DE19710996A1 - Drilling tool with cutting inserts - Google Patents

Abstract

The drilling tool has a shaft (1) with recesses for at least two exchangeable cutting inserts (2). It has cutting edges extending to the external diameter of the endface of the shaft and corners creating the diameter of the boring, fitted in each recess. One cutting insert has a longer cutting edge at the end face than the other, which is offset about 180 degrees. There is also an exchangeable centre cutting insert (3), with at least one one-sided cutter arranged so that its effective diameter exceeds that of the longer cutting edge of the outer cutting insert.

Description

The invention relates to a drilling tool for drilling in solid material or Drilling out with a shaft with recesses for at least two interchangeable ones Cutting inserts whose cutting edges up to the outer diameter of the end face of the Enough shaft and create the bore cylinder wall with two cutting corners, the one cutting insert has a longer cutting edge on the front side than the has another cutting insert arranged offset by approximately 180 ° and one exchangeable center cutting insert, which has at least one centering tip adjoining recessed one-sided cutting edge, which is designed so that the outer radius of the one-sided cutting part has a larger effective diameter has than the inner diameter of the longer cutting edge of the outer Cutting insert.

Furthermore, the invention relates to cutting inserts with at least three rake faces delimiting cutting corners and their arrangement in connection with the Center cutting insert, which has at least one centering tip and with at least an adjacent, recessed, one-sided cutting edge.

Drilling tools with exchangeable cutting inserts as in WO 9302824 A1 described, work so that only one on the outer diameter of the bore Cutting corner is used and only one cutting edge the inner part of the Bore created. This type of drilling tools is single-edged drills. In contrast, the proposed drilling tool drills on the outer drilling diameter and in the center with two cutting edges.

A drilling tool with a drilling knife is shown in EU 0 625 395 A1. The The drilling knife is in one piece and has two starting from the center tip Cutting edges, both of which extend to the outer diameter of the drill. Disadvantageous here is that a separate one for each different drilling diameter Drilling knife is required.  

DE 37 33 298 contains a multi-purpose tool in which at least two Inserts are provided. A cutting edge protrudes radially on the tool, so that the cutting edge can be used for turning. This cutting edge can be on the forehead extend to the center of the tool shank so that they can also be used for drilling and Face milling can be used. The other cutting edge is on the circumference of the tool arranged and therefore suitable for shoulder milling.

DE 44 16 040 A1 shows a double-edged drilling tool with two 180 ° in Offset circumferential cutting in which the two cutting edges from Bore diameter up to the tool center and work minimally extend beyond. This cutting arrangement means that only a very restricted drilling diameter application area per cutting insert size is feasible.

DE 22 36 100 discloses a drilling tool in which the drill shank has one or is equipped with several inserts and a pointed drill-like in the center of the shaft flat center edge with a flat shaft or one with a round shaft is. Also with this tool the must for different drilling diameters Insert size or and the point drill-like center cutting edge different be large because both cutting inserts have the same cutting edge lengths and from outer diameter of the point-like center cutting edge up to Hole diameter is sufficient. The disadvantage of this type of tool is that the chips in the narrow area of the transition between center cutting edge and cutting insert can fix, which then significantly affects the drilling process.

The object of the invention is to provide a multi-bladed drilling tool centering cutting edge and exchangeable cutting inserts which the same cutting inserts and the center cutting edge by different Arrangement in different shaft designs different Can generate drilling diameter.

The object is achieved in that with a new type of center cutting insert, which both with at least one center cutting edge, the one centering and  leading task when drilling, and with an axially recessed, adjacent, one-sided cutting edge is equipped, as well as at least two in outer drill area arranged and with different lengths of cutting edges working cutting inserts drilled, the two outer cutting edges with their outer cutting corners to the wall of the hole.

The center cutting insert is advantageously designed on two sides, so that after Wear of one cutting side the second can be used. To the Clamping and fixing the center cutting edge is provided in an inner cone a clamping screw with a cone engages so that the center cutting insert in its Seat down, axially backwards and on the opposite side from the one-sided cutting edge rests radially in the mounting hole.

This arrangement ensures that those occurring during drilling Cutting forces in all three directions of force on the opposite surfaces in the Shaft are transferred.

According to the outer diameter area of the end face of the bore performed with cutting inserts, the cutting edges of different lengths exhibit. Both outer cutting corners of the two cutting inserts work on the same diameter, namely the drilling diameter. When cutting with the longer cutting edge, the inside cutting corner must have a smaller or reach at least the same radius as the outer cutting corner of the one-sided Cut the center cutting insert, the cutting planes of the one-sided Cutting edge of the center cutting insert and the long cutting edge of the Cutting insert offset by about 180 ° on the other side of the Drill radius are arranged. The other cutting insert has a shorter one Cutting edge length, the max. from the drilling diameter to close to the radius of the one-sided cutting edge of the center cutting insert can suffice.

For example, known triangular, square, roman or hexagonal cutting inserts come, but they have to be different because the edge lengths are of different lengths.

An advantage of the cutting insert arrangement described above is that the boring of holes is relatively free of lateral forces, and with a pre-drilling off diameter that is larger than the diameter that the short Covers the cutting edge of the cutting insert working on the borehole diameter, completely free of lateral forces.  

If the cutting inserts are rectangular according to the invention, they have two short cutting edges and two long cutting edges. The short cutting edge will placed in extension to the one-sided cutting edge of the center cutting insert. The outside cutting corner lies on the borehole radius. The length The cutting edge is arranged in the shaft of the drilling tool by approximately 180 °, and in such a way that the external cutting corner also works on the radius of the drill. The internal cutting corner of the long cutting edge of the cutting insert must cover the same or smaller radius than the outer cutting corner of the one-sided Cut the center cutting insert. When drilling is now in the areas of Centering tip, from the inner cutting edge radius of the short cutting edge of the Cutting set up to the outer bore diameter and in the Area of coverage between the one-sided cutting edge of the center cutting set and the internal cutting edge of the long cutting edge of the Cutting insert with half the feed per revolution. In the rest of the bore end area, the corresponding cutting area leads the Machining with the full feed per revolution.

The cutting edges of both cutting inserts are larger at an angle α of 0 ° to 20 ° arranged so that those working on the smaller radius Lead the cutting parts axially. This cone also results in a centering effect of the drilling tool and thus advantageously the drill also for package drilling, d. H. suitable for drilling in clamped plates. If a particularly smooth bore surface is to be produced, the Cutting inserts with the external minor cutting edge not or only with one tilted small angle with respect to the bore wall. To get a better one to achieve the centering effect of drilling through the drilling process Cutting inserts at a larger angle to the vertical to the hole. This angle can be 20 ° or more, being general Drilling a good drilling result for this type of tool in the range of 2 ° up to 6 °.

The cutting inserts have rake faces with the known chip shape grooves and / or Chip form elements on, in order to form short chips as possible also when machining different materials and with different technology data to reach.

As a rule, the cutting inserts have holes into which a clamping screw engages to clamp the cutting insert. These holes weaken the  Cutting insert especially in the smaller dimension areas, so that risk of breakage consists. In addition, the clamping screws can not be made too small because then they are no longer manageable and tangible.

In a further embodiment of the invention it is therefore provided that Cutting inserts for smaller drilling diameter ranges instead of a clamping hole to provide a trough-shaped or differently shaped recess in the one appropriately trained nose engages on a clamping finger. When tensioning the Clamping fingers with the tensioning screw will place the cutting insert on the support surface and pressed against the two side supports in the shaft. This is achieved, for example due to the offset position of the clamping hole in the clamping finger to the threaded hole in the shaft.

The internal coolant supply through the shaft is used for cooling and lubrication Drilling process and to remove the chips. A central coolant hole is provided. On the drilling side of the shaft, this drilling is widened on one side Inclusion of the center cutting insert. The center cutting insert is partially included Recesses formed so that coolant directly from the coolant bore the individual cutting points on the center cutting insert can.

In addition, one or more face coolant holes can be arranged at an angle be that in addition from the coolant hole, the coolant to the active points the cutting inserts.

Through this forehead coolant hole can be provided with an angle Expression keys are inserted around a possibly stuck To be able to express center cutting insert. This ensures that after Loosen the clamping screw of the center cutting insert not only manually can be pulled out, but also with a central ejector from the End of the shank which is inserted through the central coolant hole and can express the center cutting insert, but also in the machine from Machining room is interchangeable with the help of a Extraction key that can be inserted through the forehead coolant hole.

Embodiments of the invention are shown in the drawings. Show it:  

Fig. 1 front view of the drilling tool according to the invention.

Fig. 2 plan view of FIG. 1.

Fig. 3 top view with 4 cutting inserts.

Fig. 4 top view with clamping fingers for the cutting inserts.

Fig. 5 a side view with the clamping fingers and cutting insert according to Fig. 4.

Fig. 6 top view with different cutting inserts.

Fig. 7 cutting insert with chip breakers on the long cutting edges.

Fig. 8 cutting insert with chip breakers on all cutting edges.

Fig. 9 section through the forehead coolant bore with a wrench.

Fig. 10 front view of the drilling tool according to the invention with a center cutting insert attached to the shaft end face.

Fig. 11 top view in FIG. 10.

Fig. 12. The drilling tool 32 with the shank and cutting inserts 2 and the center cutting insert 3.

The front view Fig. 1 of the drilling tool shows that the shaft ( 1 ) on the outer diameter offset by about 180 ° carries two cutting inserts ( 2 ) and in the middle the center cutting insert ( 3 ).

The clamping screw ( 4 ) is advantageously provided with a cone tip ( 29 ). Appropriate eccentrically arranged taper bores in the center cutting insert for the threaded hole for the clamping screw ( 4 ) fix the cutting insert in the correct position when tightening it in the intended axial systems ( 7 ) and in the front part of the coolant bore ( 23 ) in the shaft ( 1 ).

Fig. 2 shows the top view of Fig. 1 and shows that the rectangular cutting inserts ( 2 ) are each designed with two long cutting edges ( 2 ') and short cutting edges ( 2 ''), which after wear by turning and changing to Come into play. This rectangular design of the cutting inserts ( 2 ) is particularly advantageous since all four cutting corners ( 24 ) and all four cutting edges ( 2 ') and ( 2 '') are used.

Fig. 3 is also a plan view of the drilling tool, but with four cutting inserts ( 2 ), the associated borehole with the diameter D and the engaged cutting edges are shown in the bottom of the borehole. The center cutting insert ( 3 ) has two centering tips ( 5 ) with the diameter dz. After loosening the clamping screw ( 4 ), the center cutting insert ( 5 ) can be turned so that the second side is used. The advance (a) of the centering tip ( 5 ) causes the entire drilling process to be guided centrally by the guide diameter dz of the centering tip. Shear forces occurring during drilling therefore do not result in the drill running, or only to a small extent. The center cutting insert (3) has in addition to the centering each one-sided cutting edges (5) (6) which are arranged at the angle α. In addition to the centering tip, this one-sided cutting edge drills a partial diameter of the borehole up to the diameter. The internal cutting insert ( 2 ), which works with the long cutting edge ( 2 '), is arranged so that it bores from the diameter di2'i to da2'i. In the coverage area di2'i daz to the covering both the center cutting insert (3) and the cutting insert (2) with the cutting edge (2 '), the feed size is fz. The area of the one-sided cutting edge ( 6 ) of the center cutting insert ( 3 ) in which there is no overlap, namely the diameter range dz to di2'i drills with twice the feed size of fz (2xtz). Different feed sizes also arise with the cutting inserts ( 2 ). According to FIG. 3, overlaps lie in the areas di2''i to da2'i, di2'a to da2''i and from di2''a to the borehole diameter D.

The wear on the cutting edges is different. It is the largest in the cutting corner area, especially on the cutting corners that the Create borehole diameter D. The arrangement of the invention Cutting inserts with overlapping areas and the arrangement of two Cutting corners on the borehole diameter D ensure an optimal balanced total service life of all cutting inserts.  

Fig. 4 shows the top view of a drilling tool which does not clamp the cutting inserts ( 2 ) as shown in Fig. 2 and Fig. 3 with clamping screws ( 8 ), but with clamping fingers ( 9 ). This can be advantageous for particularly small cutting inserts ( 12 ), but also for full drilling in hardened materials in which the cutting inserts consist of extremely hard cutting materials, such as cutting ceramics.

Fig. 5 shows the cutting insert ( 12 ) and clamping finger ( 9 ) in the side view of Fig. 4. With the clamping finger ( 9 ), the cutting insert ( 12 ) is pressed into the insert seat so that it is on the support surface ( 15 ) and the two side systems ( 16 ) and ( 17 ). For this purpose, the clamping screw is arranged so that it not only exerts an axial force when tightening the clamping finger ( 9 ) but also a horizontal force component F which, for example with the help of the radial system ( 10 ), tensions the cutting insert over the nose in the clamping finger in the three necessary directions of force .

Fig. 6 shows that instead of the rectangular cutting inserts, triangular cutting inserts ( 19 ) or square cutting inserts ( 20 ) can also be used. The inventive overlap between the cutting inserts is achieved by the different edge lengths. Fig. 6 is only one example of how a double-edged tool according to the invention can be realized by means of cutting inserts with other than the rectangular cutting inserts ( 2 ) or ( 12 ) in connection with the center cutting insert.

In Fig. 7, a cutting insert is shown, having on each long cutting edge (2 ') comprises a clamping switch (21). This creates two unequal and narrower chips on the cutting edge compared to the relatively wider chip, as would arise with the uninterrupted cutting edge. This has a favorable effect when removing the chips, particularly in the case of relatively deep bores or when removing unfavorable chips.

As another possibility, 8 is shown in Fig., That the chip breaker (22) can also be used on the short cutting edge. This is particularly advantageous when drilling relatively large diameters, since the chips produced here are very wide and therefore difficult to remove. The chip breakers are advantageously placed on the cutting edges in such a way that the cutting edge which is subsequently arranged through 180 ° also carries out the removal not carried out by the chip breaker.

Fig. 9 is the section of FIG. 1 through the front coolant bore ( 25 ). The shaft ( 1 ) of the drilling tool is provided with a central coolant hole ( 23 ). This coolant hole changes into an extension to accommodate the center cutting insert ( 3 ). The center cutting insert with recesses ( 27 ) is designed so that part of the coolant supplied can exit axially parallel on the end face and is available directly at the drilling point for cooling and lubrication. However, this coolant flow also serves above all to remove the chips that arise, in particular the chips that arise on the rake faces of the centering tip and the one-sided cutting edge of the center cutting insert with the associated chip shape geometries, not shown. In order to increase the total coolant flow, one or more coolant bores ( 25 ) are additionally arranged on the end face.

The center cutting insert ( 3 ) can be pulled out of the front of the seat manually after loosening the clamping screw. In order not only to have to work with a centrally inserted ejector in the event of a center cutting insert ( 3 ) possibly jammed by chips, the end coolant bore ( 25 ) is designed and arranged according to the invention in such a way that the center cutting insert ( 3 ) is used with a curved ejection key ( 26 ). can be pulled out or pushed out.

Fig. 10 shows in connection with the plan view Fig. 11 as an example that the center cutting insert ( 33 ), in contrast to the center cutting insert ( 3 ), can be designed differently and arranged on the end face of the shaft ( 10 ), but also the one-sided cutting edge ( 6 ) and centering tip ( 5 ). This center cutting insert is also double-edged. The seat for this center cutting insert ( 33 ) has a bearing surface ( 35 ) which is arranged recessed to the end face of the shaft ( 1 ); it is tensioned with the clamping screw ( 34 ). It is also shown as an example that the position of the one-sided cutting edge ( 6 ) is offset by the angle β from the cutting corner of the centering tip ( 5 ). This can be particularly advantageous when drilling on inclined or uneven surfaces.

Claims (19)

1. drilling tool for drilling in solid material or for boring with a shaft ( 1 ) with recesses for at least two interchangeable cutting inserts ( 2 , 19 , 20 ) whose cutting edges ( 2 ', 2 '') up to the outer diameter of the end face of the shaft ( 1 ) are sufficient and produce the hole D with the cutting corners ( 24 ) and are each arranged in a recess, characterized in that one cutting insert ( 2 , 20 ) has a longer cutting edge on the end face than the other arranged cutting insert offset by approximately 180 ° ( 2 , 19 ) and that an interchangeable center cutting insert ( 3 , 33 ) which is equipped with at least one centering tip ( 5 ) arranged centrally in the shaft ( 1 ) and at least one with an adjoining recessed one-sided cutting edge ( 6 ) which is designed such that the outer radius of the one-sided cutting part describes a larger effective diameter than the inner effective diameter that of the longer cutting edge edge ( 2 ') of the outer cutting insert ( 2 ). 2. Drilling tool according to claim 1, characterized in that the centering tip ( 5 ) in the center of the drilling tool predrilled furthest forward in the borehole and the other cutting corners are further back. 3. Drilling tool according to claim 1 and 2, characterized in that the angular position β of the cutting corners of the centering tip ( 5 ) to the one-sided cutting edge ( 6 ) is of different sizes. 4. Drilling tool according to claim 1 to 3, characterized in that the The cutting corners are axially further back with increasing effective radius. 5. Drilling tool according to claim 1 to 4, characterized in that the cutting inserts ( 2 ) with their cutting edges ( 2 'or 2 '') are arranged at the same angle α with respect to the perpendicular to the borehole axis. 6. Drilling tool according to claim 1 to 5, characterized in that the angle α is preferably from greater than 0 ° to 20 °.   7. Drilling tool according to claim 1 to 6, characterized in that the shaft with central coolant hole is provided. 8. Drilling tool according to claim 1 to 7, characterized in that the center cutting insert is received in the end of the central coolant bore and an adjacent semicircular extension ( 31 ) with axial contact. 9. Drilling tool according to claim 1 to 8, characterized in that the center cutting insert ( 3 ) can be ejected through the central coolant bore ( 23 ) with an ejection rod. 10. Drilling tool according to claim 1 to 8, characterized in that in addition one or more end coolant holes ( 25 ) are provided. 11. Drilling tool according to claim 1 to 10, characterized in that an expression key ( 26 ) can be passed through the front coolant bore ( 25 ). 12. Cutting inserts ( 2 ) for drilling in solid material or for boring with a rectangular basic shape and two long cutting edges ( 2 ') and two short cutting edges ( 2 ''), characterized in that they are used in pairs on the borehole diameter, one with the long one and the other with the short cutting edge. 13. Cutting inserts ( 2 ) according to claim 12, characterized in that a trough-shaped depression ( 28 ) is provided instead of a fastening hole for clamping the cutting insert ( 2 ). 14. Cutting inserts ( 2 ) according to claim 12 and 13, characterized in that chip breaks ( 21 ) on the long cutting edge ( 2 ') are provided. 15. Cutting inserts ( 2 ) according to claim 12 to 14, characterized in that chip breakers ( 22 ) are provided on the short cutting edge ( 2 ''). 16. Cutting inserts ( 2 ) according to claim 12, characterized in that chip breaks ( 21 ) on the long cutting edge ( 2 ') and chip breaks ( 22 ) are arranged on the short cutting edge ( 2 ''). 17, the center cutting insert (3/33) for drilling in solid material, characterized in that it is provided at least one centering point (5) with a diameter (dz) and having at least one unilateral stationary back cutting edge (6). 18. Center cutting insert according to claim 17, characterized in that it is at least provided with a tapered bore for clamping. 19. Center cutting insert according to claim 17 and 18, characterized in that the one-sided recessed cutting edge ( 6 ) is arranged at the same angle α as the cutting inserts ( 2 , 19 , 20 ).