US2372794A

US2372794A - Machine for grinding twist drills

Info

Publication number: US2372794A
Application number: US488727A
Authority: US
Inventors: Ricks Fred
Original assignee: United Shoe Machinery Corp
Current assignee: United Shoe Machinery Corp
Priority date: 1942-06-17
Filing date: 1943-05-27
Publication date: 1945-04-03
Anticipated expiration: 1962-04-03

Description

Examiner F. RICKS April 3, 1945.

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Examine:

April 3, 1945. F. RlcKs MACHINE FOR GRINDING TWIST DRILLS Filed May 27, 1943 4 Sheets-Sheet 2 .Eri A April 3, 1945. F. RlcKs MACHINE FOR GRINDING TWIST DRILLS Filed May 27, 1943 4 Sheets-Sheet 3 m/ NS N .mi

MACHINE FOR GRINDING TWIST DRILLS Filed May 27, 1945 4 Sheets-Sheet 4 Fig. 8.

Examinp Patented Apr. 3, 1945 iiramllle MACHINE F OR GRINDING TWIST DRILLS Fred Ricks, Leicester, England, assigner to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application May 27, 1943, Serial No. 488,727 In Great Britain June 17, 1942 11 claims.

This invention relates to grinding machines and is herein illustrated and described as embodied in a machine for sharpening the cutting edges of twist drills. While this operation is frequently performed manually, a considerable degree of skill on the part of the operator is necessary to obtain satisfactory results and even with the exercise of skill it is rarely possible to grind the cutting edges with a high degree of accuracy. Grinding machines are sometimes provided with devices on which a drill may be held by the operator while the device is moved relatively to a grinding wheel to cause one cutting edge of the drill to be sharpened and material behind the cutting edge ground away to provide clearance, the drill then being rotated on the device by the operator for similar treatment of the other cutting edge. In the use of such a device, however, the operator not only has to hold and rotate the drill, and to bring first one edge and then the other into grinding position on the device, but also has to use his judgment in so grinding each edge of the drill that the point of the drill will be central when the operation is finished. It is evident that the accuracy of the work thus done is largely if not entirelyv dependent upon the skill of the operator.

It is an object of the present invention to provide a machine for sharpening drills accurately without requiring skill on the part of the operator.

In accordance with this object the illustrated machine is provided with a grinding tool which moves in an annular path and with a drill holder movable in one direction to carry a drill across the interior of the annulus of the path of the grinding tool and then into the path to cause one cutting edge of the tool to be ground, the drill holder then being movable in another direction to carry the drill across the interior of the annulus of the path of the grinding tool and then into the path at a different location to cause another cutting edge of the tool to be grcund. In the illustrated machine the grinding tool consists of an abrasive wheel rotated about its own axis and also moved in an orbital path. The drill holder consists of a turret having various sized holes for drills of different diameters and provided with a device which not only secures a drill in the turret but which also holds the turret against rotation to maintain the drill in operating position. The turret is moved back and forth to bring the drill into the path of the abrading tool to cause one cutting edge of the drill to be sharpened and then to move the drill across the annulus of the path of the abrading Wheel to cause the other cutting edge of the tool to be sharpened. The illustrated machine is further provided with a gage positioned adjacent to the abrading wheel and engageable with the end of the drill to position the drill axially in the turret before the drill is moved into the path of the abrading wheel.

These and other features of the invention will be described as embodied in an illustrative machine and pointed out in the appended claims.

Fig. 1 is a front elevation, partly in section, of the aforementioned illustrative machine;

Fig. 2 is a left end elevation of the machine shown in Fig. l;

Fig. 3 is a detail view illustrating the positioning of a drill about its own axis in the apparatus shown in Figs. 1 and 2;

Fig. 4 is a plan view of certain parts shown in Fig. 1:

Fig. 5 is a section taken on the line V-V of Fig. 4;

Fig. 6 is a left end elevation illustrating the operation of the apparatus shown in Figs. 1 and 2;

Fig. 7 is a front elevation, partly in section, of a modified machine;

Fig. 8 is a left end elevation of the machine shown in Fig. 7

Fig. 9 is a sectional plan view on the line IX- IX of Fig. 8; and

Fig. 10 is a sectional plan view on the line X-X of Fig. 8.

The supporting structure of the machine shown in Figs. 1 and 2 consists of a frame I0 adapted to be supported on a work bench. Journaled in a bearing I2 on the frame I0 is a shaft I4 upon the right end of which is secured a flywheel I6. A handle Ilmounted upon the flywheel provides for the turning of the shaft I4. Extending radially from the left end of the shaft I4 is an arm 2t which carries a bearing 22 for a shaft 24 ex- 'tending parallel to the shaft I4. Secured upon the left end of the shaft 24 is an abrading tool 26 in the form of a grinding wheel having an annular operative surface 28 which lies in a cone having its vertex in the axis of the shaft 24. The elements of this cone make an angle of 59 degrees to the axis of the cone, which is the usual angle of the cutting edges of a. drill to the axis of the drill. Mounted upon the right end of the shaft 24 is a pinion 30 which meshes with a stationary internal gear 32 concentric with the shaft I4 and carried by a, disk 34 which constitutes a part of the machine frame I0. It is evident that turning of the shaft I4 by the handle I8 will impart an orbital movement of the abrading tool 26 in an annular path about the axis of the shaft I4 and also a rotation of the abrading tool about its own axis, that is the axis of the shaft 24. The pitch diameter of the pinion is three-quarters of an inch and the pitch diameter of the internal gear is four inches, so that during each revolution of the driving shaft the abrading wheel is rotated five and one-third revolutions.

Extending axially from the left end of the shaft I4 is a pin 36 having a flat end face 38 adapted to engage the point of a drill to position the drill longitudinally along the axis of the shaft I4. The periphery of the abrading tool 26 extends close to the pin 36, with allowance for clearance.

A double edged twist drill to be sharpened is secured in a turret 40 which is mounted upon a carriage 42 with provision for free rotation of the turret about an axis extending in the direction of the axis of the shaft |4. of a pair of

parallel disks

44 and 46 mounted on a shaft 48 which is journalled in the carriage 42. Extending co-axially through the disks 46 and 48 are a pair of holes u for receiving a drill of relatively small diameter. The

disks

44 and 46 are provided with three other pairs of co-axial holes 5|, 53 and 55, of progressively increasing diameter for larger drills, all of these holes being angularly spaced at intervals of angles of 90 about the axis of the turret, and being equidistant from the axis. Communicating with each of the holes in the disk 44 and extending radially to the periphery of the disk is a bore 52. Secured upon the carriage 42 is a support 54 having an internally threaded opening, the axis of which is horizontal and radial with respect to the disk 44. Mounted in this threaded opening is a screw 56 having a knurled head 58 and a smooth shank 60 beyond the threaded portion. The screw 56 operates somewhat in the manner of a set screw, the shank 60 being adapted to enter any one of the radial bores 52 and to clamp the drill in the associated drill-receiving hole 50 when the turret has been rotated into proper position. The screw 56 furthermore holds the turret against rotation from this operating position. When the drill is thus clamped in the turret its axis is at the same level as the axis of the gage pin 36.

The carriage 42 has formed in it a guideway which slidingly engages a stationary horizontal bar 62 secured on the frame I0 and extending in a direction parallel to the axis of the screw 56. A retaining plate 64 secured to the carriage by screws 66 engages the outer face of the bar 62 and holds the carriage upon the bar. The carriage 42 has a downwardly extending portion 68 in which is formed a vertical guideway 10. Engaging the guideway is a pin 'I2 mounted upon a crank arm 14 which extends from a hub 16. J ournaled in the lower portion of the frame I0 ls a rock shaft 18 upon the left end of which is mounted the hub 16 vand upon the right end of which is mounted a hub 80 from which extends a crank arm 82 carrying a cam roll 84. Formed in the face ofthe ywheel I6 is a cam groove 86 which is engaged by the roll 84. Rotation of the flywheel I6 will thus cause a rocking movement of the arm 82 which will be transmitted through the shaft 18 to the arm 14 and which will cause the pin 12 to impart a reciprocatory movement to the carriage 42. The amplitude of this reciprocation may be varied by adjustment. To this end the arm 14 is provided with a longitudinal slot 88 in which the pin 12 may be moved a greater or less radial distance along the arm 14. 'I'he The turret consists pin 12 has a smooth shank portion extending through the slot 88 and a threaded end portion 90 extending outside of the slot. A clamping nut 92 threaded upon the end portion 90 acts througha washer 94 to clamp the crank arm against a collar 96 on the pin 12.

The carriage 42 may be locked in an intermediate or neutral position with the drill in the turret in axial alinement with the gage pin 36, and the flywheel I6 may be held against undesired rotation, by means of a pin 98 (Fig. 1) slidably mounted in a bearing in the frame I0 and engageable with an opening |00 in the flywheel. The pin 98 is connected by a block |62 to a pin |04 slidably mounted in a bearing |06 secured in the left wall of the lower portion of the frame I0, the pins 98 and |04 being offset from each other. Secured upon the pin |04 is a sleeve |08 (Figs. 4 and 5) which slidably engages the interior of a cylinder I I0 extending from the bearing |06, the sleeve |08 having a radial pin I|2 which engages a bayonet slot ||4 formed in the cylinder IIO. A knurled head I I6 on the sleeve |08 enables the operator to manipulate the sleeve for the purpose of locking the pin I|2 in the slot I|4 to maintain the flywheel and the carriage stationary and for the purpose of releasing these members when desired.

When the carriage 42 is locked in neutral position and the shank 60 is inserted into the appropriate bore 52 the drill-receiving holes 50 will be in axial alinement with the gage pin 36, and longitudinal or axial adjustment of the drill is effected by bringing the point of the drill into contact with the gaging surface 38 before tightening the screw 56 to clamp the drill in the turret. It is necessary also to provide for angular or rotary adjustment of the drill about its own axis. Such adjustment is obtained by the use of a plurality of thin plates |I8 (Fig. 3) secured on the righthand face (i. ethe face which is nearer to the gage pin 36) of the disk 46, one of these plates being associated with each of the drill-receiving holes. Each plate 8 has an edge portion so arranged in overlapping relation to its associated hole as to engage the edges of one of the flutes of the drill to control the angular position of the drill. When a drill is positioned axially by the gage pin 36, the plate I|8 will so control the angular position of the drill as to cause one of its cutting edges to extend upwardly and to the left (when the machine is viewed from the left) at an angle of about twenty-two and one-half degrees to a vertical plane passing through the axis of the drill, and the other cutting edge will extend'downwardly and to the right at a similar angle. This angle, however, may be altered by suitable adjustment of the plates II6 if it is desired to provide more or less clearance or to vary the angle of the cutting edge of the drill.

Before beginning the operation the drill D is inserted in one of the drill receiving holes, foi example the hole 50, and the screw 56 is turnec. far enough to lock the turret against rotation by 'causing the shank 6|) to enter the bore 52 associated with the h ole 50. The drill is then gaged, both axially and angularly, by bringing its point into contact with the gaging surface 38 of the pin 36. The drill is then clamped in the turret by turning the knurled head 58 to tighten the screw 56. The operator then releases the flywheel by drawing the knurled head II6 away from the cylinder |I0. Upon turning the handle I8 in a clockwise direction (which will appear counterclockwise in Fig. 2), the grinding wheel 26 will Uli lauw' be given its rotary and orbital movements already described and the carriage 42 will be moved to carry the drill from its central position rearwardly into the path of the operative surface 28 of the grinding wheel. One of the two cutting edges of the drill will be ground by the wheel 26 and the material adjacent to that cutting edge will be removed to provide clearance. Proper grinding to produce a suitable cutting edge with clearance adjacent thereto results from the eccentric relation of the drill to the axis of the orbit of the grinding tool and from the gaging of the drill as already described. Continued rotation of the iiywheel will cause the carriage to retrace its path, moving forwardly and crossing the annulus of the orbit of the grinding wheel to bring the other cutting edge of the drill into grinding position. Continued rotation of the flywheel will bring the carriage back to a neutral position whereupon the ywheel may be locked and the drill may be released.

The operative face 28 of the abrading tool is so arranged relatively to the gaging surface 38 of the gage pin, and therefore of the drill to be ground, that only a relatively small amount can be ground from the drill without resetting the drill against the gage pin. This relatively small amount is, however, usually sufficient to sharpen the drill; but if the drill appears not properly sharpened after being ground in the manner above described it may, of course, be reset against the gage pin and ground again.

In the modied machine shown in Figs. 7, 8, 9 and 10 a grinding wheel |50 is driven by power about its own axis but is moved in an orbital path by the operator. The drill is clamped in a turret |52 similar to the turret 40 but mounted for swinging movement forwardly or rearwardly by the operator instead of for reciprocation in timed relation to the orbital movement of the grinding i wheel.

The modified machine has a driving shaft |54 rotatably mounted in a sleeve |56 which in turn is rotatably mounted in a suitable bearing in a frame |58. Extending from the right-hand end of the shaft |54 is a crank |60 by which the operator may turn the shaft. Mounted on the sleeve |56 is a pulley |62 which may be driven by a belt from any suitable source of power. Also mounted upon the sleeve |56 is a gear |64 which meshes with a pinion |66 on a shaft |68 parallel t the driving shaft |54 and journaled in a bearing formed in an arm or block secured upon the left-hand end of the driving shaft |54. The

grinding wheel |50 is mounted upon the left end of the shaft |68.

The modified machine has a rotary turret comprising a pair of disks |12 and |14 similar to the

disks

Journaled in the carriage |18 is a spindle |84 connected at one end to a crank |86 and having formed on its opposite end an eccentric |88 which engages a recess |90 in the vertical guideway |80. A half turn of the crank |86 from the position shown in Fig. 8 serves to rotate the eccentric |88 and thereby to raise the carriage |18 to bring a. drill in the turret into alinement with 9, gage later to be described. The disks |12 and |14 have holes |94 of different sizes to receive different sizes of drills. Communicating with each of the drill receiving holes in the disk |12 is a radial hole to accommodate the smooth shank of a. clamping screw |98 threaded in a support 20| mounted on the carriage |18. Secured upon the disk |14 are plates similar to the plates ||6 for insuring proper angular adjustment of the drill about its own axis.

Slidably mounted in the block |10 for movement in a direction parallel to the axis of the shafts |54 and |68 is the shank 202 of a gage 204 having an end face engageable with the point of a drill to determine the axial or longitudinal adjustment of the drill in the turret. Threaded into the block |10 is an adjusting screw 206 having a pair of collars 208 which embrace a shouldered portion of the gage 204 to control the axial adjustment of the gage.

The swinging frame |82 is pivoted on axially alined screws 2|0 and 2|2 in the frame |58. A handle 2|4 extending from the frame enables the operator to swing the frame about the axis of the screws 2|0 and 2|2 to an extent limited by a. stop 2|6 which is engageable with the oDpOsite sides of a recess 2|8 formed in a portion of the swinging frame |82. The stop 2|6 consists of a stud adjustably mounted in a slot 220 formed in the frame |58 of the machine, the slot extending toward or from the axis of the swinging frame |82 to enable the amplitude o-f oscillation of the swinging frame about its axis to be varied.

The pivotal axis of the frame |82 is intersected by the extended axis of the driving shaft 54. The turret is arranged to be secured in operating position by the screw |98 with the selected drillreceiving hole uppermost and when the drill is clamped in the drill-receiving hole and the turret is locked in operating position by the screw |98, with the carriage |18 in its lowermost position, the axis of the drill will be at the level of the axis of the driving shaft 54; and when the swinging frame |82 is rotated about its axis to its mid position, the axis of the drill will coincide with the axis of the driving shaft |54.

When the grinding wheel occupies its lowermost position, as shown in Fig. 7, the gage 204 will occupy its uppermost po-sition which is above the extended axis of the driving shaft 54. In

order to bring the drill up to the level of the gage the crank |86 is given a half turn. The drill is then moved in the drill-receiving hole |94 until the point of the drill engages the operating end face of the gage 204. When the longitudinal and rotary adjustment of the drill has thus been obtained, the drill is clamped in the turret by tightening the screw |98, and the crank |86 is then turned downto bring the carriage |18 into its lowermost or operating position.

The gage 204 is preferably adjusted to intercept the point of the drill short of (i. e. to the left of, as viewed in Fig. 7) the pivotal axis of the swinging frame |82. The drill thus points toward the axis without quite reaching it, and as the frame swings about the ax'fs the entire drill moves bodily with the frame.

In the use of this modified form of the machine the swinging frame |82 is swung to one side as far as permitted by the stop 2|6. The operator then turns the crank to bring the power driven grinding wheel into engagement with one of the cutting edges to sharpen the edge and to remove material from the vicinity of the edge to provide clearance. He then swings the frame into its opposite limiting position to bring the other cutting edge of the drill into the orbital path of the grinding wheel and turns the crank |60'to move the grinding wheel into position for operation on that cutting edge. In this modified machine, the cutting edges of the drill are positioned in substantially vertical planes and when the drill is swung about the axis of the swinging frame |82 into either of its limiting positions, one cutting edge of the drill and the face behind the cutting edge lie in the path of the grinding wheel as the latter is moved around bodily by the operator, and as the grinding wheel is moved past said edge and said face, the edge is sharpened and the face is so ground or backed-off as to provide clearance behind the edge. When the drill has been moved about the axis of the swinging frame into its opposite swinging position, the other cutting edge and the face adjacent thereto will be similarly treated. By adjustment of the stop 206, the angle of the drill relatively to the grinding wheel, and, therefore, the backing-off behind the cutting edges may be varied and by adjustment of the gage 204 the position of the point of the drill relatively to the axis about which the swinging frame oscillates may be varied to effect a variation in size of the extreme end of the point of the drill.

It will be apparent that both illustrative constructions may readily be operated by unskilled or practically unskilled labor since it is only necessary to place a drill to be ground in the turret with its point against the gage 36 or the gage 204, and after clamping the drill, to move the grinding wheel around the drill, and also, in the modified construction, to swing the turret forwardly or rearwardly.

Having described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

l. A drill grinding machine comprising a grinding element movable in a circular path, said grinding element having an operating face which is angularly disposed with respect to the plane of said circular path, and a drill holder movable in one direction to carry a drill therein across the interior of the circular path of the grinding element and then into a portion of said path to present one cutting edge of the drill to the angularly disposed face of the grinding element, said drill holder being also movable in another direction to carry the drill again across the interior of the circular path of the grinding element and then into a different portion of said path to present another cutting edge of the drill to the angularly disposed face of the grinding element.

2. A drill grinding machine, comprising a conical grinding element, means for moving said grinding element in a circular path, a holder for a drill, and means for moving said holder to bring the drill rst into the path of said grinding element to present one cutting edge of the drill to said conical grinding element and then across said path to present another cutting edge of the drill to said conical grinding element.

3. A drill grinding machine comprising a conical rotary grinding tool, means for moving said grinding tool in an orbital path about an axis which is parallel to the axis of rotation of the grinding tool, a holder for a drill, and means for moving said holder rst across the orbit of said path and then into a portion of said path to present one edge of the drill to said conical grinding tool, and then across said orbit and into a different portion of said path to present another edge of the drill to said conical tool.

4. A drill grinding machine, comprising a rotary grinding tool, means for moving said grinding tool in an orbital path about an axis, a holder for supporting a drill substantially on said axis, a gage positioned substantially on said axis and engageable with the end of the drill in the holder to determine the position of the drill along the axis, means for securing the drill in gaged position in the holder, and means for moving the holder'to cause the drill to traverse the orbit of the path of the grinding tool for the purpose of bringing different cutting edges of the drill successively into the path of the grinding tool.

5. A drill grinding machine, comprising a rotary grinding tool having a, conical operating face, means for moving said grinding tool in an orbital path, a holder for a drill, and means operated by said moving means for moving said holder to cause the drill to traverse in different directions the orbit of the path of the grinding tool to bring different cutting edges of the drill successively into positions wherein said cutting edges will be engaged by the conical operating face of the grinding tool.

6. A drill grinding machine, comprising a rotary grinding tool, a support for said grinding tool mounted for rotation about an axis eccentric to the axis of rotation of the grinding tool, means for rotating said support about the axis of the support, a cam on said rotating means, a holder for a drill, a carriage on which said holder is mounted, and means operated by said cam for moving the carriage back and forth to cause the drill to travel across the orbit of the path of the grinding tool and into said path at different localities thereof to effect the grinding of diierent cutting edges of the drill in succession.

'7. In a drill grinding machine, a rotary turret having openings parallel to the axis of the turret to receive drills of various sizes, said turret also having an equal number of radial openings each of which extends from the periphery of the turret to a corresponding drill-receiving opening, a support adjacent to said turret, a clamping member mounted in said support for movement radial to said tunet and adapted to enter the radial openings in said turret, and means for operating said clamping member to cause it to exert a radial clamping pressure against a drill in one of said drill-receiving openings and to hold the turret against rotation with the drill in operating position.

8. A drill grinding machine comprising a grinding wheel having a conical working face, means for moving said grinding wheel in an orbital path, a holder for a drill, and means for swinging said drill holder about an axis which intersects at right angles the axis of said orbital path to present rst one cutting edge of the drill to said conical working face and then to present the other cutting edge to said conical working face.

9. A drill grinding machine comprising a grinding wheel having a conical abrading surface, a holder for a drill, a. support for said drill holder constructed and arranged for pivotal movement about an axis parallel to the plane of rotation of the grinding wheel, to enable a drill in said holder to be moved between two limiting positions wherein two cutting edges of the drill are brought into grinding engagement with said conical abrading surface at angles proper for thel grinding of each edge, and a stop for determining said limiting positions.

l0. A drill grinding machine comprising a beveled grinding wheel, means for moving said grinding wheel in an orbital path, a holder for a drill, a gage adjacent to said grinding wheel for determining the longitudinal position of the.

drill within the holder, and means for moving said drill holder to cause the point of the drillrst to enter the path of said grinding wheel to cause one' cutting edge of the drill to be ground and then to traverse the orbit of the path of the grinding wheel to bring another cutting edge of the drill into position to be ground, said drill holder being movable to a position wherein the drill may be brought into contact with said gage while the drill is being positioned in the holder.

Il. A drill grinding machine comprising a bev` eled grinding wheel, means for moving said grinding wheel in an orbital path, a holder for a drill, a support for said drill holder'constructed and arranged for pivotal movement of the drill about an axis at right angles to the axis of the orbit of the grinding wheel to enable the drill to be swung in opposite directions into the path ot the grinding wheel for the grinding of opposite cutting edges, said holder being constructed and arranged to maintain the drill in a position wherein the drill points toward said pivotal axis, and a gage adjacent to said grinding wheel and engageable with the drill to determine the longitudinal position of the drill in the holder, said support having a guiding portion parallel to said pivotal axis, and said drill holder being slidable on said guiding portion to enable the drill to be brought from a position of contact with said gage into an operating position away from said gage.

FRED RICKS.