Grinding tool set

Abstract

A grinding tool set comprises first 1A and second 1B grinding tools for grinding spaced apart features of a cylindrical wall. The first grinding tool comprises a shaft, and a first annular grinding lo

Description

The present invention relates to grinding tools for grinding an engine block or, more generally, a metal workpiece having a cylindrical surface. Background For many years, engine blocks have been machined on multi-axis machining centres which perform multiple machining operations such as drilling, thread tapping and milling. An engine block is mounted on a fixturing whilst the machining operations are performed, and the individual tools are mounted on HSK spindle adaptors and are stored in a tool changer (magazine) until they are needed. A tool is removed from the magazine, used to perform its operation, and returned to its position in the magazine. In an engine block, the cylinder bores may be spray coated. Where a cylinder bore needs to be machined, such as to form a chamfer, a cutting tool is used, and the cutting tool needs to cut through the (relatively hard) spray coating and cut into the underlying (relatively soft) base material. The base material may be aluminium if the engine block has been cast in aluminium material. The cutting tool has to apply a force which is large enough to cut through the spray coating, and this large force may cause vibration and deflection of the cutting tool. As a result, the cutting tool may have a low tool life, the cycle time may be longer than is desirable, and the final quality of the end product may be lower than is desirable. A low tool life and a long cycle time are undesirable because they increase the overall manufacturing cost. The spray coating may be an ultra-hard thermically sprayed coating, and the large transfer of energy into the coating during the cutting operation (turning or milling) may weaken the bond to the underlying base material (the aluminium of the engine block). Summary According to an aspect of the present invention, there is provided a grinding tool set comprising first and second grinding tools for grinding first and second features which are spaced apart along a longitudinal axis of a cylindrical wall, wherein: the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location; the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location; the first grinding location is annular and supports a first grinding ring for grinding the first feature; and the second grinding location is annular and supports a second grinding ring for grinding the second feature. The cylindrical wall may be a cylinder bore of an engine block, and the cylinder bore may have a spray coating. The first and second features that are to be machined may be at respectively the bottom end and top end of the cylinder bore and involve machining through the spray coating and into an underlying base material. By replacing the previously-used cutting operations (using carbide milling or hobbing cutters) and instead using grinding operations, it is possible to machine a bi-metal structure (of a relatively-hard coating on a relatively-soft base material) without the machining (the grinding) causing the coating to lift away from the base material. Each grinding tool has a longer tool life (approximately 50% longer) than the cutting tool that it supersedes, and the grinding tool also has a shorter (faster) cycle time (approximately 50% shorter). The first and second grinding rings may each comprise an abrasive coating, such as a layer of diamond grit. The coating may be galvanically connected to the base material of the shaft or the rotary body. The coating may be an electro-plated coating wherein an electro-plated metal (such as nickel) encapsulates a particulate abrasive (such as diamond grit). The shaft of the first grinding tool may include a coolant passage system which has coolant outlets in the first grinding ring. The rotary body of the second grinding tool may include a coolant passage system which has coolant outlets in the second grinding ring. The shaft of the first grinding tool may have a proximal end and a distal end. The first grinding location may be at the distal end. The coolant passage system of the first grinding tool may comprise an axial passage running from the proximal end towards the distal end of the shaft, and a first set of radial passages running from the axial passage to the first grinding location and to a first set of the coolant outlets. The axial passage may be a central axial passage located on the longitudinal axis of rotation of the shaft. The coolant passage system of the second grinding tool may comprise an axial passage inside the rotary body, and a second set of radial passages running from the axial passage to the second grinding location and to a second set of the coolant outlets. The axial passage may be a central axial passage located on the axis of rotation of the rotary body. When grinding, the supply of a coolant fluid to a grinding location assists the grinding operation. The coolant fluid may provide lubrication to the surface that is undergoing the grinding operation and may remove (carry away) the ground-away (abraded) material. Each coolant passage system may be configured to supply the coolant fluid to the respective grinding location at a relatively high pressure and at a relatively low volumetric flow rate. The diameter of the respective coolant outlets may be configured to achieve this. The first set of coolant outlets may have an outlet diameter which is less than an outlet diameter of the second set of coolant outlets. The first grinding ring may have an outer diameter and an inner diameter. The second grinding ring may have an outer diameter and an inner diameter, and the outer diameter of the second grinding ring may be greater than the outer diameter of the first grinding ring. The inner diameter of the second grinding ring may be greater than the inner diameter of the first grinding ring. Overall, the second grinding ring may be bigger (wider) than the first grinding ring when the second grinding ring is intended to perform a grinding operation which is at an open end of a cylindrical bore, such that full insertion of the second grinding ring into the cylindrical bore is not required, compared with the first grinding ring which is intended to perform a grinding operation which requires the first grinding ring to be fully inserted into the cylindrical bore. A central shaft portion may be positioned between the proximal end and the distal end of the shaft of the first grinding tool and have a shaft diameter which is smaller than the inner diameter of the first grinding ring. This may assist in preventing the part of the shaft which is not used in the grinding operation from making unwanted contact with (clashing with) the cylindrical wall during the grinding of the first feature of the cylindrical wall. The first grinding ring may be configured for performing a lower chamfering operation and / or an undercut operation. Correspondingly, the first feature of the cylindrical wall may comprise a lower chamfer and / or an undercut. The first grinding ring may include a first annular portion which is cylindrical and which is configured for performing the undercut operation. The first grinding ring may include a second annular portion which is conically tapered and which is angled towards a proximal-end connecting portion of the shaft and the second annular portion of the first grinding ring is configured for performing the lower chamfering operation. The second annular portion of the first grinding ring may be an edge portion. The first annular portion of the first grinding ring may be contiguous with the second annular portion of the first grinding ring. The second grinding ring may be configured for performing an upper chamfering operation and / or a spotfacing operation. Correspondingly, the second feature of the cylindrical wall may comprise an upper chamfer and / or a spotfaced surface. The second grinding ring may include a first annular portion which is conically tapered and which is angled away from a proximal-end connecting portion of the rotary body and the first annular portion of the second grinding ring may be configured for performing the upper chamfering operation. The second grinding ring may include a second annular portion which is perpendicular to the axis of rotation of the rotary body and which is configured for performing the spotfacing operation. The first annular portion of the second grinding ring may be an edge portion. The second annular portion of the second grinding ring may be contiguous with the first annular portion of the second grinding ring. An HSK holder may be connected to a proximal-end connecting portion of the shaft of the first grinding tool. Thus, the tool may be made compatible with existing tool magazines which are configured to accept any tool which has a standard design of HSK holder. An HSK holder may be connected to a proximal-end connecting portion of the rotary body of the second grinding tool. Thus, the tool may be made compatible with existing tool magazines which are configured to accept any tool which has a standard design of HSK holder. The overall length of the first grinding tool may be at least 20% greater than the overall length of the second grinding tool, more preferably at least 30% greater, or at least 40% greater, or at least 50% greater, or at least 60% greater. The greater overall length of the first grinding tool gives the first grinding tool a greater working reach for performing its grinding operation compared with the working reach of the second grinding tool for performing its grinding operation. The HSK holder and the shaft or rotary body may be of a unitary construction (a monobloc). The HSK holder of the first grinding tool may be smaller than the HSK holder of the second grinding tool. For example, the first grinding tool may use an HSK 63 holder (spindle), and the second grinding tool may use an HSK 100 holder (spindle). According to an aspect of the present invention, there is provided a multi-axis machining centre comprising a tool magazine containing a grinding tool set which is in accordance with the present invention. The machining centre may be a 5-axis machining centre. The machining centre may have a rotary drive which is configured to accept a standard design of HSK holder. Thus, each of the different tools which have the standard design of HSK holder and which are stored in the tool magazine may, when needed to be used, be fitted onto the rotary drive. According to an aspect of the present invention, there is provided apparatus comprising: a workpiece having a cylindrical bore, such as a cylinder bore of an engine block; and a grinding tool set comprising first and second grinding tools for grinding first and second annular features which are spaced apart along a longitudinal centre line of the cylindrical bore; wherein: the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring for grinding the first annular feature; and the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location which is annular and supports a second grinding ring for grinding the second annular feature. The first and second grinding rings may each comprise an abrasive coating, such as a layer of diamond grit. The coating may be galvanically connected to the base material of the shaft or the rotary body. The coating may be an electro-plated coating wherein an electro-plated metal (such as nickel) encapsulates a particulate abrasive (such as diamond grit). The workpiece may comprise a metal body such as metal block (e.g. an engine block). The cylindrical bore of the metal body may have a spray coating at least at the intended positions of the first and second features. The metal body may be made of metal which is softer than the spray coating of the cylindrical bore, and preferably the metal is aluminium. The cylindrical bore may have a top end and a bottom end, and the top end of the cylindrical bore may be configured to permit the first and second grinding tools to be separately inserted thereinto. The bottom end of the cylindrical bore may be closed or the workpiece may be configured to prevent the first and second grinding tools from being inserted into the bottom end of the cylindrical bore. Underneath the bottom end of the cylindrical bore may be structure which impedes or prevents the first and second grinding tools from approaching the cylindrical bore from the direction of the bottom end of the cylindrical bore. For an engine block, access is typically not possible from underneath the engine block (into the cylinder bores) because of obstructions caused by the complicated shape of the part of the engine block which supports the crankshaft. For an engine block, the space above the top end of a cylinder bore is clear of structure, and the first and second grinding tools can have unimpeded access to the cylinder bore from above. Thus, the direction of insertion of each of the first and second grinding tools may be downwards, down into the top end of a particular cylinder bore. When grinding an engine block having a plurality of cylinder bores, such that grinding operations will be performed on a first cylinder bore, then on a second cylinder bore etc., the use of the first and second (i.e. separate) grinding tools is advantageous in relation to improving the tolerance characteristics. The separate (first and second) grinding tools prevent any potential tolerance stack issues when moving from one cylinder bore to the next cylinder bore. A tolerance stack is undesirable because it could affect the positioning of the second grinding tool within a particular cylinder bore and could create a smaller upper chamfer on one side of the cylinder bore and a larger upper chamfer at the opposite side of the cylinder bore. According to an aspect of the present invention, there is provided a method of performing grinding operations on a cylinder bore, the method comprising: providing a grinding tool set which comprises first and second grinding tools, wherein the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring, and the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location which is annular and supports a second grinding ring; feeding the shaft of the first grinding tool into the cylinder bore and bringing the first grinding ring into contact with a bottom end portion of the cylinder bore; rotating the shaft of the first grinding tool so that the first grinding ring performs an undercut operation and grinds an annular undercut at the bottom end portion of the cylinder bore; extracting the first grinding tool from the cylinder bore; bringing the second grinding ring of the second grinding tool into contact with a top end portion of the cylinder bore; and rotating the rotary body of the second grinding tool so that the second grinding ring performs an upper chamfering operation and grinds an annular upper chamfer at the top end portion of the cylinder bore. When grinding the annular undercut, the shaft of the first grinding tool may rotate whilst the longitudinal axis of rotation of the shaft undergoes circular interpolation inside the cylinder bore. When grinding the annular upper chamfer, the rotary body of the second grinding tool may rotate whilst the axis of rotation of the rotary body undergoes circular interpolation inside the cylinder bore. The longitudinal axis of the first grinding tool may follow an orbital path whilst the first grinding tool rotates. The axis of rotation of the second grinding tool may follow an orbital path whilst the second grinding tool rotates. After the grinding of the annular undercut, the first grinding tool may index radially inwards away from the annular undercut towards a longitudinal centre line of the cylinder bore and then the first grinding tool is extracted from the cylinder bore. The second grinding tool may be positioned so as to bring the second grinding ring into contact with a deck face which is at the top end portion of the cylinder bore and which is perpendicular to the longitudinal centre line of the cylinder bore. The grinding of the annular upper chamfer by the second grinding ring may be performed so that the annular upper chamfer is created between the deck face and the cylinder bore. During the grinding of the annular upper chamfer, the second grinding ring may also perform a spotfacing operation on the deck face around the cylinder bore. During the grinding of the annular undercut at the bottom end portion of the cylinder bore, the first grinding ring may also perform a lower chamfering operation and grind an annular lower chamfer at the bottom end portion of the cylinder bore at a position above the annular undercut. The cylinder bore may have a spray coating at least at the positions where the undercut operation and the upper chamfering operation are performed. The spray coating may be present on the entire cylinder bore between the top and bottom end portions of the cylinder bore. The cylinder bore may be a spray-coated cylinder bore in an engine block which is a casting of metal which is softer than the spray coating of the cylinder bore. The metal may be aluminium. The grinding operations that are performed on the cylinder bore may serve to fill any porosity left in the aluminium of the engine block at the top and bottom end portions of the cylinder bore as a result of the casting process. In some circumstances, it may be desired to perform a single grinding operation on a component feature of a workpiece. According to an aspect of the present invention, there is provided a method of performing a grinding operation on a spray coating of a cylindrical bore such as a cylinder bore, the method comprising: providing a grinding tool which comprises a rotary body having an axis of rotation and a grinding location which is annular and supports a grinding ring; bringing the grinding ring of the grinding tool into contact with the spray coating of the cylindrical bore; and rotating the rotary body of the grinding tool so that the grinding ring performs a grinding operation and grinds a feature (e.g. an annular feature) through the spray coating of the cylindrical bore and into underlying base material. The cylinder bore may be a cylinder bore of an engine block. If the engine block has a plurality of cylinder bores, the grinding operation may be repeated successively on a sequence of the cylinder bores. For example, if the cylinder bores are arranged in a row, the grinding tool may progress along the row and perform the grinding operation in turn at each cylinder bore. The grinding ring may comprise an abrasive coating, preferably a layer of diamond grit. The spray coating may be a thermically sprayed coating. The rotary body of the grinding tool may include a coolant passage system which has coolant outlets in the grinding ring. When the abrasive coating of the grinding ring is grinding through the hardness of the spray coating, coolant may be supplied via the coolant passage system to the site of the grinding operation to cool the grinding site and to flush away abraded particles of the spray coating. Conveniently, an HSK holder may be connected to a proximal-end connecting portion of the rotary body of the grinding tool. The spray coating may coat an underlying metal base material which is softer than the spray coating. The underlying metal base material may be cast aluminium. The cylinder bore may have a top end and a bottom end, and the spray coating may coat the cylinder bore from the top end to the bottom end. The grinding of the annular feature may involve removing a localised annular band of the overall spray coating. The localised annular band may comprise 20% or less (or 15% or less, or 10% or less, or 5% or less) of the overall spray coating before the grinding operation is performed. When grinding the annular feature, the rotary body of the grinding tool may rotate whilst the axis of rotation of the rotary body undergoes circular interpolation inside the cylinder bore. The maximum diameter of the part of the grinding tool that projects into the cylinder bore may be less than the diameter of the cylinder bore, such that when moving the grinding ring into position at the intended site of the grinding operation the grinding tool does not come into contact with (does not clash with) the surface of the cylinder bore. At the intended site of the grinding operation, the grinding tool may index radially outwards to bring the grinding ring into contact with the spray coating of the cylinder bore. The grinding operation may be performed, whilst the grinding tool undergoes circular interpolation inside the cylinder bore. The grinding tool may index radially inwards, and the grinding tool may be extracted from the cylinder bore. A feature mentioned above in relation to one aspect of the present invention may be combined into another aspect of the present invention. Brief description of the drawings Some embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Figs. 1 and 2 are side views of the two tools of a first embodiment of a grinding tool set in accordance with the present invention, wherein Fig. 1 shows the first (long) grinding tool and Fig. 2 show the second (short) grinding tool. Fig. 3 shows the first grinding tool of Fig. 1 when inserted into a cylinder bore of an engine block, wherein the grinding tool is positioned for performing a grinding step of grinding an undercut and a lower chamfer. Fig. 4 is an enlarged view of part of Fig. 3 and shows the undercut and the lower chamfer. Fig. 5 shows the second grinding tool of Fig. 2 when inserted into the cylinder bore of the engine block, wherein the grinding tool is positioned for performing a later grinding step of grinding an upper chamfer and performing a spotfacing operation. Fig. 6 is an enlarged view of part of Fig. 5 and shows the upper chamfer and the spotfacing. Fig. 7 is a longitudinal cross-sectional view of the first grinding tool. Fig. 7A is an enlarged view of part of Fig. 7 and shows the first grinding ring. Fig. 8 is an exploded front perspective view of the first grinding tool of Fig. 7. Fig. 9 is a front perspective view of the first grinding tool of Fig. 7. Fig. 10 is a rear perspective view of the first grinding tool of Fig. 7. Fig. 11 is front perspective view of the first grinding tool of Fig. 7 wherein the grinding tool is shown in longitudinal cross-section. Fig. 12 is a longitudinal cross-sectional view of the first grinding tool of Fig. 7. Fig. 13 is a longitudinal cross-sectional view of the second grinding tool. Fig. 13A is an enlarged view of part of Fig. 13 and shows the second grinding ring. Fig. 14 is an exploded front perspective view of the second grinding tool of Fig. 13. Fig. 15 is a front perspective view of the second grinding tool of Fig. 13. Fig. 16 is a rear perspective view of the second grinding tool of Fig. 13. Fig. 17 is front perspective view of the second grinding tool of Fig. 13 wherein the grinding tool is shown in longitudinal cross-section. Fig. 18 is a longitudinal cross-sectional view of the second grinding tool of Fig. 13. Fig. 19 shows the first and second grinding tools side by side so as to illustrate the overall length of the first grinding tool relative to the overall length of the second grinding tool. While the invention is susceptible to various modifications and alternative forms, some embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description of these embodiments are not intended to limit the invention to the particular forms disclosed. In addition, although individual embodiments may have been discussed, the invention is intended to cover combinations of those embodiments. The invention covers all modifications, equivalents and alternatives falling within the spirit and the scope of the present invention as defined by the appended claims. Description of some embodiments A first embodiment of a grinding tool set will now be described with reference to Figs. 1 to 19. The grinding tool set comprises a first grinding tool 1A and a second grinding tool IB which is shorter than the first grinding tool 1 A. Fig. 19 shows the first and second grinding tools side by side so as to illustrate the overall length TL1 of the first grinding tool 1A relative to the overall length TL2 of the second grinding tool IB. For the present embodiment, the overall length TL1 is about 70% greater than the overall length TL2. The greater overall length of the first grinding tool gives the tool a greater working reach for performing its grinding operation compared with the working reach of the second grinding tool for performing its grinding operation. The first grinding tool 1A (see Fig. 1) comprises a shaft 2 and an HSK holder 3 A. The HSK holder 3 A has a standard design which allows it to plug into a rotary drive 4A of a machining centre. The rotary drive 4A is depicted in dashed line in Fig. 1 but is not depicted in the other Figures for reasons of clarity. The body of the shaft 2 and the HSK holder 3 A are made of steel as an integral single body (a monobloc). An example of the steel that may be used is Steel 42CrMoS4V (42CrMoS4 +QT) Material 1.7227. The shaft 2 and the HSK holder 3 A are rotatable around a longitudinal axis of rotation 11 of the tool 1 A. The shaft 2 and the HSK holder 3 A may be driven to rotate around the axis 11 by the rotary drive 4A. The shaft 2 has a distal end 21 and a proximal end 22. A first annular grinding location 23 is located at the distal end 21. A first grinding ring 5 is electro-plated as an abrasive layer onto the steel body at the first grinding location 23. In relation to the electro-plating to form the grinding ring, the steel body of the shaft 2 is submerged in an electrolyte (with masking applied to the areas of the steel body other than the first grinding location 23) such that nickel is deposited at the first grinding location 23 whilst encapsulating a particulate abrasive in the form of man-made (synthetic) diamond crystals (so-called diamond grit). In this way, the abrasive is adhered to (galvanically connected to) the steel body of the shaft 2 at the first grinding location 23 to form an abrasive coating or layer. The shaft 2 includes a nose portion 25 in front of the first grinding ring 5, a central shaft portion 26 behind the first grinding ring 5 and a proximal-end connecting portion 27 which is to the rear of the central shaft portion 26 and which serves to connect the rear end of the shaft 2 to the front end of the HSK holder 3 A. The first grinding ring 5 has an outer diameter DI and an inner diameter D2. The central shaft portion 26 has a shaft diameter D5, and the shaft diameter D5 is less than the inner diameter D2. The first grinding ring 5 incorporates grooves 51 which are circumferentially uniformly spaced apart around the periphery of the first grinding ring 5 and which are helically orientated relative to the longitudinal axis of rotation 11 of the grinding tool 1 A. Each groove 51 incorporates, at the base of the groove, two coolant outlets 71. The helical orientation may improve the flow of the coolant during the grinding operation performed by the first grinding ring 5 (compared with grooves which are parallel to the rotational axis 11). The improved flow may assist with removing the aluminium chips resulting from the grinding of the engine block so that the chips are removed before they can “weld” themselves to the abrasive surface of the first grinding ring 5 and thereby degrade the grinding performance of the first grinding ring 5. Also, a helical groove has a greater surface area for dispensing coolant during grinding, compared to a longitudinally-aligned groove. The first grinding ring 5 includes a first annular portion 52 which is cylindrical and which is configured for performing an undercut operation. The first grinding ring 5 also includes a second annular portion 53 which is conically tapered and which is angled towards (faces towards) the proximal-end connecting portion 27 and the second annular portion 53 is configured for performing a lower chamfering operation. The second annular portion 53 is an edge portion and the first annular portion 52 is contiguous with the second annular portion 53. Each groove 51 is located primarily in the first annular portion 52 and has a front end which extends to the front end of the first annular portion 52 and a rear end which breaks into the front end of the second annular portion 53. The second grinding tool IB (see Fig. 2) comprises a rotary body 9 and an HSK holder 3B. The HSK holder 3B has a standard design which allows it to plug into a rotary drive 4B of a machining centre. The rotary drive 4B is depicted in dashed line in Fig. 2 but is not depicted in the other Figures for reasons of clarity. The rotary body 9 and the HSK holder 3B are made of steel as an integral single body (a monobloc). An example of the steel that may be used is Steel 42CrMoS4V (42CrMoS4 +QT) Material 1.7227. The rotary body 9 and the HSK holder 3B are rotatable around an axis of rotation 12 of the tool IB. The rotary body 9 and the HSK holder 3B may be driven to rotate around the axis 12 by the rotary drive 4B. The HSK holder 3A of the first grinding tool 1A may be an HSK “63” holder (spindle) and is smaller than the HSK holder 3B of the second grinding tool IB which may be an HSK “100” holder (spindle). The rotary body 9 has a nose portion 95 in front of a proximal-end connecting portion 97 which serves to connect the rear end of the rotary body 9 to the front end of the HSK holder 3B. A second annular grinding location 94 is located between the nose portion 95 and the proximal-end connecting portion 97. A second grinding ring 6 is electro-plated as an abrasive layer onto the steel body at the second grinding location 94. In relation to the electro-plating to form the grinding ring, the steel body of the rotary body 9 is submerged in an electrolyte (with masking applied to the areas of the steel body other than the second grinding location 94) such that nickel is deposited at the second grinding location 94 whilst encapsulating a particulate abrasive in the form of man-made (synthetic) diamond crystals (so-called diamond grit). In this way, the abrasive is adhered to (galvanically connected to) the steel body of the rotary body 9 at the second grinding location 94 to form an abrasive coating or layer. The second grinding ring 6 has an outer diameter D3 and an inner diameter D4. The outer diameter D3 is greater than the outer diameter D1 of the first grinding ring 5. The inner diameter D4 is greater than the inner diameter D2 of the first grinding ring 5. The second grinding ring 6 incorporates L-shaped grooves 61 which are circumferentially uniformly spaced apart around the periphery of the second grinding ring 6. Each groove 61 incorporates, at the base of the groove, a single coolant outlet 72. The second grinding ring 6 includes a first annular portion 62 which is conically tapered and which is angled away from the proximal-end connecting portion 97 and the first annular portion 62 is configured for performing an upper chamfering operation. The second grinding ring 6 also includes a second annular portion 63 which is perpendicular to the longitudinal axis of rotation 12 and which is configured for performing a spotfacing operation. The first annular portion 62 is an edge portion and the second annular portion 63 is contiguous with the first annular portion 62. For each groove 61, part of the groove is located on the first annular portion 62 and is generally aligned with the longitudinal direction of the rotational axis 12 of the second grinding tool IB and has a front end which extends to the front end of the first annular portion 62. The coolant outlet 72 is contained in this part of the groove. The other part of the groove 61 is located on the second annular portion 63 and extends generally radially outwards to the outer circumferential edge of the second annular portion 63 with a (slight) spiral twist relative to the rotational axis 12. Figs. 3 to 6 show how the grinding tools 1A, IB of Figs. 1 and 2 may be used to perform grinding operations on a cylinder bore 81 of an engine block 8. The body of the engine block 8 is cast aluminium, and the aluminium forms a relatively-soft base material for a relatively-hard spray coating which lines the inside of the cylinder bore 81 from a top-end portion 82 to a bottom-end portion 83 of the cylinder bore 81. The spray coating 84 may be applied in a vacuum by feeding a wire to a spray tool which melts the wire to form a spray which is sprayed at high pressure onto the cylinder bore 81 as the spray tool follows a spiral track down from the top to the bottom ofthe cylinder bore 81. The wire may be in accordance with ISO 14919:2015-5.3-1,6-1 which is the ISO standard that covers different types of wire suitable for thermal spray coating. The hardness range of the spray coating may be between 400-550 HV01. The cylindrical wall of the cylinder bore 81 has a longitudinal axis (a centre line) 85. At the start of the sequence of steps for performing grinding operations on the cylinder bore 81, the grinding tool 1A is positioned above the engine block 8 with its rotational axis 11 aligned with the centre line 85 of the cylinder bore 81. The tool 1A descends into (is fed into) the cylinder bore 81 along the centre line 85 until the first grinding ring 5 is level with the bottom-end portion 83. The tool 1A then indexes radially outwards to bring the first grinding ring 5 into contact with the spray coating 84 at the bottom of the cylinder bore 81. This positioning is shown in Fig. 3. The tool 1A rotates about its rotational axis 11 (in response to being rotated by the rotary drive 4A) whilst the rotational axis 11 is moved in a circular orbital path around the centre line 85 so that the tool 1A undergoes circular interpolation inside the cylinder bore 81. The first grinding ring 5 performs a grinding operation and grinds an undercut 86 and a lower chamfer 87 into the bottom-end portion 83. The undercut 86 and the lower chamfer 87 are more easily seen in the enlarged view of Fig. 4. The undercut 86 is ground by the first annular portion 52 of the first grinding ring 5. The lower chamfer 87 is ground by the second annular portion 53 of the first grinding ring 5. Coolant is discharged from the coolant outlets 71 and carries away the abraded material of the spray coating 84 and the underlying metal of the body of the engine block 8. The grinding operation performed by the first grinding ring 5, by grinding through the spray coating material and some of the underlying metal at the bottom end of the cylinder bore, forms a neat, finished bottom edge to the spray coating of the cylinder bore whilst also creating a clearance undercut at the bottom of the cylinder bore. The tool 1A then indexes radially inwards to move the rotational axis 11 back into alignment with the centre line 85 of the cylinder bore 81. The tool 1A is then raised and is extracted out of the cylinder bore 81. The tool 1A may be returned to the tool magazine (not shown) of the machining centre. Then, the grinding tool IB is positioned above the engine block 8 with its rotational axis 12 aligned with the centre line 85 of the cylinder bore 81. The tool IB descends towards the cylinder bore 81 along the centre line 85 until the second grinding ring 6 is level with the top-end portion 82. The tool IB then indexes radially outwards until the second grinding ring 6 is in contact with the top-end portion 82 of the cylinder bore 81, as shown in Fig. 5 and in the enlarged view of Fig. 6. The tool IB rotates about its rotational axis 12 (in response to being rotated by the rotary drive 4B) whilst the rotational axis 12 is moved in a circular orbital path around the centre line 85 so that the tool IB undergoes circular interpolation inside the cylinder bore 81. The second grinding ring 6 performs a grinding operation and grinds an upper chamfer 88 and a spotfaced surface 89 at the top-end portion 82. The upper chamfer 88 and the spotfaced surface 89 are shown in the enlarged view of Fig. 6. The spotfaced surface 89 is produced on a deck face 810 around the top end of the cylinder bore 81. The upper chamfer 88 is ground by the first annular portion 62 of the second grinding ring 6. The spotfaced surface 89 is ground by the second annular portion 63 of the second grinding ring 6. Coolant is discharged from the coolant outlets 72 and carries away the abraded material of the spray coating 84 and the underlying metal of the body of the engine block 8. The grinding operation performed by the second grinding ring 6, by grinding through the spray coating material and some of the underlying metal at the top end of the cylinder bore, forms a neat, finished top edge to the spray coating of the cylinder bore whilst also creating a spotfaced surface around the top of the cylinder bore. The tool IB then indexes radially inwards to move the rotational axis 12 back into alignment with the centre line 85 of the cylinder bore 81. The tool IB is then withdrawn from the cylinder bore 81 and may be returned to the tool magazine (not shown) of the machining centre. By using grinding operations, it is possible to machine a bi-metal structure (of a relatively-hard spray coating on a relatively-soft base material of the engine block) without the machining (the grinding) causing the coating to lift away from the base material. Each grinding tool has a longer tool life (approximately 50% longer) than the cutting tool that it supersedes, and the grinding tool also has a shorter (faster) cycle time (approximately 50% shorter). Because the central shaft portion 26 has a shaft diameter which is smaller than the inner diameter D2 of the first grinding ring 5, and because the proximal-end connecting portion 27 has a diameter which is smaller than the inner diameter D2 of the first grinding ring 5, the part of the shaft which is above the first grinding ring 5 is prevented from making unwanted contact with (clashing with) the cylindrical wall of the cylinder bore 81 during the grinding of the features 86 and 87. As may be seen in Fig. 3, the shaft 2 remains clear of the cylinder bore 81 during the grinding operation of the first grinding tool 1 A. The overall length of the central shaft portion 26 and the proximal-end connecting portion 27 is greater than the tool insertion depth required for inserting the first grinding tool 1A into the cylinder bore 81 to position the first grinding ring 5 at the level of the intended features 86 and 87. In the exploded views of the first and second grinding tools 1 A, IB such as Fig. 8 and Fig. 14, the first grinding ring 5 is shown separated from the main body of the shaft 2, and the second grinding ring 6 is shown separated from the rotary body 9, as if the grinding rings are separately manufactured before being mounted on the shaft 2 or on the rotary body 9. The depiction is merely for ease of visual depiction and to assist the reader in understanding the shape of the grinding rings 5, 6. As explained above, the first and second grinding rings 5, 6 are abrasive layers which are deposited in-situ by means of electro-plating. The longitudinal cross-sectional views of the first grinding tool 1A show more detail of a coolant passage system 7 A of the first grinding tool 1A that ends at the coolant outlets 71 (not visible in Fig. 7, but see instead Figs. 1,3, 4 and 8 to 10) where the coolant is discharged during the grinding operations performed by the first grinding ring 5. The coolant passage system 7A includes a central axial passage 73A which extends from the rear end of the HSK holder 3 A to the front end of the shaft 2 where the passage is closed by a screw-threaded plug 28. A first set of radial passages 74 extends from the central axial passage 73 A to the coolant outlets 71. Figs. 11 and 12 show the entrances to the first set of radial passages 74 of the coolant passage system 7A. Thus, overall, in the coolant passage system 7A, during a grinding operation, coolant may flow axially along the central axial passage 73 A and then flow radially along the radial passages 74 and then exit from the coolant outlets 71. The longitudinal cross-sectional views of the second grinding tool IB show more detail of a coolant passage system 7B of the second grinding tool IB that ends at the coolant outlets 72 (not visible in Fig. 13, but see instead Figs. 2, 5, 6, 14 and 15) where the coolant is discharged during the grinding operations performed by the second grinding ring 6. The coolant passage system 7B includes a central axial passage 73B which extends from the rear end of the HSK holder 3B to the front end of the rotary body 9 where the passage is closed by a screw-threaded plug 98. A second set of radial passages 75 extends from the central axial passage 73B to the coolant outlets 72. Figs. 17 and 18 show the entrances to the second set of radial passages 75 of the coolant passage system 7B. Thus, overall, in the coolant passage system 7B, during a grinding operation, coolant may flow axially along the central axial passage 73B and then flow radially along the radial passages 75 and then exit from the coolant outlets 72. The coolant outlets 71 may have an outlet diameter which is less than an outlet diameter of the coolant outlets 72. The supply of the coolant fluid to the grinding locations assists the grinding operations. The coolant fluid provides lubrication to the surface that is undergoing the grinding operation and removes (carries away) the ground-away (abraded) material. The coolant passage systems are configured to supply the coolant fluid to the grinding locations at a relatively high pressure and at a relatively low volumetric flow rate. This is achieved by selecting the size and the different diameters of the coolant outlets 71, 72. Fig. 13 A shows more detail of the second grinding ring 6 and how it includes, at the rear of the grinding ring, a third annular portion 64 in the shape of a lip. Fig. 7A shows more detail of the first grinding ring 5 and how it includes, at the front of the grinding ring, a third annular portion 54 in the shape of a lip. The lip portions 54, 64 are non-fimctional in the sense that, during the grinding operations, they do not contribute to the grinding away of material of the engine block. In some circumstances, it may be desired to perform only a single grinding operation on a component feature of a workpiece, such as on the cylinder bore 81 of the engine block 8. 5 A single grinding operation may be performed by the first grinding tool 1A or by the second grinding tool IB. For example, the first grinding tool 1A of Fig. 1 may be used to perform the grinding operation shown in Figs. 3 and 4 without the second grinding tool IB then being used to perform a grinding operation. 10 Alternatively, the second grinding tool IB of Fig. 2 may be used to perform the grinding operation shown in Figs. 5 and 6 without previously using the first grinding tool 1A to perform a grinding operation.

Claims

1. A grinding tool set comprising first and second grinding tools for grinding first and second features which are spaced apart along a longitudinal axis of a cylindrical wall, wherein:the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location;the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location;the first grinding location is annular and supports a first grinding ring for grinding the first feature; andthe second grinding location is annular and supports a second grinding ring for grinding the second feature.

2. A grinding tool set according to claim 1, wherein the first and second grinding rings each comprise an abrasive coating, preferably a layer of diamond grit.

3. A grinding tool set according to claim 1 or 2, wherein the shaft of the first grinding tool includes a coolant passage system which has coolant outlets in the first grinding ring.

4. A grinding tool set according to any preceding claim, wherein the rotary body of the second grinding tool includes a coolant passage system which has coolant outlets in the second grinding ring.

5. A grinding tool set according to any preceding claim, wherein:the shaft of the first grinding tool has a proximal end and a distal end; and the first grinding location is at the distal end.

6. A grinding tool set according to any preceding claim, wherein:the first grinding ring has an outer diameter and an inner diameter;the second grinding ring has an outer diameter and an inner diameter; andthe outer diameter of the second grinding ring is greater than the outer diameter of the first grinding ring.

7. A grinding tool set according to claim 6, wherein the inner diameter of the second grinding ring is greater than the inner diameter of the first grinding ring.

8. A grinding tool set according to claim 5, wherein a central shaft portion is positioned between the proximal end and the distal end of the shaft of the first grinding tool and has a shaft diameter which is smaller than the inner diameter of the first grinding ring.

9. A grinding tool set according to any preceding claim, wherein the first grinding ring is configured for performing a lower chamfering operation and / or an undercut operation.

10. A grinding tool set according to claim 9, wherein the first grinding ring includes a first annular portion which is cylindrical and which is configured for performing the undercut operation.

11. A grinding tool set according to claim 9 or 10, wherein the first grinding ring includes a second annular portion which is conically tapered and which is angled towards a proximal-end connecting portion of the shaft and the second annular portion of the first grinding ring is configured for performing the lower chamfering operation.

12. A grinding tool set according to claim 10 and claim 11, wherein the second annular portion of the first grinding ring is an edge portion and the first annular portion of the first grinding ring is contiguous with the second annular portion of the first grinding ring.

13. A grinding tool set according to any preceding claim, wherein the second grinding ring is configured for performing an upper chamfering operation and / or a spotfacing operation.

14. A grinding tool set according to claim 13, wherein the second grinding ring includes a first annular portion which is conically tapered and which is angled away from a proximal-end connecting portion of the rotary body and the first annular portion of the second grinding ring is configured for performing the upper chamfering operation.

15. A grinding tool set according to claim 13 or 14, wherein the second grinding ring includes a second annular portion which is perpendicular to the axis of rotation of the rotary body and which is configured for performing the spotfacing operation.

16. A grinding tool set according to claim 14 and claim 15, wherein the first annular portion of the second grinding ring is an edge portion and the second annular portion of the second grinding ring is contiguous with the first annular portion of the second grinding ring.

17. A grinding tool set according to any preceding claim, wherein an HSK holder is connected to a proximal-end connecting portion of the shaft of the first grinding tool and an HSK holder is connected to a proximal-end connecting portion of the rotary body of the second grinding tool.

18. A multi-axis machining centre comprising a tool magazine containing a grinding tool set according to any one of claims 1 to 17.

19. Apparatus comprising:a workpiece having a cylindrical bore; anda grinding tool set comprising first and second grinding tools for grinding first and second annular features which are spaced apart along a longitudinal centre line of the cylindrical bore;wherein:the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring for grinding the first annular feature; andthe second grinding tool comprises a rotary body having an axis of rotation and a second grinding location which is annular and supports a second grinding ring for grinding the second annular feature.

20. Apparatus according to claim 19, wherein the first and second grinding rings each comprise an abrasive coating, preferably a layer of diamond grit.

21. Apparatus according to claim 19 or 20, wherein the workpiece comprises a metal body and the cylindrical bore therein has a spray coating at least at the intended positions of the first and second features.

22. Apparatus according to claim 21, wherein the metal body is made of metal which is softer than the spray coating of the cylindrical bore, and preferably the metal is aluminium.

23. Apparatus according to any one of claims 19 to 22, wherein:the cylindrical bore has a top end and a bottom end;the top end of the cylindrical bore is configured to permit the first and second grinding tools to be separately inserted thereinto; andthe bottom end of the cylindrical bore is closed or the workpiece is configured to prevent the first and second grinding tools from being inserted into the bottom end of the cylindrical bore.

24. A method of performing grinding operations on a cylinder bore, the method comprising: providing a grinding tool set which comprises first and second grinding tools, wherein the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring, and the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location which is annular and supports a second grinding ring;feeding the shaft of the first grinding tool into the cylinder bore and bringing the first grinding ring into contact with a bottom end portion of the cylinder bore;rotating the shaft of the first grinding tool so that the first grinding ring performs an undercut operation and grinds an annular undercut at the bottom end portion of the cylinder bore;extracting the first grinding tool from the cylinder bore;bringing the second grinding ring of the second grinding tool into contact with a top end portion of the cylinder bore; androtating the rotary body of the second grinding tool so that the second grinding ring performs an upper chamfering operation and grinds an annular upper chamfer at the top end portion of the cylinder bore.

25. A method according to claim 24, wherein:when grinding the annular undercut, the shaft of the first grinding tool rotates whilst the longitudinal axis of rotation of the shaft undergoes circular interpolation inside the cylinder bore; andwhen grinding the annular upper chamfer, the rotary body of the second grinding tool rotates whilst the axis of rotation of the rotary body undergoes circular interpolation inside the cylinder bore.

26. A method according to claim 24 or 25, wherein:after the grinding of the annular undercut, the first grinding tool indexes radially inwards away from the annular undercut towards a longitudinal centre line of the cylinder bore and then the first grinding tool is extracted from the cylinder bore;the second grinding tool is positioned so as to bring the second grinding ring into contact with a deck face which is at the top end portion of the cylinder bore and which is perpendicular to the longitudinal centre line of the cylinder bore; andthe grinding of the annular upper chamfer by the second grinding ring is performed so that the annular upper chamfer is created between the deck face and the cylinder bore.

27. A method according to claim 26, wherein:during the grinding of the annular upper chamfer, the second grinding ring also performs a spotfacing operation on the deck face around the cylinder bore.

28. A method according to any one of claims 24 to 27, wherein:during the grinding of the annular undercut at the bottom end portion of the cylinder bore, the first grinding ring also performs a lower chamfering operation and grinds an annular lower chamfer at the bottom end portion of the cylinder bore at a position above the annular undercut.

29. A method according to any one of claims 24 to 28, wherein:the cylinder bore has a spray coating at least at the positions where the undercut operation and the upper chamfering operation are performed.

30. A method according to any one of claims 24 to 29, wherein the cylinder bore is a spray-coated cylinder bore in an engine block which is a casting of a metal which is softer than the spray coating of the cylinder bore, and preferably the metal is aluminium.

31. A method of performing a grinding operation on a spray coating of a cylinder bore, the method comprising:providing a grinding tool which comprises a rotary body having an axis of rotation and a grinding location which is annular and supports a grinding ring;bringing the grinding ring of the grinding tool into contact with the spray coating of the cylinder bore; androtating the rotary body of the grinding tool so that the grinding ring performs a grinding operation and grinds an annular feature through the spray coating of the cylinder bore.

32. A method according to claim 31, wherein the cylinder bore is a cylinder bore of an engine block.

33. A method according to claim 31 or 32, wherein the spray coating is a thermically sprayed coating.

34. A method according to any one of claims 31 to 33, wherein the spray coating coats an underlying metal base material which is softer than the spray coating.

35. A method according to any one of claims 31 to 34, wherein the cylinder bore has a top end and a bottom end, and the spray coating coats the cylinder bore from the top end to the bottom end, and the grinding of the annular feature involves removing a localised annular band of the overall spray coating.

36. A method according to any one of claims 31 to 35, wherein, when grinding the annular feature, the rotary body of the grinding tool rotates whilst the axis of rotation of the rotary body undergoes circular interpolation inside the cylinder bore.Amendments to the claim have been filed as follows:04 06 25CLAIMS1. A grinding tool set comprising first and second grinding tools for grinding first and second features which are spaced apart along a longitudinal axis of a cylindrical wall, wherein:the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first 5 grinding location;the second grinding tool comprises a rotary body having an axis of rotation and a second grinding location;the first grinding location is annular and supports a first grinding ring for grinding the first feature; and10 the second grinding location is annular and supports a second grinding ring for grindingthe second feature;wherein:the first grinding ring has an outer diameter and an inner diameter;the second grinding ring has an outer diameter and an inner diameter; and15 the outer diameter of the second grinding ring is greater than the outer diameterof the first grinding ring, and wherein the inner diameter of the second grinding ring is greater than the inner diameter of the first grinding ring.

2. A grinding tool set according to claim 1, wherein the first and second grinding rings each 20 comprise an abrasive coating, preferably a layer of diamond grit.

3. A grinding tool set according to claim 1 or 2, wherein the shaft of the first grinding tool includes a coolant passage system which has coolant outlets in the first grinding ring.25 4. A grinding tool set according to any preceding claim, wherein the rotary body of the secondgrinding tool includes a coolant passage system which has coolant outlets in the second grinding ring.

5. A grinding tool set according to any preceding claim, wherein:30 the shaft of the first grinding tool has a proximal end and a distal end; andthe first grinding location is at the distal end.04 06 256. A grinding tool set according to any preceding claim, wherein a central shaft portion is positioned between the proximal end and the distal end of the shaft of the first grinding tool and has a shaft diameter which is smaller than the inner diameter of the first grinding ring.5 7. A grinding tool set according to any preceding claim, wherein the first grinding ring isconfigured for performing a lower chamfering operation and / or an undercut operation.

8. A grinding tool set according to claim 7, wherein the first grinding ring includes a first annular portion which is cylindrical and which is configured for performing the undercut 10 operation.

9. A grinding tool set according to claim 7 or 8, wherein the first grinding ring includes a second annular portion which is conically tapered and which is angled towards a proximal-end connecting portion of the shaft and the second annular portion of the first grinding ring 15 is configured for performing the lower chamfering operation.

10. A grinding tool set according to claim 8 and claim 9, wherein the second annular portion of the first grinding ring is an edge portion and the first annular portion of the first grinding ring is contiguous with the second annular portion of the first grinding ring.2011. A grinding tool set according to any preceding claim, wherein the second grinding ring is configured for performing an upper chamfering operation and / or a spotfacing operation.

12. A grinding tool set according to claim 11, wherein the second grinding ring includes a first 25 annular portion which is conically tapered and which is angled away from a proximal-end connecting portion of the rotary body and the first annular portion of the second grinding ring is configured for performing the upper chamfering operation.

13. A grinding tool set according to claim 11 or 12, wherein the second grinding ring includes 30 a second annular portion which is perpendicular to the axis of rotation of the rotary body and which is configured for performing the spotfacing operation.

14. A grinding tool set according to claim 12 and claim 13, wherein the first annular portion of the second grinding ring is an edge portion and the second annular portion of the second 35 grinding ring is contiguous with the first annular portion of the second grinding ring.04 06 2515. A grinding tool set according to any preceding claim, wherein an HSK holder is connected to a proximal-end connecting portion of the shaft of the first grinding tool and an HSK holder is connected to a proximal-end connecting portion of the rotary body of the second 5 grinding tool.

16. A multi-axis machining centre comprising a tool magazine containing a grinding tool set according to any one of claims 1 to 15.10 17. Apparatus comprising:a workpiece having a cylindrical bore; anda grinding tool set comprising first and second grinding tools for grinding first and second annular features which are spaced apart along a longitudinal centre line of the cylindrical bore;15 wherein:the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring for grinding the first annular feature; andthe second grinding tool comprises a rotary body having an axis of rotation and a second 20 grinding location which is annular and supports a second grinding ring for grinding the second annular feature;wherein:the first grinding ring has an outer diameter and an inner diameter;the second grinding ring has an outer diameter and an inner diameter; and25 the outer diameter of the second grinding ring is greater than the outer diameterof the first grinding ring, and wherein the inner diameter of the second grinding ring is greater than the inner diameter of the first grinding ring.

18. Apparatus according to claim 17, wherein the first and second grinding rings each comprise 30 an abrasive coating, preferably a layer of diamond grit.04 06 2519. Apparatus according to claim 17 or 18, wherein the workpiece comprises a metal body and the cylindrical bore therein has a spray coating at least at the intended positions of the first and second features.5 20. Apparatus according to claim 19, wherein the metal body is made of metal which is softerthan the spray coating of the cylindrical bore, and preferably the metal is aluminium.

21. Apparatus according to any one of claims 17 to 20, wherein:the cylindrical bore has a top end and a bottom end;10 the top end of the cylindrical bore is configured to permit the first and second grindingtools to be separately inserted thereinto; andthe bottom end of the cylindrical bore is closed or the workpiece is configured to prevent the first and second grinding tools from being inserted into the bottom end of the cylindrical bore.1522. A method of performing grinding operations on a cylinder bore, the method comprising: providing a grinding tool set which comprises first and second grinding tools, wherein the first grinding tool comprises a shaft having a longitudinal axis of rotation and a first grinding location which is annular and supports a first grinding ring, and the second grinding tool20 comprises a rotary body having an axis of rotation and a second grinding location which is annular and supports a second grinding ring;feeding the shaft of the first grinding tool into the cylinder bore and bringing the first grinding ring into contact with a bottom end portion of the cylinder bore;rotating the shaft of the first grinding tool so that the first grinding ring performs an25 undercut operation and grinds an annular undercut at the bottom end portion of the cylinder bore;extracting the first grinding tool from the cylinder bore;bringing the second grinding ring of the second grinding tool into contact with a top end portion of the cylinder bore; and30 rotating the rotary body of the second grinding tool so that the second grinding ringperforms an upper chamfering operation and grinds an annular upper chamfer at the top end portion of the cylinder bore.04 06 2523. A method according to claim 22, wherein:when grinding the annular undercut, the shaft of the first grinding tool rotates whilst the longitudinal axis of rotation of the shaft undergoes circular interpolation inside the cylinder bore; and5 when grinding the annular upper chamfer, the rotary body of the second grinding toolrotates whilst the axis of rotation of the rotary body undergoes circular interpolation inside the cylinder bore.

24. A method according to claim 22 or 23, wherein:10 after the grinding of the annular undercut, the first grinding tool indexes radially inwardsaway from the annular undercut towards a longitudinal centre line of the cylinder bore and then the first grinding tool is extracted from the cylinder bore;the second grinding tool is positioned so as to bring the second grinding ring into contact with a deck face which is at the top end portion of the cylinder bore and which is perpendicular 15 to the longitudinal centre line of the cylinder bore; andthe grinding of the annular upper chamfer by the second grinding ring is performed so that the annular upper chamfer is created between the deck face and the cylinder bore.

25. A method according to claim 24, wherein:20 during the grinding of the annular upper chamfer, the second grinding ring also performsa spotfacing operation on the deck face around the cylinder bore.

26. A method according to any one of claims 22 to 25, wherein:during the grinding of the annular undercut at the bottom end portion of the cylinder 25 bore, the first grinding ring also performs a lower chamfering operation and grinds an annular lower chamfer at the bottom end portion of the cylinder bore at a position above the annular undercut.

27. A method according to any one of claims 22 to 26, wherein:30 the cylinder bore has a spray coating at least at the positions where the undercutoperation and the upper chamfering operation are performed.

28. A method according to any one of claims 22 to 27, wherein the cylinder bore is a spray-coated cylinder bore in an engine block which is a casting of a metal which is softer than the spray coating of the cylinder bore, and preferably the metal is aluminium.04 06 25Application No: GB2410018.2Examiner: Kris WojciechowskiClaims searched: 1-36Date of search: 13 March 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1, 2, 5, 8-23, 31-36 JP2023071055 A (KUBOTA CORP) See figures X 1-5, 17- 23, 31-35 US 10751849 B2 (ROSSETTI et al.) See figures X 1,2,5 JP2019025612 A (OKAMOTO MACHINE TOOL WORKS) See figures v A 31-36 JP5794017B2 (NISSAN MOTORS) See figuresCategories:X Document indicating lack of novelty or inventive A Document indicating technological background and / or state step of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category'. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:www.gov.uk / ipoInternational Classification:Subclass Subgroup Valid From B24D 0007 / 18 01 / 01 / 2006 B24B 0005 / 06 01 / 01 / 2006 B24B 0005 / 14 01 / 01 / 2006 B24B 0005 / 40 01 / 01 / 2006 B24D 0005 / 02 01 / 01 / 2006 B24D 0005 / 10 01 / 01 / 2006 B24D 0007 / 02 01 / 01 / 2006 B24D 0007 / 10 01 / 01 / 2006www.gov.uk / ipo

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