Rotary cutting tool assembly

Abstract

The present invention relates to a rotary cutting tool assembly comprising a toolholder which has a central tool holding receptacle, and a cutting tool which has a holding projection that can be detachably held in the tool holding receptacle and via which the cutting tool is secured to and radially centered on the tool, wherein the holding projection has at its free end a pin-like, first centering section and an adjoining externally threaded section, wherein the holding projection ends in a radially outwardly projecting shoulder having an end face abutment surface, and the tool holding receptacle has an internally threaded section for receiving the externally threaded section and a first centering seat section which is positioned deeper within the tool holding receptacle and in which the centering section of the cutting tool is held.

Claims

1. A rotary cutting tool assembly comprising: a toolholder having a central axis and comprising a central tool holding receptacle, the tool holding receptacle including a first centering seat section, an internally threaded section having an axial length (1) that extends between a start of the internally threaded section and a start of the first centering seat section, the internally threaded section adjoining the first centering seat section and a second centering seat section, and a cutting tool having a central axis and comprising a holding projection detachably held in the tool holding receptacle, the holding projection including a cylindrical-shaped first centering section extending axially from an end face thereof and having an axial length (L), and an externally threaded section adjoining the first centering section, the holding projection further including an end face abutment surface distal the end face and formed by a shoulder projecting radially outward from a second centering section of the cutting tool and the second centering section disposed between the externally threaded section and the end face abutment surface, the second centering section having an outer diameter larger in magnitude than an outer diameter of the externally threaded section, wherein the axial length (L) of the first centering section of the cutting tool is greater in length than the axial length (1) of the internally threaded section of the toolholder, wherein an axial length of the holding projection is 1.8 to 3 times larger than an outer diameter of the end face abutment surface, and wherein the central axis of the cutting tool is aligned with the central axis of the toolholder when the holding projection is received in the tool holding receptacle of the toolholder.

2. The rotary cutting tool assembly according to claim 1, wherein an axial length of the second centering section is at most 50% of an axial length of the externally threaded section.

3. The rotary cutting tool assembly according to claim 1, wherein the first and second centering sections of the cutting tool and the first and second centering seat sections of the toolholder are designed with the same fit.

4. The rotary cutting tool assembly according to claim 1, wherein the central axis of the cutting tool is aligned with the toolholder when the first centering section of the cutting tool is received by the first centering seat section of the toolholder.

5. The rotary cutting tool assembly according to claim 1, wherein the central axis of the cutting tool is aligned with the toolholder when the first and second centering sections of the cutting tool are received by the first and second centering seat sections of the toolholder.

6. The rotary cutting tool assembly according to claim 1, wherein the cutting tool holds at least one interchangeable cutting insert.

7. The rotary cutting tool assembly according to claim 1, wherein: the toolholder includes a cooling channel that ends in the tool holding receptacle, and the cutting tool includes a cooling channel that starts at the end face of the first centering section.

8. The rotary cutting tool assembly according to claim 1, where an axial length of the second centering section is at most 30% of an axial length of the externally threaded section.

9. The rotary cutting tool assembly according to claim 1, wherein the first centering section of the toolholder has a diameter, and an axial length (a), via which a front end of the first centering section engages in the first centering seat section when the externally threaded section of the cutting tool starts to engage the internally threaded section of the toolholder, is at least 20% of the diameter of the first centering section of the toolholder.

10. The rotary cutting tool assembly according to claim 1, wherein the cutting tool further comprises a puncture formed between the second centering section and the end face abutment surface.

11. A rotary cutting tool assembly comprising: a cutting tool having a central axis and comprising a holding projection detachably held in the tool holding receptacle, the holding projection including a cylindrical-shaped first centering section extending axially from an end face thereof and having an axial length (L), and an externally threaded section adjoining the first centering section, the holding projection further including an end face abutment surface distal the end face and formed by a shoulder projecting radially outward from a second centering section of the cutting tool, and the second centering section disposed between the externally threaded section and the end face abutment surface; and a toolholder having a central axis and comprising a central tool holding receptacle, the tool holding receptacle including a first centering seat section capable of receiving the first centering section of the cutting tool, an internally threaded section having an axial length (1) that extends between a start of the internally threaded section and a start of the first centering seat section, the internally threaded section adjoining the first centering seat section, the internally threaded section capable of receiving the externally threaded section of the cutting tool, and a second centering seat section capable of receiving the second centering section of the cutting tool, the second centering section having an outer diameter larger in magnitude than an outer diameter of the externally threaded section, and the second centering seat section adjoining the first centering seat section via the internally threaded section, wherein the axial length (L) of the first centering section of the cutting tool is greater in length than the axial length (1) of the internally threaded section of the toolholder, wherein an axial length of the holding projection is 1.8 to 3 times larger than an outer diameter of the end face abutment surface, and wherein the cutting tool is concentric with the toolholder when the holding projection of the cutting tool is received in the tool holding receptacle of the toolholder.

12. The rotary cutting tool assembly according to claim 11, wherein the second centering section has an outer diameter larger than an outer diameter of the externally threaded section, and wherein the second centering seat section additionally secures the cutting tool in the toolholder.

13. The rotary cutting tool assembly according to claim 11, wherein an axial length of the second centering section is at most 50% of an axial length of the externally threaded section.

14. The rotary cutting tool assembly according to claim 11, wherein the axial length of the second centering section is at most 30% of an axial length of the externally threaded section.

15. The rotary cutting tool assembly according to claim 11, wherein the first and second centering sections and the associated first and second centering seat sections are designed with the same fit.

16. The rotary cutting tool assembly according to claim 11, wherein the central axis of the cutting tool is concentric with the toolholder when the first centering section of the cutting tool is received by the first centering seat section of the toolholder.

17. The rotary cutting tool assembly according to claim 11, wherein the central axis of the cutting tool is concentric with the toolholder when the first and second centering sections of the cutting tool are received by the first and second centering seat sections of the toolholder.

18. The rotary cutting tool assembly according to claim 11, wherein the cutting tool holds at least one interchangeable cutting insert.

19. The rotary cutting tool assembly according to claim 11, wherein the first centering section of the toolholder has a diameter, and an axial length (a), via which a front end of the first centering section engages in the first centering seat section when the externally threaded section of the cutting tool starts to engage the internally threaded section of the toolholder, is at least 20% of the diameter of the first centering section of the toolholder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a sectional view through an optional embodiment of the rotary cutting tool assembly according to the invention with a cutting tool not yet screwed into the toolholder.

(3) FIG. 2 shows the rotary cutting tool assembly according to FIG. 1 at the beginning of the centering process,

(4) FIG. 3 shows the rotary cutting tool assembly according to the invention of FIG. 1 with partially screwed-in cutting tool, and

(5) FIG. 4 shows the rotary cutting tool assembly according to the invention with a cutting tool completely held within the toolholder.

DETAILED DESCRIPTION

(6) FIG. 1 shows a rotary cutting tool assembly in the form of a milling cutter or a drill and having a toolholder 10 and a cutting tool 12, which carries at its tip (not shown here) one or more cutting edges and/or one or more interchangeable cutting plates.

(7) The toolholder 10 has a central tool holding receptacle 14 in the form of an opening which starts from a counter surface 16. The central axis A of the tool holding receptacle 14 extends perpendicularly to the counter surface 16. A cooling channel 18, a first centering seat section 20, an adjoining internally threaded section 22 and a thereto adjoining second centering seat section 24 extend centrally to the central axis A.

(8) The first and the second centering seat section 20, 24 extend centrally to the central axis A. The internally threaded section 22 also extends centrally to the axis A, as far as this is possible with the manufacturing accuracy. A centric alignment of the cooling channel 18 may be advantageous but is not mandatory.

(9) On its end opposite to its cutting edges and visible in FIG. 1, the cutting tool 12 has a holding projection 26 with different sections. Starting from the free end 28, a pin-like, first centering section 30 is provided on the holding projection 26, said first centering section being adjoined by an externally threaded section 32. A second centering section 36 is provided between the externally threaded section 32 and an end face abutment surface 34 formed by an outwardly projecting shoulder. A puncture 38 forms the transition between the second centering section 36 and the abutment surface 34. Here, too, the abutment surface 34 extends at a right angle to the central axis A.

(10) The cutting tool 12 also has a central axis A, which constitutes a centering axis as well. This central axis A should be aligned with the central axis A of the toolholder when the two parts are secured to each other. Opposite and diametrically oriented flat surfaces 42 serve as the engagement of a tool with which the cutting tool 12 can be screwed into the toolholder 10.

(11) The threads 22, 32 are designed as metric threads.

(12) The axial length of the second centering section 36 should be at most 50%, in particular at most 30%, of the axial length of the externally threaded section.

(13) The axial length of the holding projection is 1.8 to 3 times the outer diameter of the end face abutment surface.

(14) The securing of the cutting tool 12 in the toolholder 10 will be explained below with reference to FIGS. 2 through 4. It should be emphasized that this securing is a releasable securing that can be reused multiple times without negatively affecting either of the two parts.

(15) First, still without turning, the cutting tool 12 with the first centering section 30 first is inserted into the tool holding receptacle 14 until the first centering section 30 penetrates into the first centering seat section 20, as shown in FIG. 2. At this time, the externally threaded section 32 is not yet screwed into the internally threaded section 22. This is made possible by the axial length L of the first centering section being greater than the axial distance I of the start of the internally threaded section 22 from the start of the first centering seat section 20, as shown in FIG. 1. If the first centering section 30 has a bevel or rounding at the free end, then the latter is not to be added to the dimensioning of the length L, as FIG. 1 shows. After the insertion of the first centering section 30 into the first centering seat section 20, the cutting tool 12 is already centered in the toolholder 10. The axes A are aligned with each other.

(16) Subsequently, as shown in FIG. 3, the externally threaded section 32 engages the internally threaded section 22 and is screwed into it. In doing so, the first centering section 30 is inserted deeper and deeper into the first centering seat section 20.

(17) Finally, at the end of the now occurring screwing-in process, the second centering section 36 arrives in the second centering seat section 24 and excludes wobble errors and additionally holds the cutting tool 12 in the toolholder 10.

(18) This assembly process is completed when the abutment surface 34 abuts against the counter surface 16 during the screwing-in process (see FIG. 4). In the process, an axial press fit is created.

(19) The two centering sections 30, 36 act as widely spaced bearings. As found in tests, the long seat achieved by the first centering section 30 stabilizes the cutting tool in the toolholder very well. This is particularly important in the illustrated exemplary embodiment, because the holding projection 26 is weakened by a cooling channel 40 that begins at the end face of the holding projection, preferably centrally extends through the cutting tool 12 and can align with the cooling channel 18.

(20) Both centering sections 30, 36 and their associated centering seat sections 20, 24 are designed with the same fit, in particular an H6/g6 fit.

(21) The axial length a (see FIG. 2), via which the front end of the first centering section 30 engages in the first centering seat section 20 when the externally threaded section 32 starts to engage the internally threaded section 22, should be at least 20% of the diameter of the first centering section 30 in order to achieve a tilting stability during the first centering.

(22) After installation, the cutting tool 12 is optimally centered in the toolholder 10; the two parts are concentric, without a bending load occurring in the holding projection 26 solely due to the securing of the components to one another. The holding projection is axially strained in elongation between the externally threaded section 32 and the abutment surface 34.

(23) The assembly is characterized by an extreme rigidity, reduced tendency to vibrate and, above all, reduced wobbling motions.