CA1075226A - Percussion drill bit - Google Patents
Percussion drill bitInfo
- Publication number
- CA1075226A CA1075226A CA291,862A CA291862A CA1075226A CA 1075226 A CA1075226 A CA 1075226A CA 291862 A CA291862 A CA 291862A CA 1075226 A CA1075226 A CA 1075226A
- Authority
- CA
- Canada
- Prior art keywords
- drill bit
- inserts
- drill
- insert
- front face
- 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
Landscapes
- Earth Drilling (AREA)
Abstract
PERCUSSION DRILL BIT
Abstract of the Disclosure A drill bit, for percussion drilling of smaller holes, comprises an outer row of circumferentially spaced button inserts of cemented carbide at the front end of the bit body while inclined at an angle to the longitudinal axis of the bit body, the shaft portion of said bit body being provided with a conical portion for being frictionally connected to a drill rod portion correspondingly conical in shape. The bit body is provided with an axially extending central button insert of cemented carbide, said central insert and peripheral inserts being blunt in shape, preferably smoothly rounded at their protruding end portions.
Abstract of the Disclosure A drill bit, for percussion drilling of smaller holes, comprises an outer row of circumferentially spaced button inserts of cemented carbide at the front end of the bit body while inclined at an angle to the longitudinal axis of the bit body, the shaft portion of said bit body being provided with a conical portion for being frictionally connected to a drill rod portion correspondingly conical in shape. The bit body is provided with an axially extending central button insert of cemented carbide, said central insert and peripheral inserts being blunt in shape, preferably smoothly rounded at their protruding end portions.
Description
Percussion drill bit The present invention relates to a drill bit, in particular for percussion drilling of smaller holes, comprising a bit body having button inserts at its fr-ont end located in an outer row of circumferentially spaced inserts, the inserts of said outer row being disposed at an acute angle with the longitudinal axis of the bit.
Drill bits equipped with button shaped inserts instead of chisel shaped inserts have shown to result in a more suitable attack against the bottom of the drill hole, primarily because of the many attack points against the hole bottom occurring as a result of using button inserts. As a result thereof the drill bit is given a more calm running through the drill hole than compared with chisel bits which decreases the strains exerted on the drilling equipment. Simultaneously more fine-grained drill cuttings, easy to flush away, will be achieved as a result thereof.
Heretofore, however, it has been technically possible ; only to use button bits for the drilling of larger holes in hard rock formations. The use of small dimensioned drill bits with button inserts has been limited to relatively loose rock formations, such as coal, schist, limestone and similar. The ; technical problems connected with the manufacture of button bits suitable only for hard rock formations have increased with decreased dimension of the drill bit. The primary reason thereto has been that the percussive forces applied to the button inserts from the rear percussive rod are too vigorous for small button inserts leading to fracture of the inserts during drilling in hard rock formations. Fracture of button inserts in larger dimensioned drill bits also seem to be a result thereof.
In accordance with the present invention it has -1- ~
surprisingly been possible to provide a drill bit with button inserts with which the disadvantages of the aforementioned kind can be overcome. The drill hit of this invention is provided with a conically -la- .
shaped shaft portion to be connected to a correspondingly shaped percussive rod portion, whereby said drill bit body being provided with a button insert at the centre of the front end.
It has been found that a frictional joint of conical shape between the bit body and the drill rod is able to substantially dampen the percussive forces exerted to the bit body from the rod which positively affects the strength of the button inserts. By providing simultaneously a central button insert, which preferably extends axially in front of the other inserts, a more favourable directing of the drill bit and, as a result thereof, more straight drill holes will be achievable. The strains will also be more favourably distributed between the centrally and peripherally located button inserts.
In accordance with one broad aspect, the invention relates to a drill bit of the type to be mounted in a drill rod through which percussion forces are to be exerted for percussion drilling, said drill bit comprising: a bit body defining a longitudinal axis and including a front face extending generally transversely relative to said axis, and ; a longitudinal shaft having a conical portion for connection to a drill rod of corresponding conical shape by means of substantially longitudinal frictional forces; an annular row of circumferentially spaced outer button inserts of cemented carbide extending outwardly of said front face of said body, said inserts being inclined at an acute angle relative to said longitudinal axis of the bit body and arranged to define the outer diameter of the hole drilled by the drill bit; a central button insert of cemented carbide extending longitudinally centrally outwardly of said f~ont face in alignment with said longitudinal axis, the outer end of said central insert
Drill bits equipped with button shaped inserts instead of chisel shaped inserts have shown to result in a more suitable attack against the bottom of the drill hole, primarily because of the many attack points against the hole bottom occurring as a result of using button inserts. As a result thereof the drill bit is given a more calm running through the drill hole than compared with chisel bits which decreases the strains exerted on the drilling equipment. Simultaneously more fine-grained drill cuttings, easy to flush away, will be achieved as a result thereof.
Heretofore, however, it has been technically possible ; only to use button bits for the drilling of larger holes in hard rock formations. The use of small dimensioned drill bits with button inserts has been limited to relatively loose rock formations, such as coal, schist, limestone and similar. The ; technical problems connected with the manufacture of button bits suitable only for hard rock formations have increased with decreased dimension of the drill bit. The primary reason thereto has been that the percussive forces applied to the button inserts from the rear percussive rod are too vigorous for small button inserts leading to fracture of the inserts during drilling in hard rock formations. Fracture of button inserts in larger dimensioned drill bits also seem to be a result thereof.
In accordance with the present invention it has -1- ~
surprisingly been possible to provide a drill bit with button inserts with which the disadvantages of the aforementioned kind can be overcome. The drill hit of this invention is provided with a conically -la- .
shaped shaft portion to be connected to a correspondingly shaped percussive rod portion, whereby said drill bit body being provided with a button insert at the centre of the front end.
It has been found that a frictional joint of conical shape between the bit body and the drill rod is able to substantially dampen the percussive forces exerted to the bit body from the rod which positively affects the strength of the button inserts. By providing simultaneously a central button insert, which preferably extends axially in front of the other inserts, a more favourable directing of the drill bit and, as a result thereof, more straight drill holes will be achievable. The strains will also be more favourably distributed between the centrally and peripherally located button inserts.
In accordance with one broad aspect, the invention relates to a drill bit of the type to be mounted in a drill rod through which percussion forces are to be exerted for percussion drilling, said drill bit comprising: a bit body defining a longitudinal axis and including a front face extending generally transversely relative to said axis, and ; a longitudinal shaft having a conical portion for connection to a drill rod of corresponding conical shape by means of substantially longitudinal frictional forces; an annular row of circumferentially spaced outer button inserts of cemented carbide extending outwardly of said front face of said body, said inserts being inclined at an acute angle relative to said longitudinal axis of the bit body and arranged to define the outer diameter of the hole drilled by the drill bit; a central button insert of cemented carbide extending longitudinally centrally outwardly of said f~ont face in alignment with said longitudinal axis, the outer end of said central insert
-2-extending longitudinally outwardly beyond the oUter ends of said outer inserts to define a pilot insert; the forwardly facing ends of each of said inserts being blunt in shape.
In accordance with another aspeCt, the invention relates to a drill bit and a drill rod for carrying said drill bit for transmitting percussion forces to said drill bit for percussion drilling, the improVement wherein said drill bit including a shaft portion defining a longitudinal axis;
said drill rod and drill bit shaft include corresponding conically shaped portions for connecting said drill bit to said drill rod by means of substantially longitudinal frictional forces; said drill bit further including: a front face extending generally transversely relative to said axis;
an annular row of circumferentially spaced oUter button inserts of cemented carbide extending outwardly of said front , face of said bit body, said inserts being inclined at an angle .I relative to said longitudinal axis of the bit body; and a central button insert Of cemented carbide extending longitudinally centrally outwardly of said front face in alignment with said longitudinal axis, the outer end of said central insert extending longitudinally outwardly beyond the ;~ outer ends of said outer inserts to define a pilot insert; the forwardly facing ends of each of said inserts being blunt in ' shape.
The inVention will be described more in detail in the following detai~ed description taXen with the accompanying drawings in whiCh:
Fig. 1 iS a side view of the bit body of the invention;
Fig. 2 is a side view of another embodiment Of the bit body of the invention;
Fig. 3 is a longitudinal seCtion View along the line III-III in Fig. 4, and Fig. 4 is a front View Of the bit body shown in Fig. 1.
-2a-The drill bit of the invention comprises a b~t body 10 which is symmetrically shaped about the drill axis. With the preferred and shown embodiment the front face of the bit body is substantially plain and provided with four button inserts 11 of cemented carbide spaced in an outer row at the front face of said bit body. The bit body is, except for the outer row of button inserts 11, eguipped with a centrally located button insert 12 of cemented carbide. All button inserts are similarly shaped and have smoothly rounded outer end portions and all inserts are conventionally secured to -`
said front face. . - -The central insert 12 should protrude axially from the -front face of the bit body at substantially the same degree as ---the other button inserts 11. - . -- -' ' , , .
. .
~-- 20 ~ - --- . . . .
_ -- - - . : . , . . :
. - ~ . ~ - . - - . - -: ~ - - - - ~ - . , . - . ~ ~ - - . . - . - , --.: ~ , - , .. . . .. ..
.
. ~ : - - , - --:~ 30 .
_ ' ~ 2b- ~ -; .. . - . -: , . ,,. . , . :
, ~ - .
The peripherally located inserts 11 are inclined at an acute angle with the longitudinal axis of the bit and suitably they extend from the front face of the bit at such an extent that the diameter of the drill hole is defined thereof. The bit body is also provided with two parallel plain ground surface portions 13 at its periphery so as to provide for drill cuttings to be flushed rearwardly between these surface portions and the wall of the drill hole. The arrangement with a central insert results in a favourable limited variation in grain size which means that peripheral recesses are not necessary for effective flushing of drill cuttings. This is essential at small dimensioned drill bits because they require that every effort is taken to avoid any shape that could weaken the bit body.
The bit body 10 has a centrally provided flushing channel 14 and one or several branch channels 15 dîsposed at an angle to said first channel, said branch channels finishing at the peripheral surface portions 13.
The preferred embodiment shown comprises a bit body, the shaft portion 16 of which is exteriorly conical in shape for being frictionally connected to a drill rod 17 having a corresponding conical bore 18. The drill rod portion having said conical bore 18 consists of a portion 19 that is upset from the remaining portion of the drill rod 17. A centrally located flushing channel 20 is provided in the drill rod.
Alternatively, the bit body 10 could be interiorly conical in shape for the receipt of an exteriorly conically shaped drill rod (not shown), if so is desirable.
According to an alternative embodiment, shown in Fig. 2, the central portion 21 of the bit body protrudes beyond the peripheral portions thereof to such amount that the central
In accordance with another aspeCt, the invention relates to a drill bit and a drill rod for carrying said drill bit for transmitting percussion forces to said drill bit for percussion drilling, the improVement wherein said drill bit including a shaft portion defining a longitudinal axis;
said drill rod and drill bit shaft include corresponding conically shaped portions for connecting said drill bit to said drill rod by means of substantially longitudinal frictional forces; said drill bit further including: a front face extending generally transversely relative to said axis;
an annular row of circumferentially spaced oUter button inserts of cemented carbide extending outwardly of said front , face of said bit body, said inserts being inclined at an angle .I relative to said longitudinal axis of the bit body; and a central button insert Of cemented carbide extending longitudinally centrally outwardly of said front face in alignment with said longitudinal axis, the outer end of said central insert extending longitudinally outwardly beyond the ;~ outer ends of said outer inserts to define a pilot insert; the forwardly facing ends of each of said inserts being blunt in ' shape.
The inVention will be described more in detail in the following detai~ed description taXen with the accompanying drawings in whiCh:
Fig. 1 iS a side view of the bit body of the invention;
Fig. 2 is a side view of another embodiment Of the bit body of the invention;
Fig. 3 is a longitudinal seCtion View along the line III-III in Fig. 4, and Fig. 4 is a front View Of the bit body shown in Fig. 1.
-2a-The drill bit of the invention comprises a b~t body 10 which is symmetrically shaped about the drill axis. With the preferred and shown embodiment the front face of the bit body is substantially plain and provided with four button inserts 11 of cemented carbide spaced in an outer row at the front face of said bit body. The bit body is, except for the outer row of button inserts 11, eguipped with a centrally located button insert 12 of cemented carbide. All button inserts are similarly shaped and have smoothly rounded outer end portions and all inserts are conventionally secured to -`
said front face. . - -The central insert 12 should protrude axially from the -front face of the bit body at substantially the same degree as ---the other button inserts 11. - . -- -' ' , , .
. .
~-- 20 ~ - --- . . . .
_ -- - - . : . , . . :
. - ~ . ~ - . - - . - -: ~ - - - - ~ - . , . - . ~ ~ - - . . - . - , --.: ~ , - , .. . . .. ..
.
. ~ : - - , - --:~ 30 .
_ ' ~ 2b- ~ -; .. . - . -: , . ,,. . , . :
, ~ - .
The peripherally located inserts 11 are inclined at an acute angle with the longitudinal axis of the bit and suitably they extend from the front face of the bit at such an extent that the diameter of the drill hole is defined thereof. The bit body is also provided with two parallel plain ground surface portions 13 at its periphery so as to provide for drill cuttings to be flushed rearwardly between these surface portions and the wall of the drill hole. The arrangement with a central insert results in a favourable limited variation in grain size which means that peripheral recesses are not necessary for effective flushing of drill cuttings. This is essential at small dimensioned drill bits because they require that every effort is taken to avoid any shape that could weaken the bit body.
The bit body 10 has a centrally provided flushing channel 14 and one or several branch channels 15 dîsposed at an angle to said first channel, said branch channels finishing at the peripheral surface portions 13.
The preferred embodiment shown comprises a bit body, the shaft portion 16 of which is exteriorly conical in shape for being frictionally connected to a drill rod 17 having a corresponding conical bore 18. The drill rod portion having said conical bore 18 consists of a portion 19 that is upset from the remaining portion of the drill rod 17. A centrally located flushing channel 20 is provided in the drill rod.
Alternatively, the bit body 10 could be interiorly conical in shape for the receipt of an exteriorly conically shaped drill rod (not shown), if so is desirable.
According to an alternative embodiment, shown in Fig. 2, the central portion 21 of the bit body protrudes beyond the peripheral portions thereof to such amount that the central
-3-button insert 12 extends axially in front of the other button inserts 11. An improved direction of the drilling operation has been found to be achievable as a result thereof which causes less strain to be exerted on the drilling equipment.
-3a-The centrally provided button insert 12 should have a thickness at least equal to the thickness of the peripheral inser~s 11 and preferably in excess thereof. At the same time the central insert 12 could be longer than the others so that it could be received in the bit body to a larger amount than the other inserts 11, as shown in Fig. 3, irrespectively of whether said central insert 12 extends from the front face to an amount equal to or in excess of the other inserts 11.
Except this measure the wear strength of the central insert could additionally be improved by using a type of cemented carbide at its manufacture, the strength of which is in excess of the strength of the carbide of the other inserts.
-3a-The centrally provided button insert 12 should have a thickness at least equal to the thickness of the peripheral inser~s 11 and preferably in excess thereof. At the same time the central insert 12 could be longer than the others so that it could be received in the bit body to a larger amount than the other inserts 11, as shown in Fig. 3, irrespectively of whether said central insert 12 extends from the front face to an amount equal to or in excess of the other inserts 11.
Except this measure the wear strength of the central insert could additionally be improved by using a type of cemented carbide at its manufacture, the strength of which is in excess of the strength of the carbide of the other inserts.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A drill bit of the type to be mounted in a drill rod through which percussion forces are to be exerted for percussion drilling, said drill bit comprising: a bit body defining a longitudinal axis and including a front face extending generally transversely relative to said axis, and a longitudinal shaft having a conical portion for connection to a drill rod of corresponding conical shape by means of substantially longitudinal frictional forces; an annular row of circumferentially spaced outer button inserts of cemented carbide extending outwardly of said front face of said body, said inserts being inclined at an acute angle relative to said longitudinal axis of the bit body and arranged to define the outer diameter of the hole drilled by the drill bit; a central button insert of cemented carbide extending longitudinally centrally outwardly of said front face in alignment with said longitudinal axis, the outer end of said central insert extending longitudinally outwardly beyond the outer ends of said outer inserts to define a pilot insert; the forwardly facing ends of each of said inserts being blunt in shape.
2. A drill bit according to claim 1, wherein said central insert has a lateral thickness at least equal to that of the other inserts.
3. A drill bit according to claim 1, wherein said conical portion of said shaft comprises an exterior surface of said shaft and which is connectible to a conical shaft of a drill rod.
4. A drill bit according to claim 1, wherein said front face includes a central portion which protrudes axially forwardly from the remainder of said transversely extending front face of said bit body so that the central insert extends axially beyond the other inserts.
5. A drill bit according to claim 1, wherein said central insert has a lateral thickness greater than that of the other inserts.
6. A drill bit according to claim 1, wherein the length of said central insert is greater than that of the other inserts and extends into the bit body a greater distance than the other inserts.
7. A drill bit according to claim 1, wherein the mantle surface of said bit body includes a pair of opposed planar and parallel surfaces.
8. A drill bit according to claim 7, wherein said body includes an axially extending flushing channel and at least one branch channel terminating at an associate one of said planar surfaces.
9. A drill bit according to claim 1, including a drill rod having a conical portion for mating with said conical portion of said shaft, said conical portion of said rod being disposed in a portion of said rod which is radially enlarged relative to the remaining portions of said rod.
10. A drill bit according to claim 1, wherein said inserts are smoothly rounded at their forwardly facing ends.
11. In combination, a drill bit and a drill rod for carrying said drill bit for transmitting percussion forces to said drill bit for percussion drilling, the improvement wherein:
said drill bit including a shaft portion defining a longitudinal axis; said drill rod and drill bit shaft include corresponding conically shaped portions for connecting said drill bit to said drill rod by means of substantially longitudinal frictional forces; said drill bit further including: a front face extending generally transversely relative to said axis; an annular row of circumferentially spaced outer button inserts of cemented carbide extending outwardly of said front face of said bit body, said inserts being inclined at an angle relative to said longitudinal axis of the bit body; and a central button insert of cemented carbide extending longitudinally centrally outwardly of said front face in alignment with said longitudinal axis, the outer end of said central insert extending longitudinally outwardly beyond the outer ends of said outer inserts to define a pilot insert;
the forwardly facing ends of each of said inserts being blunt in shape.
said drill bit including a shaft portion defining a longitudinal axis; said drill rod and drill bit shaft include corresponding conically shaped portions for connecting said drill bit to said drill rod by means of substantially longitudinal frictional forces; said drill bit further including: a front face extending generally transversely relative to said axis; an annular row of circumferentially spaced outer button inserts of cemented carbide extending outwardly of said front face of said bit body, said inserts being inclined at an angle relative to said longitudinal axis of the bit body; and a central button insert of cemented carbide extending longitudinally centrally outwardly of said front face in alignment with said longitudinal axis, the outer end of said central insert extending longitudinally outwardly beyond the outer ends of said outer inserts to define a pilot insert;
the forwardly facing ends of each of said inserts being blunt in shape.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA291,862A CA1075226A (en) | 1977-11-28 | 1977-11-28 | Percussion drill bit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA291,862A CA1075226A (en) | 1977-11-28 | 1977-11-28 | Percussion drill bit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075226A true CA1075226A (en) | 1980-04-08 |
Family
ID=4110154
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA291,862A Expired CA1075226A (en) | 1977-11-28 | 1977-11-28 | Percussion drill bit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1075226A (en) |
-
1977
- 1977-11-28 CA CA291,862A patent/CA1075226A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |