Background of the invention Medium Density Fibreboard (MDF) such as that known under the trade mark CRAFTWOOD, is manufactured from a combination of resin and very fine wood fibres. During the manufacturing process some types of MDF are finished with a very dense outer surface which is given to provide the surface with a very smooth finish so that the board can be painted or otherwise coated without the need to sand. The elimination of sanding give such board the advantage that dangerous dust is not generated and removes a whole process step before a finial finish is given.

This has led to a very wide acceptance of such MDF. Other materials such as masonite also have a dense outer layer but such a material is not as dense as MDF.

A dense outer layer of MDF causes difficulties for trades people when assembling such MDF into a structure such as for example architraving, skirting board or frame or boarder material. Such operations are typically carried out using sophisticated self tapping screws which were developed for fibre board use. Such screws do not have self drilling capability as the self drilling capability adds greatly to the cost of such screws. The fibre board screws tend to have only a sharp point which is designed for softer material whereby application of pressure to the point embeds the point into the material so that the start of the thread is actually in the material. However when such screws are used with MDF, the sharp screw point does not penetrate the dense outer layer. This can have disastrous results for the tradesperson, as they are normally applying great force and may result in the screw slewing off in one direction.

This will can cause injury to the tradesperson or damage to the MDF workpiece as well as be generally inconvenient.

A time consuming, and fiddly fabrication function is the need to countersink a screw into a surface into which a screw is to be assemble. Countersinking represents another difficulty for a tradesperson which is exacerbated when MDF is involved.

This countersinking can be done by drilling a pilot hole, countersinking the pilot hole and then driving in the screw.

With the advent of self-drilling and tapping screws and powered screwdrivers, pilot holes no longer required to be drilled.

Some self-tapping, self-drilling screws do have formations on a countersinking head which are adapted to assist the screw to countersink itself as the screw rotates and the head engages the surface. However by the time the countersinking head has reached the surface in which it is to be counter sunk the speed of the screw has been reduced. This reduces the ability of the formations on the screw's head to properly countersink. One difficulty with self-drilling self-tapping screws is that many of them never fully countersink. This is because once they reach the surface, the power to drive may not be sufficient. Or alternatively, sometimes they snap by virtue of the amount of power being used to drive the screw in.

Another difficulty which can occur is that the female thread can strip inside the material if the screw is rotated with too much power or speed.

These are some of the many difficulties which can occur with countersinking screws. To date the problem of countersinking screws has been troublesome and annoying. Some of these problems are exacerbated when countersinking is required to be done in materials which have a very dense or hard outer surface and this surface must first be breached before ease of countersinking occurs. Examples of such materials include a custom board or MDF board which material may also be sold under the trade mark CRAFTWOOD.

Disclosed in US patent 3207196, issued and published on 21 September 1965, is a countersinking tool which combines a screw driving bit and counter sinking bit. However, the countersinking bit is stated to be an abrading, wearing or rubbing bit so as form a depression. Because of this abrading feature, the cutting tool of US 3207196 is not able to form a depression into modern materials such as MDF-board as such boards have a very dense outer surface.

Some countersinking screw heads are manufactured so as to include a series of elongated triangular prism formations along the slant height of a countersunk head. These prism formations have a great deal of difficulty counter sinking a screw in an MDF-board due to the density of the surface of the board. One difficult is that MDF's density leads to the head of the screw fracturing from the shank.

If the screw head does not fracture from the shank, another difficult is that it can take several attempts at tightening and loosening the screws so as to be able to properly counter sink the head into the surface of an MDF-board.

These prisms, due to the extra steps needed to countersink the heads of countersinking screws, are generally inefficient.

It is an object of the present invention to provide a countersinking screw which ameliorates, at least in part, at least one of the disadvantages of the prior art.

Summary of the Invention The invention provides a screwdriving tool having a shank adapted to be rotationally driven about its longitudinal axis; and a cutting tip located on the screw driving tool at the end opposite to said shank, said cutting tip being laterally off set from said longitudinal axis so as to produce a starter hole for a self tapping screw when the said tool is pressed against a surface and the tool is rotated.

The at least one cutting tip, or each cutting tip when there is more than one cutting tip, is that part of the tool which is located at the furthest distance away from the shank, measured in a direction which is parallel to said longitudinal axis.

The screwdriving tool can be of a flat blade variety or a four blade variety such as cross shape or Phillips head type.

The cutting tip can be formed by a concave cut out intersecting with the screw driving end with the cutting tip converging to either a point or a surface.

The invention provides a screwdriving and countersinking tool having a narrow end and a broad end said narrow end having a screw engaging means so as to be able to drive a screw when said screw engaging means has engaged a screw, said tool having formed thereon, between said narrow end and said broad end, a countersinking means, said narrow end including as part of said screw engaging means a shearing means to allow said narrow end to engage a surface to be countersunk and to remove material from said surface when said tool is rotated.

Preferably said tool has, when viewed in side elevation, a generally triangular configuration.

Preferably said tool has a generally pyramidal shape.

Preferably said tool has a generally conical shape.

Preferably said tool has one or more screwdriving members as its screw engaging means.

Preferably said tool has a Phillips head configuration as its screw engaging means.

Preferably screw engaging means has at, at least one terminus, said shearing means.

Preferably said tool includes at least one continuous shearing formation which is located between said narrow end and said broad end.

Preferably said tool includes more than one discontinuous shearing formation which are located between said narrow end and said broad end.

Preferably said more than one discontinuous shearing formations are overlapping.

Preferably said shearing formations and other parts of the tool which are not insertable into a screw head, are able to perform the countersinking function, and at the same time are safe to contact when the tool is rotating.

Preferably said shearing formations are formed from cuneiform or triangular elongated shearing members.

Preferably said countersinking means operates to form a countersunk recess in a material by rotating in a direction which is opposite to the direction said tool must rotate to drive as screw into said material.

The invention also provides a screwdriving tool to drive a screw into a surface, said tool including a converging screw engagement end which has a formation to engage a screw, said formation also forming part of a countersinking means formed on the remainder said tool, wherein said countersinking means is also formed on said engagement end with said countersinking means at least in part being insertable into a recess in said screw, said recess being used to drive said screw into a surface.

Preferably said countersinking means operates to form a countersunk recess in a material by rotating in a direction which is opposite to the direction said tool must rotate to drive said screw into said material.

The invention also provides a countersinking screw having slot located in a head for driving said screw and a threaded shank extending away from said head, said screw having a longitudinal axis of rotation around which said screw is constructed, said head being of a generally conical formation which is converging in the direction from said head to said threaded shank, said head having at least one discontinuous circumferential surface therearound, said head including at least one blade portion thereon, said blade potion being characterised by a cutting surface which lies in a plane which is at an angle relative to a plane which includes said axis of rotation, said head being

further characterised by the said at least one circumferential surface starting at a first slant line location and ending at a second slant line location, said first slant line location being at a first end of said cutting surface and said second slant line location being at a second end of said cutting surface, said first end of said cutting surface being radially displaced away from said axis of rotation by a distance which is greater than the radial displacement of said second end of said cutting surface.

Preferably said screw includes at least one blade portions on said countersinking head and the same number of broken circumferential surfaces around said countersinking head.

Preferably there is more than one blade portions equi-spaced on said countersinking screw head.

Preferably said cutting surface, when viewed from a direction normal to said cutting surface, has a generally triangular shape.

Preferably said cutting surface converges in the direction from said head to said threaded shank.

Preferably said cutting surface lies in a plane which contains said axis of rotation and a radius from said axis of rotation.

Preferably said cutting surface includes at least one surface which has its direction defined by a direction line normal to said surface or by a direction line normal to a tangent to said surface, whereby said direction line is skewed relative to said axis of rotation.

Preferably said cutting surface is a helical or part helical surface.

Preferably said cutting surface has a slope on it wherein at any point on said surface, said surface inclines in a direction away from said point, when said direction away from said point is opposite to the direction required to secure said screw into a material.

Brief description of the drawings An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a combination screwdriving and countersinking bit prior to engagement with a countersinking screw.

Figure 2 illustrates a perspective view of the bit of Figure I.

Figure 3 illustrates a plan view of a second embodiment of a combination screwdriving and countersinking bit.

Figure 4 illustrates a side elevation of the bit of figure 3, prior to engagement of a countersinking screw.

Figure 5 illustrates a plan view of a third embodiment of a combination screwdriving and countersinking bit.

Figure 6 illustrates a side elevation of the bit of figure 3, prior to engagement of a countersinking screw.

Figure 7 illustrates one of the bits of figures 1 to 6 in use during a countersinking operation.

Figure 8 illustrates one of the bits of figures 1 to 6 in use during a screw driving operation.

Figure 9 illustrates a Phillips head screw driving bit having a gouging or cutting tip.

Figure 10 illustrates a flat blade screw driving bit having a gouging or cutting tip.

Figure 11 illustrates a hexagonal blade screw driving bit having a gouging or cutting tip.

Figure 12 illustrates a side elevation of a first embodiment of a countersinking screw.

Figure 13 illustrates a side elevation of the screw of figure 12.

Figure 14 illustrates a side elevation of a second embodiment of a countersinking screw.

Figure 15 illustrates a side elevation of the screw of figure 14.

Figure 16 illustrates a screw of figure 12 or figure 14 in use.

Detailed description of the embodiments Illustrated in Figure 1 and 2 is a straight fluted generally conical shaped tool 2. In side elevation as in figure 1 the tool 2 has a generally triangular shaped profile. The tool 2 has a base 4 from which extends a rotation shaft 6 of the hexagonal type. The tool 2 is illustrated as a rotary bit for inserting into an electric screwdriver or other powered screwdriving rotation driving means such as a drill, pneumatic drill etc. However, It will be readily understood that the present invention can be applied to manually or hand operated tools such as hand powered screwdrivers or drills for that matter.

The tool 2 has a relatively broad base 4 by comparison to a relatively narrow screwdriving end 10. The screwdriving end 10 has a screw driving tip 8. The screw driving end 10 occupies approximately half the height of the tool 2, with the rest of the height of the surface engagement portion of the tool 2 being made up of the countersinking section 12.

The screwdriving end 10 is made up of four radiating wing/members 14,16,18 and 20. The wing members 14,16, 18 & 20 have straight and parallel forward and rearward sides 11 and 13 which are parallel to the longitudinal axis 5 of the shaft 6, and are radially oriented to the longitudinal axis 5. The outer surfaces 15 of the members 14,16,18 and 20 are at an angle 17 to the longitudinal axis and at an angle 17A to the straight sides 11 and 13 on each member 14,16,18 and 20. The members 14,16,18 and 20 form a cross in underneath plan view. The cross is insertable into a cross shape cavity 22 which is generally located in Phillips head screws 23.

At the very terminus and near the apex of the members 14,16,18 and 20 is a blade portion or cutting tip 24. On the member 14 the cutting tip 24 is an inclined plane which angles in one direction, whereas on the member 20 the cutting tip 24 is an inclined plane in the opposite direction when viewed as in fig I. All the cutting tips 24, when the tool 2 is rotated about an axis 5 present the forward edge 24A to engage the surface which will have a counter sunk recess formed therein. The surfaces 15 A behind the cutting edges 24A are also at an angle to the longitudinal axis 5. That is the end of the surfaces 15A furthermost from the longitudinal axis 5 are further away from the base 4 by comparison to the opposite end of the surfaces 15A (which opposite end is nearest to the longitudinal axis 5). This places each of the surfaces 15A at an angle which forms a concave end.

If desired only one of the members 14,16,18 or 20 need have a cutting tip 24 or 2 or more of the members 14,16, 18 and 20 can have such blades. In the countersinking segment 12 the members 14,16,18 and 20 extend back

towards the base 4 and have formed thereon at their forward edges 24B a similar cutting edge to cutting edge to cutting tip 24. Four additional countersinking blades 28 (see fig 1) can be located intermediate the forward edges 24B on member 14,16,18 and 20 but these four additional counter sinking blades 28 are only preferable and are not illustrated in fig 2.

The tool 2 as illustrated in fig 2 has the countersinking segment 12 constructed from members which extend a considerable distance radially from a central body portion 23. However if desired the countersinking segment 12 can be formed on a conical or pyramidal surface, with the shearing formation projecting only a relatively short distance away from the body.

Whilst the tool 2 has a generally triangular configuration in side elevation as illustrated in Figure 1, it can be seen from the Figure 2 that a pyramidal or conical shape is an appropriate description of its overall general shape. It will be noted in figure I that the tool 2 has the members 14,16,18 and 20 terminating in a cutting edge 53, which is parallel to the longitudinal axis 5. Whereas, for the sake of illustration the tool 2 of fig 2 includes no such cutting edge 53. The effect of these differences will be discussed later.

The screw driving end 10 and countersinking segment 12 need not be continuous all the way from the screwdriving end 10 back to the base 4. They may need to be continuous along the length of the respective segments but otherwise the cutting tips and cutting edges, on the members on which they are mounted can be angularly offset. In which case they will need to either overlap or in side elevation one will need to terminate in a plane which is the beginning of the other.

Referring now to figures 7 and 8, in use the tool 6 is attached to a drill 300 or other portable rotation means. In use the drill 300 is rotated so that the tool 2 can rotate and engage a surface 302 of a member 304 thereby countersinking the surface to form a counter sunk recess 306 as forward edges 24A and 24B of the tool 2 engage the surface 302. The countersinking segment 12 will progress to a depth in the region of outer width or diameter 31 of the tool 2. The outer diameter 31 is preferably equal to or greater than the outer diameter of the head of the screw 23.

Depending upon the material of the member 304 into which a countersunk recess 306 is to be formed, and the type of screw 23 utilise, it may not be necessary for the outside diameter of countersunk recess 306 to be greater or equal to the outside diameter of the head of the screw 23. If the countersinking screw 23 has shearing formations or capacity on the outside surface of the countersinking head, then the outside diameter of the countersunk recess can be less than the outside diameter of the screw, if the material is of a timber, timber composite or fibre board or like material such as custom board or MDF board.

If no prior art screw countersinking formations were present on the outside surface of the screw 23, then the outside diameter of the countersunk recess 306 in the member 304 may need to be equal to or greater than the outside diameter of the head of the screw 23.

In the case of the tool 2 illustrated in fig 1, if the tool 2 is inserted into a surface to the depth of the base 4, a countersunk recess will be formed which will include a cylindrical portion immediately below the surface. The cylindrical portion is formed by the cutting edge 53 which is parallel to the longitudinal axis 5. The cutting edge 53 will result in a neater, smoother, cleaner finish to the recess and can be timber plugged or puttied if necessary.

The absence of the cutting edge 53 from the tool 2 of fig 2, can result in the same cylindrical portion being formed in the material, but there is risk is that the surface and edges of the cylindrical portion may not be as clean and precise. The tool of fig 2 is better adapted to form only a tapered countersunk recess without a cylindrical portion.

This does not mean to say that the tool of fig 2 could not be used to exactly the same purposes as the tool of fig 1.

Referring once again to figures 7 and 8, once the desired depth of countersunk recess 306 has been achieved, a screw 23 is placed on the screw driving tip 8 and the operator then depresses the end 308 of the screw 23 into the countersunk recess 306 in the member 304. By rotating the screw 23 (which is a self-drilling. self-tapping screw), the screw driver tip 8 and the drill 300 will force the screw 23 into the position shown in figure 8, by rotating the screw 23 until the top surface of the countersinking head of screw 23 is at or below the surface 302 of member 304 into which the countersunk recess 306 was formed.

As the members 14,16, 18 and 20 are inside the cross shaped recess 22 of the screw 23, the cutting tips 24 and forward edges 24A of members 14,16,18 and 20 will not attempt countersink the screw head 23 because there is no relative rotation between the screw and cutting tips 24. The absence of relative rotation is a result of the surfaces of the recess of the screw resting parallel to the side surfaces of the members 14,16,18 and 20.

Whilst it is advantageous for those portions of the tool 2 which are engaged into the recesses 22 of the screw to be relatively sharp, it is preferred that the countersinking segment have cutting edges which are not particularly sharp.

This will help to prevent injury to the user as the user may have their hand near to the tool, to hold the screw onto the screw driving end 10. These cutting edges need not be sharp but by virtue of the speed of rotation of the drill will execute an effective countersinking operation.

The cutting tips 24, the cutting edges 24A and 24B (and the cutting edge 53 if it is present) do not necessarily need to be sharp, or tempered and sharp, if the tool 2 is to be used with timber or timber type products such as MDF (medium density fibre board) custom board (as sold under the trade mark CRAFTWOOD). However, if the tool 2 is to be utilised with metals, then the cutting edge will more than likely need to be sharp, and possibly tempered as well. One of the difficulties of tempering however, is that the metal of tool 2 can become brittle, and may fracture when used as a screwdriver. However, it is expected that other treatments of the metal will provide sufficient strength while maintaining for as long as possible a relatively sharp cutting edge.

In the embodiment described with respect to the drawings, there is formed a concave end in the screw driving tip 8.

When used to countersink, this concave end will form at the base of the countersunk recess, a relatively small and shallow mound or conical projection. This mound or projection will not impair the effectiveness or operation of the tool 2. However, if desired, the concave end can be replaced by a flat planar end, that is the cutting edges 24A are all included in a single plane, which plane is perpendicular to the longitudinal axis 5. Alternatively, the cutting edges could be made to form a convex end. However, the depth of the convex end will also be dependent upon the size of the recess 22 in the screw 23, to ensure a proper screw driving ability.

The tool 2 can be made of magnetic material, so that screws 23 might be attracted to the tool 2 and thereby stay in position, as the user threads the screw into the wall. This obviates the need for the operator to use their free hand to support the screw.

Illustrated in figure 3 is a combination bit 2B to countersink and drive a screw 23 (see figure 4). The bit 2B has many features in common with the features bit 2 of figures I and 2. These similar features are like numbered with the features of figs I &2. Because of this commonality the purpose and structure of all features will not be discussed.

The cutting edges 24B and 53 of the countersinking portion 12 when viewed in the plan view of figure 3 includes a cutting face 11 and rear face 13 on each of eight wing members 14,14A, 16,16A, 18,18A, 20,20A, which converge toward the axis of rotation 5. The cutting edges 24B and 53 of the bit 2B are formed from the intersection of the cutting face 11 together with a tapered outer surface 15. The bit 2B of figures 3 and 4 will perform its countersinking function when it rotates clockwise in the plan view of fig 3, which is the same direction as the direction of rotation to drive a screw into a material or board. This is also similar to the embodiment of figures 1 and 2.

Illustrated in figures 5 and 6 is a bit 2C similar to that of figures 3 and 4, and like parts have been like numbered.

The difference between the bit 2B of figures 3 and 4, and the bit 2 of figures 5 and 6, is that the countersinking segment 12 has its cutting face 11 on the opposite sides of the wings 14, 14A, 16, 16A, 18,18A, 20 and 20A to the cutting faces 11 on the bit of figures 3 and 4. The location of these cutting faces means that the bit 2C performs its countersinking function in the opposite direction, namely counterclockwise in plan view of figure 5. The bit 2C of figures 5 and 6 performs its screw driving functions in the same direction as the bit of figures 3 and 4.

The wings members 14A, 16A, 18A, and 20A extend from the end proximate to the shaft 6 or base 4 towards the screw driving end 10, but do not extend into the screw driving end 10, otherwise the wing members 14A, 16A, 18A, and 20A will interfere with the engagement of the screw driving end in the slot 22 of screw 23.

The ends of the members 14,16,18,20, at the lower end of the screw driving segment 10 of bit 2C of figures 5 and 6, have inclined surfaces 15A, which are angled to provide cutting edges 24 which cut in the anti clockwise direction. The inclined surfaces 15A are at an angle whereby the cutting edge 24 projects downwardly from the wing members 14,16,18,20, by comparison to the rearward edge of the inclined surfaces 15A.

This feature ensures that the cutting edge 24 and surface 15A will not interfere with or damage the driving slot in the screw 23. The rearward face 13 of the wing members is opposite to the cutting surfaces 11, which engages the sides of the slot 22 of the screw 23.

To operate the bit of figures 5 and 6, the operator simply mounts the bit 2C into a reversible drill or other rotary tool. To form a countersunk recess in a material to receive the screw 23, the operator rotates the bit 2C in an anti clockwise direction. To cut or shave countersunk recess, the cutting edges 24B and 53 engage and are moved or rotated relative to the surface receiving the countersunk recess. Once the desired depth of countersinking is reached, the operator reverses the direction of rotation of the drill or rotary tool. Upon doing this or before, the operator attaches a screw such as screw 23 onto the screw driving end 10 of the bit 2C of figures 5 and 6. By then activating the drill or rotary tool, as the tip of the threaded end of the screw 23 is in the base of the countersunk recess, the screw 23 will be inserted into the material and the recess so that the top surface of the screw 23 is at or below the surface of the material.

While the above described bits are illustrated including four or eight cutting surfaces or edges, it will be readily understood that the present invention is applicable to tools, bits and screws having at least one, or one or more cutting surfaces or edges.

Illustrated in figure 9 is a screwdriving tip 500 which has a central longitudinal axis of rotation 502 and a screw driving end 504 and a shank 506. The shank 506 includes a hexagonal drive end 508 for connection into a powered screwdriver, drill, manual hex drive or other means to rotate the tip 500 and thus drive screws into a surface. If desire the shank 506 can be connected to a conventional screw driver handle.

The screwdriving end 504 is of the Phillips head variety having four orthogonal blades 510. The blades 510 are formed in a conventional way on the end of the shank 506. The screw driving end 504 varies from a conventional Phillips head screw driving end by each blade 510 terminating in a cutting, gouging or carving tip 512, which is formed (in this instance) by a cavity or concave recess 516 intersecting with the blades 510. This intersection forms cuneiform cutters which project away form a base surface 518 located at the terminus of the screw driving end 504 at the central axis of rotation. The location of an extremity of tip 512 relative to any point on the shank 506 is a greater distance away from that point on the shank than the location of the base surface 518.

The tips 512 terminating in an edge 520 is the preferred arrangement, however, if desired they could be made to terminate with a point, or even a rounded edge or surface. Any appropriate terminus can be used which will allow the tip 512 to cut into a material into which a screw is to be inserted.

The embodiment of figure 9 is illustrated as being of the Phillips head variety. However, the invention embodied in figure 9 can be embodied in a flat head type screw driver, or other type of screw driving formations. For example in figure 10 the flat blade screw driver tip 530 has a concave recess 532 in its tip 534, which forms a cutting, gouging or carving tip 536 at the ends of each of the blades 530. Whereas in figure 11 is a hex drive tip 540 as is used to drive screws with a hex recess in their head. The tip 540 has six cutting, gouging or carving tips 542 at each of the apexes between adjacent sides of the hex tip 540.

In operation, the screwdriving tips 500,530 or 540 are used in the following manner. The bit 500,530 or 540 is inserted into a drill, screwdriver or handle. The tip is then placed against a surface into which a screw is to be inserted so as to cut, gouge or carve the surface to expose a softer under surface which is usually present under a dense layer such as exists in MDF. Once a small cut, gouge or carving has been made, the tradesperson removes the tip from the surface, to expose an annular groove in the surface of the material. This groove will have an outside diameter equal to the maximum distance that the extremity of the tip 512,536 or 542 is away from the central axis of rotation. Into the annular groove, against the softer material the point of a self tapping fibre board screw can be positioned. As it is a less dense material or layer, the screw thread will engage that material or layer, will the screw head covering up the rest of the annular groove and hiding it from view.

While the above description in relation to figures 9 10 and 11 shows multiple cutting, gouging or carving tips 512, 536 and 542, there need only be present one such tip. To ensure that the moments applied to the screwdriving tip are at least equal so as to prevent the screw diving tip from dancing over the surface, it is preferable that there be two such tips located on opposite sides of the central axis of rotation of the screw driving bit.

Illustrated in figures 12 and 13 is a countersinking screw 100 which has a countersinking head 102 and a threaded shank 103.

The screw 100 includes four cutting surfaces 113 which extend away from the central axis of rotation 105 in a direction parallel to a plane containing the axis 5. The head 102 has an equal number of circumferential surfaces 106, such that one circumferential surface 106 starts at the outward end of the cutting surface 113 and extends in a curved path around the head 102 to terminate at the beginning of the inward end of an adjacent and rearwardly located (with reference to the direction of rotation to countersink) cutting surface 113. This forms a saw tooth pattern around the outside of the screw head 102. The cutting surfaces taper or converge in the direction of the head 102 to the threaded shank 103 of the screw 100.

In use, as the screw 100 is driven into a surface in which the screw 100 must be countersunk, the cutting surfaces 113 will engage the surface of a material, only as the a drill or screw drives and rotates the cutting surfaces 113.

The rotation of the screw 100 will force the cutting surfaces 113 to cut as they simultaneously engage the material and rotate around the axis of rotation 5 and move inwardly towards the material.

The illustrated screw 100 has its cutting surfaces in a plane which contains the axis of rotation of the screw 10 as well as a radius from that axis of rotation, but this is only preferable.

In figures 14 and 15 is illustrated a countersinking screw 100A. The screw of figures 14 and 15 has many similar features to the screw 100 of figures 12 and 13 and like features have been given the same reference numeral followed by the letter"B".

In figures 14 and 15, the cutting surfaces 113A are effectively inclined planes which slope upwardly from their lower most starting point (closest to the shank of the screw) towards a location which is in an anti clockwise direction from the starting point.

The cutting surfaces 113A are illustrated as having a generally planar outermost surface to shave or cut the material into which the screw 100A is to be secured. However, if desired the cutting surfaces 113A of screw 100A can be curved or include a curved portion. In which case the direction of a part of that cutting surface 113A, defined by a direction line normal to the cutting surface or by a direction line normal to a tangent to the cutting surface, is preferably such that the direction line is skewed relative to the axis of rotation of the screw 100A.

The cutting surface 113A as illustrated exhibits the feature that the slope on it can be defined by considering any point on the cutting surface between the ends of the cutting surface. The cutting surface inclines in a direction away from that point, the direction being generally such as to cause rotation in a rotation direction opposite to that required to secure said screw into a material.

Alternatively the cutting surface can be a helical or part helical surface, but this feature is not illustrated in the drawings.

Illustrated in figure 16 is a screw of figure 12 or 14 in use, showing how the cutting surfaces 113 or 113A shave and eject a shaving from the material into which the screw 100 or 100A is being inserted. One advantage of the embodiments of the present invention is that in use there is provided a cavity in a forward direction (clockwise direction in the casse of a normal right handed screw thread) which provides a volume or space for the swarf or

shaving to be located and pass through during the operation of the screw 100 or 100A. This ensures an efficient operation of the cutting surfaces 113 or 113A by preventing them from getting clogged up by the swarf or shavings.

While the above described screws are illustrated including four cutting surfaces or edges, it will be readily understood that the present invention is applicable to screws having at least one, or one or more cutting surfaces or edges.

It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.