US3851424A

US3851424A - Apparatus for re-sharpening the cutting edges of a drill

Info

Publication number: US3851424A
Application number: US00295472A
Authority: US
Inventors: H Kawaragi
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-06
Filing date: 1972-10-06
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

An apparatus for re-sharpening the cutting edges of a drill is designed to support a drill to be re-sharpened so that the axis of the drill is so inclined with respect to the grinding surface of a cup-shaped grinding wheel as to conform to the point angle of the drill. The apparatus is so arranged that the drill is rotated about its axis for substantially 540 degrees while the drill is revolved for substantially 360 degrees about the axis of a surface on which the drill is supported and that the drill is reciprocally moved toward and from the grinding wheel to alternately bring both of the chisel edges of the drill into grinding contact with the grinding surface of the grinding wheel whereby the land and the chisel edges of the drill are all regularly ground.

Description

CUTTING EDGES OF A DRILL lnventor: Hiroshi Kawaragl, 10-9 Oomorinishi l-chome, Tokyo, Japan Filed: Oct. 6, 1972 Appl. No.: 295,472

[1.8. CI. 51/133, 51/219 R Int. Cl B241) 3/26 Field of Search 5l/133, 119, 120, 105 R,

51/219 R, 219 PC, 237 M, 288, 95 WH References Cited UNITED STATES PATENTS 51/219 PC X' ited States Patent 1 [111 3,851,424 awaragi [451 Dec. 3, 1974 1 APPARATUS FOR RE-SHARPENING THE Primary Examiner-Donald 0. Kelly Assistant ExaminerNicholas P. Godici Attorney, Agent, or Firm-Frank J. Jordan [5 7 ABSTRACT An apparatus for re-sharpening the cutting edges of a drill is designed to support a drill to be re-sharpened so that the axis of the drill is so inclined with respect to the grinding surface of a cup-shaped grinding wheel as to conform to the point angle of the drill. The apparatus is so arranged that the drill is rotated about its axis for substantially 540 degrees while the drill is revolved for substantially 360 degrees about the axis of a surface on which the drill is supported and that the drill is reciprocally moved toward and from the grinding wheel to alternately bring both of the chisel edges of the drill into grinding contact with the grinding surface of the grinding wheel whereby the land and the chisel edges of the drill are all regularly ground.

3 Claims, 9 Drawing Figures APPARATUS FOR RE-SHARPENING TI-IE CUTTING EDGES OF A DRILL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for resharpening the cutting edges of a drill.

2. Description of Prior Art In general, it is known that, in order to economically use a drill, it is advisable to re-sharpen the cutting edges of the drill after the drilling operation thereof before the drill is used to its completed operative life. The resharpening has heretofore been carried out by one of flat grinding, conical grinding, cylindrical grinding etc. With the flat grinding, the flank of the drill is ground to be flat so that the chisel edges of the drill are apt to be linear, with a resultant disadvantage that the resharpened drill is tended to produce a rifled bore of not a true circular-section. The conical grinding is most conveniently employed because this kind of drill resharpening is the simplest way to shape the edges of the drill. The edge grinding by this way, however, required that the drill be revolved along a conical plane so as to re-produce a conical point on the drill. The grinding machine for this kind of grinding operation is thus required to have a complicated mechanism for the accurate and precise motion of the drill to be ground. The cylindrical grinding is substantially similar to the conical grinding and shapes the flank of the drill during the movement of the drill along a part of its cylindrical plane. When a cylindrical plane of a large radius of curvature is employed for the grinding of a drill, the resultant ground drill edges have nearly linear shapes. Thereis another method of grinding drill edges in which the drill to be ground is fixed while a grinding wheel is caused to have a planetary motion while rotated about its axis. It is said that this grinding method is suited and appropriate for grinding drill of relatively softer materials but not for drills of relatively harder materials. In addition, the grinding method has a difficulty in keeping the accuracy of the mechanism for supporting the grinding wheel in such a manner as to cause the wheel to have a planetary motion and simultaneously rotate the wheel about its axis.

With the state of the art briefly discussed above, there has been a demand in the art for a novel proposal on an apparatus which would be accurately and simply achieves re-sharpening of used drills.

SUMMARY OF THE INVENTION It is an object of the present invention to obtain resharpening of a drill, in which the point of the drill is mechanically accurately brought into grinding contact with the grinding surface of a rotating grinding wheel in such a manner that the grinding angle is appropriate for the shape of the drill point.

It is another object of the present invention to make it possible to so adjust the grinding angle of drills with respect to the grinding surface of a rotating grinding wheel as to accomodate the shapes of the lands of various kinds of drills whereby kinds of drills can be resharpened.

It is a further object of the present invention to provide a grinding machine for mounting a drill to be ground which machine has a construction for simple and reliable operation and in which a selected one of mannual and automatic drive means can be mounted for the simplified operation of the machine.

It is a still further object of the present invention to provide a grinding machine for mounting a drill to be ground which machine can be assembled and disassembled for the simplified repairment and exchange of structural elements of the machine.

The apparatus for re-sharpening the cutting edges of a drill according to the present invention is designed to perform an entirely novel grinding method which may be called helical grinding. The apparatus may preferably have a drill supporting sleeve which is adapted to be rotated about its axis while the sleeve is simultaneously revolved with a cylindrical plane having its axis coincident with the axis of the main shaft of the grinding machine. The apparatus is arranged such that the drill supported by the sleeve is rotated for 540 about its axis while the drill is revolved for 360. This automatically causes the lands of the drill to be alternately brought into grinding contact with the grinding surface of the grinding wheel during one complete revolution of the drill so that the surfaces of the point angle and the lip relief angle and the thinning are simultaneously ground. The apparatus of the invention is also so designed that the grinding angle is adjustable to accomodate the point angle and the lip relief angle of a particular drill to be ground with a resultant advantage that drills of different diameters can be easily set in their grinding positions regardless of their diameters. The

apparatus of the invention provides another advantage that the thinning of a drill resharpened with the apparams of the present invention extends from the center helically outwardly to provide the drill with sharp cutting effect on a workpiece.

The above and other objects, features and advantages of the present invention will be made apparent by the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 5 illustrates in a further enlarged sectional view the portion of FIG. 4 encircled by rectangular broken line 5 shown in FIG. 4;

FIG. 6 is a fragmentary side view showing a cam surface on a guide ring;

FIG. 7 diagrammatically illustrates the relationship between the drill point and the grinding wheel in respective steps of grinding operation;

FIG. 8 diagrammatically illustrates the rotation of the drill point during one revolution of a drill supporting sleeve; and

FIG. 9 illustrates, partly in an enlarged gragmentary section and partly in an enlarged perspectively view, the drill point and the grinding wheel.

DESCRIPTION OF A PREFERRED'EMBODIMENT Referring to FIG. 1 of the drawings, there is shown an embodiment of the apparatus for re-sharpening the edges of drills according to the present invention. The apparatus has a base 11 and a housing 12 mounted on the top of the base. The housing is of a compact design and disposed a level appropriate for an operator standing by the apparatus to operate the apparatus. A cupshaped grinding wheel 14 is mounted on the housing 12 in such a manner that the grinding wheel has its working or grinding surface exposed to the exterior of the housing and is driven by a drive mechanism in the housing so as to be rotated in a counterclockwise direction as viewed substantially from the left in FIG. 1. The housing 12 is provided on the top thereof with an illumination means 13. The housing 12 may also be provided on the peripheral surface thereof with means for controlling the rotation of the grinding wheel 14 and means for regulating the forward and rearward movements of the grinding wheel. These means are not a part of the invention and are not shown in the drawings.

On the front wall of the housing 12 is rigidly mounted a shelf 16 on which is mounted a base 17 of an arm 18 which supports a body for holding and actuating a drill 19 to be re-sharpened. The arrangement is such that, at the initial stage of drill re-sharpening operation, the drill 19 is so positioned that the axis of the drill is in alignment with the horizontal diameter of the grinding surface of wheel 14.

The drill holding and actuating body 20 is provided with a drill supporting sleeve 21 mounted on the body 20 and having its axis eccentric with respect to the axis of the body 20. The latter is also provided with a rotary actuator 22 mounted on an adjacent wall of the body 20.

As will be best seen in FIG. 2, the rotary actuator 22 has a gear casing 31 provided on the above-mentioned adjacent wall of the body 20. In the illustrated embodiment of the invention, the gear casing 31 preferably has a portion 31 having its axis extending obliquely at an angle with respect to the axis of the major portion of the casing 31. In the portion 31 of the gear casing 31 is mounted a tubular member 23. A shaft 25 of an actuating wheel 24 extends through the tubular member 23 and supported thereon at appropriate axially spaced points for smooth rotation by means of ball bearings 26 mounted in the tubular member 23. The inner end of the shaft 25 is secured to an appropriate gear which is preferably in the form of a bevel gear 27. In the major portion of the gear casing 31 is provided a shaft 32 for rotatably supporting an intermediate gear wheel which has thereon a bevel gear portion 28 in meshing engagement with the gear 27 and a spur gear portion 29 integral with the bevel gear portion 28.

The drill supporting sleeve 21 on the drill holding and actuating body 20 is so constructed as to removably receive and support a drill 19 to be re-sharpened. In addition, the drill supporting sleeve 21 has its rear portion disposed within the rear portion of the body 20 and having its outer peripheral surface formed into a spur gear 33 which is in meshing engagement with the spur gear portion 29 on the intermediate gear wheel 30 so that the rotation of the actuation wheel 24 is transmitted through the intermediate gear wheel 30 to the spur gear 33 to rotate the drill holding and actuating body 20 in a direction.

A covering sleeve 34 is mounted on the front portion of the drill holding and actuating body 20 and has its inner peripheral surface formed into an internal gear 35. A two-diameter gear 36 is rotatably mounted on the front wall of the drill holding and actuating body 20 and has its small diameter gear portion 37 in meshing engagement with the internal gear 35. The gear 36 has its large diameter gear portion 38 in driving connection with an external gear 40 formed on the outer peripheral surface of the front portion of the drill supporting sleeve 21 via a planetary gear 39 mounted on the front wall of the body 20 for rotation independently of the gear 36. The gears are in mutual meshing engagement at a gear ratio so predetermined that the drill support ing sleeve 21 is rotated for a predetermined angle while the drill holding and actuating body 20 has a single turn or revolution.

The body 20 is received in and supported by an outer sleeve 41. More specifically, the outer sleeve 41 has a guide ring 42 received in the sleeve at substantially axial central portion thereof. The guide ring 42 is pivotally connected at a pair of diametrically opposed and preferablyhorizontally spaced points to the inner peripheral surface of the outer sleeve 41 by means of coaxial pins 43 secured to the sleeve 41 so that the guide ring 42 is rotatable within a limited angular range about the axis of the pins 43 for the purpose to be described later. The drill holding and actuating body 20 extends through the guide ring 42.

On the top of the outer sleeve 41 is mounted a knob 44 (FIGS. 3 and 4) having a shaft 45 rotatably extending radially inwardly through the wall of the outer sleeve 41. The shaft 45 has its inner end portion rigidly connected with an eccentric member 46 having an eccentric shaft 47 secured to the bottom face of the member 46 and slidably received in a recess formed in the outer peripheral surface of the guide ring 42 at the top portion thereof so that the rotation of the knob 44 rotates the guide ring 42 within a limited angular range about the horizontal axis of the pins 43 for the purpose to be described later.

An actuation ring 48 is rigidly mounted on the peripheral outer surface of the front portion of the drill holding and actuating body 20 at such a position that the ring 48 has its inner side face extending substantially in parallel relationship with the guide ring 42. The actuation ring 48 is formed in the inner side face thereof with a recess in which is mounted a roll 49 having a peripheral portion extending from the recess inwardly toward the guide ring 42 for rolling contact therewith. The portion 20' of the drill holding and actuating body 20 axially rearwardly of the guide ring 42 extends radially outwardly so as to face the guide ring 42. In that portion of the body portion 20 which is axially aligned with the roll 49 is provided a ball 50 axially urged against the guide ring 42 by a spring 51 mounted in said portion. The pressure force of the spring 51 may be adjusted by means of an adjust screw 52. The guide ring is deformed at a predetermined circumferential portion thereof to provide a cam surface 53. It will be appreciated that upon relative rotation between the actuating body 20 and the guide ring 42 with its opposite side faces contacting the roll 49 and the spring-loaded ball 50, the actuating body 20 is given a slight axial reciprocated movement by the cam effect produced by the cooperation of the cam surface 53, the roll 49 and the ball 50. This reciprocated movement is transmitted to the drill holding and actuating body 20. It will be also appreciated that a single cam surface 53 on the guide ring 42 produces a single stroke of the body 20 per each revolution thereof. The circumferential portion of the guide ring 42 at which the cam surface 53 is formed in the ring may be so determined as to enable a drill to be brought into grinding contact at a desired portion with the grinding wheel. The knob 44 is mannually operable to adjust the distance between the opposite ends of the axial reciprocal movement of the body 20.

In operation, a drill 19 held by a chuck independent from the drill supporting sleeve 21 of the body 20 in such a position as to be operative to act on a workpiece is inserted into the sleeve 21 to the extent that the point of the drill extends from the forward end of the sleeve 21 an appropriate distance. Then the drill is fastened to the sleeve 21 by a tightening screw ring 54 on the rearward end of the sleeve. Since the drill holding and actuating body 20 supported by the arm 18 on the base 17 is movable in a horizontal plane about a vertical axis of a locking means 55, the body 20 can be moved into a position in which the point of the drill 19 is in contact with the grinding surface of the grinding wheel 14 at an angle appropriate for the point angle of the drill 19. The grinding wheel 14 may, if required, be forwardly moved or fed so as to obtain an appropriate grinding contact position for the initiation of grinding operation which is performed in the following manner.

When the actuation wheel 24 is operated to rotate the drill holding and actuating body 20, the latter provides a cycle of operation in which the drill 19 is moved into grinding contact with the grinding wheel 14 at a land surface a in a position A shown in FIG. 7 and is successively moved past B through F positions as the body 20 rotates and is eventually reached by a position G which is located at the same circumferential portion of the revolution of the body 20 as the position A but in which the drill 19 is in grinding contact with the grinding wheel 14 at another land surface b. More specifically, the drill 19 is caused to rotate for 540 degrees (1.5 turns) while the drill holding and actuating body 21) has a revolution for 360 (1 turn) so that the land surfaces a and b of the drill are alternately brought into grinding contact with the grinding surface of the grinding wheel 14. The drill 19 is rotated at a position axially spaced from the grinding wheel 14 until the drill is axially moved into grinding contact therewith. When the revolution of the body 20 moves the drill to a position just upstream of the position for its engagement with the grinding wheel 14, the body 20 revolves the drill 19 in the same direction as the rotation of the grinding wheel 14 while the body 20 is moved forwardly to axially in-feed the drill point in such a manner that the chisel edge of the drill projects just a distance into a circular space defined by the inner edge (FIG. 9) of the grinding wheel 14. Then the body is moved axially rearwardly to retract the drill from the grinding positron.

The described operation will be repeated to assure that both lands on the drill point are alternately uniformly brought into grinding contact with the working surface of the cup-shaped grinding wheel 14 which is rotated at a high speed for the precise and accurate re- 6 sharpening of the drill edge.

What is claimed is: 1. An apparatus for re-sharpening the cutting edges of a drill, including;

a housing having a cup-shaped grinding wheel mounted thereon so as to be either moved forwardly by a driving mechanism in said housing or rotated in a predetermined direction by said driving mechanism;

a drill holding and actuating body having a drill supporting sleeve extending axially therethrough, said sleeve being designed to support a drill in such a manner that the axis of said drill is so inclined with respect to the grinding surface of said grinding wheel that the surfaces of the cutting edges of said drill are in grinding contact with said grinding surface;

an actuation wheel the rotation of which is transmitted through an intermediate gear wheel to a spur gear on the rear portion of said drill holding and actuating body, said intermediate gear being in meshing engagement with said spur gear;

a gear train comprising an internal gear on a covering sleeve mounted on the forward portion of said drill holding and actuating body, a two-diameter gear wheel in meshing engagement with said internal gear, and a planetary gear in meshing engagement with said two-diameter gear and with an external gear on the outer peripheral surface of the forward portion of said body;

a guide ring mounted on said body substantially at an axially central portion thereof, said guide ringbeing pivotally connected by pins on the inner pe' ripheral surface of an outer sleeve and having a cam surface formed on a side face of said ring at a circumferential portion thereof;

a knob having a shaft extending radially inwardly therefrom, said shaft having an eccentric shaft mounted on the inner end of said shaft and being in sliding engagement with the top portion of said guide ring so that the rotation of said knob causes a pivotal motion of said guide ring; and

means for axially moving said drill holding and actuating body, said means comprising an actuation ring on the peripheral outer surface of said body having a roll in rolling contact with a side face of said guide ring and a ball mounted on the outer periphery of said body and urged by a spring against the other side face of said guide ring.

2. An apparatus as defined in claim 1, in which said drill holding and actuating body is supported by an arm having a base mounted on a table provided on a front wall of said housing, said base being so mounted on said table that said body is movable about a locking means.

3. An apparatus as defined in claim 1, in which said drill is'supported such that the axis of said drill is so inwheel.

Claims

1. An apparatus for re-sharpening the cutting edges of a drill, including; a housing having a cup-shaped grinding wheel mounted thereon so as to be either moved forwardly by a driving mechanism in said housing or rotated in a predetermined direction by said driving mechanism; a drill holding and actuating body having a drill supporting sleeve extending axially therethrough, said sleeve being designed to support a drill in such a manner that the axis of said drill is so inclined with respect to the grinding surface of said grinding wheel that the surfaces of the cutting edges of said drill are in grinding contact with said grinding surface; an actuation wheel the rotation of which is transmitted through an intermediate gear wheel to a spur gear on the rear portion of said drill holding and actuating body, said intermediate gear being in meshing engagement with said spur gear; a gear train comprising an internal gear on a covering sleeve mounted on the forward portion of said drill holding and actuating body, a two-diameter gear wheel in meshing engagement with said internal gear, and a planetary gear in meshing engagement with said two-diameter gear and with an external gear on the outer peripheral surface of the forward portion of said body; a guide ring mounted on said body substantially at an axially central portion thereof, said guide ring being pivotally connected by pins on the inner peripheral surface of an outer sleeve and having a cam surface formed on a side face of said ring at a circumferential portion thereof; a knob having a shaft extending radially inwardly therefrom, said shaft having an ecceNtric shaft mounted on the inner end of said shaft and being in sliding engagement with the top portion of said guide ring so that the rotation of said knob causes a pivotal motion of said guide ring; and means for axially moving said drill holding and actuating body, said means comprising an actuation ring on the peripheral outer surface of said body having a roll in rolling contact with a side face of said guide ring and a ball mounted on the outer periphery of said body and urged by a spring against the other side face of said guide ring.

3. An apparatus as defined in claim 1, in which said drill is supported such that the axis of said drill is so inclined with respect to the grinding surface of said cup-shaped grinding wheel that the surfaces of the edges of said drill are in grinding contact with said grinding surface, said apparatus being designed to have an initial grinding position in which the axis of said drill is aligned with the horizontal diameter of said grinding wheel.