GB2092034A

GB2092034A - Boring tool

Info

Publication number: GB2092034A
Application number: GB8135639A
Authority: GB
Original assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Current assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Priority date: 1981-01-29
Filing date: 1981-11-26
Publication date: 1982-08-11
Also published as: NL190925C; ATA464081A; NL190925B; SE8106468L; FR2498502A1; SE447074B; DE8106316U1; IT8125060A0; DE3108438C2; IT1139727B; CH654232A5; DE3108438A1; AT383070B; FR2498502B1; GB2092034B; NL8105409A

Abstract

A boring tool or annular tool 1 has a cylindrical shank 2, 3 with external swarf ducts 5 running from cutting plates 4 secured to the head end 3 of the shank towards the clamping end 2 which is, in use, clamped in a machine tool. The head end 3 is a separable portion detachably secured to the shank clamping end 2 by an arrangement in which fitting pins 14 screw- threadably engaged in the clamping end are located in fitting holes 16 in the head portion 3. The opposed faces 10 and 11 of the head portion 3 and the clamping end 2 are clamped together by the action of retaining pins 18 secured by retaining screws 19, the retaining pins 18 bearing on the inner surfaces of respective transverse bores 17 in the fitting pins 14 in a direction determined by cooperation between the ends of the retaining pins 18, the inner ends of the retaining screws 19, and recesses 23 formed in the head portion 3. The head portion 3 may be a different diameter from the remainder of the shank, and the shank may include intermediate pieces between the head portion 3 and the clamping end 6. <IMAGE>

Description

SPECIFICATION Improvements in boring tools The invention relates to a boring tool having a substantially cylindrical shank and at least two cutting plates arranged exchangeably on the front head portion of the shank and adjoined by at least two swarf ducts extending to a rear clamping portion of the shank, the swarf ducts being open outwardly of the shank.

Such known boring tools (see German Laidopen Patent Specification 27 30 418) usually have spiral swarf ducts.

Despite the most careful machining of the boring tool shank and of the cutting plates employed therein, it may happen that swarf becomes jammed or cutting edges break away. Since this generally happens deep inside a bore, such disturbances are generally not noticed immediately, so that sometimes not only the cutting plate itself, but also the boring tool shank, is damaged. As a rule, damage of this kind occurs in the head portion of the shank. It may happen in such case that the shank becomes damaged to such an extent that it is no longer suitable for holding the cutting plates satisfactorily. Since the head portion and the clamping portion consists of one piece in the known boring tool, the entire tool must then be replaced by a new one.Such boring tools with working diameters of 50 mm or more are comparatively costly, however, and boring tools with larger working diameters are not as a rule available from stock. In addition to the replacement cost, therefore, there may also be a lengthy delivery time. Another disadvantage of the known boring tools consists in that each tool can always be used only for a precisely defined working diameter.

The problem underlying the invention, therefore, is to provide a boring tool of the kind mentioned at the beginning which following damage to its head portion can be restored simply and economically and which, if necessary, is suitable for machining bores of different diameters within a certain range of working diameter.

According to the invention, this problem is solved in that the shank is formed of at least two separable portions and the clamping portion is detachably connected to the head portion which, at its back remote from the cutting plates, bears directly or indirectly with a radially extending plane end face against radially extending plane front face of the clamping portion, at least two cylindrical fitting pins are let into and fixed in the front face of the clamping portion, the fitting pins being engageable in corresponding fitting holes in the end face of the head portion, and on the head portion there are provided retaining means for acting on the fitting pins, or vice versa.

In the event of any kind of major damage to the head portion of the boring tool, the damaged head portion can be removed from, for example, the clamping portion after releasing the retaining means and be replaced by a new head portion. The new head portion is substantially cheaper than a complete boring tool, because only a fraction of the material necessary for making a complete boring tool is required to make it and, moreover, the many machining operations which are necessary at the rear clamping portion are eliminated. The clamping portion can continue to be used in each case. Suitable auxiliary means, for example boring templates, can ensure that the freshly prepared head portions fit the already available and still usable clamping portion.

In such a boring tool embodying the invention, the fitting pins and the retaining means acting on them have important functions. The fitting pins provide for a satisfactory transmission of force between the head portion and the clamping portion in the circumferential direction and transversely of the axis of the boring tool. They also serve, however, to locate the head portion in a predetermined position with respect to the clamping portion.

This is important in order that the walls of the swarf ducts of the head portion may merge free from steps or shoulders into the walls of the swarf ducts of the clamping portion. Each shoulder, in fact, could lead to a disturbance in the removal of swarf. Moreover, the fitting pins centre the head portion with respect to the clamping portion. Finally, the fitting pins also serve to act on or engage the retaining means. This is an important function, because on account of the swarf ducts and additional coolant bores being present in the head portion and the clamping portion only comparatively little room is available for accommodating the retaining means.

Another advantage consists in that within a certain range of working diameter range one head portion can be exchanged for another with a somewhat larger or smaller working diameter in order to obtain different working diameters. In addition, head portions of different lengths can be exchanged for one another so as thereby to achieve greater boring depths.

In an advantageous embodiment of the invention, there can be inserted between the head portion and the clamping portion at least one intermediate piece which is designed like the front end of the clamping portion at its front end facing the head portion and whose rear end facing the clamping portion is designed like the back of the head portion. Thus an extensively variable boring tool system is provided.

Clamping portions with different conical or tapered shanks which are matched to the receptacles of widely varying machine spindles can be produced as adapters and exchanged for one another. Connection be tween the clamping portions and the intermediate piece takes place in the same way as normally between a head portion and the clamping portion. The join between the intermediate piece and the clamping portion is provided approximately where the swarf ducts would begin in a standard one-piece boring tool.

It is also possible to employ intermediate pieces of different lengths and, if necessary, of different diameters. In each case a head portion is then fixed to their front end by means of the fitting pins and the retaining means. In this way, the boring tool can be very easily adapted both in its length and in its diameter to a particular machining operation. A multi-part boring tool of this kind has a more vibration-resistant behaviour, since the individual parts of limited length are less vibration-exciting in themselves and pass on vibrations to a lesser degree where they join.

Although boring tools with so-called annular bits are known wherein the annular bit carries exchangeable cutting plates and also the front end of a hollow shank can be screwed on, in such boring tools, the annular bit is in the form of a cylindrical hollow body. Removal of the swarf takes place through the interior of the annular bit and the interior of the shank.

For connecting the annular bit and the shank, the bit has an internal thread and the front end of the shank has an external thread. This construction, however, cannot be used for boring tools in which swarf ducts open on the outside are provided in the shank.

The invention will now be described in more detail, solely by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial plan view and a partial longitudinal section of a first embodiment of the boring tool; Figure 2 is a partial side view of a second embodiment; Figure 3 is a partial longitudinal section of the second embodiment on the line Ill-Ill of Fig. 4; Figure 4 is a cross-section on the line IV-IV of Fig. 3; Figure 5 is a side view of a complete boring tool embodying the invention; Figure 6 is a side view of a third embodiment; Figure 7 is a partial longitudinal section of the third embodiment.

Fig. 5 shows a complete boring tool 1, which has a substantially cylindrical shank.

The front head portion 3 of the shank is detachable from the rear clamping portion 2 of the shank. At least two exchangeable cutting plates 4 are provided on the head portion 2. The shank has two spiral swarf ducts or grooves 5 adjoining the cutting plates 4, these ducts being open outwardly of the shank. These swarf ducts 5 extend from the cutting plates 4 to the clamping portion 2 of the shank. The clamping portion 2 may likewise be of cylindrical form at its rear end or, as shown in the drawing, be provided with a cone 6 which serves for accommodation in a machine tool. Moreover, the clamping portion 2 also has a central coolant bore 7 (Figs. 1 and 2) which is connected to two or more coolant ducts 8 (Figs. 1 and 2) provided in the head portion 3. These coolant ducts 8 open out in the front end face of the head portion 3 in the vicinity of the cutting plates 4.Supply of the coolant to the coolant bore 7 is effected via a coolant ring (not shown) surrounding the clamping portion 2 and a transverse coolant inlet bore 9 provided in the clamping portion.

In comparison with the clamping portion 2, the head portion 2 is short and the join between the two portions 2, 3 is arranged in the region of the swarf ducts 5.

The head portion 3 is provided at the back, remote from the cutting plates 4, with a radially extending plane end face 10 which bears against a corresponding radially extending plane front face 11 of the clamping portion 2. The front face 11 of the clamping portion 2 has two diametrically opposite fitting holes 12 and coaxial threaded holes 13 joining up therewith. Moreover, two fitting pins 14 are provided, each of which has a threaded tail portion 15 at its end directed towards the clamping portion 2. By means of this threaded tail portion 15 the fitting pin is screwed into the threaded hole 13, the pin engaging in the fitting hole 12.

Provided in the end face 10 of the head portion 3 are two fitting holes 16 extending coaxially with the cylindrical fitting pins 14.

The front ends of the fitting pins 14 project beyond the front face 11 and engage in these fitting holes 16. As a result, the head portion 3 is located in a predetermined position with respect to the clamping portion 2, so that, as can be seen from Fig. 2, the walls of the swarf ducts 5 provided in the head portion 3 are exactly in alignment with the walls of the swarf ducts 5 provided in the clamping portion 2.

In its front end, each fitting pin 14 has a transverse bore 17 extending radially with respect to the axis B of the boring tool. A retaining pin 18 is guided slidably in this transverse bore 17. A retaining screw 19 is arranged in the head portion 3, the axis C of the screw likewise extending radially with respect to the axis B of the boring tool. At its radially inner end, the retaining screw 19 has a conical tail 20 which engages in a corresponding conical recess 21 in the retaining pin 18. The retaining pin 18 has at its radially inner end a conical tail 22 which engages in a corresponding conical recess 23 in the head portion 3. The centre Z of this conical recess 23 is arranged to be coaxial with the axis C of the retaining screw 19.The apex angles of the conical tails 20, 22 and of the conical recesses 21, 23 are of the same size and are preferably about 90 .

It is important that the axis C of the retaining screw 19 is not exactly in alignment with the axis D of the transverse bore 17. The axis C of the retaining screw 19 is at a distance A from the end face 10 of the head portion 3, this distance being a little greater than the distance a of the axis D of the transverse bore 17 from the front face 11 of the clamping portion 2. The difference between the two distances A and a may be about 0.5 mm.

If the retaining screw 19 is tightened, its conical tail 20 comes into abutment against that side of the conical recess 21 in the retaining pin 18 which is remote from the front face 11. As the screw 19 is tightened the retaining pin 18 is shifted in the axial direction until its conical tail 22 comes into abutment in the recess 23 and in fact on that side which is towards the front face 11. As a result, a force directed towards the clamping portion 2 is exerted on the head portion 3 and presses the end face 10 hard against the front face 11. If the bias of each of the two retaining screws is, for example, 2000 kp, a force of 4000 kp directed towards the boring tool axis originates from each retaining screw, so that a contact force of the head portion 3 against the clamping portion 2 amounting to a total of 8000 kp is produced.This force is more than sufficient, especially as the transmission of the torque takes place via the fitting pins 14, which are subjected to shearing stresses by the torque.

If the head portion 3 is to be replaced, it is merely necessary to screw the retaining screws 19 out and the retaining pins 18 can then be removed. In order to facilitate this, each of the retaining pins 18 may be provided with a threaded bore into which a longer pin likewise having a thread at its front end can be screwed. By means of this longer pin, each of the retaining pins can then be withdrawn from the transverse bore 17. The head portion 3 can then be pulled off the fitting pins 14 and be exchanged for a new head portion.

Thus, in every case in which only the head portion is damaged, it is necessary to replace only the head portion 3. The material needed for making the head portion is about only one seventh of the material which is needed for a complete boring tool.

In the embodiment shown in Figs. 2 to 4, parts with the same function are designated by the same reference numbers as in Fig. 1, so that the above description applies in an equivalent manner. In this embodiment, however, the fitting pin 14' is provided with a longitudinal bore 24. By means of a fixing screw 25 passing through this longitudinal bore 24 and engaging in the threaded hole 1 3, the fitting pin 14' is fixedly connected to the clamping portion 2. In the head portion 3', a retaining screw 19 can be screwed in radially with respect to the axis of the fitting pin 14'.This retaining screw engages by means of its conical tail 20 in an annular recess 26, the cross-section of which tapers conically towards the axis of the fitting pin. in this case also, the arrangement is such that the axis C of the retaining screw 19 is at a distance A from the end face 10 of the head portion 3 which is a little greater than the distance a of the centre Z of the recess 26 from the front face 11. When the retaining screw 19 is tightened, its conical tail 20 comes into abutment in the recess 26 on one side and forces the head portion at its end face 10 against the front face 11. To exchange the head portion 3', it is merely necessary to screw the retaining screws 19 out a little.

In the embodiment shown in Figs. 6 and 7, parts having a like function are also designated by the same reference numbers as in Figs. 1 to 5 and the description given in connection with the embodiment according to Figs. 1 and 5 likewise applies in an equivalent manner. In this embodiment, however, the retaining pin 18' and the retaining screw 19' are somewhat differently formed. The retaining pin is provided at both ends with conical tails 22, 22a, respectively. The tail 22 engages in a conical recess 23 provided in the head portion 3. The conical tail 22a cooperates with a conical recess 27 provided in the retaining screw 19'. In this case also, the axis C of the retaining screw 19' is at a distance A from the end face 10 which is a little greater than the distance a of the axis D of the transverse bore 17 from the front face 11.If the retaining screw 19' is tightened, its conical recess 27 comes into abutment against that side of the conical tail 22a which is towards the front face 11. As a result, the retaining pin 1 8' is shifted in the axial direction until its conical tail 22 comes into abutment in the recess 23 and in fact on that side which is likewise towards the front face 11. In this way, a force directed towards the clamping portion 2 is exerted on the head portion 3 and presses the end face 10 hard against the front face.

The length of the retaining pin 18' is advantageously a little less than the diameter of the fitting pin 14. The result of this is that when the retaining screw 19' is released and the two parts 3, 2 are shifted with respect to one another, the retaining pin 18' can enter the transverse bore 17 completely. Due to the conical form of its tail 22 and the conical recess 23, the retaining pin 18' is pushed into the transverse bore 17. The apex angle of the conical tails 22, 22a and of the recesses 23, 27 is also about 90 in this embodiment.

In order to be able to adapt the boring tool to different machining requirements, in the embodiment shown in Fig. 6 an intermediate piece 28 can be inserted between the head portion 3 and the clamping portion 2, this intermediate piece being designed like the front end of the clamping portion 2' at its front end facing the head portion 3 and its rear end facing the clamping portion 2' being designed like the back of the head portion 3.

Therefore, a radially extending plane front face 11 with fitting pins 14 is provided at the front end 28a and a plane end face 10 with corresponding fitting holes 16 is provided at the rear end 28b. The diameter of the fitting pins 14 and of the fitting holes 16 and their radial distance frem the axis of the boring tool correspond in the intermediate piece 28 to the corresponding arrangement in the head portion 3 and the clamping portion 2', so that if necessary the head portion 3 could also be fixed directly to the clamping portion 21.

In the first place, in the embodiment of the boring tool shown in Fig. 6, the head portion 3 can be exchanged in the event of damage in the same way as in the previously described embodiment. In addition, however, the clamping portion 2' can also be exchanged. This is necessary, for example, when the boring tool is to be used in another machine which has a different receptacle for the cone 6 in its spindle, for instance a receptacle with a different cone angle. In this case, the clamping portion 2' is exchanged for another clamping portion whose cone 6 is suitable for the corresponding receptacle. Instead of a cone, the clamping portion 2' could also have a cylindrical shank or a fixing flange.

Moreover, by employing various intermediate pieces 28, the boring tool can be adapted very well to the particular machining operations. Intermediate pieces 28 of various lengths can be employed and, for example, also two or more intermediate pieces. It is also possible to attach intermediate pieces having a somewhat larger or smaller diameter to the shank portion 2' and head portions with corresponding diameters are then mounted on these intermediate pieces.

The intermediate piece 28 is provided with swarf ducts 5 which are suitably spiral. In Fig.

6, however, for clarity, these swarf ducts 5 are shown in rectilinear form. The join between the intermediate piece 28 and the clamping portion 2' is advantageously made where the swarf ducts 5 have not yet begun.

The different portions of the shank of an embodiment which includes one or more intermediate portions can be held together by arrangements as shown in Figs. 1, 3 and 4 also.

Other embodiments can be constructed, in which, for example, on the clamping portion 2' shown in Fig. 6 a head portion is mounted which is designed to be similar to a core or annular bit.

Claims

1. A boring tool having a substantially cylindrical shank and at least two cutting plates arranged exchangeably on the front head portion of the shank and adjoined by at least two swarf ducts extending to a rear clamping portion of the shank, the swarf ducts being open outwardly of the shank, wherein the shank is formed of at least two separable portions and the clamping portion is detachably connected to the head portion which, at its back remote from the cutting plates, bears directly or indirectly with a radially extending plane end face against a radially extending plane front face of the clamping portion, at least two cylindrical fitting pins are let into and fixed in the front face of the clamping portion, the fitting pins being engageable in corresponding fitting holes in the end face of the head portion, and on the head portion there are provided retaining means for acting on the fitting pins, or vice versa.

2. A boring tool according to claim 1, wherein in comparison with the clamping portion the head portion is short and the joint between the two portions is arranged in the region of the swarf ducts.

3. A boring tool according to claim 1 or 2, wherein there can be inserted between the head portion and the clamping portion at least one intermediate piece which is designed like the front end of the clamping portion at its front end facing the head portion and whose rear end facing the clamping portion is designed like the back of the head portion.

4. A boring tool according to claim 1 or 3, wherein each fitting pin is connected to the clamping portion and/or the intermediate piece by means of a screw connection.

5. A boring tool according to claim 4, wherein the fitting pin is provided with a threaded tail portion at its end directed towards the clamping portion and/or the intermediate piece, this threaded tail portion being screwed into a threaded hole in the clamping portion and/or in the intermediate piece.

6. A boring tool according to claim 4, wherein the fitting pin has a central bore through which a fixing screw screwed into a thread hole in the clamping portion and/or in the intermediate piece passes.

7. A boring tool according to claim 1 or 3, wherein the retaining means is a retaining screw screwed into the head portion radially with respect to the axis of the fitting pin and engaging by means of a tail provided at its radially inner end in a recess in the fitting pin.

8. A boring tool according to claim 7, wherein the tail is conical and the recess tapers conically towards the axis of the fitting pin.

9. A boring tool according to claim 8, wherein the axis of the retaining screw is at a distance from the end face of the head portion which is a little greater than the distance of the centre of the recess from the front face of the clamping portion.

10. A boring tool according to claim 8, wherein each fitting pin has a transverse bore extending radially with respect to the axis of the boring tool, the axis of the transverse bore being at a distance from the front face of the clamping portion which is a little smaller than the distance of the axis of the retaining screw from the end face, and in the transverse bore there is slidably guided a retaining pin whose radially outer end facing the retaining screw has a conical recess and whose radially inner end engages by means of a conical tail in a conical recess provided in the head portion, the centre of which latter recess is arranged coaxially with the axis of the retaining screw.

11. A boring tool according to claim 1, wherein each fitting pin has a transverse bore extending radially with respect to the axis of the boring tool, the axis of the transverse bore being at a distance from the front face of the shank which is a little smaller than the distance of the axis of a retaining screw which can be screwed into the head portion radially with respect to the axis of the fitting pin from the end face, and in the transverse bore there is slidably guided a retaining pin whose radially outer end facing the retaining screw engages by means of a conical tail in a conical recess in the retaining screw and whose radially inner end engages by means of a conical tail in a conical recess provided in the head portion, the centre of which latter recess is arranged coaxially with the axis of the retaining screw.

1 2. A boring tool according to claim 11, wherein the length of the retaining pin is smaller than the diameter of the fitting pin.

13. A boring tool according to any one of the preceding claims, wherein the apex angle of the tail and of the recess is of the same size and is about 90 .

14. A boring tool substantially as described hereinbefore with reference to Figs. 1, or Figs. 2, 3 and 4, or Figs. 6 and 7 of the accompanying drawings.

15. A boring tool according to claim 1 and substantially as described hereinbefore with reference to Fig. 5 of the accompanying drawings.