CUTTING TOOL

Description

Description

[0001] The invention relates to a cutting tool, in particular a reaming tool for fine machining a bore or a milling tool, according to the preamble of patent claim 1.

[0002] Reaming is a machining process with a geometrically defined cutting edge. In contrast to solid boring or boring, only small chip cross-sections are used in pre-machined holes. The stock removal allowances or reaming allowances in diameter are typically in the range of 0.1 to 0.5 mm. A reaming tool should ensure high hole quality across many components, with the smallest possible tolerances in the diameter, as well as in the shape and position of the hole and its roughness. In this context, it is known from WO2015 / 055364 to fix a cutting head to a base body via a permanent solder connection. The cutting edges are then ground to the desired size in a subsequent production step.To redirect the coolant to the cutting edge area, a distributor is inserted into a coolant channel of the cutting head and secured by a clamping screw screwed into the front shaft section of the base body. In this configuration, various tolerances play a role in the gap of the coolant passage under the distributor, particularly the thickness of the solder joint, the height of the cutting head, the width of the distributor's web, and the position of the internal thread in the base body. As a result, the coolant distribution gap may not be sufficiently large to ensure adequate supply to the cutting edge area.

[0003] To increase the performance of reaming tools, it has also proven effective to design the cutting head as a sintered carbide blank, which can be reworked to a certain extent by turning and grinding. However, drilling coolant channels is not possible in this case.

[0004] From DE 10 2013 015 252 A1, a coolant supply to a skiving tool is known, in which a skiving wheel holder has a central bore into which a hollow screw is inserted as a holder for a cover, wherein the cover rests on its outer circumference on the edges of the toothing.

[0005] Based on this, the object of the invention is to further improve the tools known in the prior art and to ensure the supply of cooling lubricant with low manufacturing costs.

[0006] To solve this problem, the combination of features specified in claim 1 is proposed. Advantageous embodiments and further developments of the invention emerge from the dependent claims.

[0007] The invention is based on the idea of ​​creating the shaped elements for a defined spacing directly in the primary mold of a sintered cutting head. Accordingly, the invention proposes that a plurality of protruding spacers are sintered onto a support or guide surface of the cutting head as primary mold elements to keep a gap free from the coolant distributor. The coolant distributor is held seated on the spacers, so that the gap defined by the spacers between the support surface and the coolant distributor remains free for the passage of coolant. The spacers are designed as geometric shaped bodies tapering to a free bearing point facing away from the support surface.This makes it possible to create suitable spacers in an integrated molding process without the need for additional tools that are subject to tolerances and without the need for post-processing. Furthermore, the required distance to create a gap can be defined precisely where this distance must be maintained, particularly for the effective flow of cooling lubricant. The manufacturing effort for designing the mold is largely independent of the quantity and is not significantly influenced by the additional spacers. A further advantage is that the remaining tool parts can be produced with less effort because, by avoiding chained spacing, extreme tolerances no longer need to be maintained.According to the invention, the cooling lubricant distributor is held seated on the spacers so that the gap defined by the spacers between the support surface and the cooling lubricant distributor remains free for the passage of cooling lubricant.

[0008] Another particularly preferred embodiment provides for the coolant distributor to be clamped to the spacers by a screw connection without a fixed connection to the base body. This allows the required distance to be determined directly on the cutting head without the need for complex mechanical structures on the base body. This also allows for smaller installation spaces or head diameters.

[0009] A particularly simple design can be achieved by screwing the coolant distributor into a centering sleeve that can move against an abutment of the cutting head.

[0010] A further design improvement provides that the centering sleeve is guided in an axial bore of the base body and, as part of the coolant supply, is provided with through-openings for the coolant.

[0011] In order to avoid interference contours, particularly for the machining of blind holes, it is advantageous if the guide surface is axially offset from a front end section of the cutting head towards the base body, with the cooling lubricant distributor being mounted within the cutting head.

[0012] In order to apply cooling lubricant to the cutting edges in a targeted manner, it is advantageous if the cutting head is provided with a recess associated with each of the at least one cutting edge, forming a radial passage for the cooling lubricant in the area of ​​a chip groove adjoining the cutting edge.

[0013] A radial deflection of the cooling lubricant in the area of ​​the cutting head can be advantageously achieved by forming the cooling lubricant distributor as a mushroom-shaped turned part made of metal, in particular steel.

[0014] A further advantageous embodiment is that spacers protrude on a side of the cutting head facing the base body, wherein the gap kept free by these spacers between a further support surface and the base body forms a solder gap for a soldering connection of the cutting head to the base body.

[0015] To ensure tilt-free centering, it is advantageous if at least three spacers are arranged circumferentially around the longitudinal center axis.

[0016] Depending on the tool configuration, it may be advantageous for an unhindered coolant flow if the spacers are arranged at the same or irregular angular distance from each other in the circumferential direction around the longitudinal center axis.

[0017] To define suitable gap dimensions, it is advantageous if the spacers have a height in the range of 0.1 to 2 mm, preferably 0.2 to 1 mm.

[0018] The invention is explained in more detail below with reference to the exemplary embodiments schematically illustrated in the drawings. They show: Fig. 1 shows a reaming tool with a sintered cutting head and a cooling lubricant distributor inserted therein in a perspective view; Fig. 2 shows the cutting head without a cooling lubricant distributor in an enlarged view; Fig. 3 shows the reaming tool according to Fig. 1 in broken axial section.

[0019] The reaming tool 10 shown in the drawing can be driven by a machine tool in rotation about its tool axis or longitudinal center axis 12 for the fine machining of a pre-machined bore in a workpiece, and can be advanced axially in order to remove a reaming allowance by machining and thus create a precisely fitting bore with a high surface quality. However, the tool axis can also be a rotational axis for a workpiece that is moved in rotation about the tool axis for machining with a stationary machine tool.

[0020] As in Fig. 1As shown, the reaming tool 10 has a stepped cylindrical base body 14 which can be clamped into the tool holder of a machine at its rear end and which carries a cutting head 16 at its front end. The cutting head 16 is formed as a sintered pressed piece made of hard metal or cermet and is provided with a plurality of ground cutting edges 18 distributed over its circumference, each of which is assigned a chip groove 20. A channel 22 extends through the base body 14 in the longitudinal direction thereof as part of a cooling lubricant supply 24 fed from the machine side, which channel 22 comprises a cooling lubricant distributor 26 inserted into the cutting head 16 on the outlet side for the radial deflection of cooling lubricant into the area of ​​the cutting edges 18 and chip grooves 20. In order to keep a defined passage gap between the one guide orThe support surface 28 of the cutting head 16 and the cooling lubricant distributor 26 have a plurality of raised, projecting spacers 30 arranged on the support surface 28, which are formed as primary forming elements during sintering.

[0021] As from Fig. 2 As can be seen, the support surface 28 is formed by an axially forward-facing annular surface which is set back from a front end section 32 of the cutting head 16, so that the cooling lubricant distributor 26 can be accommodated in the cutting head 16 without axial projection. In order to direct the cooling lubricant away from the support surface 28 into the area of ​​the cutting edges 18, the cutting head 16 is provided with a plurality of recesses 34, each opening into a chip groove 20. These recesses 34 are introduced after the sintering of the cutting head 16 during its grooving, thereby enabling flexible allocation depending on the number of ground cutting edges 18.

[0022] In the embodiment shown, three spacers 30 are arranged circumferentially distributed around the longitudinal center axis 12. The spacers 30 expediently have a height in the range of 0.2 to 1 mm. The spacers 30 have a geometric shape tapering toward their support point, for example, a spherical shape.

[0023] In principle, it is also possible for the pitch or angular spacing of the spacers 30 to be adapted to the number of cutting edges 18. Depending on the configuration of the cutting edges 18, it is also conceivable for the spacers 30 to be arranged with an irregular pitch, so that the coolant flow radially to the cutting edges 18—the number of which can vary depending on the application, with otherwise constant tool dimensions—is not impeded.

[0024] To secure the coolant distributor 26, a centering sleeve 36 is provided, which is mounted in the base body 14 with limited axial movement. The centering sleeve 36 has an internal thread 38 and is provided with axial grooves 40 on the casing side for the passage of coolant.

[0025] How best to Fig. 3As can be seen, the mushroom-shaped coolant distributor 26 can be screwed into the internal thread 38 of the centering sleeve 36 with a threaded extension 42. The centering sleeve 36 is pulled against an axial shoulder 44 of the cutting head 16, while the coolant distributor 26, with its radially projecting head piece 46, sits firmly on the spacers 30. The clamping connection is thus realized without a fixed connection to the base body 14. As a result, a defined gap 48 remains free as a coolant passage between the support surface 28 of the sintered cutting head 16 and the head piece 46 of the coolant distributor 26, which is manufactured as a turned part made of metal, without connection tolerances to the base body 14 playing a role.

[0026] In principle, it is also possible for spacers 30' to be sintered onto a support surface of the cutting head 16 facing the base body 14 to ensure a defined gap there. For example, the spacers 30' can protrude from a rear conical surface 28' of the cutting body 16 to keep a solder gap 48' free for a solder connection opposite a front conical surface 50 of the base body 14.

[0027] Outside the scope of the invention, it is fundamentally conceivable that, instead of raised spacers 30, suitable recesses are formed into the support surface 28 of the cutting head 16 to create a radial passage for the cooling lubricant. The cooling lubricant distributor 26 can rest directly on the support surface 28 with its head piece 46.

Claims

1. Machining tool, in particular a reaming tool for precision machining of a hole or a milling tool, comprising a main body (14) which has a longitudinal central axis (12) and can be clamped in a tool holder, a cutting head (16) which is attached to the free end of the main body (14) and is formed, by primary shaping, as a sintered piece provided with at least one cutting edge (18), and comprising a cooling lubricant feed (24) which is guided axially through the main body (14) and has a cooling lubricant distributor (26) inserted into the cutting head (16) for diverting cooling lubricant into the region of the at least one cutting edge (18), characterized in that a plurality of protruding spacers (30, 30') for keeping a gap clear with respect to the cooling lubricant distributor (26), as elements formed by primary shaping, are sintered on a support surface (28) of the cutting head (16), the cooling lubricant distributor (26) being held seated on the spacers (30, 30'), so that the gap (48) between the support surface (28) and the cooling lubricant distributor (26), which is defined by the spacers, remains clear for the passage of cooling lubricant, the spacers (30, 30') being designed as spherical, conical, wedge-shaped or curved geometric shaped bodies which taper toward a free bearing point facing away from the support surface (28).

2. Tool according to claim 1, characterized in that the cooling lubricant distributor (26) is clamped onto the spacers (30) by a screw connection without a fixed connection to the main body (14).

3. Tool according to claim 1 or 2, characterized in that the cooling lubricant distributor (26) is screwed into a centering sleeve (36) which can be moved against an abutment (44) of the cutting head (16).

4. Tool according to claim 3, characterized in that the centering sleeve (36) is guided in an axial hole in the main body (14) and, as part of the cooling lubricant feed (24), is provided with through-openings (40) for cooling lubricant.

5. Tool according to any of claims 1 to 4, characterized in that the support surface (28) is axially set back toward the main body (14) with respect to a front end portion (32) of the cutting head, the cooling lubricant distributor (26) being mounted within the cutting head (16).

6. Tool according to any of claims 1 to 5, characterized in that the cutting head (16) is in each case provided with a recess (34) which is assigned to the at least one cutting edge (18) and forms a radial passage for the cooling lubricant in the region of a flute (20) adjoining the cutting edge (18).

7. Tool according to any of claims 1 to 6, characterized in that the cooling lubricant distributor (26) is a mushroom-shaped turned part made of metal, in particular steel.

8. Tool according to any of claims 1 to 7, characterized in that a plurality of protruding spacers (30') for keeping a gap clear with respect to the main body (14), as elements formed by primary shaping, are sintered on a further support surface (28') of the cutting head (16).

9. Tool according to claim 8, characterized in that the spacers (30') protruding from the further support surface (28') protrude from a side of the cutting head (16) that faces the main body (14), the gap (48') kept clear by the spacers (30') forming a solder gap for a solder connection to the main body (14).

10. Tool according to any of claims 1 to 9, characterized in that at least three spacers (30, 30') are distributed in the circumferential direction around the longitudinal central axis (12).

11. Tool according to any of claims 1 to 10, characterized in that the spacers (30, 30') are arranged at equal or irregular angular distances from one another in the circumferential direction around the longitudinal central axis (12).

12. Tool according to any of claims 1 to 11, characterized in that the spacers (30, 30') have a height in the range of 0.1 to 2 mm, preferably 0.2 to 1 mm.