WO2008004934A1

WO2008004934A1 - E text as een esta s e y t s ut o ty to rea as o ows: holder member, grinding machine and method for grinding a rock drill bit

Info

Publication number: WO2008004934A1
Application number: PCT/SE2007/000595
Authority: WO
Inventors: Arne Bergquist
Original assignee: Sandvik Intellectual Property Ab
Priority date: 2006-07-05
Filing date: 2007-06-19
Publication date: 2008-01-10
Also published as: SE0601473L; SE530119C2

Abstract

The present invention relates to a holder member (1) for a rock drill bit in connection with the rock drill bit being to be ground, the holder member (1) comprising a cover (20), an attachment member (21) fitted on the cover (20) for the mounting of the holder member (1) on a frame (5) or the like. The invention also relates to a grinding machine as well as a method for grinding rock drill bits. Characteristic of the holder member (1) according to the present invention is that it comprises an internal part (22), which is rotatable in relation to the cover (20) around a rotational axis (C-C), a clamping member (25) fixedly connected with the internal part (22), which clamping member is intended to receive a rock drill bit, members (40) to rotate the internal part (22) in relation to the cover (20), as well as members (60) to record positions, in relation to each other, of rock-machining members of the rock drill bit.

Description

A HOLDER MEMBER FOR A ROCK DRILL BIT AND A METHOD FOR GRINDING A ROCK DRILL BIT

Technical Field of the Invention

The present invention relates to a holder member for a rock drill bit as well as a method for grinding the rock-machining members of a rock drill bit according to the preamble of the independent claims.

Prior Art

In the grinding of rock drill bits, wherein said rock drill bits may be equipped with buttons or with chisel bits, new positions of the rock drill bit are indexed forward manually by the operator in charge of the grinding. When for instance a button is finish ground, the grinding machine is stopped and the grinding spindle including the grinding cup thereof is raised from the rock drill bit. Next, the operator loosens the joint that exists between the rock drill bit and a holder member for the rock drill bit, and then the operator manually indexes forward a new position of the rock drill bit by rotating the same in relation to the holder member and/or making a lateral move of the holder member, said adjustment of the position of the rock drill bit entailing that a new button will come into position to be ground. This manual procedure has to be repeated after a button is finish ground. If the rock drill bit instead is equipped with chisel bits, a manual indexing of the rock drill bit is correspondingly made so that a not yet ground chisel bit is positioned for grinding.

Objects and Features of the Invention

A primary object of the present invention is to provide a holder member for a rock drill bit provided with buttons that automatically indexes between at least the rock-machining members provided on the rock drill bit that consist of peripheral buttons. Another object of the present invention is that according to an alternative embodiment of the holder member, automatic indexing should be effected also between the rock-machining members in the form of front buttons.

Still another object of the present invention is to provide an efficient handling in connection with a rock drill bit being finish ground and the next rock drill bit is to be ground.

At least the primary object of the present invention is realised by means of a holder member having the features defined in the appended independent claim 1. Preferred embodiments of the invention are defined in the dependent claims.

Brief Description of the Drawings

Below, a preferred embodiment of the invention will be described, reference being made to the accompanying drawings, wherein:

Fig. 1 shows a side view of a grinding machine, in which a holder member according to the present invention is included;

Fig. 2 shows a front view of the grinding machine according to Fig. 1 ;

Fig. 3 shows a vertical section through a holder member according to the present invention;

Fig. 4 shows a section according to the line IV through a freewheel hub included in the holder member according to Fig. 3;

Fig. 5 and 6 schematically shows how rotation of an internal part of the holder member takes place by means of a freewheel hub;

Fig. 7 shows a control panel for the user of a grinding machine that comprises a holder member according to the present invention;

Fig. 8 shows a block diagram of the units included in the control equipment for a grinding machine that comprises a holder member according to the present invention;

Fig. 9 shows a vertical section through an alternative embodiment of a holder member according to the present invention;

Fig. 10 shows a section through an indexing disc included in the holder member according to Fig. 9; and Fig. 11 shows a perspective view of the indexing disc.

Detailed Description of Preferred Embodiments of the Invention

The grinding machine shown in Figs. 1 and 2 comprises two holder members 1 according to the present invention, a grinding head 3 as well as a frame 5, the holder members 1 and the grinding head 3 being mounted on the frame 5, which comprises a foot portion 7 that rests against a support (not shown). The grinding head 3 has a centre axis B-B.

Furthermore, the frame 5 comprises a slide 9 that is horizontally displaceable in relation to the frame 5. On the slide 9, two fixing members 14 are mounted for the holder members 1 , wherein the assembly of the holder members 1 on the slide 9 will be described more thoroughly below. Each of the two holder members 1 carries a rock drill bit B provided with buttons, which is clamped on the associated holder member 1. This will be further described below.

By the fact that the slide 9 carries two holder members 1 , a drill bit B can be ground while a drill bit B to be ground is mounted on the free holder member 1. When a drill bit B is finish ground, the slide 9 is displaced laterally so that the finish ground drill bit B assumes a parking position. In doing so, the other holder member 1 including the associated rock drill bit B thereof will automatically assume an active position for grinding. Now, the finish ground rock drill bit B can be removed and a new rock drill bit B to be ground is mounted on the associated holder member 1 , and then the method described above proceeds as long as there are rock drill bits B to be ground.

The grinding head 3 is mounted on a vertical part 11 of the frame 5, the grinding head 3 being displaceable relation to the vertical part 11 by means of an arrangement not shown. The grinding head 3 comprises a grinding spindle 12, which rotates around the longitudinal axis thereof as well as moves along the generatrix of a cone. At the free end thereof, the grinding spindle 12 carries a replaceable grinding cup 13.

The holder member 1 shown in Fig. 3 comprises an external cover 20 as well as a spigot 21 mounted on the cover 20, the spigot 21 being fixed in relation to the cover 20. As is seen in Fig. 1 , the spigot 21 is mounted on the slide 9 via a fixing member 14, in which the spigot 21 is rotatably mounted. The fixing member 14 is in turn fixedly mounted on the slide 9, i.e., the fixing member 14 is fixed in relation to the slide 9. As is seen from the dashed position of the drill bit B positioned under the grinding spindle 3 in Fig. 2, the holder member 1 including the drill bit B can be laterally tilted/turned, around an axis D-D into a position where the peripheral buttons can be ground. The fixing member 14 is shaped in such a way that said tilted position may be set by the operator since the position may vary between different drill bits. The upright position of the holder member 1 shown in Fig. 2 is used when the front buttons are to be ground.

As is seen in Fig. 3, the holder member 1 also comprises an internal part 22, which is rotatable in relation to the cover 20 via two first ball bearings 23. In the embodiment illustrated, the internal part 22 is rotatable in relation to a rotational axis C-C. At the top, the internal part 22 carries a clamping member 25 for a rock drill bit, an internal space of the rock drill bit B receiving an upright 26 of the clamping member 25, see Figs. 1 and 2. The upright 26 comprises in turn a supporting element 27, which is carried by the internal part 22, the supporting element 27 having an upper conical portion 28. Through the supporting element 27, a piston rod 29 extends, which at the lower end thereof carries a first piston 30 and at the upper end thereof carries a conical element 31 , which is fixed in relation to the piston rod 29. Between the conical portion 28 and the conical element 31 , the piston rod 29 is surrounded by a number of jaws 32.

The first piston 30 is received in a chamber 33 formed in the internal part 22. The parts of the chamber 33 situated on both sides of the first piston 30 can be pressurized, for instance by means of air, wherein the first piston 30 can be brought to be displaced in the chamber 33. When the first piston 30 is displaced downward in Fig. 3, also the piston rod 29 will be displaced downward. In that connection, cooperation between the conical portion 28 and the conical element 31 will displace the jaws 32 radially outward, which entails that the rock drill bit is clamped and fixed in relation to the clamping member 25.

The holder member 1 according to the present invention also comprises a freewheel hub 40, which surrounds a diameter-reduced portion 41 of the internal part 22. The diameter-reduced portion 41 is also rotatable around the rotational axis C-C. In Fig. 4, a section through the freewheel hub 40 and associated components is shown, said type of freewheel hub being prior art. In order to describe the constructive design and the function of the freewheel hub 40 as well as associated components, reference is also made to Figs. 5 and 6.

The freewheel hub 40 is provided outside the diameter-reduced portion 41 , the freewheel hub 40 comprising a set of driver members 42 that abut against the diameter-reduced portion 41. As is most clearly seen in Figs. 5 and 6, the driver members 42 are inclined, wherein the importance of this will be explained below. The freewheel hub 40 also comprises a disc-shaped driving element 43, which surrounds the driver members 42. The disc-shaped driving element 43 is formed to co-operate with two second ball bearings 44, which also abut against the diameter-reduced portion 41. In the periphery of the disc-shaped driving element 43, a recess 45 is formed, in which a pin 46 fixed in relation to the internal part 22 is received, see Fig. 3. The pin 46 traverses an intermediate portion of a pressure-medium cylinder 47, which is fixedly mounted in a through-going hole 24 in the cover 20 in such a way that when two second pistons 48 included in the pressure-medium cylinder 47, as well as an intermediate part 49, move to-and-fro, the pin 46 is driven since it traverses the intermediate part 49. This is indicated by means of the arrows P1 and P2 in Figs. 5 and 6. Preferably, the second pistons 48 of the pressure-medium cylinder 47 are driven by compressed air, wherein nipples (not shown) for compressed air may be connected in the area of the ends of the through-going hole 24.

Since the pin 46 is received in the recess 45, also the disc-shaped driving element 43 will be driven, i.e., rotate around the common rotational axis C-C of the diameter-reduced portion 41 and the disc-shaped driving element 43. When the second pistons 48, as well as the intermediate part 49, move toward the left, see Fig. 5, the disc-shaped driving element 43 will rotate clockwise, see the arrow P3. By virtue of the inclination of the driver members 42, they engage the diameter-reduced portion 41 and drive the same, which is indicated by the arrow P4. When the second pistons 48 and the intermediate part 49 have reached the left end position thereof, the driving of the diameter-reduced portion 41 ceases. The second pistons 48 and the intermediate part 49 are now brought to move toward the right, see Fig. 6, by the fact that compressed air is introduced at the left end of the pressure-medium cylinder 47. In doing so, the pin 46 will move toward the right and the disc-shaped driving element 43 is rotated counter-clockwise, see the arrow P5 in Fig. 6. In that connection, no driving of the diameter-reduced portion 41 will take place since the driver members 42, because of the inclination thereof, only are dragging against the diameter-reduced portion 41. When the second pistons 48 and the intermediate part 49 have reached the right end position thereof in Fig. 6, a reversal of the displacement of the second pistons 48 and the intermediate part 49 takes place by the fact that compressed air is introduced at the right end of the pressure-medium cylinder 47. Upon displacement of the second pistons 48 and the intermediate part 49, driving of the diameter-reduced portion 41 will again take place in the way that has been described above. Thus, by activating the freewheel hub 40 and the pressure-medium cylinder

47, the internal part 22 may be brought to rotate clockwise, which means that also the clamping member 25 and the drill bit are rotated clockwise. This motion may be used to index the drill bit in connection with the buttons of the drill bit being to be ground. Underneath the freewheel hub 40, a brake mechanism 50 is located, which comprises a brake disc 51 , which is fixedly connected to the internal part 22, as well as a braking cylinder 52. When a certain position for grinding has been indexed forward, the brake mechanism 50 is activated and locks the internal part 22 against rotation. In that connection, an acute free end of the braking cylinder 52 comes into engagement with a groove along the circumference of the brake disc 51 , the braking cylinder 52 being actuated by a radially inwardly directed force, which, for instance, may be generated in a pneumatic way.

At the lower end of the holder member 1 , an angle sensor 60 is fitted, which by means of pulses senses when the internal part 22 is turned in relation to the cover 20. The angle sensor 60 is used when, for instance, the position of the buttons in a drill bit should be programmed. In an exemplifying and not limiting purpose, it may be mentioned that the angle sensor 60 may generate 1024 pulses/revolution.

In Fig. 7, a control panel is shown which is included in the peripheral equipment of a grinding machine according to Figs. 1 and 2. Before grinding of a certain type of drill bit is to be effected, a removal of values for previously ground drill bits is made, this being made by the fact that the user presses the push-button "TOTAL RESET" on the control panel. In that connection, an input signal, IN_Total Reset, is generated in the microprocessor denominated CPU1 in Fig. 8. Now, the operator mounts the drill bit to be ground on the clamping member 25, the drill bit being clamped by activating the knob BIT LOCK on the control panel. In that connection, an input signal IN_Bit Lock is generated to the CPU1 and the first piston 30 is displaced so that the jaws 32 clamp the drill bit. In order to lock the holder member 1 in relation to the frame 3, the knob BIT HOLDER LOCK on the control panel is activated. In that connection, an input signal IN_Bit Holder Lock is generated to the CPU1 and the fixing member 14 locks the holder member 1 against turning.

Since it frequently happens that the drill bits to be ground have damaged buttons, it is an advantage for the user to be able to choose which button that should not be ground, this taking place by the push-button "BUTTON CHOICE/RESET" on the control panel, however the knob at the top to the left on the control panel should be in the position "DO NOT Grind/BUTTON CHOICE". By pressing the push-button "BUTTON CHOICE/RESET" on the control panel a certain a number of times, the buttons that should not be ground are chosen. For instance, pressing three times on the push-button "BUTTON "CHOICE/RESET" entails that button number 3 is not ground. The push-button pressings generate an input signal IN_Button Choice to the microprocessor that has been given the designation CPU2 in Fig. 8. In order to confirm the button choice made, the light-emitting diode is light up at the numeral 3. In that connection, the operator has to allocate the buttons of the drill bit numbers according to a determined pattern, i.e., button No. 1 , button No. 2 and so on. The microprocessor CPU2 is connected with the microprocessor CPU1 , whereby the choice made concerning the buttons that should not be ground is stored in a suitable way in said microprocessors.

The control equipment according to the present invention also offers the possibility that the operator instead may choose which buttons that are to be ground. In order to make such a choice, the knob at the top to the left on the control panel is set in the position GRIND BUTTON.

The positions of the buttons included in the drill bit are programmed by the fact that the drill bit is attached on the holder member in the way described above, it being assumed that the peripheral buttons are to be ground, i.e., the drill bit is inclined a certain angle, see the solid-line position in Fig. 2 of the drill bit situated right opposite the grinding head 3. The operator then releases the brake by pressing the push-button BRAKE on the panel. The bit may now be turned by hand in the same direction as it is turned by the cylinder 47. Button No. 1 is then turned in the position for grinding right opposite the grinding cup 13 and the grinding head is lowered so that the grinding cup 13 assumes the correct position for grinding of button No. 1. When positioning of button No. 1 is completed, hold is left of the push-button BRAKE, the internal part 22 being locked in relation to the cover 20. This position of button No. 1 of the drill bit is now saved by pressing the push-button SAVE ANGLE on the control panel, this in turn generating an input signal IN_Save angle as well as an input signal lN_Angle Sensor to the CPU1. In connection with the input signals thereof to the CPU1 , the effect of the brake 50 is cancelled by an output signal OUT_Brake from the CPU1. The user now turns forward button No. 2 of the drill bit so that it is positioned right opposite the grinding cup 13, and then the brake 50 is activated by pressing the push-button BRAKE on the control panel. This generates an input signal IN_Brake to the CPU1. The internal part 22 is now fixed in relation to the cover 20. This position of button No. 2 of the drill bit is now saved by pressing the push-button SAVE ANGLE on the control panel, this in turn generating an input signal IN_Save angle as well as an input signal IN_Angle Sensor to the CPU1. In that connection, the angle sensor 60 records the angle that the drill bit has been turned between the position of button 1 and button 2. In connection with the input signals to the CPU1 , the effect of the brake 50 is cancelled by an output signal OUT_Brake from the CPU1. In order to program an additional button in the grinding position, the push-button BRAKE has to be pressed again and the drill bit be turned by hand into the position according to the above description.

When the programming of the position of all peripheral buttons is finished, the operator may test the programming without grinding of the buttons being effected. In that connection, the operator positions button No. 1 in the correct position in relation to the grinding cup 13, and then the operator presses the push-button INDEX TEST on the control panel. This generates an output signal OUTJRotation of Indexer, MV1 from the CPU1. Now, the holder member 1 will index forward all programmed positions of the buttons and the operator can monitor that the positions are correct in relation to the grinding cup 13. The proper indexing is carried out by means of the freewheel hub 40 described above, which accordingly rotates the internal part 22, via the diameter-reduced portion 41 , in relation to the cover 20.

A feature of the control equipment according to the present invention is that, upon indexing of the next button, the angle sensor 60 controls the angle that the drill bit should be turned. In order to minimize the risk of erroneous positioning, a restriction is made of the rotation that the freewheel hub 40 makes when the button approaches the position in question, this taking place by an output signal OUT_Restriction of rotation, MV2 from the CPU2. In practice, this means that the rotation of the internal part 22 slows down when the button to be ground approaches the grinding position thereof.

Before the operator begins the grinding, the time that each button should be ground has to be chosen. This is carried out by the fact that the operator turns the knob GRINDING TIME on the control panel, see Fig. 7. In that connection, the operator may set the number of seconds that each button should be ground, the grinding time being shown in the display situated to the right of the knob GRINDING TIME. The activation of the knob GRINDING TIME by the operator generates an input signal to the microprocessor denominated CPU3, see Fig.8, as well as an output signal OUT_Display from the CPU3. By the fact that the CPU3 is connected with the CPU1 , a control of the grinding time for each button will take place. For small drill bits, the grinding time is normally less than one (1) minute, while for larger bits, the grinding time may amount to 1-2 min. The grinding time is the same for all buttons of a rock drill bit.

After the programming of the positions of the buttons has been made and the grinding time for each button has been chosen, it is ready for grinding. In that connection, the operator positions button No. 1 in the correct position in relation to the grinding cup 13, and then the operator presses the push-button START on the control panel, see Fig. 7. In doing so, an output signal OUT_signal START Grinding Motor is generated from the CPU1. Grinding of the buttons of the drill bit now takes place in the programmed order, the holder member 1 indexing forward the next button when the previous button is finish ground. In connection with the next button being indexed forward, the brake 50 is released and the freewheel hub 40 provides rotation of the internal part 22 in relation to the cover 20.

In Figs. 9 and 10, an alternative embodiment of the holder member 101 according to the present invention is shown. The constructive design of the holder member 101 corresponds largely to the holder member 1 described above. In that connection, the components in Figs. 9 and 10 in principle common to the two embodiments have been added the numeral "1" in front of the reference designations given in Figs. 3-6.

The principal difference is that the holder member 101 is provided with an indexing disc 160, while the holder member 1 is provided with an angle sensor 60. The indexing disc 160 is fixedly connected to the internal part 122 via the diameter- reduced portion 141 and also forms a brake mechanism 150 in the embodiment of the holder member 101 shown in Fig. 9. Such as is indicated by dashed lines in Fig. 10, the indexing disc 160 is provided with a first inductive sensor 161 and a second inductive sensor 162, which are arranged next to each other. As is seen in Fig. 11, the indexing disc 160 comprises a first flange 163 and a second flange 164. In the first flange 163, a first recess 165 is received, which co-operates with the first inductive sensor 161, which accordingly records when the indexing disc 160 has rotated an entire revolution. In the second flange 164, a number of second recesses 166 are received, six in the embodiment illustrated. The positions of said recesses 166 are related to the button configuration of a certain drill bit, i.e., it is not necessary to program the positions of the buttons in case an indexing disc is used. Obviously, the indexing disc has to be exchanged when a drill bit having another button configuration is to be ground. In a portion 167 of the indexing disc 160 situated between the flanges 163 and 164, a number of conical cavities 168 are arranged. The indexing disc 160 works in principal in such a way that the recess 165 and the adjacent recess 166 are right opposite the respective inductive sensor 161 and 162. After the operator having started the grinding, the first button being ground, the indexing disc 160 will be imparted a rotation by the fact that the internal part 122 rotates, which is executed by the freewheel hub 140. When the second inductive sensor 162 senses a second recess 166, the rotation of the internal part 122 ceases and the brake mechanism is activated, the braking cylinder co-operating with a conical recess 168. Grinding of the next button is now carried out. When the grinding of said button is ready, the brake mechanism is inactivated and the indexing disc 160 is rotated again until the second inductive sensor records the next recess 166, which means that the rotation is stopped, the brake mechanism 150 is activated and grinding is carried out of the next button. This procedure is repeated until the first inductive sensor 161 records the recess 165, which indicates that the indexing disc 160 has rotated one revolution, i.e., the grinding is completed.

Above, a device and a method to grind peripheral buttons of a rock drill bit have been described. However, only a relatively simple modification of the device according to the present invention is required in order to also make it usable to grind front buttons. In that connection, the drill bit assumes a "vertical" position, i.e., the dashed position under the grinding head 3 in Fig. 2. A programming of the positions of the front buttons is carried out in a way corresponding to that of the peripheral buttons. Upon indexing of the next button, for the peripheral buttons, only a rotation of the internal part 22; 122 is required. In case of the front buttons, a lateral move is also required in the horizontal direction in the plane of the paper in Fig. 2. Thus, in that connection, a linear displacement of the slide 9 takes place transverse to a centre axis B-B of the grinding head 3. However, this can easily be achieved by the fact that members providing a lateral displacement of the slide 9 are connected to the slide 9. In an exemplifying and not limiting purpose, it may be mentioned that a motorized screw or a pressure-medium cylinder may be connected to the slide 9 to impart the slide 9 a lateral displacement, i.e., a displacement horizontally if the frame 5 is situated on a horizontal support. In connection with programming being to be made, the slide 9 may be disengaged so that a lateral displacement of the slide 9 can be effected manually at the same time as the internal part 22; 122 is rotated manually. In the proper grinding, the displacement member connected to the slide 9 is activated in connection with the indexing, i.e., upon the feed of the next button, both a rotation of the internal part as well as a linear lateral displacement are carried out, this being controlled by a microprocessor or the like in the corresponding way as has been described above in the grinding of the peripheral buttons.

In the description above, grinding is carried out of buttons of rock drill bits. However, it is also possible within the scope of present invention to grind rock drill bits that are provided with chisel bits, and if so the grinding head being provided with a grinding wheel that has a geometry adapted to the chisel bits.

The holder member according to the present invention can be used together with the majority of grinding machines for rock drill bits on the market. Particularly, it should be pointed out that the holder member according to the present invention advantageously could be used together with the grinding machine disclosed in the Swedish patent application No. 0600530-0. This grinding machine comprises a frame and a grinding head, the grinding head comprising a rotatable grinding spindle. The free end of the grinding spindle is intended to drivingly and replaceably carry a grinding cup. The grinding spindle has a first rotational axis, the grinding spindle being intended to rotate around the same as well as also around a second axis. The first rotational axis of the grinding spindle is arranged to assume at least two positions, one position of which is collinear with the second rotational axis.

Claims

1. A holder member (1 ; 101) for a rock drill bit in connection with the rock drill bit being to be ground, the holder member (1; 101) comprising a cover (20; 120), an attachment member (21 ; 121) fitted on the cover (20; 120) for the mounting of the holder member (1 ; 101) on a frame (5) or the like, characterized in that the holder member (1; 101) comprises an internal part (22; 122), which is rotatable in relation to the cover (20; 120) around a rotational axis (C-C), a clamping member (25; 125) fixedly connected with the internal part (22; 120), which clamping member is intended to receive a rock drill bit, members (40; 140) to rotate the internal part (22; 122) in relation to the cover (20; 120), as well as members (60; 160) to record positions, in relation to each other, of rock-machining members of the rock drill bit.

2. Holder member according to claim 1,character-ized in that the member to rotate the internal part (22; 122) is a freewheel (40; 140).

3. Holder member according to claim 1 or 2, c h a r a c t e r-i z e d in that the member to record positions of the rock-machining members is an angle sensor (60) or an indexing disc (160).

4. Holder member according to any one of the preceding claims, characterized in that the cover (20; 120) is tumable in relation to the frame around an axis (D-D) perpendicular to the rotational axis (C-C) of the internal part (22; 122).

5. A grinding machine to grind a rock-machining member of a rock drill bit, the grinding machine comprising a frame (5) and a grinding head (3), the grinding head (3) comprising a rotatable grinding spindle (12), the free end of the grinding spindle (12) being intended to drivingly and replaceably carry a grinding member (13), at least one holder member (1 ; 101) for the rock drill bit being mounted on the frame (5), characterized in that the holder member (1; 101) comprises an internal part (22; 122), which is rotatable in relation to the cover (20; 120) around a rotational axis (C-C), a clamping member (25; 125) fixedly connected with the internal part (22; 120), which clamping member is intended to receive a rock drill bit, members (40; 140) to rotate the internal part (22; 122) in relation to the cover (20; 120), members (60; 160) to record positions, in relation to each other, of rock-machining members of the rock drill bit, and that the grinding machine has members to displace the holder member (1; 101) laterally in relation to a centre axis (B-B) of the grinding head (3).

6. Grinding machine according to claim 5, c h a r a c t e r-i z e d in that it comprises two holder members (1 ; 101), and that the holder members (1 ; 101) are mounted on a laterally displaceable slide (9).

7. A method for grinding a rock drill bit c h a r a c t e r-i z e d by recording, in a determined priority, of positions, in relation to each other, of rock-machining members ^' of the rock drill bit, in that a first rock-machining member of the rock drill bit is positioned in the recorded position thereof, that the first rock-machining member is ground, that the next following rock-machining member is indexed forward automatically on the basis of the previously made position recording, that the next following rock-machining member is ground, that indexing and grinding of additional rock-machining members are carried out until the desired number of rock-machining members of the rock drill bit have been ground.

8. Method according to claim 7, c h a r a c t e r i z e d in that the indexing is carried out at a lower speed when the rock-machining member approaches the position for grinding.

9. Method according to claim 7 or 8, c h a r a c t e r-i z e d in that the indexing consists of a rotation of the rock drill bit around an axis (C-C).

10. Method according to claim 9, c h a r a c t e r i z e d in that the indexing also comprises a linear displacement of the rock drill bit laterally.