Milling tool for simultaneous roughing and finishing operations Technical field The object of the invention is a milling tool having a tool body, a shank portion, and cutting edges adapted for machining a workpiece, the cutting edges being disposed on the tool body. Background art

Milling tools are devices generally applied in machining technology for removing stock from workpieces.

Fig. 1 illustrates the operation of a conventional shank-type milling tool. The tool revolves around its own axis with an angular velocity ω and also advances with an instantaneous velocity v relative to the workpiece. The tool body 5 has cutting edges arranged either parallel with the axis of symmetry of the tool S or along a helical line coaxial with the axis of symmetry T. These cutting edges are the peripheral edges 1 of the tool S.

The peripheral edges 1 are arranged on flutes 2 protruding from the tool body, with chip grooves 3 being disposed between adjacent flutes 2.

A common feature of presently applied conventional peripheral edge configurations is that all peripheral edges 1 are located on a single cylindrical surface having a uniform diameter. A further common feature of conventional peripheral edge configurations is that a single peripheral edge 1 is disposed on each flute 2.

Conventional milling tools generally comprise so called chip-breaking grooves 4. This solution involves disposing grooves shifted axially by different amounts (in the direction of the major axis of the tool S) on subsequent edges, thereby improving the usability and durability of the tool.

Milling tools are usually applied in everyday practice for roughing and finishing operations. Roughing operations involve removing a relatively larger amount of stock, while during the subsequent finishing operation a relatively smaller amount of stock is removed.

United States patent description No 3,456,316 discloses a double-land end milling tool, essentially characterised by that on each flute of the tool a cutting edge and a non-cutting edge is arranged, where the non-cutting edge follows the cutting edge in the direction of rotation.

Surfaces machined by the cutting edges are mechanically worked by the subsequent non-cutting edges, thereby improving the dimensional accuracy and the surface roughness of these surfaces. The operating principle of this solution is the same as the principle of the so-called ironing operation that is for long applied in relation to broaching tools.

A similar solution is disclosed in the document US 4,990,036, where machining is carried out utilising a cutting insert. The insert has cutting edge sections adapted for roughing operations and finishing edge sections, where the latter are laterally displaced relative to the direction of feed of the insert and have smaller cutting depth than the roughing edge sections or are adapted for mechanical working. Disclosure of invention

The objective of the present invention is to provide a tool that is capable of performing roughing and finishing operations simultaneously.

The present invention is based on the recognition that it is possible to simultaneously arrange both roughing edges and finishing edges on each of the flutes of the tool.

The objective of the invention is accomplished by providing a milling tool having a tool body, a shank portion and cutting edges adapted for machining a workpiece, the cutting edges being arranged on the tool body or on insert plates, and is characterised by that each flute of the tool comprises both roughing and finishing edges. A preferred embodiment of the milling tool according to the invention has a shank-type or disc-type configuration. According to another preferred embodiment of the milling tool according to the invention chip-breaking grooves are disposed on the roughing edges of the tool.

A further preferred embodiment of the milling tool according to the invention has cutting insert plates, where the peripheral edges of each insert plate are formed by adjoining edge sections of different geometrical arrangement. Brief description of drawings

A known-art milling tool implementation as well as a preferred embodiment of the milling tool according to the present invention are explained in detail with reference to the attached drawings, where

Fig. 1 shows a conventional, known-art shank-type milling tool in operational position,

Fig. 2 is the schematic view of the shank-type milling tool according to the invention,

Fig. 3 shows the radial dimensions of the roughing and finishing edges of the milling tool according to the invention,

Fig. 4 shows the axonometric view of an embodiment of the milling tool according to the invention comprising chip-breaking grooves, Fig. 5 is the schematic view of the disc-type milling tool according to the invention,

Fig. 6 shows an embodiment of the disc-type milling tool according to the invention comprising chip-breaking grooves. Best mode of carrying out the invention. Fig 1 illustrates the geometrical arrangement of known-art milling tools presented in detail above in the section describing the prior art for the milling tool according to the present invention.

Fig. 2 is the schematic view of the shank-type milling tool according to the invention, showing the peripheral roughing edge 1 and the peripheral finishing edge 1' arranged on a common flute 2, as well as the arrangement of the chip groove 3.

Fig. 3 shows the way how the radial dimensions R1 , R1' of the roughing and finishing edges are defined. As it has been pointed out above, the radial distance R1 of roughing edges from the rotational axis of the tool is smaller than the radial distance R1' of the finishing edges. The difference corresponds to the theoretical thickness of stock removed by the finishing edges of the tool.

Fig. 4 illustrates an embodiment of the shank-type milling tool according to the invention having chip-breaking grooves.

Fig. 5 shows the schematic view of the disc-type milling tool according to the invention, where peripheral roughing edges 1 and peripheral finishing edges 1' are arranged on a common flute 2 disposed on a tool body 5 that also comprises chip, grooves 3. ' ^■■ ■" ^' ■ ^■' ■ Fig. 6 illustrates the axonometric view of an embodiment of the disctype milling tool according to the invention comprising chip-breaking grooves, clearly showing the configuration of a peripheral roughing edge 1 and a peripheral finishing edge V arranged on a common flute 2.

The peripheral roughing edge 1 comprises chip breaking grooves 4 arranged perpendicularly to the peripheral roughing edge 1.

Fig. 6 clearly shows the configuration of the flutes 2 arranged along the circumference of the tool body 5.

According to the embodiment shown in Fig. 6, the tool body 5 comprises eight flutes 2 . On each flute 2 one peripheral roughing edge 1 and one peripheral finishing edge V is disposed. Between two adjacent flutes 2 a chip groove 3 is disposed.

To facilitate chip removal, chip breaking grooves 4 are disposed on the peripheral roughing edges 1. With the above described arrangement of the inventive milling tool the quality of the machining operation can be improved together with an increase of tool edge lifetime.

List of references

S tool M workpiece v instantaneous velocity ω angular velocity

Δ theoretical thickness of stock removed by the finishing edges of the tool

R1 radial distance of the roughing peripheral edge from the axis of rotation of the tool

R1 ' radial distance of the finishing peripheral edge from the axis of rotation of the tool

1 peripheral roughing edge

V peripheral finishing edge 2 flute

3 chip groove

4 chip breaking groove

5 tool body