Method and apparatus for manufacturing a blank for a rotary cutting tool
A blank for a rotary tool for chip removing machining, such as a helix drill or an end mill is formed by advancing a mixture of hard metal powder and carrier through an extrusion passage. The mixture is fed past a core having pins secured thereto for forming respective internal holes through the mixture. Then the mixture is advanced through a rotary part that is rotating about a center axis of the extrusion passage, wherein the rotary part and the internal holes become twisted to a predetermined pitch. The mixture is also advanced past a plurality of shaping parts which project transversely into the extrusion passage for shaping exterior chip flutes in the mixture, e.g., by embossing or cutting. The mixture is allowed to harden into a green body, and the green body is then sintered to form a blank.
1. A method for manufacturing a blank for a rotary tool for chip removing machining, comprising the steps of:
A) mixing a hard metal powder and a carrier,
B) inserting the mixture into an extrusion machine in which the mixture is heated to a temperature rendering the mixture flowable,
C) advancing the flowable mixture in a feed direction through an extrusion passage and past a core having rigid pins secured thereto for forming respective internal holes through the mixture, thereafter
D) advancing the mixture through a rotary part that is rotating about a center axis of the extrusion passage, wherein friction between the mixture and the rotary part causes the mixture to be twisted, whereby the internal holes become twisted to a predetermined pitch, thereafter
E) allowing the mixture to solidify and form a green body, and
F) sintering the green body to form a blank.
2. The method according to claim 1 , further including, subsequent to step C, and prior to step D, the step of advancing the mixture past a plurality of shaping parts projecting transversely into the extrusion passage for shaping exterior chip flutes in the mixture.
3. The method according to claim 2 , wherein the shaping is performed by embossing.
4. The method according to claim 2 , wherein the shaping is performed by cutting.
5. The method according to claim 2 , further comprising the step of retracting the shaping parts out of the extrusion passage for terminating the shaping of chip flutes in the mixture as the mixture continues to be advanced through the extrusion passage.
6. The method according to claim 1 , wherein the blank is a helix drill blank.
7. The method according to claim 1 , wherein the blank is an end mill blank.
8. Apparatus for making a green body for a tool for chip removing machining, the apparatus comprising a housing in which are mounted a die and a rotary part together forming a extrusion passage for conducting a flowable mixture; the rotary part being rotatable about a center axis of the extrusion passage; a core mounted in a nozzle and carrying rigid pins disposed in the extrusion passage for forming respective internal holes through a mixture being conducted, the rigid pins terminating axially short of the rotary part.
9. The apparatus according to claim 8 , further including a plurality of shaping parts having respective inner ends projecting transversely into the extrusion passage upstream of the rotary part for shaping chip flutes in a mixture being conducted.
10. The apparatus according to claim 9 , wherein the inner ends of the shaping parts are retractable out of the extrusion passage.
11. The apparatus according to claim 10 , wherein the shaping parts comprise embossing members.
12. The apparatus according to claim 10 , wherein the shaping parts comprise cutting members.
13. The apparatus according to claim 9 , wherein a location of the inner ends of the pins along the axis of the extrusion passage corresponds to a location of downstream ends of the pins.