Cutting tool

Abstract: The present invention relates to a cutting tool having a head segment releasably attached to a shank segment. According to one aspect of this invention there is provided a cutting tool comprising: (i) a head segment (102) rotatable around an axis thereof and a forward end portion having at least one cutting-insert (3) receiving seat and a rearward end portion; (ii) a shank segment (101) rotatable around an axis thereof having a forward end portion adapted to be coaxially joined with the rearward end of the head segment and a rearward end portion adapted to be fixedly secured to a machine spindle; (iii) an engaging tapered hole (121) coaxially formed on one of the above segments; (iv) an engaging tapered projection (120) coaxially formed on the other one of the segments and engagingly fitted into the hole.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool comprising a head segment and a shank segment, especially a cutting tool wherein the head segment is releasable from the shank segment. 2. Related Art FIGS. 12 and 13 show a conventional cutting tool which has a generally cylindrical cutting tool body 10 having a shank segment 11 and a head segment 12. The shank segment 11 is adapted to be fixedly secured to a machine spindle (not shown) so that the cutting tool body 10 can be rotated about an axis passing thereof. The shank segment 11 is made of a high-rigid material such as a cemented carbide alloy which can be used for preventing deflection or chatter vibration of the body 10. The head segment 12 has a generally hemispherical forward end and a rearward end and is made of an easy-processing material such as a steel. In general, at least one insert receiving recess is formed in the forward end of the head segment 12, in which a cutting insert 3 is fixed by a clamp screw 4, while the reward end of the head segment 12 is joined with the shank segment 11 at a joint portion 13 by means of brazing. However, the conventional cutting tool described above has some problems: (i) it is difficult to detach the head segment from the shank segment because they are joined each other by the braze as mentioned above, so that the head segment can hardly be exchanged for another one when the head segment is damaged or when a different type of the head segment is required; (ii) it is also difficult to bring the end face of the head segment in contact with the end face of the shaft segment with a required accuracy, so that the head segment and/or shank segments requires at least one positioning marker or positioning mechanisms. FIG. 14 shows another type of a conventional cutting tool in accordance with the preamble of claim 1, which is fabricated for solving the above problem (i). As shown in the figure, an external thread 17 is coaxially provided with the shank segment 14, while an internal thread (not shown) is coaxially formed on the head segment 15. Consequently, these segments 14 and 15 are joined by threads so that the head segment can be easily replaced with another one. In this case, however, the internal and external threads have their own tolerances so that it is difficult to adjust the relative position between the head 15 and the shank 14 in a circumferential direction. For example, it is difficult to adjust the relative circumferential position between a cutting insert 3 and a chamfered corner 16 of the shank 14 when the head 15 and the shank 14 are tightened with the external thread 17. Accordingly, the above described joining means cannot be used for the work rotating cutting method but can be used for the tool-rotating cutting method. Furthermore, it is difficult to fabricate the external thread in a unitary construction with the shank when the shank is made of a cemented carbide alloy. In addition, in the case that an external thread segment is manufactured from an easy-processing material such as steel and joined with the shank segment by means of brasing, additional processing steps or the like would be required, resulting in the complicated fabricating process of the cutting tool. According to the invention there is provided a cutting tool comprising: a steel head segment rotatable around an axis thereof and having a forward end portion having at least one cutting-insert receiving seat and a rearward end portion; a shank segment rotatable around an axis thereof having a forward end portion coaxially joined with the rearward end portion of the head segment, and a rearward end portion adapted to be fixedly secured to a machine spindle; an engaging tapered hole coaxially formed in said head segment; and an engaging tapered projection in the form of a general conical frustum coaxially formed on the shank segment and engagingly fitted into said tapered hole, wherein the shank segment and the engaging projection are a unitary construction made of a cemented carbide. The cutting tool further comprises means of immobilizing the projection in the hole so as to ensure that relative position of the projection and the hole is maintained. The above immobilizing means includes: at least one internal thread communicating between the hole and the external surroundings through a peripheral surface of the segment; and at least one clamp screw respectively threaded through each internal thread, in which a bottom end of the clamp screw is contacted with a surface of the engaging projection. In a preferred embodiment of the invention, the engaging projection further includes a flat portion on its peripheral surface thereof for receiving the bottom end of the clamp screw. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be apparent from the following description, reference being made to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown. In the drawings: FIG. 1 is a front view of a cutting tool in accordance with an embodiment of the present invention; FIG. 2 is an end view of the cutting tool of FIG. 1 as seen in the direction indicated by the arrows XI in FIG. 1; FIG. 3 is an end view of the cutting tool of FIG. 1 as seen in the direction indicated by the arrows XII in FIG. 1; FIG. 4 is an exploded view of the cutting tool of FIG. 1; FIG. 5 is an expanded partial sectional view of a part of the cutting tool of FIG. 1; FIG. 6 is a front partial sectional view of a part of a cutting tool in accordance with a modified embodiment of the present invention; FIG. 7 is a front partial sectional view of a part of a cutting tool in accordance with a still further modified embodiment of the present invention; FIG. 8 is a cross-sectional view of the cutting tool of FIG. 7; FIG. 9 is another cross-sectional view of the cutting tool of FIG. 7; FIG. 10 is a front partial sectional view of a part of a cutting tool in accordance with an example of the present invention; FIG. 11 is a front elevation partly in section of a part of a cutting tool in accordance with an example of the present invention; FIG. 12 is a front elevation of a conventional cutting tool; FIG. 13 is an end view of the cutting tool of FIG. 12; and FIG. 14 is a front elevation of another conventional cutting tool. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Various embodiments of the present invention will be described hereinafter with reference to the accompanying drawings in which the same reference characters are used to designate like parts or elements in several views. [Example 1] FIGS. 1 to 5 depict a cutting tool in accordance with the present invention comprising a shank segment 101 and a head segment 102. The shank segment 101 has two end portions: a forward end portion coaxially provided with an engaging projection 120 adapted to be joined with the head segment 102; and a rearward end portion which is adapted to be fixedly secured to a machine spindle (not shown). The engaging projection 120 is in the form of a general conical frustum. In this example, the shank segment 101 and the engaging projection 120 are fabricated in a unitary construction and also they are made of a cemented carbide alloy. Referring to FIG. 1, a peripheral surface of the shank segment 101 has a chamfered portion 114 in the axial direction thereof. This chamfered portion is parallel to a flat portion 124 formed on a peripheral surface of the head segment 102. The head 102 segment, which is made of a steel, has a forward end portion and a rearward end portion. The forward end is adapted to receive a cutting insert 3 thereon, while a rearward end portion is adapted to be joined with the shank segment 101. In addition, an engaging tapered hole 121 is coaxially formed therein. The head segment 102 also comprises: an internal thread 122 communicating between the hole 121 and the external surroundings through a peripheral surface of the head 102; and a clamp screw 122 threads through the internal thread. FIG. 2 is an end view of the cutting insert of this example. In this figure, a surface of the chamfered portion 114 is peripherally arranged on the shank segment 102 at an angle of  with respect to a top end of the cutting insert 3 (in this example,  is 90°). In addition, the axis of the clamp screw 122 is inclined to the axial direction of the head segment 102 so as to keep a top end of the cramp screw 122 away from the forward end of the head segment 102. In FIG. 5, the inclination of the clamp screw 122 is indicated by a reference character α. Also, as shown in the figure, the clamp screw 122 is inclined at an angle of more than 90°. On the other hand, a surface of the flat portion 123 is perpendicular to the axis of the clamp screw 122 and thus it is inclined at an angle of β ( β = α - 90° ). Consequently, as shown in FIG. 5, a bottom face 124 of the clamp screw 122 can be contacted with the surface of the flat portion 123. According to the above described construction, the shank segment 101 and the head segment 102 are joined with each other by the following steps: (i) thrusting a clamp screw 122 loosely into an internal thread 122 of the head segment 102 in such a manner that the bottom face 124 of the clamp screw 122 is not projected from an the internal thread; (ii) positioning the shank segment 101 and the head segment 102 in the peripheral direction; (iii) inserting the engaging projection 120 of the shank segment 101 loosely into the engaging hole 121 of the head segment 102; and (iv) tightening the clamp screw 122 into the internal thread so as to touch the bottom face 124 of the clamp screw 122 with a surface of the flat portion 123 of the engaging projection 120. The shank segment 101 and the head segment 102 are joined with each other in the peripheral direction with a high accuracy by tightening the clamp bolt 127 into the internal thread 126 so as to move the engaging projection 120 toward a bottom face of the engaging hole 121. In this example, there is an interval portion 125 between the head and the shank segments and thus the cutting tool has a groove at a joint between these segments. It is noted that the head segment 102 cannot be slipped off from the shank segment 101 because the clamp screw 122 acts as a stopper when the clamp screw 122 is tightened to the head segment 102 at an angle α of over 90°. [Example 2] FIG. 6 depicts a cutting tool in accordance with the present invention which differs from the cutting tool of the example 1 in that the clamp screw 122 is arranged at an angle α of 90°. [Example 3] FIGS. 7 to 9 depict a cutting tool in accordance with the present invention which differs from the above examples in that a different type of clamp screw 122' is provided with the head segment 102 and a grooved portion 132 is formed in a peripheral surface of the engaging projection 120. In this embodiment, the clamp screw 122' comprises a threaded portion and a protruded portion, which is characterized in that a diameter of the protruded portion 133 is smaller than that of the threaded portion. The grooved portion 132 is formed so as to have a flat bottom face 132a which is parallel to the chamfered portion 114 and a width (h') which is slightly greater than the diameter (h) of the protruded portion 133 of the clamp screw 122'. Therefore the clamp screw 122' is tightly engaged with the grooved portion 132. As described above, a cutting tool according to the present invention can be fabricated without using the brazing method or the like for joining the head and shank segments, which can be easily attached and detached from the head segment. The present embodiments are illustrative, since the scope of the invention is defined by the appended claims.

Claims: A cutting tool comprising: a steel head segment (102) rotatable around an axis thereof and having a forward end portion having at least one cutting insert (3) receiving seat and a rearward end portion; a shank segment (101) rotatable around an axis thereof having a forward end portion coaxially joined with said rearward end portion of the head segment (102), and a rearward end portion adapted to be fixedly secured to a machine spindle; an engaging hole (121) coaxially formed in said head segment (102); an engaging projection (120) coaxially formed on the shank segment (101) and engagingly fitted into said hole (121); said shank segment (101) and said engaging projection (120) being a unitary construction made of a cemented carbide; said cutting tool further comprising means for immobilizing said projection (120) in said hole (121) so as to ensure that relative position of said projection (120) and said hole (121) is maintained; characterized in that said engaging hole (121) is tapered and said engaging projection (120) is in the form of a general conical frustum; said immobilizing means including; at least one internal thread communicating between said tapered hole (121) and the external surroundings through a peripheral surface of said head segment (102); and at least one clamp screw (122) respectively threaded through each internal thread, in which a bottom end (124) of said clamp screw (122) is contacted with a surface (123) of said engaging tapered projection (120). A cutting tool according to Claim 1, wherein said engaging tapered projection (120) further includes a chamfered portion (123) on an outer peripheral surface thereof for receiving said bottom end of the clamp screw (122). A cutting tool according to Claim 2, wherein said chamfered portion (123) is formed as a grooved portion having a flat bottom face thereof with which the clamp screw (122) is tightly engaged. A cutting tool according to Claim 2, wherein said clamp screw (122) is inclined to an axial direction of the head segment (102) at an angled α of more than 90°, while a surface of said chamfered portion (123) is perpendicular to an axis of said clamp screw and is inclined to the axial direction of the head segment at an angle of α - 90°. A cutting tool according to one of Claims 1 to 4, wherein said shank segment (101) further comprises at least one chamfered portion (114) on a peripheral surface thereof.

Inventors: NAKAYAMA MASAAKI, OKAWA MASAYUKI, SAITO JUNICHI, NAKAYAMA, MASAAKI, OKAWA, MASAYUKI, SAITO, JUNICHI, NAKAYAMA, MASAAKI, C/O TSUKUBA-SEISAKUSHO, OKAWA, MASAYUKI, C/O TSUKUBA-SEISAKUSHO, SAITO, JUNICHI, C/O TSUKUBA-SEISAKUSHO
Applicants: MITSUBISHI MATERIALS CORP, MITSUBISHI MATERIALS CORPORATION
Application year: 1992
Main classification: B23B29
IPC codes: B23B31, B23B29