distance between the circumferential face and the drilling axis.
BRIEF DESCRIPTION OF THE DRAWING
Reference is now made to the accompanying drawings, in which the single Figure is a side elevation of a pro-furred embodiment of the invention.
The rotary drill bit consists of a drill bit body 1, a connecting spigot 2 for connecting to a drill string (not shown), and a cutting head 3. The cutting head 3 comprises a circumferential face 5 extending parallel to its longitudinal centre axis 4 and an end face 6 contain-using from the circumferential face 5 into a central area.
The circumferential face 5 is a roughly cylindrical envelope which projects radially relative to the bit body 1 and merges via a chamfer 7 into the smaller diameter of the bit body 1. The diameter defined by the envelope of the circumferential face 5 is designated as d.
The surface of the circumferential face 5 is inter-rutted by a plurality of longitudinally extending grooves 8 which permit the free passage of drilling fluid and cuttings.
The end face 6 of the cutting head 3 is conical and projects in the direction of drilling. The drilling axis 9 of the cone is parallel to and offset from the long-tudinal centre axis 4 of the cutting head 3 which is at-signed with the longitudinal axis of the connecting spigot
DRILL BIT
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to drill bits and more part-ocularly concerns drill bits for use in drilling bore holes in underground formations.
5 Description of Prior Art U.S. Patent No. 2,953,3S4 describes a drill bit for drilling bore holes into earth formations. The drill bit includes a cutting head which has a circumferential cult-in face and an end cutting face both having an axis 10 which is spaced from the axis of rotation of the drill bit during drilling. This arrangement produces an eccen-trig rotation of the cutting head so that the bore-hole produced is larger in diameter than the diameter of the cutting head.
This arrangement has the advantage that it can be withdrawn from a bore-hole without damaging the cutting faces and can also be used for increasing the depth of an existing bore-hole or for reaming an existing bore-hole without damaging the cutting faces.
The application of this type of drill bit is limited however because it requires a drill core to centre and guide it during drilling operations. If the drill core breaks, if there is a pilot hole or if the underground formation being drilled is not sufficiently firm the 25 drill bit will tend to rotate about its own axis so that the bore-hole will be the same diameter as the cutting head of the drill bit.
It is an object of the present invention to provide an improved drill bit for drilling bore holes in under-30 ground formations. It is a further object of the invent lion to provide a drill bit which is capable of drilling a bore hole of a diameter larger than the diameter of the drill bit and which has improved centering reliability.
SUMMARY OF THE INVENTION
According to the present invention we provide a drill bit for drilling bore holes comprising a connecting spigot for connecting to a drill string, said spigot having a longitudinal axis of no-station, a cutting head having a longitudinal axis, said cutting head comprising a circumferential face having an axis which is substantially coincident with the cutting head axis and an end face projecting away from lo said spigot and having a drilling axis, said drilling axis of the end face of the cutting head being substantially aligned with the axis of no-station of the spigot and said cutting head axis being spaced from and substantially parallel to the axis of rotation of the spigot.
Preferably the end face of the cutting head is at least partially conical in shape.
Advantageously the circumferential face has a first surface portion radially more remote from the axis of rotation of the spigot and a second surface portion fad-tally nearer said axis, the first surface being relative-lye more wear-resistant than the second surface.
The drill bit of the invention has an end face pro-jetting away from the spigot and has a drilling axis which is aligned with the axis of rotation of the spigot.
Thus the drill bit tends to centre itself relative to the drilling axis, especially when the end face is conical in shape. The positioning of the cutting head axis spaced from the axis of rotation provides an eccentric drilling action whereby a bore hole having a diameter larger than that of the cutting head is achieved.
The drill bit is effective in soft or frangible underground formations and can also be used in pilot holes provided that the pilot hole radius is shorter than the shortest distance between the circumferential face and the drilling axis.
BRIEF DESCRIPTION OF THE DRAWING
Reference is now made to the accompanying drawings, in which the single Figure is a side elevation of a pro-furred embodiment of the invention.
The rotary drill bit consists of a drill bit body 1, a connecting spigot 2 for connecting to a drill string (not shown), and a cutting head 3. The cutting head 3 comprises a circumferential face 5 extending parallel to its longitudinal centre axis 4 and an end face 6 contain-using from the circumferential face 5 into a central area.
The circumferential face 5 is a roughly cylindrical envelope which projects radially relative to the bit body 1 and merges via a chamfer 7 into the smaller diameter of the bit body 1. The diameter defined by the envelope of the circumferential face 5 is designated as d.
The surface of the circumferential face 5 is inter-rutted by a plurality of longitudinally extending grooves 8 which permit the free passage of drilling fluid and cuttings.
The end face 6 of the cutting head 3 is conical and projects in the direction of drilling. The drilling axis 9 of the cone is parallel to and offset from the long-tudinal centre axis 4 of the cutting head 3 which is at-signed with the longitudinal axis of the connecting spigot
2. The amount of offset is indicated by the eccentricity e.
The conical surface of the end end face 6 defines an 30 angle with the drilling axis 9 of the cone. Usually the angle ox will be between 30 and 60 depending upon the nature of the underground formation being drilled.
In harder rock formations the angle is preferably about 55 as shown in the drawing. In particularly soft form-35 anions it is advantageous to reduce the 55 angle shown ~L235~2 in the drawing so that a larger centering area for the drill bit can be presented.
During drilling the drill bit is rotated about the axis of the spigot and the drilling axis 9 of the cone so that the side of the circumferential area 5 furthest away from the drilling axis 9 describes an envelope of dram-ever D. This diameter D is larger by double the accent-Rosetta e than the diameter d of the envelope of the air-cumferential area 5.
The bore hole 11 is thus drilled with an inside die-meter D, because the drill bit is centered on its no-rational axis by the cone point 10 about the drilling axis 9 when it is placed on the bore hole bottom 12.
During a stationary drilling operation, the entire end face 6 of the cutting head 3 engages with the bore hole bottom 12 and thus helps to centre the drill bit. More-over, the drill bit can also be centered if an existing pilot hole is to be drilled out to a large diameter, pro-voided the radius of the pilot hole is smaller than the shortest distance of the circumferential face 5 of the cutting head 3 to the drilling axis 9.
If the drill bit is to be used only for drilling out pilot holes the part of the end face 6 directly in the area of the drilling axis 9 does not need to be provided with cutting material and can be of a shape other than conical. It is sufficient for only the part of the end face 6 which engages with the underground formation and adjoins the circumferential face 5 to be conical. Reduce lion of the amount of cutting material provided reduces the cost of the drill bit.
Depending on the formation which is to be drilled, all known types of cutting material can be employed.
These include diamond coatings with impregnated diamonds or diamonds set in the surface, discrete cutting elements or cutting elements arranged in rows with synthetic or .
~35~
natural diamonds in known configurations, and other wear-resistant cutting elements.
The drilling fluid supply can be such as to meet the requirement of the cutting elements selected.
The portion of the circumferential face 5 which is furthest away from the drilling axis 9 and stressed to a particularly high degree can be provided with a more wear-resistant layer than the opposite side of the air-cumferential face 5.
.
The conical surface of the end end face 6 defines an 30 angle with the drilling axis 9 of the cone. Usually the angle ox will be between 30 and 60 depending upon the nature of the underground formation being drilled.
In harder rock formations the angle is preferably about 55 as shown in the drawing. In particularly soft form-35 anions it is advantageous to reduce the 55 angle shown ~L235~2 in the drawing so that a larger centering area for the drill bit can be presented.
During drilling the drill bit is rotated about the axis of the spigot and the drilling axis 9 of the cone so that the side of the circumferential area 5 furthest away from the drilling axis 9 describes an envelope of dram-ever D. This diameter D is larger by double the accent-Rosetta e than the diameter d of the envelope of the air-cumferential area 5.
The bore hole 11 is thus drilled with an inside die-meter D, because the drill bit is centered on its no-rational axis by the cone point 10 about the drilling axis 9 when it is placed on the bore hole bottom 12.
During a stationary drilling operation, the entire end face 6 of the cutting head 3 engages with the bore hole bottom 12 and thus helps to centre the drill bit. More-over, the drill bit can also be centered if an existing pilot hole is to be drilled out to a large diameter, pro-voided the radius of the pilot hole is smaller than the shortest distance of the circumferential face 5 of the cutting head 3 to the drilling axis 9.
If the drill bit is to be used only for drilling out pilot holes the part of the end face 6 directly in the area of the drilling axis 9 does not need to be provided with cutting material and can be of a shape other than conical. It is sufficient for only the part of the end face 6 which engages with the underground formation and adjoins the circumferential face 5 to be conical. Reduce lion of the amount of cutting material provided reduces the cost of the drill bit.
Depending on the formation which is to be drilled, all known types of cutting material can be employed.
These include diamond coatings with impregnated diamonds or diamonds set in the surface, discrete cutting elements or cutting elements arranged in rows with synthetic or .
~35~
natural diamonds in known configurations, and other wear-resistant cutting elements.
The drilling fluid supply can be such as to meet the requirement of the cutting elements selected.
The portion of the circumferential face 5 which is furthest away from the drilling axis 9 and stressed to a particularly high degree can be provided with a more wear-resistant layer than the opposite side of the air-cumferential face 5.
.
Claims
1. A drill bit for drilling bore holes comprising a connecting spigot for connecting to a drill string, said spigot having a longitudinal axis of rotation, a cutting head having a longitudinal axis, eccentric of the spigot axis, said cutting head comprising a circumferential face having an axis which is substantially coincident with the cutting head axis and an end face projecting away from said spigot, said end face being substantially conical and coaxial with the axis of rotation of said spigot, said conical end face terminating at a point axially opposite said spigot.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1420612 | 1984-04-14 | ||
| DEP3414206.1-24 | 1984-04-14 | ||
| DE8411809 | 1984-04-14 | ||
| DEG8411809.1 | 1984-04-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1235112A true CA1235112A (en) | 1988-04-12 |
Family
ID=25752015
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000478795A Expired CA1235112A (en) | 1984-04-14 | 1985-04-11 | Drill bit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1235112A (en) |
-
1985
- 1985-04-11 CA CA000478795A patent/CA1235112A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |