Cutting tool

Abstract

Disclosed herein is a cutting tool comprising: a tool shank having an axis of rotation and further comprising a tool head at one end thereof, the tool head comprising a layer wherein the layer of the tool head comprises a cutting surface formed from polycrystalline CVD diamond, and wherein the cutting surface comprises a plurality of appendages, wherein a sharpness ratio beta of the cutting tool is in a range of about 0.01 to about 1.5, and wherein the sharpness ratio beta is a ratio of an average height H (mm) of the appendages to an average overlap length L (mm) between two adjacent appendages, a method of manufacturing the above tool head and the use of the cutting tool in a method of cutting brittle materials.

Description

Technical Field

[0001] The present disclosure relates to a cutting tool. Specifically, it relates to a cutting tool for cutting brittle materials (such as glass). More specifically, it relates to a cutting tool including a cutting surface formed from polycrystalline CVD diamond, wherein the cutting surface includes a plurality of appendages (i.e., protrusions) that serve as cutting elements. Background Art

[0002] Micro end mills are used in milling operations during the construction of, for example, mobile phone housings. Mobile phone housings are typically made of aluminum, polycarbonate, glass, or ceramic. One of the existing technologies is diamond electroplated micro end mills. In electroplated tools, hundreds of individual diamond grains are embedded in a binder on the surface of the tool head to provide multiple cutting surfaces and edges. However, one problem with electroplated milling cutters is that the diamond grains tend to fall out of the binder, causing the workpiece to be easily scratched by the fallen grains. Another problem is that diamond electroplated tools have a limited service life and need to be replaced regularly, and each time the tool needs to be replaced, production costs increase. As an alternative, polycrystalline diamond (PCD) end mills can be used. However, such tools require flutes to provide a defined cutting surface, and machining the tool head to form the required flutes is an additional processing step.

[0003] The object of the present invention is to solve the above-mentioned problems of existing cutting tools, such as abrasive grain shedding, tool life and requirements for forming grooves, thereby providing an improved cutting tool. Summary of the Invention

[0004] According to a first aspect, a cutting tool is provided, comprising: a tool shank having a rotational axis, and the tool shank further comprising a tool head at one end thereof, the tool head comprising a layer, wherein the layer of the tool head comprises a cutting surface formed of polycrystalline CVD diamond, and wherein the cutting surface comprises a plurality of appendages (i.e., protrusions), wherein the sharpness ratio β of the cutting tool is in the range from about 0.01 to about 1.5, wherein the sharpness ratio β is the ratio of the average height H (mm) of the appendages (i.e., protrusions) to the average overlapping length L (mm) between two adjacent appendages (i.e., protrusions).

[0005] β=H / L Formula 1

[0006] In this disclosure, the terms "satellite" and "protrusion" are considered to be fully interchangeable and synonymous. A "satellite" refers to a body, in other words, a protrusion, that projects from and is integrally formed with a polycrystalline CVD diamond cutting surface as described herein. The satellite serves as a cutting element.

[0007] As an option, the cutting tool has a sharpness ratio β in the range of about 0.01 to about 0.5, optionally in the range of about 0.01 to about 1.

[0008] Alternatively, the appendages (ie, protrusions) have an average height H (mm) of about 0.005 mm to about 0.025 mm.

[0009] As an option, the average overlapping length L (mm) between two adjacent appendages (ie, protrusions) is from about 0.02 mm to about 1 mm.

[0010] Alternatively, the appendages (ie, protrusions) have an average diameter D of about 0.005 mm to about 0.025 mm.

[0011] Alternatively, the area density C of the appendages (ie, protrusions) is about 50 / mm 2 About 1000 pieces / mm 2 .

[0012] As an option, CD ≥ 1 (ie, C times D is greater than or equal to 1), where C is the area density of the appendages (ie, protrusions) (per square millimeter) and D is the average diameter of the appendages (ie, protrusions) (mm).

[0013] As an option, the appendage (ie protrusion) is continuously curved.

[0014] As an option, the tool head comprises at least one further layer, wherein the layers are axially displaced from each other and separated by a non-cutting portion of the tool head.

[0015] As an option, at least one of the at least one further layer comprises a cutting surface formed from polycrystalline CVD diamond, wherein the cutting surface is as defined herein.

[0016] As an option, each layer comprises a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface is as defined herein.

[0017] As an option, the tool comprises at least two layers.

[0018] As an option, the tool comprises at least three layers.

[0019] As an option, at least one layer is configured for an operation selected from any one of rough machining, semi-finishing and finishing.

[0020] As an option, two or more layers are configured for the same operation, eg roughing, semi-finishing, finishing.

[0021] As an option, each layer is configured differently relative to the remaining layers.

[0022] As an option, at least one layer has a diameter that is different from the diameters of the other layers.

[0023] As an option, the tool head is cylindrical and non-tubular.

[0024] As an option, the overall height of the tool head is no more than 12 mm.

[0025] As an option, the total height of the tool head is not less than 0.5 mm.

[0026] As an option, the outer diameter of the tool handle is selected from any one of not more than 15 mm, not more than 10 mm, and not less than 6 mm.

[0027] As an option, the tool shank and / or the tool head comprises cemented carbide.

[0028] As an option, at least one layer of the tool head comprises cemented carbide.

[0029] The material to be cut may optionally include any one of glass, ceramic, polymer, composite material, metallic material, and metal-ceramic composite material.

[0030] The tool handle may optionally further include a conduit for delivering compressed air to the tool head to expel cutting waste.

[0031] According to a second aspect, there is provided a method of manufacturing a cutting tool head, the method comprising the steps of:

[0032] a. Provide disc blanks;

[0033] b. machining at least one preform tool head from the disc;

[0034] c. forming a layer in the preform tool head, thereby forming a tool head comprising a layer; and

[0035] d. depositing polycrystalline diamond on the layer of the tool head using a chemical vapor deposition method to form a cutting surface of polycrystalline CVD diamond on the layer, wherein the cutting surface includes a plurality of appendages (i.e., protrusions), wherein the sharpness ratio β of the cutting tool is in the range of 0.01 to 1.5, wherein the sharpness ratio β is the ratio of the average height H (mm) of the appendages (i.e., protrusions) to the average overlapping length L (mm) between two adjacent appendages (i.e., protrusions).

[0036] As an option, a laser is used to form the layer in the preform tool head.

[0037] As an option, the method further includes repeating step c as needed to form a tool head comprising at least two layers, each layer comprising a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface includes a plurality of appendages (i.e., protrusions), and wherein the layers are axially displaced from each other and separated by non-cutting portions of the tool head.

[0038] As an option, the method further comprises repeating step c as needed to form a tool head comprising a plurality of layers.

[0039] As an option, the method further includes repeating steps c and d as needed to form a tool head comprising at least two layers, each layer comprising a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface includes a plurality of appendages (i.e., protrusions), and wherein the layers are axially displaced from each other and separated by non-cutting portions of the tool head.

[0040] As an option, the method further includes repeating steps c and d as needed to form a tool head comprising at least two layers, wherein at least one layer comprises a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface comprises a plurality of appendages (i.e., protrusions), and wherein the layers are axially displaced from each other and separated by non-cutting portions of the tool head.

[0041] As an option, the method further includes repeating step c as needed to form a tool head comprising a plurality of layers, wherein at least two of the plurality of layers comprise cutting surfaces formed from polycrystalline CVD diamond, wherein the cutting surface comprises a plurality of appendages (i.e., protrusions), wherein the layers are axially displaced from each other and separated by non-cutting portions of the tool head.

[0042] As an option, the chemical vapor deposition of polycrystalline diamond comprises hot-filament chemical vapor deposition.

[0043] According to a third aspect, there is provided use of the cutting tool described herein in a method of cutting (eg, grinding) a brittle material (eg, any of glass, ceramic, polymer, composite material, metallic material, and metal-ceramic composite material). BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0045] Figure 1 is a perspective view of a tool having a tool head according to a first embodiment of the present invention;

[0046] Figure 2 yes Figure 1 A front view of the tool;

[0047] Figure 3 yes Figure 2 Enlarged view of the middle X section;

[0048] Figure 4 is a schematic outline diagram of a CVD diamond cutting surface, which shows how to determine the height H of the protrusion;

[0049] Figure 5 is a schematic plan view of a CVD diamond cutting surface, which shows how to determine the overlapping length L (mm) between two adjacent appendages (ie, protrusions);

[0050] Figure 6 is a schematic plan view of a CVD diamond cutting surface illustrating how the area density C of appendages (i.e., protrusions) is determined;

[0051] Figure 7 yes Figure 6 An enlarged view of section Y in FIG. 1 and illustrating how to determine the diameter D of the appendage (i.e., protrusion);

[0052] Figure 8 is a front view of a second embodiment of a tool head;

[0053] Figure 9 is a front view of a third embodiment of a tool head;

[0054] Figure 10 is a front view of a fourth embodiment of a tool head;

[0055] Figure 11 yes Figure 9 An annotated version of the tool header.

[0056] Throughout the embodiments, like components are denoted by like reference numerals, and further description is omitted for the sake of brevity. DETAILED DESCRIPTION

[0057] By way of example, the following description relates to cutting glass, but it should be understood that the same tool configuration can be used to cut (e.g., grind) other types of materials, such as other types of brittle materials. A non-limiting list of materials that can be cut includes glass, ceramics, polymers, composites, metallic materials, and metal-ceramic composites.

[0058] First reference Figures 1 to 3 A cutting tool is generally designated 10. The tool includes a tool shank 12 having a longitudinal axis of rotation 14 and further includes a tool head 16 at one end of the tool shank 12. The tool head 16 includes at least one layer 18 (i.e., platform or level). The additional layers are axially displaced relative to the initial layer. Thus, a tool having multiple layers has layers that are coaxially aligned and adjacent to each other.

[0059] The cutting surface of the tool head 16 is formed from chemical vapor deposited (CVD) polycrystalline diamond (PCD). The cutting surface includes a plurality of appendages (i.e., protrusions). These appendages (i.e., protrusions) arise from the CVD polycrystalline diamond cutting surface and are integral with the cutting surface. The appendages (i.e., protrusions) are formed from CVD polycrystalline diamond. The appendages (i.e., protrusions) function similarly to the diamond grit embedded in conventional diamond electroplated tools described above, i.e., they serve as cutting elements. Because the appendages (i.e., protrusions) are part of the CVD diamond coating, they are less likely to fall out of the binder. In addition, these appendages (i.e., protrusions) eliminate the need to machine grooves on the tool head because they serve as cutting elements, eliminating a machining step in the manufacture of the tool head compared to the conventional PCD tools described above. Therefore, the cutting tool disclosed herein is an improvement over conventional end mills.

[0060] The tool head serves as a substrate for the polycrystalline CVD diamond coating. Thus, the tool head may be formed from or include any suitable substrate for CVD coating of polycrystalline diamond. For example, the tool head may be formed from or include a metal carbide, such as tungsten carbide, silicon carbide, and / or silicon nitride.

[0061] The number average height H of the appendages (i.e., protrusions) can be about 0.005 mm to about 0.025 mm, optionally about 0.010 mm to about 0.020 mm, optionally about 0.015 mm to about 0.020 mm. The number average height H of the appendages (i.e., protrusions) is measured according to methods known to those skilled in the art, for example, using a scanning electron microscope (SEM). An example method is as follows: An SEM image is taken perpendicular to the cutting surface so that the complete outline of the appendages (i.e., protrusions) can be seen. The distance from the base to the tip of the appendage (i.e., protrusion) is then measured in a direction perpendicular to the cutting surface, as Figure 4 This process is performed on at least 100 appendages (ie, protrusions) to obtain a number average (ie, mean) height H of the appendages (ie, protrusions).

[0062] The average overlap length L between two adjacent appendages (i.e., protrusions) may be from about 0.02 mm to about 1 mm, alternatively from about 0.05 mm to about 1 mm, alternatively from about 0.1 mm to about 1 mm, alternatively from about 0.1 mm to about 0.75 mm, alternatively from about 0.2 mm to about 0.5 mm. The average overlap length L between two adjacent appendages (i.e., protrusions) is measured according to methods known to those skilled in the art, for example, using an SEM. An exemplary method is as follows: An SEM image is taken perpendicular to the cutting surface so that the appendages (i.e., protrusions) can be seen from above, i.e., so as to provide an example. Figure 5 The distance from the center of one appendage (i.e., protrusion) to the center of the adjacent appendage (i.e., protrusion) is then measured as a straight line, as Figure 5 This process is then repeated for each appendage (ie, protrusion) in the image (at least 100 appendages (ie, protrusions)) to obtain the number average (ie, mean) overlap length L between two adjacent appendages (ie, protrusions).

[0063] The sharpness ratio β of the cutting tool is calculated by taking the ratio of the average height H of the appendages (i.e., protrusions) to the average overlap length L between two adjacent appendages (i.e., protrusions). The desired sharpness ratio β depends on the type of material to be cut. For efficient cutting of brittle materials (such as glass), it has been found that the sharpness ratio β should be in the range of about 0.01 to about 1.5, optionally in the range of about 0.01 to about 1.25, optionally in the range of about 0.01 to about 1, optionally in the range of about 0.01 to about 0.75, optionally in the range of about 0.01 to about 0.5, optionally in the range of about 0.05 to about 0.25, optionally in the range of about 0.10 to about 0.25, and optionally in the range of about 0.15 to about 0.25.

[0064] The area density C of the appendages (i.e., protrusions) may be about 50 / mm 2 About 1000 pieces / mm 2 , optionally about 100 / mm 2 About 900 pieces / mm 2 , optionally about 100 / mm 2 About 800 pieces / mm 2 , optionally about 200 per mm 2 About 700 pieces / mm 2 , optionally about 300 per mm 2 About 600 pieces / mm 2 , optionally about 400 pcs / mm 2 About 500 pieces / mm 2 The area density C of the appendages (ie, protrusions) can also be measured using methods known to those skilled in the art, such as using SEM. Example methods include Figure 6 As schematically shown in FIG. 4 , a SEM image of a plan view of the cutting surface is obtained, as when the average overlap length L between two adjacent appendages (ie, protrusions) is measured. Figure 6As schematically shown in FIG, a square area having a side length P containing at least 100 appendages (i.e., protrusions) is identified, and the number of appendages (i.e., protrusions) is counted within or partially within the square area. The area density C of the appendages (i.e., protrusions) is then calculated by dividing the number of appendages (i.e., protrusions) by the square of the side length P of the square to obtain the number of appendages (i.e., protrusions) per unit area. In this disclosure, the area density is expressed as per mm2 (i.e., mm -2 ) is expressed in units.

[0065] From the same SEM image, the average diameter D of the appendages (i.e., protrusions) can be measured. This is done by measuring each appendage (i.e., protrusion) in a square area along its longest axis (e.g., Figure 7 The average diameter D of the appendages (i.e., protrusions) can be from about 0.005 mm to about 0.025 mm, alternatively from about 0.010 mm to about 0.020 mm, alternatively from about 0.010 mm to about 0.015 mm.

[0066] When the area density C (per mm 2 ) and the average diameter D (mm) of the appendages (i.e., protrusions) is greater than or equal to one (i.e., CD ≥ 1), the coating design is particularly suitable for cutting brittle materials. If the area density C (per mm) of the appendages (i.e., protrusions) is 2 ) and the average diameter D (mm) of the appendages (ie, protrusions) is less than one, the coating design may not be suitable for cutting brittle materials.

[0067] In some embodiments, the appendage (i.e., protrusion) can be continuously curved. For example, the appendage (i.e., protrusion) can be substantially dome-shaped, or the appendage (i.e., protrusion) can be substantially elliptical, semi-elliptical, spherical, hemispherical, oval, and / or semi-oval.

[0068] Figure 3 A first embodiment of a tool head 16 is shown. The tool head 16 includes three layers 18a, 18b, and 18c and a cutting element 22. Layer 18a corresponds to the layer closest to the tool shank, layer 18c corresponds to the layer farthest from the tool shank, and layer 18b corresponds to the layer axially located between layers 18a and 18c. Each layer 18 is separated from adjacent layers 18 by a non-cutting portion 17 of the tool head 16.

[0069] The notch element 22 is configured to carve a correspondingly shaped notch in a workpiece, such as a microphone hole in a cell phone housing. By way of example only, the notch element 22 may have a diameter of up to 1 mm and a height of up to 1 mm. The notch element 22 is entirely optional and may be omitted.

[0070] exist Figure 8 , an exemplary tool head 24 is shown. In this example, only a single layer 18a is provided.

[0071] Now turn Figure 9 , shows another embodiment of the tool head 26. In this embodiment, three layers 18a, 18b, 18c are again provided, each layer being separated from the adjacent layer by a non-cutting portion. Each of the three layers 18a, 18b and 18c is configured for a finishing operation. However, all three layers can be configured for roughing, or alternatively, they can all be configured for semi-finishing. The advantage of a construction in which all layers are configured for the same cutting (e.g. grinding) operation is that it extends the service life of the tool by a factor of "n", where "n" is the number of layers. When the first layer (whichever layer is used first) wears, the spindle can then be extended or retracted appropriately to move one of the other layers into the appropriate position. This process is repeated as needed and when needed, depending on the number of layers 18 provided. Since all three layers wear at the same rate, the operating life of the tool is maximized.

[0072] In another embodiment, three layers 18a, 18b, 18c are again provided, each layer being as Figure 9 The tool is shown separated from adjacent layers by a non-cutting portion 17. The first and second layers 18a, 18b are each configured for semi-finishing cutting operations. Only the third layer 18c is configured for finishing cutting operations. One advantage of this configuration is that, unlike the example given in the previous paragraph, it does not require additional tool changes between cutting operations. The tool is multifunctional and can be used for more than one specific cutting operation, thereby reducing machine downtime and maximizing operating equipment efficiency. A tool configured for more than one type of cutting operation can be considered a "multi-tool."

[0073] The inventors have discovered that during use, the layers farthest from the shank 12 experience the greatest forces and torques, and therefore, in principle, will wear at the greatest rate. Higher torques also lead to lower stability and higher vibrations. It is important to consider that wear patterns vary for different cutting operations. For example, during finishing, wear is often entirely abrasive, while during semi-finishing, chipping can also occur. These factors can lead to premature tool failure. Therefore, it is important to consider the relative position of layers 18 and their configuration for specific cutting operations.

[0074] It is preferred to position the layer configured for finishing operations farthest from the tool shank because finishing operations require less force and produce less wear. By positioning the two layers configured for semi-finishing closer to the tool shank, the wear rates on the three layers 18 are balanced and the life of the three layers 18 is maximized. Furthermore, since the probability of chipping failure from these cutting operations is higher, by providing a greater number of layers for semi-finishing and roughing, the tool provides operational redundancy and enables the rapid replacement of subsequent layers, thereby minimizing machine downtime.

[0075] Because finishing operations produce half the wear of semi-finishing processes, the life of layers configured for finishing is approximately twice that of layers configured for semi-finishing. Therefore, the optimal ratio is to use twice as many layers for semi-finishing cutting operations as for finishing. For example, for a tool with six total layers, four of those layers would be used for semi-finishing and two of those layers would be used for finishing. Continuing this example, for a tool with twelve total layers, eight of those layers would be used for semi-finishing and four of those layers would be used for finishing.

[0076] In another embodiment, not shown, all layers 18 may be configured specifically for roughing operations. In another embodiment, not shown, not all layers include cutting surfaces formed from polycrystalline CVD diamond as disclosed herein. It is contemplated that different layers of the tool may include different cutting surfaces adapted, for example, to cut different materials or perform different operations, thereby increasing machining efficiency. In another embodiment, not shown, all layers include cutting surfaces formed from polycrystalline CVD diamond as disclosed herein.

[0077] In another embodiment not shown, substantially the entire tool head is coated with polycrystalline CVD diamond.In another embodiment not shown, only the cutting surface of the tool head is coated with polycrystalline CVD diamond.

[0078] In one embodiment, the tool head does not include any grooves. In another embodiment, the tool head is substantially free of grooves.

[0079] Since layers configured for roughing experience more wear than layers configured for semi-finishing, the proportion of layers configured for roughing will be at least twice the number of layers configured for semi-finishing, and typically three to four times. For example, a single tool configured for all three cutting (e.g., grinding) operations may have a total of nine layers, e.g., six layers for roughing, two layers for semi-finishing, and one layer for finishing.

[0080] Now turn Figure 10, shows another embodiment of a tool head 28. In this embodiment, two layers 18a and 18b are provided, each layer being separated from an adjacent layer by a non-cutting portion, and the tool head is provided with a notching element 22.

[0081] In any of the above embodiments, the tool shank 12 may comprise a cemented carbide metal carbide, such as tungsten carbide, although other suitable materials, such as silicon carbide and silicon nitride, are also contemplated. Optionally, the tool shank 12 includes a conduit (not shown) for delivering compressed air to the tool head to expel cutting waste from the cutting surface.

[0082] In any of the above embodiments, the tool head 16 may be cylindrical and non-tubular.

[0083] refer to Figure 11 The total height of tool head 16 is indicated at 36 and is the sum of height 38 of layered portion 32 and height 40 of upper portion 34. Optionally, height 36 of tool head 16 is between 0.5 mm and 12 mm. Optionally, height 36 of tool head 16 is between 1 and 10 mm. Optionally, height 36 of tool head 16 is 6 mm. Height 38 of layered portion 32 may be in the range of 0.5 to 6 mm, for example, 2.5 mm. Optionally, height 36 of tool head 16 is no greater than 12 mm.

[0084] The outer diameter of the tool 10 is indicated at 42 and is the largest, outermost diameter of any of the layers 18 and the tool shank 12. The individual layers 18 may have different diameters from one another depending on, for example, which cutting (e.g., grinding) operation they are configured for. Alternatively, all layers 18 may have the same diameter.

[0085] Preferably, the outer diameter of the tool 10, 24, 26, 28 is no greater than 15 mm. Optionally, the outer diameter 42 of the tool is 10 mm. In one example of a tool, the total height of the tool including the tool handle 12 and the tool head 16 may be approximately 200 mm.

[0086] The height 44 of each layer 18 (measured axially, the same as the previous height measurement) depends on the number of layers 18 and the height 38 of the substrate. For example, for a tool head 16 having a tool head height 36 of 6 mm, the height 38 of the layered portion is 2.5 mm, and for three layers, the height 44 of each layer is 0.6 to 0.7 mm.

[0087] The above parameters of the cutting surface of the or each layer, i.e. the sharpness ratio β, the average height H (mm) of the appendages (i.e. protrusions), the average spacing length L (mm) between two adjacent appendages (i.e. protrusions), the average diameter D of the appendages (i.e. protrusions) and the area density C of the appendages (i.e. protrusions), are optimized depending on whether the purpose of the cutting operation is roughing, semi-finishing or finishing in cutting glass or other similar brittle materials. The roughing cutting operation is usually intended to prepare the surface of the workpiece before the finishing operation. Its purpose is to machine the size to a "rough" size of the final size. Its appearance may not be very important, as the main purpose is to quickly remove a relatively large amount of material. The semi-finishing cutting operation is usually the next stage after roughing. Its purpose is to bring the size even closer to the final size. The finishing cutting operation is the last stage of machining the workpiece. The minimum amount of workpiece material is removed, the workpiece is machined to the required size, the final size is obtained, and sometimes the surface is further improved.

[0088] A method for manufacturing one of the tool heads described is described as follows: a carbide disc blank is provided, and a preformed tool head is machined from the disc. Layers are formed into the preformed tool head, for example using a laser. This step is repeated as needed, for example to form a tool head comprising at least two layers, wherein the layers are axially displaced from one another and separated by a non-cutting portion of the tool head. Finally, polycrystalline diamond is deposited onto the tool head, for example using chemical vapor deposition (CVD). Hot-filament CVD is typically used, but other forms of CVD, such as microwave plasma CVD, may be used. A final finishing operation may be required on the deposited diamond layer on the tool head.

[0089] The cutting tool of the present invention can be used in cutting brittle materials. The brittle material can be any one of glass, ceramics, polymers, composite materials, metal materials, and metal-ceramic composite materials.

[0090] In summary, the inventors have designed a cutting tool that maximizes tool life and improves cost / benefit performance. This is achieved by using a tool head comprising a layer having a CVD diamond cutting surface comprising a plurality of appendages (i.e., protrusions) as described herein.

[0091] While the invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention as defined by the following claims.

Claims

1. A cutting tool, comprising: a tool shank having an axis of rotation and further comprising a tool head at one end of the tool shank, the tool head comprising a layer, wherein the layer of the tool head comprises a cutting surface formed of polycrystalline CVD diamond, and wherein the cutting surface comprises a plurality of appendages, wherein the sharpness ratio β of the cutting tool is in the range of about 0.01 to about 1.5, The sharpness ratio β is the ratio of the average height H (mm) of the appendages to the average overlapping length L (mm) between two adjacent appendages. 2 . The cutting tool according to claim 1 , wherein the average height H (mm) of the appendages is about 0.005 mm to about 0.025 mm.

3. The cutting tool according to claim 1 or claim 2, wherein the average overlapping length L (mm) between two adjacent appendages is about 0.02 mm to about 1 mm.

4. The cutting tool according to any one of the preceding claims, wherein the average diameter D of the appendages is from about 0.005 mm to about 0.025 mm.

5. The cutting tool according to any one of the preceding claims, wherein the area density C of the appendages is about 50 / mm 2 to about 1000 / mm 2 .

6. The cutting tool according to any one of the preceding claims, wherein CD ≥ 1, wherein C is the area density (per mm2) of the appendages. 2 ), and D is the average diameter of the appendages (mm).

7. The cutting tool according to any one of the preceding claims, wherein the appendage is continuously curved.

8. A cutting tool according to any one of the preceding claims, wherein the tool head comprises at least one further layer, wherein the layers are axially displaced from each other and separated by non-cutting portions of the tool head.

9. The cutting tool of claim 8, wherein at least one of the at least one further layer comprises a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface comprises a plurality of appendages as defined in claim 1.

10. The cutting tool of claim 8, wherein each layer comprises a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface comprises a plurality of appendages as defined in claim 1.

11. The cutting tool according to any one of claims 8 to 10, wherein the cutting tool comprises at least two layers.

12. A cutting tool according to any one of claims 8 to 11, wherein the tool comprises at least three layers.

13. The cutting tool according to any one of claims 8 to 12, wherein at least one layer is configured for an operation selected from any one of roughing, semi-finishing and finishing.

14. The cutting tool according to any one of claims 8 to 13, wherein two or more layers are configured for the same operation.

15. A cutting tool according to any one of claims 8 to 14, wherein each layer is configured differently relative to the remaining layers.

16. The cutting tool according to any one of claims 8 to 15, wherein at least one layer has a different diameter relative to the other layers.

17. A cutting tool according to any one of the preceding claims, wherein the tool head is cylindrical and non-tubular.

18. The cutting tool according to any one of the preceding claims, wherein the overall height of the tool head is not more than 12 mm and / or wherein the overall height of the tool head is not less than 0.5 mm.

19. The cutting tool according to any one of the preceding claims, wherein the outer diameter of the tool shank is selected from any one of not more than 15 mm, not more than 10 mm, and not less than 6 mm.

20. A cutting tool according to any one of the preceding claims, wherein the tool shank and / or the tool head comprises cemented carbide.

21. A method of manufacturing a cutting tool head, the method comprising the steps of: a. Provide disc blanks; b. machining at least one preform tool head from the disc; c. forming a layer in the preform tool head, thereby forming a tool head comprising a layer; as well as d. depositing polycrystalline diamond on the layer of the tool head using a chemical vapor deposition method to form a polycrystalline CVD diamond cutting surface on the layer, wherein the cutting surface includes a plurality of appendages, wherein the cutting tool has a sharpness ratio β in the range of about 0.01 to about 1.5, wherein the sharpness ratio β is the ratio of the average height H (mm) of the appendages to the average overlapping length L (mm) between two adjacent appendages.

22. The method of claim 21 further comprising repeating step c as needed to form a tool head comprising at least two layers, each layer comprising a cutting surface formed of polycrystalline CVD diamond, wherein the cutting surface comprises a plurality of appendages, wherein the layers are axially displaced from one another and separated by a non-cutting portion of the tool head.

23. A method according to claim 21 or claim 22, wherein the chemical vapour deposition of polycrystalline diamond comprises hot-filament chemical vapour deposition.

24. Use of a cutting tool according to any one of claims 1 to 20 in a method of cutting brittle materials.

25. The use according to claim 24, wherein the brittle material is any one of glass, ceramic, polymer, composite material, metallic material, and metal-ceramic composite material.

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