a drilling tool 1 according to an embodiment of the invention is shown in a perspective view in fig1 , in a side view in fig2 and in a plan view in fig3 . the drilling tool 1 is composed of a support shank 2 and of a cutting insert 3 fitted to the support shank 2 . in the axial direction 4 , the support shank 2 has essentially two different functional regions — a cylindrical clamping region 5 of constant diameter , which is clamped in a chuck ( not depicted ) for connecting the drilling tool 1 to a machine , and a fluted region 6 which has a maximum radial extent varying in the axial direction 4 and which functions together with the cutting insert 3 as an actual cutting tool . arranged on the end of the fluted region 6 which is remote from the clamping region 5 is the cutting insert 3 , which can be seen separately from various perspectives in fig4 to fig6 . in simple terms , the cutting insert 3 is fixed to the support shank 2 by inserting a fastening pin 7 , integrally formed on the cutting insert 3 , into a central recess ( not shown ) in the end face of the support shank 2 and by pressing two peripherally arranged lobes 8 on the cutting insert 3 into correspondingly formed receptacles 9 on the support shank 2 on the basis of a rotation of the cutting insert 3 relative to the support shank 2 . the details of this fastening can be seen from patent document ep 1 476 269 b1 , which comes from the applicant , the disclosure of which is incorporated by reference herein . the configuration of the cutting insert 3 , in particular the cutting edge geometry , is likewise based on inventions of the applicant . these inventions are described in de 10 2006 025 294 a1 and in de 2009 012 725 already mentioned and not yet published , the contents of which are also incorporated by reference herein . accordingly , the cutting insert 3 has an asymmetrical main lip 15 split in two into a guide lip 10 having a supporting land 12 and a guide land 23 trailing the supporting land 12 and into a clearance lip 13 having a trailing clearance portion 14 . it should be noted here that , depending on the point of view , it is also possible to refer to two main lips a , b connected to one another by a chisel edge 16 , instead of a two - part main lip 15 . both alternatives are common in the corresponding technical literature . in the case of the exemplary embodiment , the asymmetry of the main lip 15 is produced by one part of the main lip 15 being swung by an angle α ( fig5 ), which is about 13 ° here , relative to its symmetrical position . this symmetrical position corresponds in this case to a position relative to the other part of the main lip at which an imaginary 180 ° rotation of the one part of the main lip about the center longitudinal axis 17 of the drilling tool 1 leads to a congruent superimposition with the other part of the main lip . however , the shapes of the end cutting edges of the two main lip parts show no relevant differences and are each substantially characterized by adjoining machined point thinning 18 . the asymmetrical design of the cutting insert 3 is continued consistently by the further cutting and guiding elements provided . secondary lips 21 adjoin the lip corners 20 in the axial direction 4 , the lip corners 20 peripherally defining the two parts of the main lip 15 , in each case in the radial direction 19 . a respective supporting land 12 , 22 is assigned to both secondary lips 21 . a guide land 23 is integrally formed peripherally on the lobe 8 , which is connected to the guide lip 10 via a main flank 24 . this guide land 23 has a significantly larger characteristic width than the two supporting lands 12 , 22 . all the other peripheral or secondary flanks 25 of the cutting insert 3 without a cutting or guiding effect are reduced in the radial extent thereof relative to the secondary lips 21 or the lands 12 , 22 , 23 on the cutting insert 3 . in this way , the risk of canting or seizing of the drilling tool 1 is kept low . three guiding lands are likewise provided on the support shank 2 . these are the guide land 28 and the two supporting lands 27 , 29 . these lands complement the corresponding lands 12 , 22 , 23 on the cutting insert 3 and form a continuous development . in interplay , the guide lands 23 , 28 and the supporting lands 12 , 22 , 27 , 29 of cutting insert 3 and support shank 2 thus guide the drilling tool 1 on the inner wall of the drill hole during the drilling operation . in analogy to the cutting insert 3 , secondary flanks 30 having a reduced radial extent are provided between the lands 27 , 28 , 29 of the support shank 2 . the region of the support shank 2 which actively guides the drilling tool 1 corresponds , in the exemplary embodiment , approximately to the first third , adjoining the cutting insert 3 , of the fluted region 6 . in that third , the support shank 2 has a constant radial extent . after that , the support shank 2 tapers in the axial direction 4 . outside the guiding region of the support shank 2 , the guide land 28 and the supporting lands 27 , 29 have no technical function , and so the geometry thereof may be varied there , for example , for the benefit of a simplified production process . furthermore , the shaping of two chip spaces 31 is essential for the asymmetrical configuration of the cutting insert 3 . one chip space 31 each is incorporated into the cutting insert 3 in such a way as to lead one part each of the main lip 15 . the chips are formed in the chip spaces 31 during the drilling operation . the walls of the chip spaces 31 thus form chip - forming surfaces . to ensure as effective a chip disposal as possible , the flutes 32 formed in the support shank 2 are adapted in their configuration to the chip spaces 31 . in this way , the flutes 32 also extend the chip spaces 31 in the axial direction 4 continuously and — apart from production tolerances — seamlessly . the asymmetrical design of the chip spaces 31 and accordingly of the flutes 32 originates in turn from the asymmetry of the main lip 15 and from the angle α resulting therefrom , which in the exemplary embodiment is about 13 °. the corresponding swing of the main lip 15 by the angle α is compensated for on the support tool by the flutes being correspondingly adjusted continuously by the magnitude of the angle α . outlet openings 33 of cooling passages open into the flutes 32 on the support shank 2 . these cooling passages serve to introduce a cooling lubricant into the drill hole during the cutting process . this configuration of the cooling passages with the outlet openings 33 thereof opening out into the flutes 32 is the subject matter of the applicant &# 39 ; s european patent application ep 16 48 642 b1 , the contents of which are incorporated by reference herein . in summary , the invention enables any desired asymmetrical configuration of the cutting insert 3 to be combined with a correspondingly adapted support shank 2 , the support shank in this case being provided with guide elements which also control and thereby improve the concentric running behavior of the drilling tool . while specific embodiments of the invention have been described in detail , it will be appreciated by those skilled in the art that various modifications and alternatives to the details provided herein could be developed in light of the overall teachings of the disclosure . accordingly , the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof .