| 1. | Rotatable tool having a replaceable tip (3) at the chip removing free end of the tool, the tool also comprising a tool body (1) having a cutting seat (9), in which the tip (3) is intended to be received, that the tool body (1) has helicoidal or straight chip channels (7), that the tip (3) has members (18) for chip removing machining, and that the cutting seat (9) and the replaceable tip (3) have mutually cooperating support surfaces (10,12,20,21) extending both in the longitudinal direction of the tool and transversely to the longitudinal direction of the tool, c h a r a c t e r i z e d in that the cutting seat (9) and the replaceable tip (3) have mutually co operating guide surfaces (15,22), which are rotationally symmetrical in respect to a longitudinal centre axis (2) of the tool, as well as members (12,17,21) for clamping the replaceable tip (3), when the same is assembled in the cutting seat (9), in the axial direction of the tool, that a locking screw (17) is received in the tool body (1), and that the locking screw (17) brings the replaceable tip (3) to cooperate with the members for clamping the replaceable tip (3) in the axial direction of the tool. |
| 2. | Tool according to claim 1, c h a r a c t e r i z e d in that the members for providing axial clamping of the replaceable tip (3) in the cutting seat (9) consist of cooperating support surfaces (12,21) of the cutting seat (9) and the replaceable tip (3), respectively, and that said support surfaces (12,21) form an acute angle with the longitudinal centre axis (2) of the tool. |
| 3. | Tool according to claim 2, c h a r a c t e r i z e d in that the acute angle is of the order of 5°. |
| 4. | Tool according to any one of claims 13, c h a r a c t e r i z e d in that the mutually cooperating guide surfaces (15, 22) are circular cylindrical. |
| 5. | Tool according to claim 1, c h a r a c t e r i z e d in that the members for providing axial clamping of the replaceable tip (3) in the cutting seat (9) consist of cooperating guide sur faces (15,22) of the cutting seat (9) and the replaceable tip (3), respectively, and that said guide surfaces (15,22) are conical in respect of the longitudinal centre axis (2) of the tool. |
| 6. | Tool according to claim 4, c h a r a c t e r i z e d in that the cone angle is of the order of 10°. |
| 7. | Tip (3) intended to be replaceably assembled in a cutting seat (9) in a tool body (1) at the chip removing free end of a rotatable tool, which tip (3) has members (18,19) for chip removing machining as well as support surfaces (20,21), which are intended to cooperate with support surfaces (10,12) of the cutting seat (9), c h a r a c t e r i z e d in that the tip (3) has guide surfaces (22), which are rotationally symmetrical in respect of a longitudinal centre axis (2) of the tip (3). |
| 8. | Tip (3) according to claim 7, c h a r a c t e r i z e d in that the guide surfaces (22) are circular cylindrical. |
| 9. | Tip (3) according to claim 7, c h a r a c t e r i z e d in that the guide surfaces are conical. |
| 10. | Tip (3) according to claim 9, c h a r a c t e r i z e d in that the cone angle is of the order of 10°. |
The invention also relates to the tip separately. The invention relates, preferably, to a drill or a milling cutter.
Prior Art A tool, in the form of a drill, of the above-defined kind is previously known'from the manufacturer Guhring, in which the drill tip is clamped in the cutting seat thereof by means of two screws. One of the screws is a stop screw, the position of which is fixed in the factory, while the second screw is a tightening screw, which is fastened manually in connection with the drill tip being assembled in the cutting seat thereof. The tightening screw is provided with a conical tip in order to clamp the loose drill tip in the axial direction of the tool.
The cutting seat has parallel side surfaces.
Aim and Features of the Invention A primary aim of the present invention is to describe a tool of the above-defined kind, where the replaceable tip is assembled in the cutting seat thereof in the tool body in a simple and user-friendly way.
Another aim of the present invention is that the tool should be balanced as regards the forces acting on the tool.
Yet another aim of the present invention is that the cut- ting forces should act towards the centre and clamp the cutting insert.
At least the primary aim of the present invention is realised by means of a tool and a tip having the features defined in the subsequent independent claims.
Short Description of the Drawings Below a preferred embodiment of a drill and a drill tip according to the present invention will be described, reference being made to the accompanying drawings, where: Fig 1 shows a perspective view of a drill according to the present invention; Fig 2 shows a perspective view, obliquely from above, of the cutting seat in the drill body, a replaceable drill tip being intended to be received in the cutting seat; Fig 3 also shows a perspective view, obliquely from above, of the cutting seat in the drill body according to Fig 2, the cutting seat in Fig 3 being regarded more in an end view than in Fig 2; Fig 4 shows a side view of the cutting seat in the drill body ; Fig 5 shows a perspective view, obliquely from above, of the replaceable drill tip according to the present inven- tion; and Fig 6 shows a view from below of the replaceable drill tip according to Fig 5.
Fig 7 shows a perspective view from the side of the drill body, wherein a replaceable drill tip being assembled in the cutting seat ; Fig 8 shows a planar view of the stage of the assembly of the replaceable drill tip that is shown in Fig 7; Fig 9 shows a side view of the drill according to the pres- ent invention, i. e. the replaceable drill tip is assembled in the cutting seat of the drill body; and Fig 10 shows a perspective view, obliquely from above, of the drill according to Fig 9.
Reference designations 1) Drill body 2) Centre axis/rotation axis 3) Drill tip 4)- 5) Shank 6)- 7) Chip channels 8)- 9) Cutting seat 10) First support surfaces 11) Central cooling duct 12) Second support surfaces 13) Clearance surface 14) Curved surfaces 15) First circular cylindrical guide surfaces 16) Holes 17) Locking screw 18) Cutting edges 19) Cutting tip 20) Third support surface 21) Fourth support surface 22) Second circular cylindrical surfaces 23) Stop face 24) Second cooling duct 25) Third cooling duct 26) Chip release surface 27) Chip release surface Detailed Description of a Preferred Embodiment of the Present Invention The drill according to the present invention illustrated in Fig 1 comprises a drill body 1 and a replaceable drill tip 3.
The drill body 1 is provided with a shank 5 and helicoidal chip channels 7 are arranged in the part of the drill body 1 which
is situated between the shank 5 and the replaceable drill tip 3. The shank 5 is intended to be received in a holder in a machine tool. The front surface of the drill body 1, i. e. the surface in which the drill tip.. 3 is assembled, is generally conical.
In Figs 2-4, a cutting seat 9 arranged in the drill body 1 is shown in more detail, the cutting seat 9 being arranged at the end of the drill body 1 which is turned from the shank 5.
The cutting seat 9 of the drill body 1 comprises a plurality of different surfaces, which should co-operate to give a satisfactory support in an optimal way for the replaceable drill tip 3 when this is assembled in the cutting seat 9. Thus, the cutting seat 9 comprises two internal, first support surfaces 10 for the replaceable drill tip 3, the first support surfaces 10 having an extension transverse to the longitudinal direction of the drill. The first support surfaces 10 are situated diametrically opposite in respect to a central cooling duct 11 of the drill body 1. Radially outwards, the first support surfaces 10 are delimited by the chip channels 7.
Furthermore, the cutting seat 9 comprises internal, second support surfaces 12 for the replaceable drill tip 3, said second support surfaces 12 forming an angle of approx. 5° to the rotation axis 2 of the drill, which also constitutes a lon- gitudinal centre axis 2 for the drill and for the replaceable drill tip 3. As is most clearly seen in Fig 4, the second sup- port surface 12 leans inwards towards the axis of rotation 2 in the direction of the open end of the cutting seat 9. The func- tion of the second support surface 12 will be described in more detail below. A clearance surface 13 is situated radially inside each one of the second support surfaces 12, it is not intended that the clearance surface 13 should abut against the replaceable drill tip 3 when this is assembled correctly in the cutting seat 9, which thus has two clearance surfaces 13 which are situated diametrically opposite in respect of the central cooling duct 11. The clearance surfaces 13 are somewhat parallel displaced in relation to respective second support surface 12 in the direction away from the centre of the drill.
Furthermore, the cutting seat 9 comprises two curved surfaces 14 extending radially, which bridge on the one hand, the surfaces 12 and 13 and on the other hand the surface 10.
The curved surfaces 14 are not intended to abut against the replaceable drill tip 3 when this is assembled in the cutting seat 9.
Furthermore, the cutting seat 9 comprises two internal, first circular cylindrical guide surfaces 15, which are situated diametrically opposite in respect to the central cooling duct 11. The internal, first circular cylindrical guide surfaces 15 join the clearance surfaces 13.
The drill body 1 has a hole 16 extending towards the centre of the drill body 1, the said hole extends from the outside of the drill body 1 and intersects one of the internal, first circular cylindrical guide surface 15. The radially extending hole 16 is intended to receive a locking screw 17, which is shown schematically in Fig 5 together with the replaceable drill tip 3. The hole 16 should be internally threaded while the locking screw 17 has an external thread.
The replaceable drill tip 3 is shown in Figs 5 and 6, the drill tip 3 having a generally elongated shape which fits into the cutting seat 9. Chip removing members in the form of two cutting edges 18 are arranged at the free end of the replaceable drill tip 3, as in the assembled state in the cutting seat 9, each and every one of which extends from opposite short sides of the replaceable drill tip 3 to a cutting tip 19 of the replaceable drill tip 3.
The replaceable drill tip 3 has a continuous, external, third support surface 20, see Fig 6, which is situated on the side of the replaceable drill tip 3 that is turned away from the cutting edges 18 for co-operation with the internal, first support surfaces 10 of the cutting seat 9.
The replaceable drill tip 3 also has two external, fourth support surfaces 21, which in the assembled state of the replaceable drill tip 3 are intended to come into abutment against the internal, second support surfaces 12 of the cutting seat 9. The external, fourth support surfaces 21 have, in that
connection, in the assembled state of the replaceable drill tip 3, a corresponding inclination as the internal, second support surfaces 12 in relation to the longitudinal centre axis 2 of the drill. In the embodiment illustrated, this inclination is approx. 5°.
For co-operation with the internal, first circular cylindrical guide surfaces 15, the replaceable drill tip 3 has two external, second circular cylindrical guide surfaces 22, which in the assembled state of the replaceable drill tip 3 in the cutting seat 9 come into co-operation with the internal, first circular cylindrical guide surfaces 15.
The replaceable drill tip 3 also has a stop face 23 for the end of the locking screw 17 which comes into abutment against the replaceable drill tip 3 when the same is clamped in the cutting seat 9. The line of force of the locking screw 17 is besides the longitudinal centre axis 2 of the drill in order to provide rotation of the replaceable drill tip 3 when the same is assembled in the cutting seat 9, see below. Suitably, the line of force of the. locking screw 17 forms an angle of approx.
30° having a radius which extending through the centre axis 2 and through the centre of the hole 16 where the hole 16 intersects the periphery of the tool body 1. In connection with the external, second circular cylindrical surfaces 22 of the replaceable drill tip 3, external, second and third cooling ducts 24 and 25 are arranged, the cooling duct 24 which is situated on the same side as the locking screw 17 having an increasing depth adjacent to the locking screw 17, in comparison with the cooling duct 25.
The replaceable drill tip 3 also has chip release surfaces 26,27 in connection with the cutting edges 18 and the drill tip 19.
At the assembly of the replaceable drill tip 3 in the cutting seat 9, the replaceable drill tip 3 is clamped in the cutting seat 9 in the way which is shown in Figs 7 and 8, i. e. the external, third support surface 20 of the replaceable drill tip 3 abuts against the internal, first support surfaces 10 of the cutting seat 9. In that connection, there has to be a cer-
tain tolerance between the internal, first circular cylindrical guide surfaces 15 of the cutting seat and the external, second circular cylindrical guide surfaces 22 of the replaceable drill tip 3. As is most clearly seen in Fig 7, the replaceable drill tip 3 is, during the initial stage of the assembly, not turned to the final position thereof but there is a play between the internal, second support surfaces 12 of the cutting seat 9 and the external, fourth support surfaces 21 of the replaceable drill tip 3. On turning of the replaceable drill tip 3 clockwise in Fig 8, the external, fourth support surfaces 21 come into abutment against the respective internal, second support surfaces 12. The turning may either take place manually or by the locking screw 17 affecting the stop face 23 of the replaceable drill tip 3. In case manual turning is used, a follow-up tightening operation has to take place by means of the locking screw 17 in order to guarantee that a satisfactory abutment is established between the internal, second support surfaces 12 and the respective external, fourth support surfaces 21. It is advantageous that the internal, second support surfaces 12 in the radial direction are situated as far away as possible from the centre of the drill body 1. Thereby, a. better torque is obtained for the support force, by which the internal, second support surfaces 12 effect the respective external, fourth support surfaces 21 of the replaceable drill tip 3.
At the turning of the replaceable drill tip 3 clockwise in Fig 8, also the internal, first circular cylindrical guide surfaces 15 will have a guiding co-operation with the respective external, second circular cylindrical guide surfaces 22, i. e. the replaceable drill tip 3 will rotate in respect of the longitudinal centre axis 2 of the drill according to the present invention.
On drilling with the drill according to the present invention, the cutting forces will effect the replaceable drill tip 3 in such a way that the same is pressed against the internal, second support surfaces 12. Once the drilling has started, the cutting forces provide a clamping and centring of
the replaceable drill tip 3 in the cutting seat 9, on one hand by co-operation between the support surfaces 12 and 21 and on the other hand between the guide surfaces 15 and 22. At that stage, the locking screw 17 has in principle no significance for the clamping of the replaceable drill tip 3 in the cutting seat 9.
In this connection, it should be pointed out that in stage where the replaceable drill tip 3 is assembled in the cutting seat 9, there is in principle no contact between the replace- able drill tip 3 and the clearance surfaces 13 or the radial, curved surfaces 14.
The replaceable drill tip 3 according to the present invention is preferably made from cemented carbide, this being sintered in a first step. Then, grinding of the geometry of the replaceable drill tip 3 is carried out in a geometry-grinding fixture having high accuracy. Preferably, the external, fourth support surfaces 21 and the external second circular cylindri- cal guide surfaces 22 are sintered while grinding only is car- ried out of the cutting edges 18, the tip 19 and the external third support surface 20.
When a replaceable drill tip 3 is consumed, the locking screw 17 is loosened and a new replaceable drill tip 3 is assembled in the cutting seat 9.
It is general for the tool according to the present invention that the tip is manufactured from cemented carbide, ceramics or another comparatively hard material. The tool body is manufactured from a comparatively softer material, pref- erably steel.
The tool according to the present invention is preferably intended for chip removing machining of metal, but it is fully possible to use the tool also for other materials in which the tool works.
Feasible Modifications of the Invention In the above-described embodiment, the guide surfaces 15 and 22 are circular cylindrical while the support surfaces 12 and 21 lean at a certain angle in relation to the longitudinal
centre axis 2 of the drill. However, within the scope of the present. invention it is also possible that the guide surfaces 15 and 22 are slightly conical in relation to the longitudinal centre axis of the drill while.. the support surfaces 12 and 21 have an extension parallel to the longitudinal centre axis 2 of the drill. Then, co-operation between the conical guide surfaces 15 and 22 will clamp the replaceable drill tip 3 in the axial direction. In this case, the cone angle is suitably of the order of 10°. It is general for the guide surfaces 15 and 22 that they should be rotationally symmetrical in respect of the longitudinal centre axis 2 of the drill.
In the above-described embodiment, the support surfaces 12 and 21 have an inclination in relation to the longitudinal centre axis 2 of the drill of approx. 5°. However, the size of this inclination/angle can be varied within the scope of the present invention, at which in an exemplifying and not limiting aim it may mentioned that the angle should be greater than 0° and less than 10°, preferably between 2° and 8°. The angle in question has to be acute. The same is valid also in case when the co-operating guide surfaces of the cutting seat and the replaceable drill tip, respectively, are conically formed, at which in that case the cone angle should be greater than 5° and less than 15°.