WO2003057437A1

WO2003057437A1 - Drill bit

Info

Publication number: WO2003057437A1
Application number: PCT/GB2003/000087
Authority: WO
Inventors: Anthony Davies; Han Shui Xiang
Original assignee: Tcl Supplies Ltd.; Hangzhou Xiaoshan Jiajia Tools Co.,Ltd
Priority date: 2002-01-14
Filing date: 2003-01-14
Publication date: 2003-07-17
Also published as: GB0200694D0; GB2388803B; GB2398753A; GB0415126D0; GB2398753B; AU2003202661A1; GB2388803A

Abstract

A high performance and versatile drill bit, for drilling curved bores, milling, countersinking and other application. A drill bit comprises a crown (6) and a shank (7) extending from the crown comprises at least three cutting blades.

Description

Drill Bit

The present invention relates to a high performance and versatile drill bit, for drilling

curved bores, milling, countersinking and other applications.

Within the context of this specification the word "comprises" is taken to mean

"includes, among other things". It is not intended to be construed as "consists of only".

Conventional drill bits, such as flat drill bits and twist drill bits, comprise cutting

blades capable of cutting only in a forwards direction. These drills lack versatility,

being able to only cut straight holes. Separate tools, for example milling tools or

countersinking bits, are needed if it is required to cut grooves, recesses or the like. In

many situations it is desirable to drill a curved hole, for example to allow insertion of

a flexible tubing without subjecting it to detrimental bending. Conventional drill bits

are only capable of producing bores to round comers that include sharp angles.

In addition to their limited scope of use, the cutting performance of known drill bits is

generally limited, with drill bits often having a poor cutting speed and smoothness of

cutting. Limitations arise due to factors such as a requirement for the application of

Jieavy pressure or frequent clogging of the drill bit with saw dust. A versatile drill bit would provide the great advantage of enabling diverse

applications, for example the cutting of recesses for installing locks and drilling of

curved bores for installing cables or tubing, to be carried with greater ease and without

the requirement for the use of multiple tools.

Drill bits are known that have the ability to cut in three directions. The known "3D

bif'described in European Patent 0181841 is a drill bit for cutting wood and other soft

materials. It comprises a crown having two forward (axial) cutting edges, two side

(radial) cutting edges and two rear (axial) cutting edges. This arrangement of cutting

edges enables the cutting of grooves, recesses and curved bores, in addition to straight

bores.

The present invention provides a new highly versatile drill bit with a cutting blade

geometry that provides a remarkably improved cutting performance over all known

drill bits.

In a first aspect the present invention provides a drill bit comprising a crown and a

shank extending from the crown, wherein the crown comprises at least three cutting

blades.

,

Preferably an embodiment of a drill bit according to the present invention provides a

drill bit wherein the crown comprises an odd number of cutting blades. Preferably an embodiment of a drill bit according to the present invention provides a

drill bit wherein the crown comprises three cutting blades. More preferably the three

cutting blades are disposed from the longitudinal axis of the drill bit at an angle of

120° with respect to each other. Even more preferably each three cutting blade is

identical.

drill bit wherein each cutting blade comprises a first axially cutting face, a radially

cutting face and a second axially cutting face. More preferably each cutting face

comprises at least one cutting edge.

Preferably an embodiment of a drill bit according to the present invention includes a

first axially cutting face having a first axially cutting edge that bisects a radius of the

crown. More preferably the first axially cutting edge trails the radius of the crown,

relative to the intended direction of rotation for cutting. In contrast, preferably the

trailing edge of the first axially cutting face lies on a radius of the crown.

Preferably an embodiment of a drill bit according to the present invention comprises a

cutting blade having a wing. Preferably, the wing is wedge shaped. More preferably

the wing extends circumferentially from the end of each blade distal to the central

longitudinal axis of the crown. More preferably the wing has a curved outer face.

Even more preferably, each wing extends circumferentially from the face of a blade adjacent the first axially cutting edge and the projecting edge of each wing forms a

radially cutting edge.

Preferably each cutting blade is provided with a wedge shaped tooth that projects from

the blade in an axial direction to a greater extent than the first axially cutting face.

More preferably the tooth tapers to form a third axially cutting edge. Even more

preferably the third axially cutting edge is provided proximal to the first axially cutting

edge. Furthermore, the third axially cutting edge is curved from a first end where it

meets the radially cutting edge to a straight portion at its opposing end on top of the

crown.

Preferably an embodiment of a drill bit according to a first aspect of the present

invention has a crown that comprises an axial tapered cutting tip positioned on the

longitudinal axis of the drill bit wherein the cutting tip projects in an axial direction

further from the shank than any other part of the crown. More preferably the cutting

tip is tapered at an angle of about 20° to about 40°. Even more preferably the cutting

tip tapers at an angle of about 25° to about 35°. Even more preferably the cutting tip

tapers at an angle of about 30°.

Preferably the tapered cutting tip is pyramidal and has three sides which are tapered at

the angles described above. Preferably an embodiment of a first aspect of the present invention comprises an

attachment portion for a drilling machine positioned adjacent the shank distal to the

crown. More preferably the attachment portion is of a wider diameter than the shank.

Even more preferably there is a collar between the shank and the attachment portion,

increasing in diameter from that of the shank to that of the attachment portion. Even

more preferably the collar has a rough texture for providing grip.

A preferred embodiment of a drill bit according to the present invention provides a

drill bit comprising a titanium nitrate (TiN0₃) coating.

drill bit comprising 1060 high carbon steel and is of the hardness HRC 45-55.

An advantage of the present invention is that it provides a drill bit comprising at least

three cutting blades, rather than the known arrangement of two cutting blades, thereby

increasing the speed of cutting and smoothness of cut.

A further advantage is that the cutting blades are more stable while cutting, thereby

reducing the chatter or vibration of the drill bit when in use. The chatter of a drill bit

according to this invention is reduced relative to known drill bits when cutting in any

one of the possible cutting directions. The reduction of chatter is most substantial

when the drill bit is used for milling in a radial direction. A further advantage of the present invention is that it provides a drill bit that has a

smoother radial cutting action than known drill bits. The cut produced is cleaner and

more accurate than that produced by any known drill bit.

A drill bit according to this invention has a particular advantage when being used to

cut a channel in a surface. A reaction force, or angular friction, is generated by each

radial cutting edge or wing. The direction of this force has a stabilising effect and

reduces any tendency of the drill bit to jump out of a channel whilst cutting. This

advantage arises due to the particular geometry of the cutting blades in relation to the

central axis of the shaft and the direction of rotation. In contrast to the invention, the

cutting blades of known drill bits are positioned so that they precede the radius, rather

than trail it. In these circumstances, the reaction force generated is directed out of the

channel and a tendency of a drill bit to jump out of the channel is increased.

A further advantage of the present invention is that it provides a drill bit with improved

cutting of wood, ejection of wood chips and thereby improved cutting speed. The gap

between the cutting blades of the present invention has a larger volume than in known

drill bits. Consequently the drill bit of the invention is less likely to clog with excess

wood chips.

An advantage of the present invention is that it provides a drill bit comprising a cutting

tip that is designed to prevent slipping. The tapered cutting tip of the present invention preferably has three sides and comes to a sharp point. It is less likely to slip than the

known four-sided cutting tips of known drill bits, wherein the tip tapers to a less sharp

point.

An advantage of the present invention is that it provides a drill bit comprising a TiN0₃

coating, providing an increase in the hardness of the drill surface. A TiN0₃ coating

thus provides a drill bit with a greater resistance to wear and therefore extends the

working life of the drill bit.

A further advantage of a TiN0₃ coating is a reduction of friction, thereby favourably

reducing the operating temperature of the drill. Additional advantages of a TiN0₃

coating are that it serves to inhibit corrosion and provides an attractive shiny finish to

the drill bit.

The improved drilling performance of a drill bit according to this invention allows a

drill bit to be manufactured from a reduced hardness of steel whilst still achieving the

same cutting speeds as with known drill bits. Conversely, a drill bit according to this

invention, comprising high performance steel gives a significant increase in

performance over known drill bits of this type, enabling drilling of harder materials

Jhan was previously possible. Additional features and advantages of the present invention are described in, and will

be apparent from, the description of the presently preferred embodiments which are set

out below with reference to the drawings in which:

Figure 1 shows a side view of a preferred embodiment of a drill bit according to the

present invention.

Figure 2 shows an end view of three cutting blades of a crown of a preferred

embodiment of a drill bit according to the invention.

Figure 3 shows a view along the longitudinal axis of a preferred embodiment of the

present invention whilst cutting a groove. The direction of rotation, fiictional force and

reaction force pointing into a channel are shown.

Figure 4 shows a view along the longitudinal axis of a drill bit where the blades

precede the radius rather than trail it. The direction of rotation, fiictional force and

reaction force pointing out of a channel are shown.

For the purposes of clarity and a concise description features are described herein as

part of the same or separate embodiments, however it will be appreciated that the

scope of the invention may include embodiments having combinations of all or some

of the features described. A preferred embodiment of a drill bit according to the invention is shown in figures 1

and 2. The drill bit comprises a crown (6); a shank (7) which extends from the crown

(6); a collar (9) adjacent the shank (7) distal to the crown (6); and an attachment

portion (8) adjacent the collar (9) and distal to the crown (6). The drill bit has a TiN0₃

coating.

The shank (7) is coaxial with the crown (6) and is of significantly smaller diameter

than the crown (6).

The crown (6) comprises a cutting tip (1) on its central longitudinal axis. The cutting

tip (1) comprises a pyramid having a base and three sides each tapered to a 30° point.

In addition, the crown (6) comprises three identical cutting blades which extend

radially from the central longitudinal axis of the crown. The cutting blades are

separated from each other by an angle of 120°.

Each cutting blade comprises a first axially cutting face having a first axially cutting

edge (2); and a second axially cutting face having a second axially cutting edge (5).

The first and second axially cuttmg faces oppose each other and the first and second

cutting edges are for cutting in opposite directions. The first axially cutting face

,bisects a radial plane of the crown at an angle of about 15°. The second axially cutting

face bisects a radial plane of the crown at an angle of about 5° to about 10°. In addition, the second axially cutting face bisects an axial plane of the crown at an angle

of about 5° to about 10°.

In addition, each cutting blade comprises a wedge shaped wing that extends

circumferentially from the end of each blade distal to the central longitudinal axis of

the crown. Each wing extends circumferentially from the face of a blade adjacent the

first axially cutting edge. The projecting edge of each wing forms a radially cutting

edge (4). The radial cutting edge (4) bisects an axial plane of the crown (6) at an angle

of 18°.

The radially outer face of the wing bisects a circumferential plane at an angle of 3° so

that the wing is radially more distant from the central longitudinal axis of the crown

adjacent the first axially cutting face than adjacent the second axially cutting face.

In addition, each cutting blade comprises a wedge shaped tooth located atop the join

between a wing and a first axially cutting face. Each tooth has a third axially cutting

face having a third axially cutting edge (3). The third axially cutting edge (3) is

provided adjacent the first axially cutting edge (2). Furthermore, the third axially

cutting edge is curved from a first end where it meets the radially cutting edge to a

straight portion at its opposing end. It should be understood that various changes and modifications to the presently

preferred embodiments described herein will be apparent to those skilled in the art.

Such changes and modifications can be made without departing from the spirit and

scope of the present invention and without diminishing its attendant advantages. It is

therefore intended that such changes and modifications are covered by the appended

claims.

Claims

1. A drill bit comprising a crown and a shank extending from the crown, wherein

the crown comprises at least three cutting blades.

2. A drill bit according to claim 1 having an odd number of cutting blades.

3. A drill bit according to claim 2 wherein the crown comprises three cutting blades.

4. A drill bit according to claim 3 wherein the three cutting blades are disposed from

the longitudinal axis of the drill bit at an angle of 120° with respect to each other.

5. A drill bit according to any preceding claim wherein each cutting blade is

identical.

6. A drill bit according to any preceding claim wherein each cutting blade comprises

a first axially cutting face, a radially cutting face and a second axially cutting

face.

,

7. A drill bit according to claim 6 wherein each cutting face comprises at least one

cutting edge.

8. A drill bit according to claim 7 comprising a first axially cutting face having a

first axially cutting edge that bisects a radius of the crown.

9. A drill bit according to claim 8 wherein the first axially cutting edge trails the

radius of the crown, relative to the intended direction of rotation for cutting.

10. A drill bit according to claim 8 or 9 wherein the trailing edge of the first axially

cutting face lies on a radius of the crown.

11. A drill bit according to any preceding claim comprising a cutting blade having a

wing.

12. A drill bit according to claim 11 wherein the wing is wedge shaped.

13. A drill bit according to claim 11 or 12 wherein the wing extends circumferentially

from the end of each blade distal to the central longitudinal axis of the crown.

14. A drill bit according to any one of claims 11 to 13 wherein the wing has a curved

outer face.

,

15. A drill bit according to any one of claims 11 to 14 wherein each wing extends

circumferentially from the face of a blade adjacent the first axially cutting edge

and the projecting edge of each wing forms a radially cutting edge.

16. A ( il bit accordmg to any preceding claim wherein each cutting blade is

provided with a wedge shaped tooth that projects from the blade in an axial

direction to a greater extent than the first axially cutting face.

17. A drill bit according to claim 16 wherein the tooth tapers to form a third axially

cutting edge.

18. A drill bit according to claim 17 wherein the third axially cutting edge is provided

proximal to the first axially cutting edge.

19. A drill bit according to claim 18 wherein the third axially cutting edge is curved

from a first end where it meets the radially cutting edge to a straight portion at its

opposing end on top of the crown.

20. A drill bit according to any preceding claim wherein the crown comprises an

axial tapered cutting tip positioned on the longitudinal axis of the drill bit wherein

the cutting tip projects in an axial direction further from the shank than any other

part of the crown.

21. A drill bit according to claim 20 wherein the cutting tip is tapered at an angle of

about 20° to about 40°.

22. A drill bit according to claim 20 or 21 wherein the tapered cutting tip is

pyramidal and has three sides, each tapered at an angle of about 20° to about 40°.

23. A drill bit according to any preceding claim comprising an attachment portion for

a drilling machine positioned adjacent the shank distal to the crown.

24. A drill bit according to claim 23 wherein the attachment portion is of a wider

diameter than the shank.

25. A drill bit according to claim 24 comprising a collar between the shank and the

attachment portion, increasing in diameter from that of the shank to that of the

attachment portion.

26. A drill bit according to claim 25 wherein the collar has a rough texture for

providing grip.

27. A drill bit according any preceding claim comprising a titanium nitrate (TiNO₃)

coating.

28. A drill bit according to any preceding claim that comprises 1060 high carbon

steel and is of the hardness HRC 45-55.

29. A drill bit substantially as described herein with reference to or as illustrated in

any of the figures of the accompanying drawings.