SHAFT TOOL WITH DETACHABLE TOP

Abstract: A shaft tool such as an end mill comprises a shaft portion (2) and a cutting portion (1). The cutting portion (1) consists of an integral cemented carbide body in one single piece, which comprises a cutting edge-provided part (3) for operative engagement with a workpiece, and a threaded part (4). The threaded part (4) is threaded into a correspondingly threaded hole (8) in the shaft portion (2). In this way, a very simple and effective joint is attained between the cutting and the shaft portions.

Description: Shaft Tool with Detachable Top The present invention relates to a shaft tool with a detachable top for metal cutting machining in accordance with the preamble of claim 1. Most rotating cutting tools comprise a shaft portion for fixing the tool in a holder and an operative cutting portion comprising cutting edges of a hard material such as cemented carbide, different ceramics, polycrystalline diamond and cubic boron nitride. The cemented carbide may be either coated or uncoated. Usually, the cutting edges consist of one or more of the edge lines on a cutting insert that is fastened upon and constitutes the active, cutting part of the operative cutting portion. This cutting insert is often fastened by a screw, the cutting insert having a through-hole, through which the screw is introduced. In other cases the cutting insert is fastened by a clamp or similar fastening or squeezing element; or by soldering or brazing. Although these well-known fastening arrangements function satisfactorily per se, they are all marred by different inconveniences. Thus, screws and clamps may for instance burst at repeated and/or too strong tightening, or they may sometimes loosen due to vibrations, which in best case makes necessary a retightening but in worst case may cause a tool breakdown. Moreover, soldering may cause brittleness and micro-cracks due to the heat when soldering, particularly in the soldered seam. Furthermore, a damaged soldered cutting insert cannot be replaced, wherefore the whole tool has to be disposed of, which of course increases costs. A further disadvantage in connection with locking screws is that it is time-consuming to screw and unscrew locking screws for the fastening of indexable cutting inserts, particularly when there are tens or even hundreds of cutting inserts to be mounted, demounted or indexed. Tools that are smaller in volume, such as end mills and drills, are usually made integrally of one single piece, whereby they consist of the same hard material as the cutting edges. This brings the advantage that the boundary layer of a screw joint, a clamp joint, a soldered seam, etc, is avoided. On the other hand, this "entirety solution" entails that the expensive and sometimes brittle and heat variation sensible hard material also is present in tool parts where it would no be necessary, for instance in the shaft portion. Still further fastening arrangements comprise wedges draw bars, etc. One drawback in connection with more bulky and material-demanding rotary cutting tools is that each individu tool requires its own material-demanding shaft portion, in spite of the fact that this portion is not worn to the same extent as the operative cutting portion. Thus, a first object of the present invention is to provide a tool which in first hand is a rotating cutting tool and which comprises a simplest possible fastening arrangement between the shaft portion of the tool and the operative cutti portion. A second object of the present invention is to decrease the material consumption when manufacturing the tool Still another object of the present invention is to lay the basis of a more flexible and polyvalent tool system. These and further objects have been attained in a suprisingly simple way by forming a cutting tool with the features as defined in the characterizing portion of claim 1. For illustrative but non-limiting purposes, an embodiment of the invention will now be further described in relation to the appended drawing. In the drawing are: Figure 1 a side view of an end mill according to the present invention, and Figure 2 a top view of the end mill according to figure 1. An end mill according to the invention comprises a top or operative cutting portion 1 and a shaft portion 2. The essential feature of the invention is that the cutting portio 1 is made of one integral piece which thus includes both the part 3 provided with cutting edges and the part 4 provided wi threads. The form of part 3 is not an essential feature of th present invention. According to the illustrated embodiment, i is formed to a ball end mill, which has helically twisted mai cutting edges 5 and end cutting edges 6 which extend into the rotation axis of the tool. Between each pair of adjacent main cutting edges extends a chip flute 7. Other examples of feasible embodiments of the part 3 provided with cutting edges is a straight end mill, a side-milling cutter and a cylindrical cutter. Another essential feature of the present invention is that the operative cutting portion 1 comprises a threaded part 4, which is intended to be threaded into hole 8 in the circular end surface of shaft portion 2, which hole is provided with a corresponding internal thread. The type of thread as such is not essential for the invention. Thus, the thread part 4 and the hole 8 can be made with different types of threads, each one being well-known as such, e.g., a V-thread with a triangular basic profile (for instance a normal metric thread or a so called M-thread) , different pipe threads, trapezoid and square threads and also so called round-threads. The extension of the thread can describe a cylinder but preferably the thread has a conical extension, as shown in figure 1. The advantage with a conical thread is of course that the threads can be engaged and disengaged from each other by a short turning, suitably less than two revolutions. The thread is suitably continuous and uninterrupted on the basically cylindrical or conical surface, although it could also comprise truncated, longitudinally extending portions. In order to make possible a fastening of the cutting portion 1 in the shaft portion 2 as stable as possible, the two portions are preferably provided with radial and/or axial abutment surfaces, suitably with both. According to figure 1, the radial abutment surfaces consist of on one hand two cylindrical outer envelope surfaces 11 and 12 situated above and underneath, respectively, the thread of the cutting portion, and on the other hand of two cylindrical, inner envelope surfaces 13 and 14 cooperating with the former and being located in the hole 8, above and underneath the hole thread, respectively. As axial abutment surfaces function on one hand the ring-shaped shoulder 15 which is located in a radial plane, between the part 3 of the cutting portion which part is provided with (a) cutting edge(s), and the thread par 4, and on the other hand the ring-shaped end surface 16 that cooperates with the former, said surface 16 being on the shaf portion 2. It is also possible to form the thread part 4 and the hole 8, respectively, with only one radial abutment surfa which then is placed above the thread, i.e., in the position corresponding to surface 11. In order to avoid an untightening of the threads during use of the tool, the direction of the thread must be t same as the direction of rotation. According to the illustrat embodiment, the tool shall rotate clock-wise, wherefore the thread part 4 has a right-hand thread. Since the production of such a cutting portion with threads is not possible by normal form pressing, or at least very complicated, the cutting insert is produced by an injection moulding technique known per se. In the plastic industry, this technique is a usual production technique for the production of different details. A paste consisting of or containing thermoplastic or ther o-setting polymers is heated to a suitable temperature and is then pressed through a die into a mould of desired geometry. In the powder metallurgy, injection moulding is used for the production of relatively complex details of metallic powder, such as cemented carbide powder. The cemented carbide powder is then mixed with polymers. After moulding, the polymer is removed, whereafter the detail is sintered in substantially the same way as for corresponding tool-pressed details. In order to simplify the screwing and unscrewing, respectively, of the cutting portion 1 in the hole 8, the former has been provided with a short cylindrical intermediat portion 9 between the cutting edge-provided part 3 and the thread part 4, the portion 9 having one or more recesses 10. This or these recesses is/are intended to function as key gri for tightening and untightening, respectively, of the cutting portion 1 by a suitable key. Suitably, the shaft portion 2 is made of steel such as tool steel. By the construction as described above, a number of adavantages have been attained. Thus, it is very easy and quick to replace different threaded tops 1 without detaching the shaft portion 2 out of its holder or out of the milling machine, e.g., from a straight end mill to a ball end mill, or from one diameter to another. Moreover, no further extra details as in the previously known technique are necessary, such as screws, clamps, wedges, draw bars, etc. Nor are any irreversible soldered seams necessary.

Claims: Claims 1. Shaft tool for metal cutting machining comprising an operative cutting portion (1) and a shaft portion (2) , c h a r a c t e r i z e d in that the cutting portion is mad as an integral cemented carbide body of one single piece comprising a cutting edge-provided part (3) for engagement wi a workpiece and a threaded part (4) which is threaded into a hole (8) with a corresponding thread in the shaft portion (2) 2. Shaft tool according to claim 1, c h a r a c t e r i z e in that the cutting portion (1) and the shaft portion (2) comprise cooperating radial (11, 12, 13, 14) and axial (15, 1 abutment surfaces, respectively, for the stabilization of the fixation of the cutting portion in the shaft portion. 3. Shaft tool according to claim 1 or 2, c h a r a c t e r i z e d in that the cutting portion is mad as a ball end mill, a straight end mill, a side-milling cutte or a cylindrical cutter. 4. Shaft tool according to claim 1, 2 or 3, c h a r a c t e r i z e d in that the threaded part (4) and the hole (8) have a conical shape. 5. Shaft tool according to claims 1 to 4, c h a r a c t e r i z e d in that the cutting portion is provided with one or more recesses (10) intended to function key grips for a suitable key for tightening and untightening, respectively, of the threaded part (4) in the hole (8) .

Inventors: HAEKANSSON BJOERN, HOLMSTROEM PER-ANDERS, PANTZAR GOERAN, ROMAN STEFAN, HAEKANSSON, BJOERN, HOLMSTROEM, PER-ANDERS, PANTZAR, GOERAN, ROMAN, STEFAN
Applicants: HAEKANSSON BJOERN, HOLMSTROEM PER ANDERS, PANTZAR GOERAN, ROMAN STEFAN, SANDVIK AB, HAEKANSSON, BJOERN, HOLMSTROEM, PER-ANDERS, PANTZAR, GOERAN, ROMAN, STEFAN
Application year: 1995
Main classification: B23C5
IPC codes: B23B31, B23C5