BLANK FOR SHAFT MILLING CUTTER

Abstract

A blank for a shaft milling tool having a generally cylindrical body of solid carbide, a rear portion and a front portion, the periphery of which front portion being designed for chip flutes to be formed therein, is made according to a method including the step of providing at least two separate green bodies having at least one axially extending inner channel, which are fitted together along a common interface and sintered together to form a unitary body. For a more economic production of blanks with radially extending channels at least one generally radially extending channel is formed in at least one of the connecting surfaces before sintering the bodies together. The channel is formed with its radially inner end configured for fluid communication with the axial channel and with a radial extension to a position corresponding to at least 40% of the outer radius of the blank.

Claims

1. A method of producing a blank for a shaft milling tool including a generally cylindrical body of solid carbide, the blank having a rear portion and a front portion, a periphery of the front portion being arranged for chip flutes to be formed therein, said method comprising: providing a first green body, the green body including the rear portion and a first part of the front portion axially adjacent the rear portion and having at least one axially extending inner channel extending at least through the first part of the front portion; providing a second green body including a second part of the front portion axially adjacent the first part, said first part of the front portion having a first connecting surface and the second part of the front portion having a second connecting surface the first and second connecting surfaces defining a common interface; forming at least one generally radially extending channel in at least one of the said first and second connecting surfaces, said channel having a radially inner end configured for fluid communication with said axial channel, the radial channel extending towards the periphery of the tool at least up to a radial position corresponding to 40% of an outer radius of the blank; and sintering the first green body and said second green body together to form a unitary blank of sintered carbide.

2. The method of claim 1, further comprising the steps of: providing the second green body with a third connecting surface on the side facing away from the first green body; providing a third green body including a third part of the front portion axially adjacent the second part and having a fourth connecting surface facing towards the second green body, the third and fourth connecting surfaces forming a common interface when fitted together; forming at least one generally radially extending channel in at least one of the third and fourth connecting surfaces, said channel having a radially inner end configured for fluid communication with said axial channel, the radial channel (4) extending towards the periphery of the tool at least up to a radial position corresponding 40% of the outer radius of the blank; and sintering the first, second and third green bodies together to form a unitary blank of sintered carbide.

3. The method according to claim 1, wherein the radial channel is formed to not extend along a straight path, the radial channel including at least one angled or curved section.

4. The method according to claim 1, wherein at least one of the first and second green bodies is presintered before forming a radial channel into a connecting surface thereof.

5. The method according to claim 1, wherein the at least one generally radially extending channel is formed by pressing or milling a groove into one or both of the connecting surfaces of the respective green body.

6. The method according to claim 1, wherein the channel is formed in only one of the connecting surfaces forming a common interface.

7. The method according to claim 1, wherein the at least one radially extending channel is formed with its radially outer end arranged at a distance from a central axis defined by the cylindrical body, the distance being within a range from between 40% and 85% of the outer radius.

8. The method according to claim 1, wherein the number of radial channels formed in a respective connecting surface is at least two.

9. The method according to claim 1, wherein the number of radial channels formed in a respective connecting surface is at least four.

10. The method according to claim 3 wherein the channels in a respective connecting surface are formed at equal angular distances.

11. The method according to claim 1, wherein at least two separate axial channels are provided, at least one of the channels being formed off center and wherein each axially extending channel is connected to different radially extending channels.

12. The method according to claim 1, wherein the connecting surfaces are formed as planar radial surfaces extending perpendicular to the axis defined by the cylindrical body.

13. The method according to claim 1, wherein the connecting surfaces are formed as rotationally symmetric mating surfaces extending rotationally symmetric with respect to the axis defined by the cylindrical body.

14. A blank for a shaft milling tool comprising a generally cylindrical body of sintered carbide, the blank having a rear portion and a front portion, in the periphery of which front portion chip spaces are to be formed, the blank including at least one axially extending channel and at least one generally radially extending channel in fluid communication with the at least one axially extending channel, wherein the blank is produced by a method according to claim 1 and wherein the at least one radially extending channel does not extend along a straight path, the radial channel including at least one angled or curved section.

15. A blank according to claim 14, wherein the at least one radial channel has a non-circular cross section.

Description

BRIEF DESCRIPTIONS OF DRAWINGS

[0061] FIG. 1 is a schematic longitudinal section through a first embodiment of a blank for a shaft milling tool according to the present invention.

[0062] FIG. 2 is another schematic longitudinal section through a second embodiment of a blank according to the present invention.

[0063] FIG. 3 is a view on a cross-section of the first and second embodiments, taken along the section lines X-X and Y-Y, respectively, in FIGS. 1 and 2.

[0064] FIG. 4 is a view on a cross-section of the first and second embodiments, taken along the section lines X-X and Y-Y, respectively, in FIGS. 5a-d,

[0065] FIGS. 5 a-d show embodiments consisting of different numbers of green bodies and including radial channels in different axial positions.

DETAILED DESCRIPTION

[0066] FIG. 1 is a schematic representation of the longitudinal section of the blank 10 of a shaft milling cutter, which is generally formed as a solid cylindrical body, which consists of a rear portion 1 and a front portion 2. As a green body viewed from the outside, the front portion 2 and the rear portion 1 are not distinguished in any way except for the fact that the front part 2 may comprise a centering tip (not shown) for handling the blank. The blank may also comprise exit openings of the radial channels, but the channels might even be formed as blind holes with dead ends 13 (cf. FIG. 3) and would then not be visible.

[0067] The front part 2 is that part of the blank 10, into which later on some chip flutes 5 may be formed one of which is shown in phantom in FIG. 1 by a dashed-dotted line. The front portion 2 in turn is formed of two members, namely a first part 6 adjacent the rear portion 1 and integrally formed therewith and a second part 7 adjacent the front end of the first part.

[0068] In the FIG. 2 embodiment, there is also provided a first part 6 of the front portion 2 as well as a second part 7, axially adjacent thereto, but in addition, there is even provided a third part 8 axially adjacent the second part 7. Any chip flute 5 is not yet provided in the blank.

[0069] A central channel 9 extends from the rear end face 11 along the axis 20 of the blank while in both embodiments of FIGS. 1 and 2 radially extending channels 4 are provided which, however, do not reach the periphery of the tool but are rather formed as blind holes with dead ends 13 at a radius which is smaller than the outer radius of the blank. This may be even better seen in FIG. 3 showing cross-sectional views of both, the first and second embodiment according to cutting lines X-X and Y-Y, respectively, in FIGS. 1 and 2 wherein the cross sectional view along the arrows X-X is a mirror image of the cross sectional view along arrows Y-Y.

[0070] Even though not visible in the figures, for any embodiment in which the channels do not extend to the periphery of the blank, and are thus not visible on the outer periphery 12 of the blank 10, the rear end face 11 of the blank may be provided with an indication of the position and course of the radial channels 4 at the respective interface(s). This would render it easier to select a proper circumferential position of the chip flutes 5.

[0071] Upon production of the blank, the rear portion 1 is unitary formed together with the first part 6 of the front portion 2, while the second part 7 of the first portion 2 is formed as a separate member. In a similar way, in the embodiment of FIG. 2, a first unitary green body is formed of the rear portion 1 and a first part 6 of the front portion 2, while a second green body 7 and a third green body 8 are separately formed.

[0072] Once the corresponding, basically cylindrical first and second (and optionally third) green bodies have been formed, they may or may not be pre-sintered, and grooves 4 will be formed into at least one of the connecting surfaces 15, 16, preferably by milling or grinding of the connecting surfaces.

[0073] Alternatively, in the actual green body state, the radial channels may also be pressed into the respective connecting surface(s) of the green body (bodies), in particular during the press forming step of the green body.

[0074] FIG. 3 shows two different cross sections of the interfaces from opposite directions X-X and Y-Y, respectively, which are mirror images of each other. In addition, the front portions of the blanks of FIGS. 1 and 2 are shown in order to identify the position and orientation of the respective cross sectional views.

[0075] According to FIG. 3, the grooves 4 are running along a more or less spiral path so that they do not extend exactly radially from the central channel 9 but have both, a radial and a circumferential component. As can further be seen from FIG. 3, all channels 4 extend from the central channel 9 along the more or less spirally wound path. The channels 4 may extend to the periphery 12 or may not extend to the periphery 12 of the blank and comprise a dead end 13 at a radius r which is between 40 and 90%, in the present example approximately 70%, of the radius R defined by the periphery 12 of the blank.

[0076] The radial position of the dead end 13 may vary in a range from between 40% to 90% of the outer diameter R. Even though in general not yet provided in the blank, chip flutes 5 are shown in full drawn lines and it is to be seen that the chip flutes 5 intersect with the channels 4 such that the dead ends 13 are removed and the channels 4 comprise an exit opening at the bottom of the respective chip flute 5. Any cooling or lubricating fluid may thus be ejected towards the work piece immediately adjacent the corresponding cutting edge or may also be directed to the cutting edge and the rake face adjacent thereto.

[0077] While not shown in FIG. 3, there might be provided additional channels 4 as blind holes which would not be opened because they would not intersect a corresponding chip flute 5, because their dead ends 13 would occur at a position between adjacent chip flutes.

[0078] Still, with a larger number of chip flutes, such as eight (having a narrower width than the chip flutes 5 as shown in FIG. 3) it would be possible to have also such additional channels 4 intersecting with the corresponding additional chip flutes, for instance in a milling cutter having eight peripheral cutting edges and correspondingly eight chip flutes 5. Accordingly, the corresponding blanks could be produced in a manner such as to be used for different types of milling cutters basically having the same diameter but different numbers of chip flutes and cutting edges.

[0079] With regard to the embodiment shown in FIG. 2, it may be noted that the radial channels provided at the interface between the first and second green body, should have channels 4 which are slightly rotated with respect to each other about the axis 20, such as to exit in the spirally wound chip flute 5 at equivalent positions.

[0080] The principle shown and described with respect to FIG. 2 would also apply for even more green bodies and a larger number of corresponding interfaces, each interface comprising the channels 4 which are formed and in particular milled or pressed into at least one of the connecting surfaces.

[0081] In another embodiment according to FIG. 4, the channels 4 would extend radially up to the periphery of the blank, while any other features of the channels would be the same as described in connection with the embodiments of FIGS. 1 to 3. With such an embodiment, the channels 4 or better to say their exit openings would be visible on the periphery 12 of the cutting portion 2.

[0082] FIGS. 5a to 5d show four additional embodiments, wherein the cross section along the lines X-X may be the same as shown in FIG. 4 for all the embodiments of FIGS. 5a to 5d.

[0083] FIG. 5a corresponds to the embodiment shown in FIG. 1 with the exception that the channels are not formed as blind holes but extend up to the periphery of the blank. The embodiment of FIG. 5c corresponds to the embodiment shown in FIG. 2 again with the exception that the channels 4 extend up to the periphery of the blank.

[0084] The embodiment shown in FIG. 5b is almost the same as the embodiment of FIG. 5c, wherein still the blank 10 is formed of three green or presintered bodies 6, 7 and 8, even though no channels 4 are provided at the interface between the green, or preferably presintered bodies 6 and 7. The presintering has the advantage that the three bodies 6, 7 and 8 may have a different hard metal composition and are selected and designed for their individual properties.

[0085] The embodiment according to FIG. 5d shows that the concept of forming optionally presintered green bodies to be sintered or fused together after radially extending channels have been formed in at least some of the connecting surfaces, may be extended to even a larger number of green bodies such as five green bodies 6, 7, 8, 17, and 18 in the example of FIG. 5d which in that case would allow the formation of radial channels in each individual chip flute at three or even four different axial positions, in order to provide the cooling/lubricating fluid along a greater length of the cutting portion, which may relevant in particular for applications in which deep groves are formed by means of a shaft milling cutter.

[0086] For the purpose of original disclosure it is to be noted that any features which may be gathered by a skilled person from the present description, the drawings and the claims, even if only described in connection with particular further features, may be combined individually as well as in arbitrary combinations with any other of the features or groups of features disclosed herein, unless this is explicitly excluded or technical conditions would render such combinations impossible or senseless. The comprehensive, explicit discussion of any combinations of features which might be thought of is dispensed with just for the sake of brevity and legibility of the description and claims.