FR2658106A1 - METHOD AND MACHINE FOR REPAIRING BUTTONS OF DRILL BIT. - Google Patents

Abstract

The invention relates to the re-machining of button bits. It relates to a rework process in which gauge knobs (21), when worn, are reworked with a chisel shape forming a top (22) which may be sharp or blunt and which is disposed radially by. relative to the bit body. This chisel shape is made with a V-groove grinding wheel. The end knobs (25) can also be machined with a chisel shape. Application to increasing the duration of drill bits.

Description

The invention relates to the sharpening of buttons of

  bit, formed of cemented carbide.

  Classic button grinders are intended for

  put the heads of the buttons back in their hemispherical

  They remove too much cemented carbide, and this can cause a reduction in bit life by reducing the amount of cemented carbide relative to the dipstick Many worn button bits are discarded when the diameter drops to below the

gauge.

  In a first aspect, the invention relates to a method of restoring a worn bit knob, in which the worn button is reconditioned by setting its head

in the form of a chisel.

  The included angle of the chisel configuration is preferably between 900 and 1300 and preferably of the order

from 110.

  A gauge button placed on a drill bit can be reconditioned by placing its scissor head, the top of

  the chisel shape being arranged radially.

  Steel can be removed from the steel body of a bit in which the button is mounted at the same time as the

button is refurbished.

  The button is advantageously restored by means of a grinding wheel having a V-shaped groove at its periphery, this grinding wheel being intended to give the desired scissor shape to the head of the button. In one embodiment, the button is handed over. in its state by placing its head in the form of a chisel having an acute apex, by using a grinding wheel having a V-shaped groove whose bottom is pointed. In another embodiment, the button is reconditioned by setting its head in the form of a chisel having a rounded top by use of a grinding wheel having a V-shaped groove whose bottom is rounded In another embodiment, the button is reconditioned by placing its head in the form of a dull chisel using a grinding wheel having a

V-shaped throat with a flat bottom.

  The grinding wheel can be used to reset the button and, at the same time, to remove steel from a

  bit body in which the button is crimped.

  In a second aspect, the invention relates to a machine for repairing a button bit, comprising a grinding wheel having a groove V at its periphery, a device for positioning a button bit relative to the grinding wheel so that a button that needs to be reconditioned is aligned with the periphery of the grinding wheel, and a device for causing relative movement between the button bit and the grinding wheel so that the button advances into the V-groove, so that the head of the button is put under

shape of a chisel.

  The machine may have a bit holder placed at the end of a bit arm for holding the button bit, the bit arm being pivotable to move the bit in a curve relative to the grinding wheel and The invention also relates to a method of repairing a bit having a steel body in which buttons are crimped, each button being rehabilitated. by rectifying its head to a chisel configuration, while steel is simultaneously withdrawn from the vicinity

of the button.

  In a fourth aspect, the invention relates to a grinding wheel for restoring a cemented carbide bit knob, the grinding wheel having a V-shaped groove formed at its periphery so that it can be scissor-shaped to the head of a cemented carbide button advancing in the throat.

  Other features and advantages of the invention

  will be better understood by reading the description

  which will follow examples of embodiment, with reference to the accompanying drawings in which: Figure 1 shows the wear of a gauge button; Figure 2 is a section along the line II-II of Figure 1 and shows the chisel shape according to the invention, superimposed on a new profile, a worn profile and a profile sharpened in a conventional manner; Figure 3 is an end view of a bit having buttons that are regrind according to the invention; Figure 4 is a side elevational view of a machine for providing new sharpening; Figure 5 is an end view of the machine of Figure 4; Figure 6 is a plan view of the machine of Figures 4 and 5; Figure 7 shows a detail of a portion of the machine shown in Figures 4 to 6, on a larger scale; Figure 8 shows a variant of grinding wheel profile; Figure 9 shows another variant of grinding wheel profile; Figure 10 shows the grinding of a knob by a wheel variant, in the direction of the arrow 10 of Figure 12; Figure 11 shows a gauge button after rework, in the direction of the arrow 11 in Figure 12; and FIG. 12 is an end view of a button bit whose buttons have been remanufactured with the grinding wheel.

represented in FIG.

  The gauge button shown in FIGS. 1 and 2 has a profile like new indicated by curve 10, with a gauge line 11. The actual wear profile of such a bit is indicated by line 12 which gives a line of FIG. gauge after wear 16, and a new conventional sharpening gives a new surface marked by the reference 13 In zones 14 and 15, the cemented carbide was removed superficially, according to the invention The surface of the steel body as new is identified by the reference 17 and the surface,

  obtained after removal of a coating, sanding, rectification

  tion or any combination of these machining

  metal, is indicated by reference 18.

  In the new sharpening process proposed by the invention, the lines 20 represent the upper part of the button in FIG. 2 This saves a considerable amount of cemented carbide and does not reduce

the gauge after wear.

  Figure 3 shows a resultant bit Flat faces 23 have been formed on the gauge buttons 21 towards the sides of the scissor-shaped radial peaks 22 The scissor-shaped tops are aligned with the head buttons 25 so that the wedge-shaped surface

is easily done.

  FIGS. 4 to 7 show a machine which is used to sharpen the buttons according to the invention. The machine has a frame 40 having a base 42 on which a

  bit arm 44 is articulated at a horizontal axis

  A rotary handle 48 acting on a threaded rod 50 causes a tilting of the bit arm

  clockwise or counterclockwise

  milk in figure 4 A square 52 and a support

  adjustable bit 54 are connected at the upper end.

  the bit arm as shown, the bit holder 54 being used to support a bit 56 to

  buttons whose buttons must be sharpened.

  A grinder arm 58 is hinged to the upper end of the frame 40 and carries a rotary grinding apparatus 60 near its end and a diamond grinding wheel 62 at the free end. In FIG. 7, the rotating spindle 64 of the apparatus 60 of rectification carries a rotary ring 66 having two sections 66 A and 66 B between which a fixed ring 68 is supported by the spindle The sections 66 A and 66 B are mutually connected by a base section 66 C which exceeds a stop 70 having an L-shape The ring 68 is attached to the pin 64 at an axial distance

  predetermined amount of the diamond wheel 62.

  During operation, when a button bit is held in the holder 54, the stop 70 is turned to a position in which it is in front of the button 72 which must be reworked. The bit is rotated on the holder 54 so that the button 72 is placed against the stop 70, and the bit is then locked on its support, in this position The rotary ring 66 is then turned on the spindle of the grinding machine so that the stop 70 is removed from the path of the grinding wheel The bit holder 54 is adjustable to allow the sharpening of any button of a bit, regardless of its angle of introduction relative to the bit.

to the bit axis.

  It should be noted that the function of the rings 66 and 68 and the stop 70 is the setting of the center of the button which must be rectified in a suitable position relative to the plane.

center of the diamond wheel 62.

  Then, the handle 48 is turned so that the button 72 advances to the diamond wheel 62 which provides the necessary sharpening of the button When the button advances to the wheel, the arm 58 moves up and down around its pivot When the operator put the

  button 72 in the desired state of sharpening, he moves the button back.

  In a variant, so that the button does not undergo excessive sharpening, a mechanical stop may be incorporated so that it limits the tilting of the support arm of the bit and therefore the distance of movement of the button 72 towards

the diamond wheel.

  In an alternative to using a machine of the type described above in which the button advances to the grinding wheel so that the desired grinding of the button is achieved, it is possible to tighten strongly the

  bit in a suitable forceps, and to manually move-

  a rotating wheel of suitable shape against the

selected button.

  The grinding wheel 62, as described in the previous example, has a profile intended to give the button a chisel shape with a pointed top.

  be undesirable, especially in the case of gauge buttons.

  Figure 8 shows a slightly different profile of grinding wheel which has a somewhat rounded bottom in the V-shaped groove so that a chisel shape is obtained with a top

  a little rounded on the sharpened button.

  In the case of the gauge buttons, a grinding wheel profile as shown in FIG. 9 is preferable. In this case, the bottom of the V-shaped groove, formed in the grinding wheel, has a plate 80 intended to give sharpened gauge knobs. who

have a blunt chisel shape.

  In all cases, the angle included between the faces

  convergent of a sharpened button is of the order of 110.

  Reference was made to the removal of a coating of

  steel body of the bit, to obtain a configuration

  ration suitable for the new shape of the buttons.

  coating or sandblasting, used for the steel body to have the desired new shape, are, however, uncomfortable operations

  bulky equipment whose transport is difficult.

  This is detrimental to the simplicity of the button remanufacturing technique by the chisel-shaped sharpening process as previously described. While chisel-sharpening can be performed on site, the removal of steel by a coating or by sanding can not

to be normally.

  The grinding wheel 82 shown in FIG. 10 has a width greater than that of the grinding wheels described above and has an internal section 84 placed between external sections 86, so that the problem posed by the removal of the steel can be solved. The internal section 84 is composed of a material suitable for the rectification of

  cemented carbide buttons themselves, while the sections

  External devices 86 are made of a material that allows

the machining of steel.

  In use, the grinding wheel 82 of Fig. 10 performs the chisel-shaped grinding operation on a button, but it acts on the steel 100 along the knob as shown in Fig. 10 and thereby removes the excess

  of steel and thus avoids the use of an additional step

  removal of steel by removal of a coating or sanding. FIG. 11 shows the grinding operation performed in the case of a gauge button 90 and the steel placed in the vicinity, in the direction of the arrow 11 in FIG. 12. The lines 92 in FIG. planned configuration of the steel body to the front face after simultaneous operations of sharpening the buttons and

machining of steel.

  Since the relative displacement of the grinding wheel and the bit is achieved for each button only in the direction of the final top of the knob, it may be noted that the steel present in the regions such as those bearing the reference 94 in FIG. is not removed as much as in areas such as those bearing the reference 96 and which are just on the sides of the

buttons.

  Finally, the gauge knobs are associated with radially inward "steel comet tails". This is not expected to be a disadvantage to the satisfactory operation of the

  bit during subsequent drilling operations.

  Initial tests carried out in the context of the invention indicate that the sharpening of the buttons of the

  bits according to the method of the invention allows an increase

  the depth of a hole that can be drilled before the bit can no longer be used, an increase in bit penetration speed, and a reduction in rework time, compared to the conventional button remaking technique. The test results are shown in the following table, including three tests conducted at the Randfontein Estates gold mine in the Republic of South Africa, at the Denison mine in Canada, and

at the Laisvall mine in Sweden.

Board

  Test number 1 2 3 Increased drilled length,% 16 12 35 Reduced gauge loss,% 40 43 Increased penetration rate,% OO 10 Reduced rework time,% 61 Of course, various modifications can be made those skilled in the art in the processes, machines and grinding wheels which have just been described solely by way of nonlimiting examples, without departing from the scope of the invention.

Claims (24)

  1 method of repairing a used bit button, characterized in that the used button (21) is returned   in condition by putting his head to a chisel shape.   2 Process according to claim 1, characterized in that the included angle of the scissor form is included between 90 and 1300.   Process according to Claim 2, characterized in   the included angle is about 1100.   Process according to any one of the claims   previous, characterized in that a gauge button (21) of a bit is reconditioned by placing its head in scissor form, the tip of the chisel being arranged radially.   Process according to any one of the claims   previous, characterized in that steel is removed from the steel body of a bit in which the button is crimped,   at the same time as the button is restored.   Process according to any one of the claims   preceding, characterized in that the buttons (21) are reconditioned using a grinding wheel (62) which has a V-shaped groove at its periphery, the groove being intended to give the   desired chisel configuration at the head of the button.   7 Method according to claim 6, characterized in that the button (21) is reconditioned by placing its head in a chisel shape having a pointed top (22) with a grinding wheel (62) having a groove V-shaped pointed (Figure 7). 8 Process according to claim 6, characterized in that the button (21) is reconditioned by putting his head   in scissor form having a rounded vertex   a wheel having a V-groove, the bottom of which is rounded (Figure 8).   9 Method according to claim 6, characterized in that the button (21) is reconditioned by placing its head in blunt chisel shape using a grinding wheel   having a V-groove with a flat bottom (Figure 9).   Process according to any one of the claims   6 to 9, characterized in that the button (21) advances   in the V groove of the grinding wheel when it is   born in rotation so that the button is machined.   Process according to any one of Claims 6 to 10, characterized in that the grinding wheel (62) is   used to restore the button and, simultaneously,   for the removal of steel from a bit body in which button is held.   12 A method of repairing a bit having a steel body in which buttons (21) are fixed, characterized in that each button (21) is reconditioned by rectification of its head to a scissor shape, with   simultaneously withdrawal of steel in the vicinity of the button.   Method according to claim 12, characterized   in that a grinding wheel (62) having a V-groove on its periphery   This is used for the repair of the button and simultaneously for the removal of steel near the button.   Process according to one of Claims 12 and 13,   characterized in that the button (21) is reconditioned by carrying out a method according to any one of Claims 6 to 10.   A tool for reshaping a button bit, characterized by a grinding wheel (62) having a V-shaped groove at its periphery, by a device (44) for positioning a button bit relative to the grinding wheel, so that a button to be reconditioned is aligned with the periphery of the grinding wheel, and a device (48) for causing relative movement of the button bit and the grinding wheel so that the button advances to the V groove and that the head   of the button takes a shape in chisel.   Machine according to claim 15, characterized by a bit holder (54) mounted at the end of an arm (44) and adapted to support a button bit, the arm being pivotable to move the button bit. in a semicircle relative to the grinding wheel and to advance the   corresponding button in the V-shaped groove formed at the grinding of the millstone.   Reconditioning wheel of a cemented carbide bit button, characterized in that the grinding wheel (62) has a V-shaped groove formed at its periphery and intended to give a chisel shape to the head of a button. cemented carbide who goes down the throat.   A grinding wheel according to claim 17, characterized in that the V-shaped groove is configured to give the button head a scissor shape having an angle included between 90 and 1300.   19 Grinding wheel according to claim 18, characterized in that the V-shaped groove has a configuration intended to give the head of the button a chisel shape having an angle included about 1100.   Wheel according to any one of the claims   17 to 19, characterized in that the bottom of the V-shaped groove is pointed so that the groove gives the button head a   scissor shape with a pointed top (Figure 7).   A grinding wheel according to any one of the claims   17 to 19, characterized in that the bottom of the V-shaped groove is rounded so that the button head has a shape of   chisel with rounded top (figure 8).   A grinding wheel according to any one of the claims   17 to 19, characterized in that the bottom (80) of the V-shaped groove has a flat surface for giving the head of the knob   a dull chisel shape (Figure 9).   Grinding wheel according to one of the claims   17 to 22, characterized in that it comprises a central section (84) intended to give a chisel shape to the head of a button, and external sections (86) between which the central section is retained and which are intended to removing steel from the steel body of a bit in which the button is attached at the same time as the chisel shape is formed in the head of the button.   Machine according to one of claims 15 and 16,   characterized in that the grinding wheel is a wheel according to one   any of claims 17 to 23.