WO1997031741A1

WO1997031741A1 - Drill

Info

Publication number: WO1997031741A1
Application number: PCT/AU1997/000123
Authority: WO
Inventors: Victor Edward J. Burton
Original assignee: Kloester, Ian, Albert
Priority date: 1996-03-01
Filing date: 1997-02-28
Publication date: 1997-09-04
Also published as: AUPN839396A0

Abstract

A drill comprising a cylindrical shaft having an axis, a single flute or groove extending along a portion of the shaft generally parallel to the axis and along a coaxial cutting head at an end of the shaft. The cutting head comprises at least one concentric extension portion of the shaft having a reduced diameter, with a respective joining surface between the shaft and adjacent extension portion and between adjacent extension portions. The flute or groove extends to an end face of an end extension portion, wherein the end face and each joining surface has a coaxial helical relief formed from a first edge of the flute or groove to a second edge thereof. The drill may have between one and four extension portions, forming a drill head having a stepwise cutting action, in use, with the edge of the flute or groove formed at the end face and each joining surface providing the cutting edges of the drill. The drill is particularly useful for the relatively fast formation of accurate round holes in a range of materials, and finds useful application in the aircraft construction industry for forming rivet holes or the like.

Description

DRILL

This invention relates to a drill. The drill of the invention finds application particularly in the relatively fast formation of accurate round holes in a range of materials using a rotary drill driving machine such as an electric hand-drill.

In a number of industries, such as the aero-space industry, it is necessary to form a very large number of holes through a range of materials and with accurate roundness. For example, in the manufacture of aircraft, portions of the aircraft body are often riveted together with many hundreds or thousands of rivets which extend through sheet material such as aluminium, carbon fibre, titanium, and composite materials. In order to insert the rivets, holes must be formed through the materials to be joined, for example using a drill. The accuracy of the roundness of the rivet holes affect the integrity of die rivet joins, and inaccurate holes can reduce the ultimate life span of the aircraft. Also, with the number of holes which need to be formed in such an industry the time and effort required to form each hole can have a significant effect upon the overall efficiency with which the aircraft is manufactured.

Ordinary twist drills have been found in some instances to produce a hole which is insufficiently accurate for the particular purposes required. Thus, where accurate hole roundness is required, often at least a three step process is used. Firstly a pilot hole is drilled, perhaps using an ordinary twist drill. Then, the pilot hole diameter is opened to a ream size, slighdy smaller than the final, required size. Finally, the hole is reamed to the required size using a reaming drill.

A reaming drill developed for the aircraft industry is illustrated in various views in accompanying Figure 1. The illustrated drill has four flutes or grooves, and it is readily apparent tiiat the drill is of a complex shape. The complex geometry of the reaming drill makes the drill relatively difficult and expensive to manufacture and to sharpen, particularly since cutting edges along four flutes must be ground. Also, the tapered geometry and multiple flutes of the reaming drill can cause the drill to chatter or vibrate during operation, which in some instances can cause the roundness of the hole to be compromised.

In accordance with the present invention, there is provided a drill for use with a rotary drill driving machine, comprising a cylindrical shaft, one end for being gripped by a driving machine, and having a drill head formed thereon, the drill head comprising a flute or groove formed in the shaft generally parallel to the axis of the shaft and having an edge thereof which passes through the shaft axis at one end of the shaft, said one end having a helical surface.

The invention also provides a drill head comprising a cylindrical shaft having a flute or groove formed tiierein generally parallel to the shaft axis, the flute or groove having opposed edges extending to an end face of the shaft with one of the edges passing through the shaft axis at said end face, wherein said end face is in the form of a helical surface extending from said one edge of the flute or groove to the other edge thereof.

The invention also provides a drill comprising a cylindrical shaft having an axis, a single flute or groove extending along a portion of the shaft generally parallel to the axis and along a coaxial cutting head at an end of the shaft, the cutting head comprising at least one concentric extension portion of said shaft of reduced diameter with a respective joining surface between the shaft and adjacent extension portion and between adjacent extension portions, said flute or groove extending to an end face of an end extension portion, wherein the end face and each joining surface has a coaxial helical relief formed from a first edge of the flute or groove to a second edge thereof.

The invention also provides a drill head comprising a pilot shaft and at least one successive coaxial drilling shaft of increased diameter, the pilot shaft and each adjacent drilling shaft being joined by way of a respective joining surface, die drill head having a flute or groove extending generally axially tiirough at least the respective joining surfaces each of which are helical in shape extending from a first edge of the flute or groove to a second edge thereof.

Preferably the flute or groove extends to an end face of die pilot shaft which is also helical in form. Preferably the first edge of the flute or groove extends through the axis of the pilot shaft at the end face such that, in cooperation with the helical shape of the end face an axial pilot drill point is formed.

In the preferred form of the invention, the flute or groove is formed with planar sides, a first side of the groove which forms said first edge extending in a radial plane through die shaft axis, and a second side of the groove which forms said second edge extending in a plane which is at least substantially parallel to another radial plane and slightly offset therefrom such that an axial drill point is formed at the pilot shaft end face in cooperation with the helical formation thereof. The angle formed between the planes of the first and second sides of the groove is preferably in the range of 90 degrees to 160 degrees. It is preferred that the groove angle be formed in the lower angle range at the time of manufacture of the drill head to allow for grinding of the first groove side during sharpening operations to increase the groove angle.

Preferably me pilot shaft end face and each joining surface is radially angled away from die pilot drill point at an angle of between about 45 degrees to about 75 degrees to the shaft axis. In a preferred form of the invention me radial angle is substantially 67.5 degrees to the shaft axis.

Various forms of the invention may employ varying numbers of drilling shafts, with one to four drilling shafts of successively increasing diameters according to their axial position with respect to the pilot shaft being preferred. The number of drilling shafts employed for a particular drill head may depend upon the diameter of the hole to be formed by the drill which corresponds to the diameter of die largest diameter drilling shaft. Accordingly the difference in diameters between adjacent drilling shafts and between the pilot shaft and adjacent drilling shaft may vary depending upon the diameter of the drill (ie of the largest drilling shaft) and the number of drilling shafts. The diameter of the pilot shaft may also be varied. The number and relative sizes of the drilling shafts and diameter of the pilot shaft may therefore be varied in order to vary me size of the plurality of cutting edges which are formed at the juncture of the first side of the flute or groove and each joining surface and, preferably, along the first edge of me flute or groove where the first side meets the end face of the pilot shaft.

The helical pitch of the joining surfaces and end face of the pilot shaft is preferably in d e range of 20 to 40 thousand s of an inch (0.51 to 1.02 millimetres) axial displacement per surface (eg per revolution). The helical pitch of die joining surfaces need not be identical, and need not necessarily be the same as the helical pitch of the pilot shaft end surface, although substantially identical pitches are preferred for most applications.

The axial length of me pilot shaft and of each drilling shaft need not be of a particular length, and need not be the same for each drilling shaft. It is preferred that d e axial lengm of the pilot shaft and of each drilling shaft be greater man the thickness of material for which me drill will be used to form holes through, because that construction ensures that only a single cutting edge operates at any given time during a drilling operation through the material. The number of drilling shafts with which a drill according to me invention is provided may also be varied according to me tiiickness of material with which the drill is to be used, with a greater number of drilling shafts (greater number of cutting edges) being preferred for drilling through thicker materials.

The invention is described in greater detail hereinafter, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a diagram showing end, side and cross-sectional views of a reaming drill according to a form of prior art;

Figure 2 is a side view of a drill according to one form of the invention; Figure 3 is an enlarged side view of a drill head of the drill of Figure 2;

Figure 4 is an enlarged end view of the drill head of Figure 3; and

Figure 5 is another enlarged end view of the drill head of Figure 3.

A drill 2 in accordance with one form of the invention is illustrated in Figure 2, comprising generally a cylindrical shaft 4 having a drill head 6 at one end diereof, witii the other end 5 being adapted to be gripped in a chuck of, for example, a gun-type electric hand drill. A flute or groove 8 is formed in the drill 2 which extends axially from the cylindrical shaft 4 tiirough the drill head 6 to an end face 20 of the drill head.

The drill head 6 of me drill 2 is illustrated in greater detail in side view in Figure 3 and end view in Figure 4. An axis 10 of the cylindrical shaft 4 is illustrated in Figure 3. The drill head 6 comprises a pilot shaft 12 which is coaxial with axis 10 and has a cylindrical body except for groove 8. At one end of the pilot shaft 12 is an end face 20, with me other end of me pilot shaft being joined to a coaxial first drilling shaft 14 by way of a first helical, frustoconical joining surface 25. The first drilling shaft 14 is coupled in turn to a coaxial second drilling shaft 16 by way of a second helical, frustoconical joining surface 27. The second drilling shaft 16 is in turn connected to a coaxial third drilling shaft 18 by way of a mird helical, frustoconical joining surface 29. The third drilling shaft 18 is integral with and of me same diameter as the cylindrical shaft 4 of the drill 2, in this instance. Each of the first, second and third drilling shafts 14, 16,18 have cylindrical body portions between their junctures to respective joining surfaces, except for the groove 8. The third drilling shaft 18 has a larger diameter man me second drilling shaft 16, which has a larger diameter than the first drilling shaft 14, which in turn has a larger diameter than the pilot shaft 12.

The groove 8 is formed between first and second opposed edges 32 and 33 which extend into planar first and second side faces. The first side face is coplanar witii a radially extending plane 35, and passes mrough the axis 10 at least at the end face 20. Preferably, e first side of the groove passes through the axis 10 along the majority of the axial length of the groove 8, at least until the groove tapers closed at its end furthest from the end face 20 (Figure 2). The second side of the groove 8 extends parallel to and displaced slighdy from a radial plane 36 which is shown in the Figures at a 90° angle to the radial plane 35.

The end face 20, and each of the joining surfaces 25,27 and 29 are helical in shape with the helical curvature of each extending from its intersection with the first edge 32 of the groove 8 around to the second edge 33 diereof . The helical pitch of die end face 20 and joining surfaces 25,27,29 is such that the axial displacement between tiieir respective intersections with the first edge 32 and second edge 33 is toward the end 5 of the drill. The end face 20 is also generally frustoconical so as to be angled with respect to a normal to the axis 10, such that a radial line across the end face 20 subtends an angle of less than 90° with the axis 10. Joining surfaces 25,27 and 29 are also angled in similar manner.

The geometry of the groove 8, having edge 32 passing through the axis 10 at die end face 20, together with the helical, frustoconical formation of the end face, enables e drill head 6 to form a drill point 24 coaxial witii axis 10. The coaxial drill point 24 enables accurate drilling with die drill 2 without a pilot hole, with initial cutting of drilled material being performed by pilot cutting edge 22 which is formed along of the first edge 32 of groove 8 at its juncture with the end face 20. Additional cutting edges 26,28 and 30 are formed at the intersection of the respective joining faces 25,27 and 29, respectively, witii me first edge 32 of the groove 8. The cutting edges 26,28,30 successively cut through the drilled material during use of die drill 2, witii swath from the drilled material passing out of the drilled hole through the groove 8.

The number of drill shafts on the drill head 6 may be varied, for example depending upon the diameter of the hole to be drilled. For example, if a larger hole is required, die drill head may be constructed with, for example, four or five drill shafts with corresponding helical joining surfaces and cutting edges, such that each cutting edge is relatively short. Accordingly, die radial width of the joining surfaces is also variable, from one drill to another, and may be different as between the joining surfaces in a single drill head. For example, it may be, in some instances, desirable to have the final joining surface (ie the joining surface which joins to the cylindrical shaft 4) to have a relatively small radial extent, such that the corresponding cutting edge is relatively small in order to provide for a good, round finish on the final hole formed by the drill.

The helical pitch of the end face 20 and joining surfaces may also be varied, and a preferred range for the helical pitch is from 20 to 40 thousandths of an inch (0.51 to 1.02 mm) of axial displacement per revolution. The helical pitch may be varied according to the number and width of the joining surfaces or, for example, depending upon the material for which the drill is adapted to be used with. Furthermore, the angle of the end face 20 and joining surfaces may be varied, with an angle of between about 45 ° to about 75° to the axis 10 being preferred. In a preferred embodiment of the invention, the radial angle is arranged to be substantially 67.5° to the shaft axis.

The axial extent of the pilot shaft 12 and drilling shafts can vary, although it is preferred that the axial extent of each be greater than the thickness of the material with which die drill is to be used. In that way, only a single cutting edge acts upon the material at any given point during the drilling operation.

Although me angle subtended by the sides of the groove 8 illustrated in the drawings is 90°, the groove angle can also be varied. Care should be taken with a groove angle of less than 90° , however, to ensure that sufficient clearance is provided for exit of the material swath during a drilling operation. Also, with a groove angle of greater than about 160°, care should be taken tiiat the drill head retains sufficient torsional integrity to perform the required drilling operations. Sharpening of the drill head is achieved by grinding of the first side of the groove 8 so as to form a new first edge 32 and respective cutting edges. The first side of the groove 8 is ground along a new radial plane such as planes 35a to 35d illustrated in Figure 5, whereby successive sharpening operations increase the groove angle. If a pilot hole is always to be provided for use with the drill 2, the groove 8 need not necessarily extend up to the end face 20, and the end face in that case may not require a radial angle or helical pitch. In that case, the pilot shaft 12 would be inserted in me pilot hole provided, and the first cutting operation of the drill 2 may be performed by the cutting edge 26 of the first joining surface 25. Alternatively, in another form the pilot shaft 12 may be of the same diameter as the cylindrical shaft 4, such ti at there are no additional steps of drilling shafts and joining surfaces therebetween.

The drill 2 can be integrally constructed from any of a range of materials, such as solid micrograin carbide or high-speed steel, such as cobalt steel or vanadium steel. Trials of embodiments of the drill have demonstrated success in drilling through the following materials, for example: aluminium from 0.005 inches to 0.25 inches thick, stainless steel from 0.019 inches to 0.062 inches thick, carbon fibre of various thicknesses, mild steel of 0.062 inches thick, titanium up to 0.08 inches thick, brass, glass, fibreglass, laminex without chipping, and brick or cement without use of an impact drill.

Drills according to die present invention have been found to produce extremely accurate, round holes in most aerospace materials up to 0.125 inches thick. The pilot shaft allows drilling into pre-drilled holes without misalignment, and the coaxial point of the pilot shaft allows drilling without a pre-drilled hole into a variety of surfaces and contours without drill wander. The drill according to an embodiment of the present invention has been found to be capable of drilling more holes than a conventional drill (for example, a standard high-speed steel twist drill), thus reducing the number of required sharpening sequences. Furthermore, sharpening of the single flute or groove of the preferred form of the drill can be accomplished quickly, easily and inexpensively. The surface finish of holes formed by the drill 2 is improved due to a burnishing effect caused by the cylindrical shaft thereof, such that minimal exit and entry burrs are formed, and those tiiat are formed tend to be easily removable.

The foregoing detailed description of the invention has been presented by way of example only, and is not intended to be considered limiting to the scope of the invention which is defined in the claims appended hereto.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not me exclusion of any other integer or group of integers.

Claims

CLAIMS:

1. A drill for use with a rotary drill driving machine, comprising a cylindrical shaft, one end for being gripped by a driving machine, and having a drill head formed thereon, the drill head comprising a flute or groove formed in the shaft generally parallel to the axis of the shaft and having a first edge thereof which passes through the shaft axis at one end of the shaft, said one end having a helical surface.

2. A drill as claimed in claim 1 , wherein the flute or groove is formed with planar sides, a first side of the groove which forms said first edge extending in a radial plane through the shaft axis, and a second side of the groove which forms a second edge extending in a plane which is at least substantially parallel to another radial plane and slightly offset tiierefrom such that an axial drill point is formed at said one end of d e shaft in cooperation with die helical surface thereof.

3. A drill as claimed in claim 2, wherein the angle formed between the planes of the first and second sides is in the range of 90 degrees to 160 degrees.

4. A drill as claimed in claim 1 , 2 or 3, wherein said helical surface has a pitch in me range of 20 to 40 thousandths of an inch (0.51 to 1.02 millimetres) axial displacement per revolution.

5. A drill head comprising a cylindrical shaft having a flute or groove formed therein generally parallel to the shaft axis, the flute or groove having opposed edges extending to an end face of the shaft with one of the edges passing through the shaft axis at said end face, wherein said end face is in the form of a helical surface extending from said one edge of d e flute or groove to die other edge thereof .

6. A drill comprising a cylindrical shaft having an axis, a single flute or groove extending along a portion of the shaft generally parallel to the axis and along a coaxial cutting head at an end of the shaft, the cutting head comprising at least one concentric extension portion of said shaft of reduced diameter with a respective joining surface between the shaft and adjacent extension portion and between adjacent extension portions, said flute or groove extending to an end face of an end extension portion, wherein the end face and each joining surface has a coaxial helical relief formed from a first edge of the flute or groove to a second edge thereof.

7. A drill as claimed in claim 6, wherein die flute or groove is formed with planar sides, a first side of die groove which forms a first edge extending in a radial plane through the shaft axis, and a second side of die groove which forms a second edge extending in a plane which is at least substantially parallel to another radial plane and slightly offset therefrom such at an axial drill point is formed at said one end of the shaft in cooperation with the helical relief thereon.

8. A drill as claimed in claim 7, wherein the angle formed between the first and second the flute or groove is in the range of 90 degrees to 160 degrees.

9. A drill as claimed in claim 6, 7 or 8, wherein the end face of said end extension portion, and each said joining surface, are radially angled at between 45 degrees and 75 degrees with respect to the shaft axis.

10. A drill head comprising a pilot shaft and at least one successive coaxial drilling shaft of increased diameter, die pilot shaft and each adjacent drilling shaft being joined by way of a respective joining surface, the drill head having a flute or groove extending generally axially through at least the respective joining surfaces each of which are helical in shape extending from a first edge of the flute or groove to a second edge tiiereof.

11. A drill head as claimed in claim 10, wherein the flute or groove extends to an end face of the pilot shaft which is also helical in form.

12. A drill head as claimed in claim 10, wherein the flute or groove is formed witii planar sides, a first side of the groove which forms a first edge extending in a radial plane through the shaft axis, and a second side of the groove which forms a second edge extending in a plane which is at least substantially parallel to another radial plane and slightly offset therefrom such that an axial drill point is formed at the pilot shaft end face in cooperation with the helical formation thereof.

13. A drill head as claimed in claim 12, wherein the angle formed between the planes of the first and second sides of the groove is in the range of 90 degrees to 160 degrees.

14. A drill head as claimed in claim 12 or 13, wherein the pilot shaft end face and each joining surface is radially angled away from the pilot drill point at an angle of between 45 degrees and 75 degrees to the shaft axis.

15. A drill head as claimed in claim 14, wherein said radial angle is substantially 67.5 degrees to die shaft axis.

16. A drill head as claimed in any one of claims 10 to 15, including between one to four drilling shafts of successively increasing diameters according to their axial position with respect to the pilot shaft.

17. A drill head as claimed in claim 10, wherein the helical pitch of the joining surfaces and end face of the pilot shaft is in die range of 20 to 40 thousandths of an inch (0.51 to 1.02 millimetres) axial displacement per revolution.