CA1097104A - Drills - Google Patents
DrillsInfo
- Publication number
- CA1097104A CA1097104A CA319,989A CA319989A CA1097104A CA 1097104 A CA1097104 A CA 1097104A CA 319989 A CA319989 A CA 319989A CA 1097104 A CA1097104 A CA 1097104A
- Authority
- CA
- Canada
- Prior art keywords
- cutting
- drill according
- lands
- drill
- faces
- 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
A B S T R A C T
The invention provides a twist drill particularly suitable for drilling holes in wooden railway sleepers.
The drill comprises a fluted body terminating at its leading end in opposed cutting faces, a threaded portion trailing the cutting faces and adapted to serve a drill feeding function, and a second set of opposed cutting faces which trail the threaded portion and which have a larger radius of cut than the leading cutting faces.
Preferably the second set of cutting faces are of sub-stantially the same diameter as that of the body.
The invention provides a twist drill particularly suitable for drilling holes in wooden railway sleepers.
The drill comprises a fluted body terminating at its leading end in opposed cutting faces, a threaded portion trailing the cutting faces and adapted to serve a drill feeding function, and a second set of opposed cutting faces which trail the threaded portion and which have a larger radius of cut than the leading cutting faces.
Preferably the second set of cutting faces are of sub-stantially the same diameter as that of the body.
Description
~97~
~HIS invention relates to drills, augers or the like.
Conventional augers for woodworking comprise a shar~
or bod~ defining helical or spiral flutes, opposed radiall~ extending cutting edges at the leading end of the shank, and an axiall~ extending screw point. Tn use the screw point engages in the wood being bored and acts to draw the auger into the wood, thus rendering the auger self-feeding~ ~ disadvantage associated with conventional augers is that the screw point is vulnerable and prone to breakage. Moreover, resharp-erling of the cutting edges is clifficult, and generally uneco~omical.
It is accordingly an object of the present invention to provide a novel drill which it is believed will have useful applica-tions.
~ccording to the invention a drill or the like comprises .
a shank or body providing a first lateral cutting edge at its leading end, material engaging means trailing the first cutting edge and adapted in use to engage material to be drilled to advance the drill into the material, and a second lateral chisel-like cutting edge '' ~
~97~
trailing the ma-terial engaging means and having a greater radius of cut than the first cutting edge.
Preferably each of the cutting edges comprises a pair of diametrically opposed chisel-like cutting faces.
Also according to the invention the ratio between the radius of cut of the first cutting edge and that of the second cutting edge is greater than 0,3. Preferably the ratio is 0,7.
~urther according to the invention the material engaging means is a screw thread or the like. ~he pitch and depth of the thread will depend on the feed rate required and -the material to be bored.
.
In one arrangement in accordance with the invention the shan~ or body defines substantially helical flutes and lands, with the tip of the shan~`providing a palr of -opposed cutting faces ha~ing a smaller cutting diameter - -thàn the land diame-ter, the lands ~eing undercut and threaded to the rear of cutting faces, with the web of the lands at the end of the undercut portion defining a second set of cutting faces, having a cutting diameter - ;
substantially equal to the land diameterO If desirable -the threaded lands may be sub-lands provided in the flutes~
It is further envisaged that the screw thread may be a ~97~(~4 multiple thread starting at the first pair of cutting faces, so that more than one circumferentially spaced cutting corner is provided at the outer extremity of each cut-ting face by the starts of the threads. Clearly the thread form and pitch could be selected to var~ clip formation at the outer regions of the cutting faces.
~hus a buttress thread form will provide a cutting corner at the outer region of the leading cutting faces, such cutting corner forming an acute angle relative to -the remainder of the cutting faceO
In order more clearly to illust;rate the invention some embodiments thereof are described hereunder purely by way of exa~ple wi-th reference to the accompanying drawings wherein :
~igure 1 is a perspective view o~ a drill in accordance with the invention, .
:~ ~igure 2 is a plan view of the tip portion of - -he drill in Figure 1, ~igure 3 is an elevation in profile of the drill .` 20 in ~igure 1, .~ .
~igure 4 is a plan view of a different embodiment of the drill in ~igure 1, and :~L09~1Q~L
Figure 5 is an elevation in profile of the arrangemen-t in ~igure 4.
Referring to the drawings a wood drill is in the form of a flu-ted shank or body 17 defining helical lands 13 and flutes or valleys 14. ~he leading portion of the drill 17 is pro~ided with a pair of opposed chisel-like cutting faces 10 which have a diameter-of cut less than the land diameter. The cutting angle and clearance angle of the faces 10 will depend on the material to be drilled.
~he land portions which trail t;he cutting ~aces 10 are undercut, RS shown in ~igure 3~ and pro~ided with a screw thread 12 on their peripheral faces. At the rear of the thread 12, where the lands rever~ to nominal diameter the webs of the lands define a second pair of chisel-like cutting faces 11. ~he ratio between the diameter of the cutting faces 10 and those of the -faces-ll is in the region of 0,7.
' . ` ' ' ` '.
In use the threads 12 will engage within the bore of a pilot hole cut by the leading cutting faces 10. It will be appreciated that engagement of the thread within the pilot bore will urge the drill into the material and thus render the drill self-feeding. ~he second set of cutting faces 11 which trail tha thread 12 will enlarge the pilot bore to the required diameter.
.
~r~971V4 Clearly many variations o~ the invention in detail exist and it is envisaged that these all fall within the scope of this disclosure. ~or example the drill point geometry can be altered to give different cutting characteris-tics in accordance with the material to be drilled. ~i~ewise the pitch and helix angl~e of the thread 12 will determine the feed rate of the drill.
Generally it will also be desirable to provide a laterally extending reaming edge 16 on the lands as illustrated to provide clearance. A variation of the drill is illustra-ted in Figure 4 and ~igure 5, wherein the thread 12 is provided on a sub-land 15, which lies between the main lands 13. Generally the drill described above is applicable to the drilling o~ wood, bu-t the drill will doubtless find applica-tion in the drilling o~ a wide variety of materials, and is in no way restricted to the drilling o~ wood.
. , In a ~urther embodiment of the invention the thread 12 - may be a multiple thread such tha-t more than one circum~erentially spaced cu-tting corner is provided at the outer extremlty of each cutting ~ace 10 b~ the starts o~ the threads~ Thus once the leading corner o~ each cutting face 10 has worn cutting action will be transmitted to the next pair o~ outer corners which have an identical ~orm and cuttîng e~iciency to the leading pair. ~ince it is well recognised that wear on the outer corners o~ the cu-tting faces o~ drills ~0~7~4 determines the drill life, the above arrangement should provide a substantial increase in drill life between resharpening.
It is further envisaged tha-t the thread form and pi-tch 5 . of the thread 12 may be selected to vary chip forma-tion at the outer regions of the cutting faces 10. ~or example, it is believed that the start of a buttress thread form will provide a cutting corner at the outer region of each cutting face 10 with such corner forming an acu-te angle relative to the remainder of the cuttin~
face. Such corner will reduce chip thickness and heat generation at the periphery of the leading end of the dr-ll resu_ting in i~proved ~ re.
' '
~HIS invention relates to drills, augers or the like.
Conventional augers for woodworking comprise a shar~
or bod~ defining helical or spiral flutes, opposed radiall~ extending cutting edges at the leading end of the shank, and an axiall~ extending screw point. Tn use the screw point engages in the wood being bored and acts to draw the auger into the wood, thus rendering the auger self-feeding~ ~ disadvantage associated with conventional augers is that the screw point is vulnerable and prone to breakage. Moreover, resharp-erling of the cutting edges is clifficult, and generally uneco~omical.
It is accordingly an object of the present invention to provide a novel drill which it is believed will have useful applica-tions.
~ccording to the invention a drill or the like comprises .
a shank or body providing a first lateral cutting edge at its leading end, material engaging means trailing the first cutting edge and adapted in use to engage material to be drilled to advance the drill into the material, and a second lateral chisel-like cutting edge '' ~
~97~
trailing the ma-terial engaging means and having a greater radius of cut than the first cutting edge.
Preferably each of the cutting edges comprises a pair of diametrically opposed chisel-like cutting faces.
Also according to the invention the ratio between the radius of cut of the first cutting edge and that of the second cutting edge is greater than 0,3. Preferably the ratio is 0,7.
~urther according to the invention the material engaging means is a screw thread or the like. ~he pitch and depth of the thread will depend on the feed rate required and -the material to be bored.
.
In one arrangement in accordance with the invention the shan~ or body defines substantially helical flutes and lands, with the tip of the shan~`providing a palr of -opposed cutting faces ha~ing a smaller cutting diameter - -thàn the land diame-ter, the lands ~eing undercut and threaded to the rear of cutting faces, with the web of the lands at the end of the undercut portion defining a second set of cutting faces, having a cutting diameter - ;
substantially equal to the land diameterO If desirable -the threaded lands may be sub-lands provided in the flutes~
It is further envisaged that the screw thread may be a ~97~(~4 multiple thread starting at the first pair of cutting faces, so that more than one circumferentially spaced cutting corner is provided at the outer extremity of each cut-ting face by the starts of the threads. Clearly the thread form and pitch could be selected to var~ clip formation at the outer regions of the cutting faces.
~hus a buttress thread form will provide a cutting corner at the outer region of the leading cutting faces, such cutting corner forming an acute angle relative to -the remainder of the cutting faceO
In order more clearly to illust;rate the invention some embodiments thereof are described hereunder purely by way of exa~ple wi-th reference to the accompanying drawings wherein :
~igure 1 is a perspective view o~ a drill in accordance with the invention, .
:~ ~igure 2 is a plan view of the tip portion of - -he drill in Figure 1, ~igure 3 is an elevation in profile of the drill .` 20 in ~igure 1, .~ .
~igure 4 is a plan view of a different embodiment of the drill in ~igure 1, and :~L09~1Q~L
Figure 5 is an elevation in profile of the arrangemen-t in ~igure 4.
Referring to the drawings a wood drill is in the form of a flu-ted shank or body 17 defining helical lands 13 and flutes or valleys 14. ~he leading portion of the drill 17 is pro~ided with a pair of opposed chisel-like cutting faces 10 which have a diameter-of cut less than the land diameter. The cutting angle and clearance angle of the faces 10 will depend on the material to be drilled.
~he land portions which trail t;he cutting ~aces 10 are undercut, RS shown in ~igure 3~ and pro~ided with a screw thread 12 on their peripheral faces. At the rear of the thread 12, where the lands rever~ to nominal diameter the webs of the lands define a second pair of chisel-like cutting faces 11. ~he ratio between the diameter of the cutting faces 10 and those of the -faces-ll is in the region of 0,7.
' . ` ' ' ` '.
In use the threads 12 will engage within the bore of a pilot hole cut by the leading cutting faces 10. It will be appreciated that engagement of the thread within the pilot bore will urge the drill into the material and thus render the drill self-feeding. ~he second set of cutting faces 11 which trail tha thread 12 will enlarge the pilot bore to the required diameter.
.
~r~971V4 Clearly many variations o~ the invention in detail exist and it is envisaged that these all fall within the scope of this disclosure. ~or example the drill point geometry can be altered to give different cutting characteris-tics in accordance with the material to be drilled. ~i~ewise the pitch and helix angl~e of the thread 12 will determine the feed rate of the drill.
Generally it will also be desirable to provide a laterally extending reaming edge 16 on the lands as illustrated to provide clearance. A variation of the drill is illustra-ted in Figure 4 and ~igure 5, wherein the thread 12 is provided on a sub-land 15, which lies between the main lands 13. Generally the drill described above is applicable to the drilling o~ wood, bu-t the drill will doubtless find applica-tion in the drilling o~ a wide variety of materials, and is in no way restricted to the drilling o~ wood.
. , In a ~urther embodiment of the invention the thread 12 - may be a multiple thread such tha-t more than one circum~erentially spaced cu-tting corner is provided at the outer extremlty of each cutting ~ace 10 b~ the starts o~ the threads~ Thus once the leading corner o~ each cutting face 10 has worn cutting action will be transmitted to the next pair o~ outer corners which have an identical ~orm and cuttîng e~iciency to the leading pair. ~ince it is well recognised that wear on the outer corners o~ the cu-tting faces o~ drills ~0~7~4 determines the drill life, the above arrangement should provide a substantial increase in drill life between resharpening.
It is further envisaged tha-t the thread form and pi-tch 5 . of the thread 12 may be selected to vary chip forma-tion at the outer regions of the cutting faces 10. ~or example, it is believed that the start of a buttress thread form will provide a cutting corner at the outer region of each cutting face 10 with such corner forming an acu-te angle relative to the remainder of the cuttin~
face. Such corner will reduce chip thickness and heat generation at the periphery of the leading end of the dr-ll resu_ting in i~proved ~ re.
' '
Claims (10)
1. A drill or the like comprising a shank or body providing a first lateral cutting edge at its leading end, material engaging means trailing the first cutting edge and adapted in use to engage material to be drilled to advance the drill into the material, and a second lateral chisel-like cutting edge trailing the material engaging means and having a greater radius of cut than the first cutting edge.
2. The drill according to claim 1 wherein each of the cutting edges comprises a pair of diametrically opposed chisel-like cutting faces.
3. The drill according to claim 1 wherein the ratio between the radius of cut of the first cutting edge and that of the second cutting edge is greater than 0,3.
4. The drill according to claim 3 wherein the ratio is 0,7.
5. The drill according to claim 1 wherein the material engaging means is a screw thread or the like.
6. The drill according to claim 1 wherein the shank or body defines substantially helical flutes and lands, with the tip of the shank providing a pair of opposed cutting faces having a smaller cutting diameter than the land diameter, the lands being undercut and threaded to the rear of the cutting faces, with the web of the lands at the end of the undercut portion defining a second set of cutting faces, having a cutting diameter substantially equal to the land diameter.
7. The drill according to claim 6 wherein the lands to the rear of the second set of cutting faces are provided with. one or more laterally extending reaming formations designed to ream a hole being drilled to a greater diameter than the land diameter, for clearance purposes.
8. The drill according to claim 6 wherein the threaded lands or sub-lands are disposed within the flutes.
9. The drill according to claim 5 wherein the screw thread is a multiple thread starting at the first pair of cutting faces, so that more than one circumferentially spaced cutting corner is provided at the outer extremity of each cutting face by the by the starts of the threads.
10. The drill according to claim 5 wherein the thread is of a buttress form adapted to provide a cutting corner at the outer region of the leading cutting faces, such cutting corner forming an acute angle relative to the remainder of the cutting face.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA78/1069 | 1978-02-23 | ||
| ZA781069 | 1978-02-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097104A true CA1097104A (en) | 1981-03-10 |
Family
ID=25572617
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA319,989A Expired CA1097104A (en) | 1978-02-23 | 1979-01-19 | Drills |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1097104A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4605347A (en) * | 1982-12-27 | 1986-08-12 | Lockheed Missiles & Space Company, Inc. | High speed drill reamer |
| US4968193A (en) * | 1986-08-18 | 1990-11-06 | Black & Decker Corporation | Self-centering drill bit with pilot tip |
| US4997322A (en) * | 1989-12-26 | 1991-03-05 | Wells Bobby L | Automobile body reamer tool |
| US5244319A (en) * | 1991-11-01 | 1993-09-14 | Greenlee Textron Inc. | Auger bit |
| US5288183A (en) * | 1986-08-18 | 1994-02-22 | Black & Decker Inc. | Self-centering drill bit with pilot tip |
| WO1996020803A1 (en) * | 1994-12-30 | 1996-07-11 | Black & Decker Inc. | A spade-type boring bit and an associated method and apparatus for forming metallic parts |
| US5842267A (en) * | 1994-12-30 | 1998-12-01 | Black & Decker, Inc. | Method and apparatus for forming parts of a predetermined shape from a continuous stock material |
| US6290439B1 (en) | 1994-12-30 | 2001-09-18 | Black & Decker, Inc. | Method and apparatus for forming parts from a continuous stock material and associated forge |
-
1979
- 1979-01-19 CA CA319,989A patent/CA1097104A/en not_active Expired
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4605347A (en) * | 1982-12-27 | 1986-08-12 | Lockheed Missiles & Space Company, Inc. | High speed drill reamer |
| US4968193A (en) * | 1986-08-18 | 1990-11-06 | Black & Decker Corporation | Self-centering drill bit with pilot tip |
| US5288183A (en) * | 1986-08-18 | 1994-02-22 | Black & Decker Inc. | Self-centering drill bit with pilot tip |
| US4997322A (en) * | 1989-12-26 | 1991-03-05 | Wells Bobby L | Automobile body reamer tool |
| US5244319A (en) * | 1991-11-01 | 1993-09-14 | Greenlee Textron Inc. | Auger bit |
| WO1996020803A1 (en) * | 1994-12-30 | 1996-07-11 | Black & Decker Inc. | A spade-type boring bit and an associated method and apparatus for forming metallic parts |
| US5697738A (en) * | 1994-12-30 | 1997-12-16 | Black & Decker, Inc. | Spade-type boring bit having chamfered corner portions |
| US5700113A (en) * | 1994-12-30 | 1997-12-23 | Black & Decker Inc. | Spade-type boring bit and an associated method and apparatus for forming metallic parts |
| US5842267A (en) * | 1994-12-30 | 1998-12-01 | Black & Decker, Inc. | Method and apparatus for forming parts of a predetermined shape from a continuous stock material |
| CN1056793C (en) * | 1994-12-30 | 2000-09-27 | 布莱克-德克尔公司 | Spade-type boring bit and associated method and apparatus for forming metallic parts |
| US6290439B1 (en) | 1994-12-30 | 2001-09-18 | Black & Decker, Inc. | Method and apparatus for forming parts from a continuous stock material and associated forge |
| US6739171B2 (en) | 1994-12-30 | 2004-05-25 | Black & Decker, Inc. | Method and apparatus for forming parts from a continuous stock material and associated forge |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |