DE8115158U1 - CUTTING TOOL HEAD, IN PARTICULAR LOWERING AND / OR FRICTION TOOL HEAD - Google Patents

Description

Patent attorney MülbenganstaSö > · M ι ■ Authorized representative at Dipl.-Ing. Volkhard Kratzsch D-7300 Esslingen European Patent Office

Telephone Stuttgart (0711) 317000 Deutsche Bank Esslingen 210906 cable «krapatent» esslingenneckar Postscheckamt Stuttgart 10004-701

Hermann BiIz GmbH S Co 15, May 19B1

73 Esslingen - Attorney's file 3235

Cutting tool head, especially countersinking and / or reaming tool head

The invention relates to a cutting tool head, in particular Countersink and / or reaming tool head, of the type otherwise defined in the preamble of claim 1. Such a The tool head is therefore single-edged or triple-edged, but can also be double-edged or with more than three Cutting · be equipped.

It is either detachably connected to a carrier or holder or in one piece with a tool shank.

Even if the cutting tool heads of this type Cutting inserts on the longitudinal edges free of cutting edges with a arcuate guide surface are provided (DE-GM 78 35 B14), the curvature of which is adapted to the cylinder wall of the bore to be produced, so that the tool extends over this bevel-like bore Guide surfaces in the bore centered radially and thereby guided, it is not possible with such tool heads even with elaborately designed machine tools with particularly high-quality spindle bearings, bores are now included low tolerance and high quality, especially with fits in

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Range e.g. 177 to IT9. This is due to the tolerances with which not only the indexable inserts are manufactured, but also in particular the mounting seats in the tool head for the indexable inserts, the bores for screwing the indexable inserts, etc. Also i is turning or exchanging the indexable inserts Responsible for ensuring that the tool head does not guarantee the level of accuracy that is otherwise only expected in fine machining. · ? ■ '

The invention is based on the object of a cutting | tool head defined in the preamble of claim 1 | Generate to create in which in the design as a single-edged tool, the at least one indexable insert; and two guide elements or edged in the design as a three-L tool, the three cutting inserts can be adjusted solution on Pas-1, either either individually
or all central and even. The setting should be problem-free
and be possible without special specialist knowledge. The effort,
in particular weight and cost, for this should if possible
be low.

With a cutting tool head, the task is the one in the upper | concept of claim 1 defined type according to the invention;

by the features in the characterizing part of claim 1
solved. Thanks to such a central and common to all existing cutting inserts and / or guide elements
and evenly radially acting adjustment device,
those in the area of the material elasticity of the head end and
thereby reversibly adjusted, the tool head can be
set in such a way that you can drill holes with a low tolerance
and high quality, especially with fits, for example in the area
IT7 to IT9 and of course also larger. The>'

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The tool head can therefore be adjusted to fit. Because of the uniform, central adjustment, the central axis is retained and thus the concentricity with which the cutting plates and / or guide elements to the tool center axis are positioned. This means that a pitch is also possible. The middle of the precisely created The hole coincides with the center of the tool head and the center to which all cutting inserts and / or guide elements have the same radial distance. The center of the hole is therefore not lost. Since the inventive Adjusting device does not rely on a radial displacement movement of the cutting plates and / or guide elements longitudinally provided guide surfaces works towards, but the uniform, radial adjustment through elastic material deformation is effected in the area of the material elasticity of the head end, this adjustment movement is reversible, without the need to apply special adjustment forces in this reverse direction. The adjustment device works only in one direction, namely radially from the inside to the outside. The reset radially from the outside to the inside happens automatically due to the elasticity of the material, when the adjustment device is reset again. • Another advantage is the relatively low cost and Weight expenditure in relation to the benefits achieved. In addition, the adjustment device is easy to use. It enables one from the manufacturer of the tool cap Adjustment for fit in the same way as with the user, and the latter also when the user uses the indexable inserts rotated or completely replaced.

Instead, the same advantages are also achieved with a design according to claim 2. This adjustability each individually is advantageous, for example, if the tool head has a very large diameter. It is also advantageous that the exact centric and coaxial machining here not applicable. An adjustment is possible individually for each bracket seat.

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Advantageous .Ation guide forms η result from the claims 3 - 5. The design according to claim 7 is particularly advantageous. The design of the expansion hole as The conical bore and the expansion core as a conical core has the advantage that the conical core is pressed into the conical bore Generates radially outwardly directed forces, diB over the entire axial length of the indexable inserts and the Bracket seats for this are uniform and of the same size. If you look at the adjustment, for example, the radially outside lying, cutting edge-free longitudinal edges of the indexable inserts, which are aligned axially parallel, this alignment is not changed when the cone core is pressed in. The indexable inserts are adjusted parallel to these longitudinal edges. It goes without saying that these adjustment movements lie in the left area.

It can be advantageous if the cone angle is in the self-locking area lies. The cone of the cone bore and the cone core can be, for example, a Morse taper. This ensures that when adjusting by screwing in the cone core, the position established due to the self-locking is maintained permanently and the cone core cannot adjust or loosen by itself.

The training according to claim 10 can be advantageous, whereby the cone core can be quickly and easily replaced with a conventional one Allen key, which is always at hand, can be adjusted. Above all, it ensures that the elements of the The adjustment device at the head end does not protrude at the front and may be in the way there.

Further, advantageous designs result from the claims 11-17 This ensures that of the expansion bore, in particular the conical bore, only the wall surfaces with the expansion core, in particular the cone core, are in contact and cooperate, which are located on the circumferential area the mounting seats for the indexable inserts and / or guide elements are located. The wall areas that

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in the circumferential direction run between them, i.e. ζ.Β. for a three-edged tool with three indexable inserts ζ. B. extend on the circumferential angle section of about BQ - 100 between two wall surfaces, however, are not in contact with the expansion core, in particular the conical core, and are then not loaded when this core is screwed in or unscrewed. If the expanding core,

in particular conical core, screwed, so it acts defined to only those wall surfaces in the peripheral region of the _Hal-:; seats that it is in contact with. It will

So there is a targeted one in the area of material elasticity

(, horizontal loading made where it is about to be adjusted

to fit is necessary. The adjustment takes place with a central | 5 order at every point on the circumference simultaneously and exactly the same, so that

I the center of the tool even after the end of the adjustment

I is preserved. The one between the wall surfaces described

I located radial recesses create a free space,

I into the elastic deformation of the material

i can dodge this elastically. Through the shape of the gutter

I these recesses, viewed in the axial direction, and the

I at least as large an axial length as that of the expansion bore, |. in particular cone beating, it is ensured that this

$ Free space into which the material can move over

I the total axial length is given on that of the cone core

I her the action of force happens.

Further advantageous embodiments contain the claims 18-20. This makes the reversibility of the

• permanent position and reproducibility guaranteed,

; as well as a highly accurate concentricity of the tapered bore with threading in the tool head and in an associated manner of the screwed-in Keeelkernes with thread shank.

It can also be advantageous if the expanding core has a preferably incorporated core mark and the end face a preferably incorporated reference mark sequence at the head end, in particular setting scale, carries. Depending on the selected taper and selected thread pitch, there is then one turn

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of the cone core sine by a predetermined circumferential angle Defined setting of the outside diameter of the tool head assigned. It is therefore particularly easy to set the desired setting by turning it accordingly of the cone core.

Further details and advantages result from the following Description.

The complete wording of the claims is not reproduced above solely to avoid unnecessary repetition, but instead only referred to by naming the claim number, which, however, all of these claim features as being expressly disclosed at this point and essential to the invention.

The invention is illustrated below with the aid of one of the drawings illustrated embodiments explained in more detail. Show it:

Fig. 1 is a schematic perspective view

a cutting tool head without a shaft or Carrier, according to a 1, embodiment.,

FIG. 2 shows a view of the underside of the cutting tool in FIG. 1,

3 shows a schematic axial longitudinal section along the line III-III in FIG. 2 with the screwed out Sprsizksrn,

4 shows a section IV of a part of the indexable insert in FIG. 2, on a larger scale .

FIG. 5 shows a view roughly according to FIG. 2 of part of a cutting tool head according to a second embodiment.

The cutting tool head in Fig. 1-4 consists in particular of a countersinking tool head and / or reaming tool head, it is In the embodiment shown, it has three cutting edges and is equipped with three interchangeable indexable inserts 10-12. These are at approximately equal circumferential angular distances from e.g.

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120 ° from each other. Such a structure is basically known CDE-Gl ⁷ I 78 35 814). As is not further shown, the cutting tool cap is either detachably connected to a shaft or carrier or in one piece with a coaxial shaft. The indexable inserts 10 to 12 are fixed in a conventional manner in associated mounting seats 13 to 15 of the head end 16 and clamped by means of screws. The indexable inserts 10 to 12 have cutting edges 18 to 20 on their lower edges in FIGS. 1 and 3, which protrude beyond the surface 17 at the front end, which are effective for countersinking and / or reaming. The opposite, parallel edges are designed as such cutting edges, so that the indexable inserts 10 to 12 can be rotated by 180 ° so that these cutting edges are then used. The two other cutting edge-free longitudinal edges of the indexable inserts 10 to 12 are, as shown in FIG 78 35 814 is under protection. The arcuate guide surface 21 runs along the section of a circular arc 23, indicated by dashed lines, which is at least approximately the same as that of the bore to be produced. In this way, the three circumferentially symmetrically arranged indexable inserts 10 to 12 with these arcuate guide surfaces are used at the same time for centering and support in the bore wall =

In the usual way, three chip flutes 24 to 26 are provided, which in the end view from below according to FIG. 2 are approximately L-shaped are, with the longer L-leg 27 to 29 approximately parallel runs to a tangent of the cylindrical head end 16. The flutes can also be designed differently.

The cutter head is provided with a central, all three cutting inserts 10 to 12 together and uniformly radially and in the range of the material elasticity of the head end 16 and reversibly acting Verstellvorrich- \

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device 30 equipped. This described direction of action of the adjusting device 30 is shown in Fig. 2 with the three arrows 31 to 33 indicated for the case that the adjusting device 30 in the direction of increasing the radial dimension of the j cutting tool head is operated. Then act in the direction of the arrow 31 to 33 on all holder seats 13 to 15 of the indexable inserts 10 to 12 evenly and simultaneously radial forces due to elastic material deformation of the head end 16, which cause an albeit extreme small radial expansion of the cutting tool head like this happens that the circle circumscribed by the arcuate guide surfaces 21 of all indexable inserts 10 to 12 is slightly increased compared to the dimension before the adjustment.

The cutting tool head is by means of the adjusting device adjustable in such a way that it enables the production of bores with low tolerances and high quality, in particular with fits in the range H7 to H9, and of course also fits larger than H9.

The adjusting device 30 has a central one at the head end 16 and a coaxial expansion bore 34 which runs exactly coaxially to the central axis of the head end 16. The expansion hole 34 is designed as a conical bore 35 which is open towards the front end and widens there.

The mounting seats 13bEi5 of the indexable inserts 10 to 12 each have from the wall of the conical bore 35 the same radial distance. A component of the adjusting device 30 is also an expanding core 36, which acts as a conical core 37 is designed, the cone angle of which corresponds to that of the conical bore 35. The cone core 37 is from the front end

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forth in the conical bore 35 can be pressed with elastic radial expansion of the conical bore 35 in the direction of the radial Arrows 31 to 33 (Fig. 2).

The cone angle of the conical bore 35 and the associated Cone core 37 is in the self-locking area and is, for example, a Morse taper. The slope of the cone can be 1:20, for example.

The conical bore 35 extends axially at least over the axial extent of the three indexable inserts 10 to 12, See FIG. 3. A threaded bore 38 which is exactly coaxial with it opens into the conical bore 35. At the cone core 37 sits a thus one-piece threaded shaft 39 which can be screwed into the threaded bore 38. Inside contains the cone core 37 a central, recessed tool application surface 40, which is designed here as a hexagon socket.

As can be seen in particular from FIG. 2, the conical bore 35 has in the radial area of the mounting seats 13 to 15 of indexable inserts 10 to 12 bafipdliche wall surfaces 41, 42 and 43, which have a relatively small circumferential extension have and with which the cone core 37 is in contact when inserted. Between these wall surfaces 41 through 43 there are radial recesses 44 through 46 in the form of recesses which are at a radial distance from the conical core 37 get lost. These recesses 44 to 46 are in the axial direction (Fig. 3] designed roughly rinnenförnrtig, as there for the return 45 can be seen. Their axial extent extends at least over the axial length of the conical bore The bottom of the channels running radially on the outside can run parallel to the conical wall of the conical bore 35. More advantageous it is, however, when, as shown in FIG. 3, the groove-shaped recesses are axially parallel in the axial direction run, so the channel bottom parallel to the cylinder wall

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of the head end 16 is aligned. |

The wall surfaces 41 to 43 extend substantially
only übar the circumferential angle range on which the mounting seats 13 to 15 with the indexable inserts 10 to 12 are arranged. In the circumferential direction between the wall surfaces 41 to 43 $ 2 material thin points are apparent in particular from FIG. Arranged with a smaller radial cross section of material as it is provided in the radial region of the ϊ Wandfl'ächen 41 to 43. These thinnest spots arise mainly from |

each between the longer L-leg 27 to 29 and the ^;

The reason for the channel-shaped recesses 44 to 4B. The latter |

have an arc shape in cross section, the arc with g

preferably constant over '· a wall surface to the [next spans.

The expansion bore 34, in particular the conical bore 35, with its |

Threaded hole 38 and also the expanding core 36, in particular '

Cone core 37, with its threaded shaft 39, are each worked exactly coaxially to run out. At least the head end
16 of the cutting tool head is along the axial length

which extends the conical bore 35, hardened as hard as a spring. :

The expanding core 36, in particular a conical core 37, with a thread I

shaft 39 is hardened and ground. With all these eggs |

Ments of the adjusting device 30 is a high level of accuracy 5

and concentricity secured. The cone core 37 has, as not j _:

is further shown, a preferably incorporated /

Core brand. The surface 17 at the head end 16 carries a. Preferred |

wisely incorporated, assigned reference mark fqlge / in particular |

Special setting scale so that the setting according to, pre-; ■ values and can be read on the scale.

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For precise adjustment of the tool head to fit the threaded shaft 39 is moved deeper into the threaded hole by means of an Allen key which engages in the hexagon socket 40 3B screwed in and thus the conical core 37 is drawn deeper into the conical bore 35. This has im Area of the wall surfaces 41 to 43 radially from the inside to | Outwardly directed forces in the area of material elasticity in the direction of arrows 31 to 33 result, namely at the same time and evenly. If one looks at the effects in the axial direction, the adjustment forces generated are on the axial extension of the indexable inserts 10 to 12 same size. The direction of arrow 31 to 33 on the holding ' Rungssitze 13 to 15 and thus the indexable inserts 10 to 12 acting forces lead to the fact that the indexable inserts 10 to 12 go slightly further to the outside. These adjustment movements are in the μ range. To this Thus, the indexable inserts 10 to 12 can be adjusted to fit, e.g. to a fit of the order of magnitude IT7 to IT9 and of course bigger too. While in the area of the wall surfaces 41 to 43, said radially outwardly directed Actuating forces act and there an elastic deformation of the material approximately in the direction of arrow 31 to 33 result, the recesses 44 to 46 enable on the one hand that the radial adjustment forces act in a targeted and defined manner only in the circumferential area where the mounting seats 13 to 15 are involved the indexable inserts TO to 12 are arranged, but not on other circumferential areas. They also favor this Recesses 44 to 46 with an axial channel run a material deformation during this adjustment on the circumferential areas, where these recesses are provided, i.e. in the intermediate area between two wall surfaces. The material can therefore adapt to the radial deformation in In the direction of arrow 31 to 33 stretch better in between and move to recesses 44 to 46.

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Once the desired setting has been made to the desired fit in the manner described, the cone core needs not to be secured because with ■ in the self-locking area lying cone angle an automatic return is prevented thanks to the self-locking. The tool is so ready to use. An adjustment in opposite directions is achieved by rotating the conical core 37 in opposite directions, thanks to the spring-hard design of at least the head end 16 and material elasticity an automatic elastic reset of the material happens, the wall surfaces 41 to 43 automatically radially against the arrows 31 to 33 migrate inward, along with the retainer seats 13 to 15 and indexable inserts 10 to 12.

In the second embodiment according to FIG. 5, instead of the central, coaxial adjustment device for each individual indexable insert, only one of which is shown schematically Indexable insert 10 'is shown, its own off-center adjusting device 3QV of the same type as in the first Embodiment provided, which is also radially and thereby in the area of the material elasticity of the head end and acts reversibly on the mounting seat of the associated indexable insert 10 '. The adjusting device 30 'has also a non-visible expansion hole with a threaded hole in which an expansion core 36 'of the same type as in first embodiment is screwed. Every expansion hole has a wall surface 41 'located in the radial region of the assigned indexable insert 10 and in the circumferential direction on both sides of this wall surface 41 'each have a radial recess 44' or 46 '. The two returns 44 ', 46' have the same design and function as the first embodiment. In this way it is possible to use each individual indexable insert, e.g. the one indexable insert 10 ', and each individual, existing guide element by means of its own, assigned adjusting device 30'

to be adjusted individually so that the entire tool head is adjusted to fit. It is particularly advantageous that an exact central and coaxial machining, which in the first embodiment requires the central adjusting device, can be omitted. The achieved individual adaptation of each individual indexable insert and each individual guide element through individual adjustment of the associated adjusting device 30 'is advantageous. The design according to the second exemplary embodiment can be useful, for example, if the tool head has a relatively large diameter or the center of ^the tool head is not available for attaching a central adjustment device, but is to be used for other purposes.

In another exemplary embodiment, not shown, is the cutting tool head is single-edged. It has a cutting insert 10 and instead of the other two Cutting inserts 11 and 12 corresponding to the same circumferential point, Guide elements also firmly held in mounting seats. The adjustment device 30 is the same designed. It then uniformly effects a radial joint adjustment of one cutting insert and the two Guide elements, as in the embodiment shown the indexable inserts 10 to 12 thanks to the arcuate Guide surface 21 (FIG. 4) are at the same time also guide elements and also cut circumferentially symmetrically if necessary In the embodiment shown with a three-edged tool, there are no additional guide elements.

In another embodiment, not shown, are only two cutting edges or even more than three cutting edges provided, if this should ever be necessary and expedient.

MülbeYgWstr.'65 ■ <· ■■■ t I r \
si; Patent attorney D-7300 Esslingen Authorized representative at Dipl.-Ing. Volkhard Kratzsch European Patent Office f Telephone Stuttgart (0711) 317000 ] ■ cable «krapatent» esslingenneckar Deutsche Bank Esslingen 210906 < Post office Stuttgart 10004-701

Hermann BiIz GmbH & Co 73 Esslingen

May 15, 1981 Attorney File 3235

summary

A cutting tool head, in particular a countersinking and / or reaming tool head, is proposed with three indexable cutting inserts arranged at approximately the same circumferential angular distances from one anotherO to 12)
in bracket seats (13 to 15). Inside are the indexable inserts). (10 to 12) fixed in place. At the head end (16) sits a 'central adjustment device (30). This affects the three turning points; _; cutting inserts (10 to 12) jointly and uniformly radially, f in the area of the material elasticity of the head end (16) | and reversible. The adjusting device (30) has at the. \ Head end (16) a central and coaxial conical bore (35) with an adjoining threaded bore (38) and also one in the
Threaded bore (38) screw-in threaded shaft (39) with a conical core (37) at the end. The cone angle is the same and lies | advantageous in the self-locking area. The conical bore (35) has i

ti only in the radial area of the indexable inserts (10 to 12) such * £

Wall surfaces (41 to 43) with the pressed-in cone core (37);

to be in contact. In the circumferential direction between the wall surfaces.,

(41 to 43) there are radial recesses (44 to 46), the g

are axially parallel grooves and a targeted material deformation |

favor in the area of elasticity. At least the head end (16) * '

is hardened as hard as a spring. At least the cone core (37) is hardened g

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and sanded. By screwing in the cone core (37), the tool head can be adjusted so that it does the production of bores with only low tolerance and high quality, in particular with fits around the area from IT7 to IT9 possible.

Claims (1)

1. Cutting tool head, in particular countersinking and / or reaming tool head, the at least one indexable insert and. in the circumferential direction guide elements arranged at approximately the same angular intervals therefrom or three at approximately equal circumferential angular intervals having mutually arranged indexable inserts (10 to 12), characterized by a central, on the at least one indexable insert and the guide elements or all three indexable inserts (10 to 12) together and evenly radially, and at the same time in the area of material elasticity of the head end (16) and reversibly acting "Adjusting device (30), by means of which the tool head can be adjusted in such a way that it reduces the production of bores Tolerance and high quality, in particular with fits in the range IT7 to IT9 or larger, enables. 2. Cutting tool head, in particular countersink and / or reaming tool head, the at least one indexable insert and arranged in the circumferential direction at approximately the same angular distances therefrom! Has guide elements or three indexable inserts arranged at approximately the same circumferential ^{angular distances from one another, characterized in that for each individual indexable insert (10 1} ) and / or each individual guide element a separate, eccentrically seated and on it radially and thereby in the area of the material elasticity of the 11 111 Head end and reversibly acting adjusting device (3D ¹ ) is provided, by means of which each indexable insert C1G ^r .) And / or each guide element can be adjusted individually and thus the tool head in such a way that it enables the production of bores with low tolerance and high quality, in particular with Fits in the range IT7 to IT9 or larger, for example. 3. Cutting tool cap according to claim 1 or 2, d a through characterized in that the adjusting device (30j 30 ') at the head end (16) has either one central and coaxial or eccentric expansion bore (34) which is open towards the front end, and one from the front end into the expansion foam (34) with elastic radial expansion of this compressible Has expanding core (36; 36 '). 4. Cutting tool head according to claims 1 and 3, characterized in that the mounting seats (13 to 15) of the at least one indexable insert and guide element or the three indexable inserts (10 to 12) each have the same radial distance from the wall (41 to 43) of the central and have coaxial spreading (34). 5. Cutting tool cap according to one of claims 1-4, d a characterized in that the expansion bore (34) axially at least 'over the axial extent the at least one indexable insert (10j10 ') and Guide elements or all three indexable inserts (10 to 12) extends. 6. Cutting tool head according to one of claims 1-5, characterized by a threaded hole (38) opening into the expansion hole (34) -3- I t I and a threaded shaft (39) on the expansion core (36 _; 36 ') that can be screwed into the threaded bore (38). 7, cutting tool head according to one of claims 1-6, characterized in that the expansion bore (34) is designed as a conical bore (35) which widens towards the front end, and that the expansion core (36; 36 ') is designed as a conical core (37) whose cone angle corresponds to that of the conical bore (35). _y •8th. Cutting tool head according to claim 7, characterized in that the cone angle is Self-locking area. 9. Cutting tool head according to claim 7 or 8, d a characterized in that the cone the conical bore (35) and the conical core [37) is a Morse taper. 10. Cutting tool head according to one of claims 1 - 9, d adurch characterized in that the expansion core (36j36 '} has at least one central, recessed tool engagement surface (40), preferably a hexagon socket. 11. Cutting tool according to one of claims 1 - 10, d a through characterized in that the expansion bore (34), in particular the conical bore (35), in the Radial area of the at least one indexable insert and guide elements or all three indexable inserts (10 to 12) located wall surfaces (41 to 43) which are in contact with the pressed-in expanding core (36), in particular conical core (37), as well as those located in the circumferential direction between the wall surfaces (41 to 43) having radial recesses (44 to 46) which run at a radial distance from the expanding core (36). 12. Cutting tool according to claims 2 .and 11, characterized in that each expansion bore, in particular a conical bore, one in the "radial region of the associated one indexable insert (10 ¹ ) or one associated guide element located wall surface (41 ') and in the circumferential direction on both sides of these in each case has a radial recess (44'j 46 '). 13. Cutting tool head according to claim 11 or 12, characterized characterized in that the expansion bore (34), in particular conical bore (35), as recesses (44 to 46; 44 '.; 46') has recesses which are approximately trough-shaped in the axial direction and at least over the axial length of the expansion bore (34), in particular 'conical bore (35), extend. 14. Cutting tool head according to claim 13, characterized in that the channel-shaped recesses run axially parallel in axial directions. 15. Cutting tool head according to one of claims 11-14, characterized in that the wall surfaces (41 to 43: 41 ") essentially only over extend the circumferential angular range on which the at least an indexable insert (10 ') and guide elements or the three indexable inserts (10 to 12) are arranged are. 16. Cutting tool head according to one of claims 11-15, characterized in that in the circumferential direction on both sides of the wall surfaces (41 to 43; 41 ') • Thin areas of material with a smaller radial material cross-section are arranged than he is in the radial area of the wall surfaces (41 to 43i 41 ') is provided. Ii -5- Ίγ. Cutting tool head according to one of Claims 11 to 16, characterized in that the recesses (44 to 46; 44 ', 46') have an arc shape in cross-section, the arc preferably having a continuous 1 Course on both sides of a wall surface (41 to 43; 41 '), e.g. from one to the next, spans. 18, cutting tool head according to one of claims 1-17, characterized by the fact that the Expansion bore (34) with its threaded bore (38) and the expansion core (36) with its threaded shaft (39) Round run exactly coaxially or in each case with an eccentric arrangement are worked exactly axially parallel. 19 «cutting tool head according to one of claims 1 - 1§, characterized in that at least the head end (16) along its axial length ' which extends the expansion bore (34), in particular the conical bore (35), is hardened as hard as a spring « . Cutting tool head according to one of Claims 1 to 19, characterized in that the Expanding core (36; 36 ') with its threaded shaft. (39) '·: is hardened and ground. . Cutting tool head according to one of claims 1 - 20, characterized in that -the expanding core (36; 36 ') is a preferably incorporated; Core brand and the face at the head end (16) a preferably incorporated reference mark sequence, in particular Setting scale., Carries.