GB2116464A

GB2116464A - Drill-grinding machine

Info

Publication number: GB2116464A
Application number: GB08306284A
Authority: GB
Inventors: Hans Schmid
Original assignee: Fritz Gottstein
Current assignee: Fritz Gottstein
Priority date: 1982-03-09
Filing date: 1983-03-08
Publication date: 1983-09-28
Also published as: CH655889A5; GB8306284D0; DE3307936C2; FR2523016A1; DE3307936A1; FR2523016B1; DE3348060C2

Abstract

A drill (18) to be resharpened is chucked in a clamping chuck (16) of a clamping head (14) so as to undergo either conical grinding or four-surface grinding on the plane surface (48) of the grinding wheel (26). A crank handle (70) serves as a drive element for executing the various movements which are necessary especially for conical grinding. To produce conical grinding, the grinding wheel (26), together with its plane grinding surface (48), remains in one position. If, instead of conical grinding, four- surface grinding is to be carried out on the tip of the drill (18), then two different angular positions between the drill (18) and the grinding wheel (26) are necessary to produce the relief-ground surfaces and the free surfaces for this purpose, the grinding wheel (26), together with its plane grinding surface (48), is pivotable about a pivot axis (B) as a result of actuation of a hand wheel (56). The pivot axis (B) extends over the plane of the grinding surface (48). As a result of such an arrangement, it is possible to carry out four-surface grinding with exact geometry, without changing the setting of the drill. <IMAGE>

Description

SPECIFICATION Drill-grinding machine The invention relates to a drill-grinding machine.

Many known drill-grinding machines are intended for grinding conical surfaces at the tip at and adjacent the cutting edges of the drill.

However, it is often also desirable to grind the tip of a drill with multiple-plane surfaces instead of conical surfaces. Known drill-grinding machines are generally designed either for grinding conical surfaces or for grinding multiple-plane surfaces. In addition, there are also known drill-grinding machines which are designed both for carrying out conical grinding and for carrying out multipleplane surface grinding. However, the disadvantage of such reversible drill-grinding machines is that the envelope surface of the grinding wheel is used to carry out the plane surface grinding, and grinding using the envelope surface does not in fact produce a plane surface, but a hollowed surface.If, however, a hollowed surface is produced on the cutting tip of the drill instead of a plane surface, this results in an unfavourable cutting angle, as a consequence of which the service life of the drill may be considerably reduced. To achieve perfect surface grinding, it is therefore necessary to carry out the process on a plane grinding surface, that is to say, for instance, on the end face of a grinding wheel.

Since, in practice, only multiple-surface grinding is ever really considered for relatively large drills, it is necessary to be able to pivot the clamping chuck appropriately in relation to the grinding wheel, in order, in one setting, to grind the two relief-ground surfaces of a double-cutting drill and, in the other setting, to grind the two free surfaces. Between the settings for these two grinding operations it is necessary to change the angle of the clamping chuck in relation to the grinding wheel. However, to avoid expensive resetting of the clamping chuck or rechucking of the drill, the pivot axis about which the chuck is rotated in order to change its angle relative to the grinding wheel must lie in the plane of the grinding surface.

A drill-grinding machine which satisfies the above-mentioned condition and is known from German Offenlegungsschrift 3,028,960, has a clamping chuck supported by an angled pivoting arm which is pivotable about a pivot axis lying in the plane of the grinding surface. However, this known drill-grinding machine is not provided with an adjusting device to enable it to grind conical surfaces, and it is mainly intended for drills of relatively small diameter, for example up to 6 mm.

For the reasons mentioned above, the clamping chuck of this known drill-grinding machine is relatively light, so that it is possible to arrange the clamping chuck on a pivoting arm without impairing its stability.

When a drill-grinding machine is also to be suitable for grinding conical surfaces, it is necessary for the clamping chuck to be provided with appropriate adjusting devices. Moreover, when such a drill-grinding machine is also to be suitable for grinding relatively large drills, for example up to a diameter of 30 mm, then because of the considerable weight of the clamping chuck and associated parts, it is no longer possible to arrange the chuck on a pivoting arm, without prejudicing stability.

A drill-grinding machine suitable for grinding conical surfaces is known, for example, from Swiss Patent Specification 330,589. This machine can be used, in addition, to carry out four-surface grinding, but this is only possible if the above-mentioned compromises are made, and there is no guarantee that the exact desired geometry for four-surface grinding will be achieved.

U.S. Patent Specification 2,724,931 discloses a drill-grinding machine in which the clamping device intended for the drill to be ground is mounted on a cross slide. The cross slide is adjustable parallel to the grinding surface of the grinding wheel by means of a crank which is connected to a gear wheel engaging a rack.

Although such a drive allows a to-and-fro movement, on the grinding wheel, of the drill to be ground, it is not suitable for the fine adjustment which may be needed for grinding specific drills or specific surfaces on the envelope surface of the grinding wheel. Grinding on the envelope surface can be important, for example, when screw taps are to be resharpened.

The aim of this invention is to provide a drillgrinding machine which is suitable both for grinding conical surfaces on drills and for carrying out multiple-surface grinding.

According to the present invention there is provided a drill-grinding machine including a grinding wheel having a plane grinding surface, a clamping chuck to hold a drill bit to be sharpened, the chuck being rotatable about its axis, which coincides with the axis of a drill bit when held therein, and the chuck also being pivotable about a first pivot axis parallel to said plane grinding surface when said wheel is in a basic position, and the chuck being arranged so that it can be fed towards the plane grinding surface in the direction of the chuck axis, wherein the grinding wheel is pivotable about a second pivot axis which extends at right angles to the first pivot axis and is in the plane of the grinding surface and is intersected by the chuck axis.

With the invention, it is possible to carry out conical or multiple-surface grinding with a single chucking of the drill and without readjustment, and it is possible to ensure fine adjustment of the drill along the grinding surface and a controlled to-and-fro movement in front of the grinding wheel. The to-and-fro movement is especially useful for carrying out multiple-surface grinding because the drill can be guided from the periphery of the grinding wheel in front of the plane grinding surface. During multiple-surface grinding, the arrangement of the grinding wheel produces a geometry which makes it necessary to pivot only the grinding wheel between grinding the reliefground surfaces and the free surfaces, so that it is not necessary to adjust the clamping chuck and drill.As a result, exact geometry of the drill tip and symmetry of the two cutting edges of the drill can be obtained.

According to a preferred feature of the invention the clamping chuck is mounted on a cross slide which is displaceably mounted on a base plate of the machine, and means are provided to engage the cross slide with either a spindle drive for fine adjustment or a pivotable lever for coarse movement.

This feature is especially advantageous when four-surface grinding is carried out, since the cross slide, together with the clamping chuck located on it, can be moved to-and-fro, by means of the pivoting lever, to grind any one of the four surfaces. The range of movement of the cross slide is preferably about 50 mm. During the movement of the cross slide by means of the pivoting lever, it becomes easier for the operator to determine the advance during the grinding operation on the basis of the resistance which arises. As a result of such an arrangement, a suitable advance speed can be determined more effectively than, for example, with the spindle drive. on the other hand, change-over to the spindle drive is appropriate when the drill to be ground has to be positioned exactly along the Xaxis.This occurs, for example, when screw taps are to be resharpened on the peripheral surface of the grinding wheel. Preferably there is the further possibility of engagement with neither the lever not spindle drive, and this allows rapid manual displacement of the cross slide which can then be engaged again either with the spindle drive or with the pivoting lever.

The invention also provides a drill-grinding machine having a grinding wheel and a clamping chuck mounted on a cross slide which is displaceably mounted on a base plate, and means to engage the cross slide with either a spindle drive, for fine adjustment, or a pivotable lever for coarse movement. Such a machine is useful for carrying out multi-surface grinding.

In order that the invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings, in which: Figure 1 shows, in a plan view, a drill-grinding machine; Figure 2 shows the three movement actions of a drill for grinding conical surfaces; Figure 3 shows, in a front view, the drillgrinding machine according to Figure 1, with the clamping head removed; Figure 4 shows a crank mechanism for executing a pivoting movement of the clamping head; Figure 5 shows a plan view of the elements for adjusting the cross slide along the X-axis; and Figure 6 shows, in a side view, the elements according to Figure 5.

The drill-grinding machine illustrated in Figure 1 has a baseplate 10 with a cross slide 12 located on it. A clamping head 14 is arranged pivotably on the cross slide 12. The clamping head 14 has a clamping chuck 16 in which a drill 18 to be resharpened is chucked. The clamping chuck 16 is preferably a six-jaw chuck to guarantee that even drills with a large diameter and a large pitch can be chucked exactly centrally. Two legs 20 and 22 extend vertically upwards from the baseplate, and between these a support 24 is arranged pivotably about a horizontal axis B. A large grinding wheel 26 and a small grinding wheel 28 are mounted in the support 24.

Located on the baseplate 10 is a first guide 30 on which a second guide 34 is adjustable along a Y-axis as a result of actuation of a hand wheel 32.

The cross-slide 12 is adjustable on the second guide 34 along the X-axis by means of a further hand wheel 36, inasmuch as a reversing lever 38 located on the second guide 34 on the side opposite the hand wheel 36 is brought into the position I. When the reversing lever 38 is in the position II illustrated, the cross slide 12 can move to and fro along the X-axis as a result of actuation of a pivoting lever 40. When the reversing lever 38 is in the zero position located between the two positions I and II, the cross slide 12 is freely movable by hand along the X-axis.

Whilst the hand wheel 36 is provided with the scale 42 serves for fine adjustment, the pivoting lever 40 is intended for moving the cross slide 12 to and fro smoothly when, for example, the tip of the drill 18 is to undergo surface grinding. The zero position of the reversing lever 38 serves for bringing the cross slide 12 quickly into another position, for example in front of the small grinding wheel 28. A scale 44 is assigned to the hand wheel 32 as well as to the hand wheel 36. The two scales 42 and 44 serve, on the one hand, for controlled fine adjustment and, on the other hand, for reproducing specific settings. It is possible to actuate the reversing lever 38 into the positions I or II only when the cross slide 12 is in specific positions along the X-axis, in order to guarantee reproducibility.

The large grinding wheel 26 driven by a first motor 46 has a plane end face 48. The small grinding wheel driven by a second motor 50 is rounded at its outer edge and is conical both on the inside and on the outside. The plane end face 48 of the large grinding wheel 26 must be located exactly on the pivot axis B. To satisfy this condition, the large grinding wheel 26 is adjustable along its axis D by means of a hand wheel 52. The hand wheel 54 located near the small grinding wheel 28 serves for adjusting the height of this grinding wheel.

A further hand wheel 56 serves for pivoting the support 24 about the pivot axis B. The pivoting angle can be read off roughly on a scale 58. A further scale 60 assigned to the hand wheel 56 allows very accurate fine adjustment of the pivoting angle.

The clamping head 14 is arranged for executing three movement actions simultaneously, in order, when the drill 18 is resharpened, to grind conical surfaces on its tip.

The three movement actions are indicated by arrows with reference to Figure 2. C denotes the axis of the drill which coincides with the axis of the clamping chuck 16 and is designated below as a chuck axis. An arrow 62 indicates the first movement action in which the drill 18 is pivoted about a point 64 located on a first vertical axis A.

The distance between the first axis A and the horizontal second axis B already mentioned depends on the diameter of the drill 18 to be resharpened. To maintain the necessary distance between the first vertical pivot axis A and the second horizontal pivot axis B, the drill 18 must be chucked in the clamping chuck 1 6 over the appropriate length.

The second movement action to obtain conical surfaces is the rotation of the drill 18 about its axis C, this movement action being indicated by th#e arrowed line 66. The third movement action is the feed movement of the drill 18 in the direction of the grinding wheel 26 along the chuck axis C.

In the case of a double-edged drill, this feed movement must take place twice per revolution.

Each feed movement is followed by a retraction.

This movement action is designated by the double arrow 68.

The clamping chuck 16 mounted in the clamping head 14 is designed to execute simultaneously the movement actions explained with reference to Figure 2, when a crank handle 70 serving as a drive element is rotated. The clamping head 14 has an intermediate plate 72 which is pivotable on the cross slide 12 about the first pivot axis A and which is lockable on the cross slide 12 by means of a locking screw 74.

The tip angle of the drill to be resharpened can be read off on a scale 76. A guide groove 78 having a radius is located in the cross slide 12 to guide the intermediate plate 72. The pivoting movement 62 (Figure 2) is executed by the clamping head 14 in relation to the intermediate plate 72. The feed movement 68 (Figure 2) is executed by the clamping chuck 16 in relation to the clamping head 14.

An adjusting wheel 80 arranged laterally on the clamping head 14 serves for changing over a step gear located between the crank handle 70 and the clamping chuck 16, so that it is possible to change over from double-edged to triple-edged drills, and if appropriate, to multiple-edged drills.

A cam disc 82 connected to the crank handle 70 via the gear mentioned is sensed by a first follower element 84. The cam disc 82 and the follower element 84, which is preferably a roller, are the first members of a transmission mechanism for converting the rotary movement produced by the crank handle 70 into the axial movement 68 (Figure 2). The cam disc 82 can be exchanged or reversed by loosening a knurled nut 86. Reversal makes it possible to resharpen lefthand cutting drills. For this purpose, the clamping head 14 must be pivoted to the right-hand side of the cross slide 12 by loosening the locking screw 74.

The further adjusting wheel 88 on the clamping head 14 serves for adjusting the stroke for the feed movement 68 (Figure 2). This stroke can be set from zero up to a maximum.

The two levers 90 and 92, each having a ball handle, serve for locking the clamping chuck 16 in predetermined angular positions. The right-hand lever 90 is intended for right-hand cutting drills and the left-hand lever 92 is intended for lefthand cutting drills. In the position I, the clamping chuck 16 is locked in the initial position which is intended for chucking and aligning the drill 18. In the position II, locking is effected for grinding the tip of the drill 18 on the small grinding wheel 28.

In the zero position, the lock is released.

The vertical pivot axis A mentioned forms a centre for the scale 76 and the guide grooves 78.

The horizontal chuck axis C intersects the first pivot axis A at right angles. The second pivot axis B extends at right angles to the first pivot axis A, but without intersecting the latter. The grindingwheel axis D of the large grinding wheel 26 intersects the second pivot axis B at right angles.

In the basic position of the support 24 and consequently of the grinding wheel 26, the plane grinding surface 48 of the large grinding wheel 26 is parallel to the first pivot axis A.

According to the invention, the second pivot axis B lies in the plane of the grinding surface 48 and intersects the chuck axis C, to make it possible to carry out, instead of the conical grinding described, surface grinding, for example four-surface grinding, of a double-edged drill, without rechucking the drill. To allow the tips of drills to be ground on the small grinding wheel 28 with the same chucking, the lower edge of the small grinding wheel 28 is located in the region of the second pivot axis B.

Figure 3 shows, in a front view, the drill grinding machine illustrated in Figure 1, but for the sake of clarity, the clamping head 14 together with the intermediate plate 72, has been omitted. It can be seen clearly from the relationship between Figures 1 and 3 that the intermediate plate 72, together with the clamping head 14, is mounted on the cross slide 12 which is illustrated in Figure 3. It is also evident from Figure 3 that the large grinding wheel 26 is surrounded by a two-part protective plate 94 which also extends partially over the plane grinding surface 48 so as to leave a gap. The small grinding wheel 28 is surrounded partially by a protective plate 96. As already mentioned, the small grinding wheel 28 is adjustable vertically as a result of actuation of the hand wheel 54.This small grinding wheel 28 serving for grinding the tips of drills is conventionally set at such a height that its lower edge is located in the vicinity of the pivot axis B. Located in the support 24, on the right, next to the large grinding wheel 26, is a recess 98 which makes access to the shell surface of this grinding wheel easier. The shell surface of the large grinding wheel 26 is subjected to stress, for example, during the resharpening of screw taps.

The support 24 carrying the two grinding wheels 26 and 28 is pivoted about the second pivot axis B by means of the hand wheel 56 and preferably via a spindle-and-rack drive (not shown) which is accommodated in the leg 20. It can readily be imagined, with reference to Figure 3, that the arrangement of the large grinding wheel 26 represents a very stable structure. To achieve perfect grinding, such an arrangement must be largely free of vibrations. This is obtained by means of the support 24 designed as a bridge.

Figure 4 illustrates a crank mechanism which is accommodated in the clamping head 14 and by means of which the clamping head 14 is connected to the intermediate plate 72 (Figure 1).

This crank mechanism serves for pivoting the clamping head 14 to and fro, in relation to the intermediate plate 72, in the direction of the arrow 62 (Figure 2), when the crank handle 70 serving as the drive is rotated. The pivoting movement takes place about the first pivot axis A which is adjacent to the tip of the drill to be resharpened.

The crank mechanism has a connecting rod 200 which is articulated between a crank 202 and a link 204. The end of the link 204 remote from the connecting rod 200 is hinged in the intermediate plate 72 by means of a pin 208. The pivotability of the link 204 is cancelled, however, when a conical locking bolt 206 is introduced into a bore located in the link. When the crank wheel 210 carrying the crank 202 is rotated by means of the crank handle 70 via gear elements not shown in any more detail, the pivoting movement in the direction of the arrow 62 of the clamping head 14 in relation to the intermediate plate 72 is produced when the link 204 is locked. The housing of the clamping head 14 is indicated by 14' in Figure 4.

When a rotary drive without a pivoting movement 62 is required, the locking bolt 206 is withdrawn from the bore in the link 204 by means of an actuating screw (not shown). At the same time, the clamping head 14 is locked on the intermediate plate 72 by means of elements (not shown). When the crank wheel 210 executes a rotary movement, the link 204 is pivoted to and fro about the pin 208. In this case, the link is ineffective.

Such a crank mechanism has essentially two advantages, namely firstly the engagement and disengagement are possible only by means of a locking bolt, and secondly that, after each locking by means of the locking bolt 206, the angle of rotation of the crank wheel 210 is again assigned to the pivoting movements in the direction 62.

Figure 5 illustrates the elements serving for displacing the cross slide 12 on the second guide 34 along the X-axis. The actuating elements already illustrated in Figure 1 are the hand wheel 36, the reversing lever 38 and the pivoting lever 40. The remaining parts of this reversible adjusting device are located within the second guide 34. A first rod 220 displaceable in a longitudinal direction is connected to the hand wheel 36 via a spindle 238. Connected to the pivoting lever 40 is a second rod 222 which is displaceable in a longitudinal direction and which is located opposite the first rod 220. The first rod 220 has several recesses 234 distributed in a longitudinal direction, and the second rod 222 likewise has several recesses 236 distributed in a longitudinal direction, an engagement element 224 located between these two rods is intended for engaging in the recesses 234.A second engagement element 226 is intended for engaging in the recesses 236 of the second rod 222. The two engagement elements 224 and 226 are the ends of a rack 232 which is displaceable by means of a gear wheel 230 (see Figure 6) in its longitudinal direction, that is to say transversely to the two rods 220 and 222. The gear wheel 230 and the rack 232 are connected, by elements not shown, to the cross slide for driving along the X-axis.

The gear wheel 230 acting as a drive element has, in its centre, a square hole through which extends a square rod 228 on which it is displaceable in an axial direction. The square rod 228, which can also be another profiled rod, is mounted rotatable and connected, fixed against rotation, at one end to the reversing lever 38. In the central position of the reversing lever 38, the rack 232 is also in its central position. It is designed in such a way that, in the central position, it engages neither in the first nor in the second displaceable rod 220, 222. In this position, the cross slide 12 can be moved freely by hand along the X-axis. When the reversing lever 38 is brought into one position, the engagement element 224 engages into one of the recesses 234 when the cross slide has previously been moved by hand to such an engagement point.The cross slide 12 can now be adjusted finely along the X-axis by means of the hand wheel 36.

When the reversing lever 38 is moved into the opposite position, the other engagement element 226 engages into one of the recesses 236 when the cross slide 12 has previously been moved by hand into one of the engagement positions. The cross slide 12 can now be moved to and fro along the X-axis as a result of pivoting of the pivoting lever 40. The travel distance of the cross slide 12, which can be obtained, can amount, for example, to 50 mm.

The recesses 234 and 236 are assigned at least to those positions in which grinding operations can be carried out. These include, for example, the grinding position for right-hand cutting drills, the grinding position for left-hand cutting drills, both positions on the large grinding wheel 26 and at least one grinding position on the small grinding wheel 28 which serves especially for grinding tips.

Claims

1. A drill-grinding machine including a grinding wheel having a plane grinding surface, a clamping chuck to hold a drill bit to be sharpened, the chuck being rotatable about its axis, which coincides with the axis of a drill bit when held therein, and the chuck also being pivotable about a first pivot axis parallel to said plane grinding surface when said wheel is in a basic position, and the chuck being arranged so that it can be fed towards the plane grinding surface in the direction of the chuck axis, wherein the grinding wheel is pivotable about a second pivot axis which extends at right angles to the first pivot axis and is in the plane of the grinding surface and is intersected by the chuck axis.

2. A drill-grinding machine according to claim 1, wherein the chuck axis intersects said first pivot axis and is at right angles thereto.

3. A drill-grinding machine according to claim 1 or 2, wherein said first pivot axis extends vertically from a base plate of the machine.

4. A drill-grinding machine according to claim 3, wherein the grinding wheel is mounted on a pivotally mounted support which extends in a horizontal direction between two legs connected to the base plate.

5. A drill-grinding machine according to claim 4, including a spindle-and-rack gear connected to a drive element for pivoting the support.

6. A drill-grinding machine according to any preceding claim, wherein the axis of the grinding wheel intersects the second pivot axis.

7. A drill-grinding machine according to any preceding claim, wherein the clamping chuck is mounted in a clamping head which is pivotable about the first pivot axis and which has a common drive element for its axial, pivotal and rotational types of movement.

8. A drill-grinding machine according to claim 7, wherein the clamping head is mounted on a cross slide which is itself displaceable horizontally on the or a base plate along X and Y-axes of which the X-axis extends parallel to the plane grinding surface.

9. A drill-grinding machine according to claim 8, wherein the common drive element for the three movements is drive-connected to a connecting rod for the pivotal movement, to a gear changeable in steps for the rotary movement and to a cam disc for the feed movement, the axes of rotation of the drive element, the crank connected to the connecting rod, the wheels of the gear and the cam disc extending parallel to the chuck axis.

10. A drill-grinding machine according to claim 9, wherein the drive connection from the drive element via the connecting rod and via the cam disc to the clamping chuck can be interrupted.

11. A drill-grinding machine according to claim 9 or 10, wherein an intermediate plate which is pivotable about the first pivot axis and lockable on the cross slide is located between the cross slide and the clamping head, the clamping head being pivotable about the first pivot axis relative to the intermediate plate, and the connecting rod located in the clamping head being articulated on a link which at its other end is hinged on the intermediate plate, and being lockable by means of a conical bolt.

12. A drill-grinding machine according to any one of claims 8 to 11, wherein the cross slide is on a guide extending along the X-axis and is selectively engageable either with a spindle drive for the purpose of fine adjustment or with a pivoting lever for coarse movement.

13. A drill-grinding machine according to claim 12, wherein the guide includes two rods which are displaceable in the longitudinal direction, one rod being displaceable by means of the spindle drive and the second rod by the pivoting lever, the cross slide having engagement elements to be selectively engaged by means of a reversing lever with the first rod or with the second rod or with neither rod.

14. A drill-grinding machine according to claim 13, wherein the reversing lever is connected to a rotatably mounted profiled rod on which is rigidly located a longitudinally displaceable drive element which is retained in the cross slide and which is connected operatively to the engagement elements.

15. A drill-grinding machine according to claim 14, wherein the driver element has a tooth pitch which engages in a rack connected to the engagement elements.

16. A drill-grinding machine according to claim 13, 14 or 15, wherein the displaceable rods have spaced apart recesses to be engaged by the engagement elements.

17. A drill-grinding machine having a grinding wheel and a clamping chuck mounted on a cross slide which is displaceably mounted on a base plate, and means to engage the cross slide with either a spindle drive, for fine adjustment, or a pivotable lever for coarse movement.

18. A drill-grinding machine constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.