WO2021078425A1

WO2021078425A1 - Deep-hole drilling tool

Info

Publication number: WO2021078425A1
Application number: PCT/EP2020/073995
Authority: WO
Inventors: Frank Fischer; Karl-Heinz Formann
Original assignee: Robert Bosch Gmbh
Priority date: 2019-10-21
Filing date: 2020-08-27
Publication date: 2021-04-29
Also published as: DE102019216144A1

Abstract

The invention relates to a deep-hole drilling tool for producing a deep-hole bore in a workpiece in a material-removing manner, comprising a drill shank (1) which has a proximal clamping portion (2) and at the distal end of which at least one drill bit (3; 3a, 3b) that extends transversely in terms of cutting geometry is arranged, which drill bit is assigned at least one flute (5; 5a, 5b) that is incorporated along the outer circumference (4) of the drill shank (1) and is intended for carrying away chips that have been removed from the workpiece by the at least one bit (3), the edge strip (8, 9) of which flute that protrudes at least one one side of the flute (5, 5a, 5b) radially from the outer circumference (4) of the drill shank (1) slidingly abuts the bore wall (10), wherein in order to prevent twist boring in the shank longitudinal direction, at least one cutting guide strip (7a, 7b; 7a', 7b') that protrudes radially from the outer circumference (4) is formed adjacently to the flute (5, 5a, 5b), which guide strip is provided with a cutting edge (11; 12) that acts in the working direction of rotation of the drill shank (1) and is intended for cutting out the bore wall.

Description

description

Title:

Deep hole drilling tool

The invention relates to a deep hole drilling tool for the machining of a deep hole bore in a workpiece, comprising a drill shank having a proximal clamping section, at the distal end of which at least one geometrically transverse cutting edge is arranged, which has at least one flute machined along the outer circumference of the drill shank for removing through the at least one cutting edge is assigned to chips removed from the workpiece, the edge of which, at least on one side, the chip flute protruding radially from the outer circumference of the drill shank, comes slidingly into contact with the wall of the bore.

The field of application of the invention extends to the production of deep-hole bores in workpieces, which preferably consist of a machinable metal. According to the applicable standards (VDI 3210), deep hole drilling begins at a drilling depth of 3 times the tool diameter. The main difficulty with deep hole drilling is to minimize the migration of the drill head center away from the set axis, although the drill shank has a lower flexural rigidity due to its length than in normal drilling.

State of the art

According to the generally known prior art, axial deviations in bores can be avoided in that there is no blunt cross cutting edge in the center of the drill tip, which only displaces or scrapes material, requires high drilling pressure and provokes lateral evasive movements of the deep hole drill. Instead, it uses the entire cross-sectional area Regularly cut by one or more cutting edges. In practice, special single-lip deep hole drills or two-lip deep hole drills are used for this purpose. There are also twist drills with a double guide chamfer, which can be used for deep hole drilling. Since the drill shank itself cannot provide a clear definition of the position of the drill head, this task is taken over by the wall of the hole that has already been drilled. Except for simple deep hole drills, one or more longitudinal webs, so-called guide strips, on the outside ensure this definition of the position. These are either left standing during the outer grinding of the outer circumference of the drill shank or specially inserted into grooves. The interaction of these guide strips with the wall of the borehole absorbs the transverse forces that arise during deep-hole drilling. Usually a pilot hole or an additional drill bushing is required at the beginning of the drilling process.

A problem with deep hole drilling called twist drilling is caused by vibrations on the deep hole drilling tool, which during the drilling process also cause Rätter phenomena and non-circular drilling to build up. Twist drilling occurs in particular at high speeds with a high feed rate at the same time, i.e. with high drilling performance. The predominant disturbing vibration is the bending vibration of the deep hole drilling tool perpendicular to the drilling axis with an oscillation frequency of less than 100 Hz. Furthermore, axial alignment of the drilling axis of the tool with the partial spindle axis of the machine is only insufficiently controllable, especially in multi-spindle machines, so that this state also contributes to the twist problem . There are also concentricity errors on the tool and concentricity errors in the

Tool holder for the interface in the machine. Overall, this leads to an inadequate drilling result, i.e. non-circular drill holes, as well as premature tool wear. Typical is the so-called polygon formation, which is shown to an observer when looking into the bore through so-called twist marks. It is therefore the object of the present invention to minimize or reduce the chattering tendencies that occur during deep hole drilling and twist drilling.

Disclosure of the invention

The object is achieved on the basis of a deep hole drilling tool according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims reproduce advantageous developments of the invention.

The invention includes the technical teaching that to avoid twist drilling and to minimize the tendency to chatter in the longitudinal direction of the shank adjacent to the flute of the deep hole drilling tool, at least one cutting guide strip protruding radially from the outer circumference is formed, which is provided with a cutting edge acting in the working direction of rotation of the drill shank for cutting free the bore wall is.

For the purpose of reducing the twist drilling, only a slight chip removal takes place, which is below the chip removal that occurs, for example, when rubbing a cylinder bore. The guide strip cutting according to the invention therefore does not lead to a substantial increase in the diameter of the drill hole diameter defined by the cutting edges of the drill head. In contrast to the prior art, a cutting guide bar is produced in that the guide bar edge, which is usually rounded, is provided with a cutting geometry.

The insofar as only slightly cutting guide bar ensures, in terms of functional integration, both safe guidance of the deep hole drilling tool in the hole and sufficient free cutting to limit the irregularities occurring on the hole wall during the deep hole drilling process, which slows down the drilling process. This minimizes the tendency to chatter and twist drilling on the one hand and reduces the risk of the deep hole drill jamming during the drilling process on the other hand. Because the inventive solution can The deep-hole bores generated no longer turn out too narrow With twist and / or non-circular drilling, the hole drilled with a conventional deep hole drilling tool is often smaller than the drill diameter.

The tool geometry according to the invention with regard to the cutting guide bar is able to greatly reduce the tendency to twist, especially in the case of two-lip deep hole drills, and to bring about the compressive strength by introducing residual compressive stresses to the required level to achieve the pulse compressive strength without subsequent increasing measures.

Tests have shown that by using a two-lip deep hole drill designed according to the invention, the cycle time with a currently used multi-spindle drilling concept can be reduced by approx. 20% compared to a single-lip deep hole drill. Furthermore, the oscillation behavior discussed above is prevented. As a result of this, subsequent brushing of the deep hole, which was usually necessary up to now, can be dispensed with, so that the production time can be further reduced.

According to a first embodiment of the invention it is provided that the drill shank is provided with a single cutting edge with an associated flute for forming a single-lip deep hole drill, which corresponds to at least one guide strip with a cutting edge. In order to ensure precise shank guidance of the drill shank, two or more guide strips should preferably be provided in combination with the individual flute.

According to a second preferred embodiment, the drill shank is provided with two cutting edges with associated flutes for forming a two-lip deep hole drill, which correspond to at least two guide strips with cutting edges. Preferably, two such guide strips are provided for the two flutes and are spaced apart from one another over the outer circumference. A fully symmetrical cross-sectional arrangement is advantageously sought in order to ensure uniform drill guidance. The flute of the single-lip deep hole drill and the two flutes of the two-lip drill with respectively associated guide strips preferably run in a straight line along the outer circumference of the drill shank. In addition, however, a helical arrangement in the form of a twist drill is also conceivable, which, in the case of special workpiece materials, ensures improved removal of the chips produced during drilling to the outside. If the deep hole drilling tool is designed in the manner of a twist drill, this preferably has a double guide bar.

According to a measure that further improves the invention, it is proposed that each cutting guide strip be assigned a secondary flute which is formed jointly with the outer circumference and runs parallel to the flute of the drill bit. As a result, space is created for the fine chips that occur slightly as a result of the free cutting with the cutting guide bar. Improved chip evacuation can be achieved in that this secondary chip flute is connected to the main chip flute of the drill bit via at least one transverse channel, so that a reliable fine chip evacuation is achieved in particular with deep bores.

The deep hole drilling tool according to the invention can be manufactured from a suitable cutting material throughout. However, it is also conceivable that the drill bit arranged at the distal end of the drill shank is formed on a hard metal head of the drill shank otherwise made of a lower alloyed tool steel, with the at least one cutting guide bar over the common outer circumference, i.e. laterally over the hard metal head and the rest of the drill shank runs.

Further measures improving the invention are shown in more detail below together with the description of preferred exemplary embodiments of the invention with reference to the figures.

Embodiments

It shows: 1 shows a perspective view of a single-lip deep hole drilling tool,

Fig. 2 is a detailed perspective view of the single-lip

Deep hole drilling tool according to FIG. 1 in the area of the drill head,

3 shows a plan view of the distal end of the deep hole drilling tool according to FIG. 1 in the borehole,

4 shows a perspective view of a two-lip deep hole drilling tool,

FIG. 5 shows a plan view of the distal end of the deep hole drilling tool according to FIG. 4 in the borehole,

6 shows a further top view of a two-lip deep hole drilling tool in the borehole according to an alternative embodiment,

Fig. 7 is a perspective view of a two-lip

Deep hole drilling tool with secondary flute according to a first embodiment, and

Fig. 8 is a perspective view of a two-lip

Deep hole drilling tool with secondary flute according to a second embodiment.

According to FIG. 1, a single-lip deep hole drilling tool consists essentially of a drill shank 1 with a proximal clamping section 2 for a tool holder on a drilling or lathe, preferably a multi-spindle lathe with drilling units. At the distal end of the drill shank 1 there is arranged a cutting edge 3 running transversely in terms of cutting geometry, which is assigned a flute 5 running along the outer circumference 4 along the drill shank 1 for removing chips removed by the cutting edge 3. The cutting edge 3 arranged at the distal end of the drill shank 1 is formed on a hard metal head 6 of the drill shank 1 which otherwise consists of a solid hard metal. According to the enlarged illustration shown in FIG. 2, a first guide bar 7a and a second guide bar 7b, which are circumferentially spaced from one another and from the chip groove 5, are formed adjacent to the flute 5 formed along the drill shank 1. Furthermore, on one side of the flute 5, a radially outwardly protruding edge strip 8 is provided, which comes into sliding contact with the wall of the bore.

In Fig. 3, the sliding edge strip 8 and the two guide strips 7a and 7b is illustrated in cross section. The flute 5 is further delimited by a second further edge strip 9 that comes to rest in a sliding manner on the bore wall 10.

According to FIG. 4, a deep hole drilling tool is designed as a two-lip deep hole drill and comprises a drill shank 1 with two front drill bits 3a and 3b. These are each assigned a flute 5a or 5b. The two cutting edges 3a and 3b are also formed here on a hard metal head 6 of the deep hole drilling tool.

As can be seen from FIG. 5, the two flutes 5a and 5b correspond to two associated cutting guide strips 7a and 7b, each with a respective cutting edge 1 and 12, arranged at a distance from one another over the outer circumference 4. In contrast, the two edge strips 8a and 8b delimiting the groove come to bear on the bore wall 10 in a sliding manner.

In a modification of this, FIG. 6 shows an embodiment in which two additional cutting guide strips 7c ‘and 7d are arranged at a distance from the edge strip 8a and the cutting guide strip 7a or from the edge strip 8b and the cutting guide strip 7b‘.

According to FIG. 7, each cutting guide strip 7a and 7b is assigned a secondary flute 13 (exemplary) which is formed jointly with the outer circumference 4 and which runs parallel to the main flute 5 (exemplary) of the cutting edge 3. In the modification of this illustrated in FIG. 8, the secondary flute 13 is connected to the main flute 5 of the cutting edge 3 via at least one transverse channel 14 in order to facilitate the removal of the fine chips that collect in the secondary flute 13.

The invention is not restricted to the exemplary embodiments described above. Modifications of this are also conceivable, for example in the direction of a twist drill, which are also covered by the scope of protection of the following claims.

Claims

Expectations

1. Deep hole drilling tool for machining a deep hole bore in a workpiece, comprising a drill shank (1) having a proximal clamping section (2), at the distal end of which at least one cutting edge (3; 3a, 3b) running transversely in terms of cutting geometry is arranged, which at least one longitudinally Flute (5; 5a, 5b) machined into the outer circumference (4) of the drill shank (1) for removing chips removed from the workpiece by the at least one cutting edge (3), of which the flute (5, 5a, 5b) is radially at least on one side from the outer circumference (4) of the drill shaft (1) protruding edge strip (8, 9) comes to bear on the bore wall (10), characterized in that to avoid twist drilling in the longitudinal direction of the shaft adjacent to the flute (5, 5a, 5b) at least one Cutting guide strips (7a, 7b; 7a ', 7b') protruding radially from the outer circumference (4) are integrally formed, which act with a rotating direction of the drill shaft (1) in the working direction the cutting edge (11; 12) is provided for cutting free the bore wall.

2. Deep hole drilling tool according to claim 1, characterized in that the drill shank (1) is provided with a cutting edge (3) with an associated flute (5) to form a single-lip deep hole drill which is provided with at least one guide strip (7a, 7b) with cutting edge ( 11; 12) corresponds.

3. Deep hole drilling tool according to claim 2, characterized in that the flute (5) corresponds to two guide strips (7a, 7b) with cutting edge (7a, 7b) arranged at a distance from one another over the outer circumference (4).

4. Deep hole drilling tool according to claim 1, characterized in that the drill shank (1) is provided with two cutting edges (3a, 3b) with associated flutes (5a, 5b) to form a two-lip deep hole drill, which is provided with at least two guide strips (7a ', 7b ') correspond to the cutting edge (1; 12').

5. Deep hole drilling tool according to claim 4, characterized in that the two chip flutes (5a, 5b) with two respectively assigned cutting guide strips (7a ', 7b') with cutting edge (1, 12 ') arranged at a distance from one another over the outer circumference (4) correspond.

6. Deep hole drilling tool according to claim 1, characterized in that the at least one flute (5a, 5b) and the guide strips (7a ‘, 7b‘) associated therewith run in a straight line along the outer circumference (4) of the drill shank (1).

7. Deep hole drilling tool according to claim 1, characterized in that the drill shank (1) is designed in the manner of a twist drill with a double guide strip (7a, 7b).

8. Deep hole drilling tool according to claim 1, characterized in that each cutting guide strip (7a, 7b) is assigned a secondary flute (13) formed jointly with the outer circumference (4) and parallel to the main flute (5) of the drill bit (3) runs.

9. Deep hole drilling tool according to claim 8, characterized in that the secondary flute (13) is connected to the main flute (5) of the cutting edge (3) via at least one transverse channel (14).

10. Deep hole drilling tool according to one of the preceding claims, characterized in that the drill bit (3) arranged at the distal end of the drill shaft (1) is formed on a hard metal head (6) of the drill shaft (1) otherwise made of a tool steel, wherein the at least one cutting guide strip (7a, 7b) extends over their common outer circumference (4).