WO2006119536A1

WO2006119536A1 - Cutting tool holding apparatus and method of use

Info

Publication number: WO2006119536A1
Application number: PCT/AU2006/000006
Authority: WO
Inventors: John Michael Willoughby
Original assignee: Ground Assault Tools Pty Ltd
Priority date: 2005-05-13
Filing date: 2006-01-06
Publication date: 2006-11-16
Also published as: US20080093912A1; CN101018927A; EP1880084A4; EP1880084A1; JP2008540875A

Abstract

A cutting tool holding apparatus (10), including in combination a cutting tool holder (14); a retainer (18) adapted to be positioned adjacent to the tool holder (14), said retainer including an aperture (18c), a base (16) including an aperture (16c) linked to the retainer aperture (18c), said base (16) adapted to support the holder (14) and the retainer (18), and a fastener (20) adapted to be inserted through the linked apertures, wherein securing the fastener in the linked apertures wedges the holder, retainer and base together and wherein at least two components of the tool holder, retainer and base contact via mating curved faces.

Description

CUTTING TOOL HOLDING APPARATUS AND METHOD OF USE

FIELD OF THE INVENTION

The invention relates to an apparatus for holding a cutting tool and methods of use thereof. In particular, the invention relates to apparatus for holding a cutting tool holder that is utilised on a ground engaging drum or wheel that excavates into the ground surface.

BACKGROUND OF THE INVENTION

There are a variety of road and mining machines that include a plurality of holders for securing cutting bits or teeth that assist in cutting into earth, asphalt, concrete or other hardened surfaces. Typically, these machines have a rotating drum, wheel or conveyor having a plurality of tool holders secured, generally by welding, cutting tools which are utilised to bite, cut, mill or trench into the hardened surface via the rotation of the drum, wheel or conveyor during operation.

It is inevitable that due to the severe environment accidental damage of known cutting tool holders and the cutting tools can occur before its normal expected lifetime. As such, there are extensive costs in replacing the cutting holders and the secured tool that cut into the hardened surface due to wear and tear as work is conducted over a high number of revolutions. In addition, the cutting tool holder may even detach completely and is not recoverable.

In current known ground engaging machinery, there can be about 80 cutting tool holders positioned on a metre wide drum or other rotating means. The drum rotates at approximately 100 revolutions per minute. As such, the cutting tool holders typically experience several million impacts with a typical force of three tonnes on each impact. Accordingly, there can be severe wear and tear on each cutting tool holder during its operational life.

Existing methods include welding a tool holder onto a rotating drum, wheel, conveyor or other rotating mechanism. Though this may appear to be initially cost efficient in setting up costs, there are also continuous applied stresses and abrasion which often quickly damages the cutting tool holder. A severe impact may fracture the weld and break off the tool holder. The requirement to replace the tool holder may be difficult when on site as it lacks practicality and can be time consuming and expensive. The cost in loss of production and replacement time proves to be even more expensive.

Other techniques in the industry require the attachment of the cutting tools via tapered locks. A problem associated with this technique is the continuous forces applied to the cutting tool can deform the tapered cavity. The force applied to the cutting tool drives the cutting tool into their respective holders, especially into the shoulders of the holder. Hence, withdrawing a cutting tool from a deformed damaged taper can be difficult. In addition, replacing a cutting tool into the damaged cavity can leave the cutting tool loose and/or misaligned.

A further technique utilises cutting tool holders having a rectangular post which is secured in a rectangular cavity employing a high tensile bolt or screw enabling attachment to a rotating drum or the like. During the life of the holder the bolt can come loose. This is due to the mating faces between the cutting tool holder and the tool holder base becoming worn making it difficult to keep the bolt tight. Periodical tensioning of the bolt is recommended, but is often impractical given the number of cutting tool holders and the environment it works in. The task of retensioning is costly and time consuming.

In addition, due to the wear and tear the bolt may become loose prematurely and the tool holder can become detached and is not recoverable. Replacement of the tool holder can be expensive due to time out and the costs for replacement.

It would be advantageous to at least substantially ameliorate the disadvantages and shortcomings of the prior art or to at least provide the public with a useful alternative. For example, it would be advantageous to provide a cutting tool holding apparatus that may assist in transferring the stress on the cutting tool when in use and to potentially avoid the required of periodically retensioning the cutting tool holder.

SUMMARY OF THE INVENTION

This invention resides broadly in a cutting tool holding apparatus, including: a cutting tool holder; a retainer adapted to be positioned adjacent to the tool holder, said retainer including an aperture, a base including an aperture linked to the retainer aperture, said base adapted to support the tool holder and the retainer, and a fastener adapted to be inserted through the linked apertures, wherein securing the fastener in the linked apertures wedges the holder, retainer and base together and wherein at least two components of the tool holder, retainer and base contact via complementary mating faces.

Preferably the secured fastener provides a wedging force between the three components of the holder, retainer and base which enables a pre-loading on the complementary mating faces that assists in self-aiignment of the three components irrespective of impacting movement forces.

In one preferred embodiment, the complementary mating faces are located on the holder and base. Preferably, the complementary mating faces are curved. More preferably the curved face of the base is a partial spherical ball and the mating curved face on the holder is a matching partial spherical indent. In a further preferred embodiment, the centre of the partial spherical ball is approximate to the radius path between tip of the cutting tool and centre of the drum, wheel, conveyor or other rotating apparatus. This may minimize the movement of the cutting tool tip from misalignment. For example, if the cutting tool holder happens to rotate slightly around the base in such a manner as to alter the angle of attack, the cutting tool still cuts at close to its designed depth.

In other preferred embodiments, the base and retainer and/or the retainer and holder also including mating curved faces. There may be additional contact points between the three components when securely fastened. For example, the tool holder legs may include two curved beveled legs straddling each side of the partial spherical ball of the base. The base may also include two curved saddles each side of the partial spherical ball of the base that have faces that match to the curved beveled legs of the tool holder to assist in aligning the tool holder with the base.

In another embodiment, the tool holder may have one or more additional curved face/s mating to a curved face/s on the retainer, wherein the curved matching faces further assist in self aligning of the three major components of the tool holder apparatus, i.e. the tool holder, retainer and base. In a further embodiment, additional curved face/s on the base may match opposing curved faces of the retainer.

All of the mating curved faces of the three components assist in self alignment of the cutting tool holder despite rotational movement stresses.

Suitably, the securing fastener asserts an initial force aligning the tool holder, retainer and base. Preferably, the securing fastener is a bolt utilised with a washer having a partially spherical underside, wherein the underside assists in aligning the securing bolt and maintaining full contact between mating faces of the washer and the retainer. Of course the fastener is not limited to a bolt and could be a screw, rivet, or other attachment means. The cutting tool holding apparatus may include a replaceable cutting tool which may be a tooth or a bit depending on the type of ground surface that needs to be excavated.

In other known methods, when the faces are subjected to forces through repeated cyclical loads the tool holder generally fails due to excessive forces. However, the present invention with mating curved faces secured by the fastener preloads the mating faces to an extent which is surprising and unexpected as the mating faces do not substantially move essentially keeping the cutting tool self- aligned.

Suitably, the base of the cutting tool holder assembly has a contacting face that matches the surface of the drum, wheel, conveyor or the like. Preferably, the cutting tool holding apparatus is attached to the surface of the drum, wheel, conveyor or the like by a weld. However, it is to be appreciated that other types of fastening connections may be employed. The base could be manufactured as an integral part of the drum, wheel or conveyor or other rotating means.

The cutting tool holding apparatus is part of a machine that enables rotation of the drum that cuts, grinds or bites into a ground surface. The components of the cutting tool holding apparatus, being the tool holder, retainer and base, all suitably have complementary mating faces that enable a matching fit so that the impact from the ground is passed from the cutting tool to each mating face to the drum or other rotation means which substantially eliminates any movement between the components. Further if there is any misalignment of the tool holder, the combination of the mating faces still maintains the cutting tool in alignment. Suitably all mating faces are smooth and blemish free.

If the cutting tool holding apparatus does not need to be constantly replaced, then it is a simple matter to replace the tooth or bit when it becomes worn. In addition, replacement of the cutting tool holding apparatus generally occurs in a "dirty" environment being on the road or in a mining situation. Any dirt in past tool holders causes problems, however the present arrangement of the mating faces of the three components of the present invention do not substantially cause misalignment, even if there is some dirt or grit.

In another aspect this invention resides in a method of excavating a ground surface utilizing a road or mining machine having a plurality of cutting tool holding apparatus as described above attachable to a rotatable ground engaging drum, wheel or conveyor, said cutting tool holding apparatus including one or more replaceable cutting tools.

As discussed above, the tool holder may include two curved beveled legs which are beatable each side of the partial spherical ball positioned centrally on one end of the base with saddles matching the two curved beveled legs. It is preferred that the centre of the radius of the curved legs and the centre of radius of the partial spherical indent are the same. The radii of two curved faces may be different in length but the centre point is the same.

Further, there may be two matching curved faces between the retainer and the base wherein the centre point of the two matching curves are the same despite differing lengths of the radii. The advantage of having the same centre point for a set of matching curved faces is that the two relative components have the ability to slide relative to each. This enables the ability to manage any side loading by providing a very substantial mechanical advantage enabling self-alignment of the components. So even if there is a side loading applied to the cutting tool tip, alignment is maintained. In a still further aspect, this invention resides broadly in a cutting tool holding apparatus, including: a cutting tool holder, a retainer adapted to be positioned adjacent to the tool holder, said retainer including an aperture, a base including an aperture linked to the retainer aperture, said base adapted to support the holder and the retainer, and a fastener adapted to be inserted through the linked apertures, wherein securing the fastener in the linked apertures wedges the holder, retainer and base together, wherein at least two or more components of the tool holder, retainer and base contact via mating curved faces, wherein there are at least two paired mating curved faces between the two or more of the components, and and wherein, the radii of the two pairs of mating curved faces have the same centre point.

Essentially the mechanical advantages are obtained by having the centre point of the radius which enables a pivoting effect that is favoured in the direction of the curve, rather than by lateral movements against the curve. As such, the components have the mechanical ability to self align no matter what the direction the forces or stress. Preferably, there are complementary sets of mating curved faces between the tool holder and the base and retainer and base. There may also be paired sets of mating curved faces between the retainer and the tool holder.

As in the present invention, with high productivity, high horsepower machine applications wear is likely to be a problem on the leading front face of the base. Since it is intended that this component is not to be required to be replaced during the expected life of the road or mining machine, it is advantageous to have a sacrificial wear plate in front of the leading face that can easily be replaced if necessary.

Preferably, the sacrificial wear component has two legs that fit into two slots or ribs in the base when fitted. Wear will occur on the face and at some stage it will be necessary to replace only the component. Since wear rates of cutting tool holding apparatus are not consistent across the drums in such machines some may need replacing before others are worn out. To make a base with sufficient material as a sacrificial plate would add substantially to the cost. The base must be made of such a material as to be able to be welded to the drum and therefore a large amount of material would be required over the life of the machine. Furthermore, a small cast sacrificial wear component with no machining or welding can be made very hard and highly abrasive resistant at low cost. Preferably, when the tooth holder is secured into position the sacrificial wear component cannot be removed from the slots or ribs by the obstruction of the tooth holder.

It is envisaged that fine material from the cutting action of the teeth will impact and build up between the sacrificial wear component and the tooth holder and base and secure the sacrificial wear component in position so as no wear occurs in the slots or ribs on the base or the front face of the tooth holder. Suitably, the sacrificial wear component may be replaced by removal of the retainer and tooth holder. The wear component is preferably of a high alloy steel or equivalent material.

Preferably, the tooth holder has a slot in the rear of the tooth holder which allows for the insertion of a tooth punch or drift whereby the punch can be used as a lever to release the retainer from a tightened position by tapping the punch with a hammer to apply an impact sufficient to release the taper lock between the three components.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that this invention may be more, readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

Fig. 1 illustrates an exploded view of a cutting tool holder apparatus in accordance to the invention as described,

Fig. 2 illustrates a side view of the cutting tool holder apparatus when assembled,

Fig. 3 illustrated a rear perspective view of the cutting tool holder apparatus when assembled,

Fig. 4 illustrates of top view of the cutting tool holder apparatus when assembled, Fig. 5 illustrates a side view of the cutting tool holder apparatus when assembled,

Fig. 6 illustrates a rear view of the cutting tool holder apparatus when assembled,

Fig. 7 illustrates a side cross sectional view of the cutting tool holder apparatus when assembled.

Fig. 8 illustrates rotated perspective views of a base,

Fig. 9 illustrates rotated perspective views of the retainer, and

Fig. 10 illustrates rotated perspective views of a tool holder.

Fig. 11 illustrates a preferred sacrificial wear component according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In addition terms such as "front", "back", "base", "top", "side", "bottom", "end", "rear", "underside" etc. refer to the orientation or configuration of a cutting tool holding apparatus when used according to the illustrations and to assist in indicating points of reference when viewing the accompanying figures. It is to be understood that these terms do not limit, the present invention to any specific orientation or configuration of the invention.

In the specification the terms "comprising" and "containing" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the terms "comprising" and "containing" such as "comprise", "comprises", "contain" and "contains".

Figures 1-11 illustrate one embodiment of a cutting tool holding apparatus 10 of the invention as described. Though not illustrated, an embodiment of the invention could include a plurality of cutting tool holder apparatuses 10 being affixed to a rotating drum, wheel, conveyor or the like and used in excavation machinery.

The cutting tool holder apparatus 10 includes a cutting tool holder 14, base 16 and retainer 18 that have interconnecting curved faces linking the apparatus together via a fastener 20, such as a bolt. The cutting tool holder 14 illustrated in Fig. 10 includes a cutting tool 12 which is inserted into the holder 14. As best illustrated in Fig. 1 , a preferred embodiment of the cutting tool 12 has a tungsten carbide tip 12a which is used as the abrasive tool for excavating into a ground surface. The cutting tool 12 includes a housing 12b upon where the tip is mounted and a collar 12c, wherein the cutting tool 12 can engage the cutting tool holder 14 using the post 12d and spring clip retainer via a matching aperture 14e in the tool holder 14.

The tool holder 14 includes a spherical indent 14a and an aperture 14e to receive the cutting tool 12. The base 16 as best show in Fig. 8 includes a partial spherical ball section 16a that matches the spherical indent 14a of the tool holder 14. Further, the base 16 includes a saddle region 16d adjacent to the partial spherical ball section 16a for enabling a straddling pair of legs 14b of the tool holder 14 to straddle the partial spherical ball section 16a. The base 16 also has a curved bevelled rear section 16b, a beveled section adjacent 16e to a securing bolt aperture 16c for engaging a securing bolt 20. It should be noted that the curved beveled sections 16b and 16e have the same radii centre point.

As illustrated in Fig. 9, the retainer 18 includes a linking aperture 18c to the base aperture 16c for receiving the securing bolt 20 and washer 22, a curved bevelled underside 18a and 18d, and beveled rear 18b and 18e.

The assembled tool cutting holder apparatus is depicted in Figs. 2 to 7, wherein the tool holder 14 resides between the retainer 18 and the base 16. When the tool holder 14 is fitted onto the base 16, there is contact between the two components on the spherical ball 16a and spherical indent 14a; and between the two legs 14b and the spherical saddle 16d.

The partial spherical ball 16a and the spherical indent 14a, allows slight pivoting of the tool holder 14 upon the central position upon the base 16, but any side loading enables self-alignment due to this arrangement. The unique curved beveled shape of the two legs 14b of the holder mates with the curved saddle 16d of the base. In addition, the curved beveled legs 14b are angled slightly inward. This unique configuration allows any lateral forces experienced by the assembly to self- align.

The retainer 18 is positioned between the tool holder 14 and the base 16 being interconnected by matching curved faces. The retainer 18 includes an aperture 18c for receiving a high tensile bolt 20 which provides the load upon the assembly. In an embodiment of the invention the bolt is accompanied by a washer 22 having a partial spherical underside that fits within a recess in the aperture. The retainer 18 includes a curved beveled underside 18a which engage the two respective curved faces of the two legs 14d of the tool holder 14. The retainer 18 also has a curved beveled underside 18d which engages against the curved beveled underside 14f of the tool holder 14 adjacent to the aperture 14e. It should be noted that the curved surfaces of 18a and 18d have the same radius centre point even though the radii have different lengths.

The curved beveled underside 18a and 18d are slightly angled inwards, while the two legs of the tool holder are angled slightly outward. This configuration allows the two components to interlock; hence any lateral forces experienced by the assembly which would allow the retainer and tool holder to slide into position, hence re-aligning during assembly.

In addition, the rear end 18b, and 18e of the retainer 18 includes a beveled face which mates with the curved beveled rear end of the base 16b and 16e. The centre point of the radii is the same for the faces 18b and 18e. As stated previously, any lateral forces applied upon the assembly will not misalign the assembly since the curved beveled shaped faces will allow the components to slide into position upon tensioning bolt 20 ensuring all components are self aligned.

Therefore in operation, the apparatus 10 may experience forces anywhere in between perpendicular and lateral. In regards to the perpendicular forces, the general curved shapes of the components allow the cutting tool holding apparatus as a whole to absorb forces generated by the tool, in particular the tensioning of the bolt 20 that preloads the mating faces of the three components 14, 16 and 18 to eliminate any sliding motion between mating faces under normal loads. Though it would be imagined that the securing bolt 20 absorb the majority of the perpendicular forces, this is not the case. The unique configuration allows each of the components to absorb the impact. While the securing bolt 20 enables the three components to be wedged together and the unique feature of the matching curved faces actually enable the tool holder apparatus 10 to self-aiign despite any stress.

An additional design feature includes the centre of the spherical ball 16a being positioned as closed to practical to the imaginary line between the tip 12a and the centre of the rotational means. The effect of tightening, the securing bolt 20 causes the forces on the tool holder 14, base 16 and retainer 18 to pass through two points. The first of which is the radius point of the mating faces of the spherical ball 16a and spherical indent 14a. The second point of contact is the radius point of the mating face of the retainer 18 and the base 16. As the radius point of the mating faces of cutting tool holder 14 and the retainer 18 does not fall along this line, a wedging action occurs upon securing the fastening bolt 20. The tightening of the bolt 20 also causes a moment arm around the radius point of the mating faces of the base 16 and the retainer 18.

Considering the environment the cutting tool holder apparatus 10 would be exposed to, a substantial amount of debris can enter into the assembly. Given the flexibility of the components, the disassembling the cutting tool holder apparatus 10 can be made with minimal effort. By removing the securing bolt 20, each of the components free, this allows for easier "change over" of tools and general maintenance. Due to the unique interconnection of the curved mating faces of the three components under tensioning by the securing bolt 20, the tool holder apparatus 10 solves the problem of having to continually re-tension the bolt due to maximizing the transferal of stress. This assists in reducing the costs of having to repetitiously replace lost cutting tool holders and reducing the time in maintenance and repairs. Further the components of the invention do not need any finishing machine due to the self alignment aspect which also reduces the costs.

As in the present invention, with high productivity, high horsepower machine applications, wear is likely to be a problem on the leading front face of the base. Since it is intended that this component is not to be required to be replaced during the expected life of the road or mining machine, it is advantageous to have a sacrificial wear plate in front of the leading face that can easily be replaced if necessary.

As shown in Figures 1 , 2, 5, 6 and 7 and in detail in Figure 11 , preferably, the sacrificial wear component 21 , has two legs 21a, that fit into two slots 16f, in the base when fitted. Wear will occur on the face 21b and at some stage it will be necessary to replace only the component. Since wear rates of cutting tool holding apparatus are not consistent across, the drums in such machines some may need replacing before others are worn out. To make a base with sufficient material as a sacrificial plate would add substantially to the cost. The base must be made of such a material as to be able to be welded to the drum and therefore a large amount of material would be required over the life of the machine. Furthermore, a small cast sacrificial wear component with no machining or welding can be made very hard and highly abrasive resistant at low cost. Preferably, when the tooth holder is secured into position the sacrificial wear component cannot be removed from the slots by the obstruction of the tooth holder.

It is envisaged that fine material from the cutting action of the teeth will impact and build up between the sacrificial wear component and the tooth holder and base and secure the sacrificial wear component in position so as no wear occurs in the slots on the base or the front face of the tooth holder. Suitably, the sacrificial wear component may be replaced by removal of the retainer and tooth holder. The wear component is preferably of a high alloy steel or equivalent material.

Preferably, the tooth holder 14 has a slot in the rear of the tooth holder which allows for the insertion of a tooth punch or drift whereby the punch can be used as a lever to release the retainer 18 from a tightened position by tapping the punch with a hammer to apply an impact sufficient to release the taper lock between the three components 18, 14, 16. The punch applies a force to 18f.

It will of course be understood that while the foregoing has been given by way of examples of this invention are intended to be illustrating and not restrictive, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth. The scope of the invention should therefore, be determined with reference to the appended claims, along with the scope of equivalents to which such claims are entitled.

Claims

1. A cutting tool holding apparatus, including: a cutting tool holder; a retainer adapted to be positioned adjacent to the tool holder, said retainer including an aperture, a base including an aperture linked to the retainer aperture, said base adapted to support the holder and the retainer, and a fastener adapted to be inserted through the linked apertures, wherein securing the fastener in the linked apertures wedges the holder, retainer and base together and wherein at least two components of the tool holder, retainer and base contact via complementary mating faces.

2. A cutting tool holding apparatus as claimed in claim 1 , wherein the secured fastener provides a wedging force between the three components of the holder, retainer and base which enables a pre-loading on the complementary mating faces that assists in self-alignment of the three components irrespective of impacting movement forces.

3. A cutting tool holding apparatus as claimed in claim 1 or claim 2 wherein the complementary mating faces are located on the holder and base.

4. A cutting tool holding apparatus as claimed in claim 3 wherein the complementary mating faces are curved.

5. A cutting tool holding apparatus as claimed in claim 4, wherein, the curved face of the base is a partial spherical ball and the mating curved face on the holder is a matching partial spherical indent.

6. A cutting tool holding apparatus as claimed in claim 5, wherein, the centre of the partial spherical ball is approximate to the radius path between tip of the cutting tool and centre of the drum, wheel, conveyor or other rotating apparatus.

7. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, the base and retainer and/or the retainer and holder also include mating curved faces.

8. A cutting tool holding apparatus as claimed in claim 7, wherein, there are additional contact points between the three components when securely fastened.

9. A cutting tool as claimed in any one of the above claims, wherein, the tool holder legs include two curved beveled legs straddling each side of the partial spherical ball of the base.

10. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, the base includes two curved partial spherical saddles each side of the partial spherical ball of the base.

11. A cutting tool holding apparatus as claimed in claim 1 , wherein, the tool holder has one or more additional curved face/s mating to a curved face/s on the retainer, wherein the curved matching faces further assist in self aligning of the three major components of the tool holder apparatus namely, the tool holder, retainer and base.

12. A cutting tool holding apparatus as claimed in 11, wherein, additional curved faces on the base match opposing curved faces of the retainer.

13. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, all of the mating curved faces of the components assist in self alignment of the cutting tool holder despite rotational movement stresses.

14. A cutting tool holding apparatus as claimed in claim 1 wherein, the securing fastener asserts an initial force aligning the tool holder, retainer and base.

15. A cutting tool holding apparatus as claimed in claim 14, wherein, the securing fastener is a bolt utilised with a washer having a partially spherical underside, wherein the underside assists in aligning the securing bolt and assists in maintaining a large contact surface between the mating faces of the washer and retainer.

16. A cutting tool holding apparatus as claimed in claim 1 , wherein, the cutting tool holding apparatus includes a replaceable cutting tool which may be a tooth or a bit depending on the type of ground surface that needs to be excavated.

17. A cutting tool holding apparatus as claimed in claim 1 , wherein, the base of the cutting tool holder assembly has a contacting face that matches the surface of the drum, wheel, or conveyor on which the tool holder apparatus is mounted.

18. A cutting tool holding apparatus as claimed in claim 17, wherein, the cutting tool holding apparatus is attached to the surface of the drum, wheel, or conveyor or the like by a weld.

19. A cutting tool holding apparatus as claimed in claim 17, wherein the base is manufactured as an integral part of the drum, wheel or conveyor.

20. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, the components of the cutting tool holding apparatus, being the tool holder, retainer and base, all have complementary, mating faces that enable a matching fit so that the impact from the ground is passed from the cutting tool to each mating face to the drum or other rotation means which substantially eliminates any movement between the components.

21. A cutting tool holding apparatus as claim in claim 19, wherein, all mating faces are smooth and blemish free.

22. A cutting tool holding apparatus as claimed in claim 20, wherein, the mating faces of the components do not substantially cause misalignment, even if there is some dirt or grit between the components.

22. A cutting tool holding apparatus as claimed in any of the above claims attachable to a rotatable ground engaging drum, wheel or conveyor, said cutting tool holding apparatus including one or more replaceable cutting tools.

23. A cutting tool holding apparatus, including: a cutting tool holder, a retainer adapted to be positioned adjacent to the tool holder, said retainer including an aperture, a base including an aperture linked to the retainer aperture, said base adapted to support the holder and the retainer, and a fastener adapted to be inserted through the linked apertures, wherein securing the fastener in the linked apertures wedges the holder, retainer and base together, wherein at least two or more components of the tool holder, retainer and base contact via mating curved faces, wherein there are at least two paired mating curved faces between two or more of the components, and wherein the two pairs of mating curved faces radii have the same centre point.

24. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, there are paired sets of mating curved faces between the tool holder and the base and retainer and base.

25. A cutting tool holding apparatus as claimed in any one of the above claims, wherein there are complementary sets of mating curved faces between the retainer and the tool holder.

26. A cutting tool holding apparatus as claimed in any one of the above claims, having a sacrificial wear component that can be replaced.

27. A cutting tool holding apparatus as claimed in claim 26, whereby the sacrificial wear component has legs that fit into slots or ribs in the base.

28. A cutting tool holding apparatus as claimed in claim 26, wherein, the sacrificial wear component is cast.

29. A cutting tool holding apparatus as claimed in claim 27, wherein when the tooth holder is secured into position the sacrificial wear component cannot be removed from the slots or ribs by the obstruction of the tooth holder.

30. A cutting tool holding apparatus as claimed in claims 26 to 29, whereby, the sacrificial wear component is replaced by removal of the retainer and tooth holder.

31. A cutting tool holding apparatus as claimed in claim 26, wherein, the wear component is preferably of a high alloy steel or equivalent material.

32. A cutting tool holding apparatus as claimed in any one of the above claims, wherein, the tooth holder has a slot in the rear of the tooth holder which allows for the insertion of a tooth punch or drift.

33. A cutting tool holding apparatus as claimed in claim 32, wherein, the punch or drift is used as a lever to release the retainer from a tightened position by tapping the punch with a hammer to apply an impact force sufficient to release the taper lock between the components.

34. A cutting tool holding apparatus as herein described with reference to the accompanying drawings.

35. A method of excavating a ground surface utilizing a road, mining or trenching machine having plurality of cutting tool holding apparatus as claimed in any of the above claims.