JP3036343B2 - End mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill used for a machine tool such as a milling machine and a machining center.

[0002]

2. Description of the Related Art In recent years, the efficiency of cutting has been improved, and end mills have been designed to cope with this. For example, the core thickness is set larger than before, and the rake angle of the outer peripheral cutting edge is set to a negative angle. Have been. As a result, high-speed, high-feed cutting can be achieved mainly in light cutting of the side surface, and high-efficiency cutting has been enabled. (For example, Japanese Patent Application Laid-Open No. 5-253726) Also, it has become possible to cope with cutting of a hard material such as hardened steel.

[0003]

However, these effects can be obtained by light cutting, and in cutting such as groove cutting, or counterboring, which has a large cutting depth, the chip pocket is narrow and the cutting is difficult. Debris clogging occurred and cutting was impossible. In addition, with a normal end mill, the tool rigidity and the cutting edge rigidity are insufficient, so that not only high efficiency cutting is not possible, but also chipping is generated due to vibration, chatter, etc., which may cause breakage, and there is a problem in stability. Was. In addition, a method of obtaining a tool rigidity by providing a core thickness in a tapered shape in the shape of a normal end mill has been devised, but it is insufficient for performing high-efficiency cutting, and there is a problem with chip dischargeability. there were.

[0004]

[Object of the present invention] In order to solve the above-mentioned problems, the present invention examines various blade shapes to increase the rigidity of the end mill, improve the chip discharge property, and achieve high performance in various cutting processes. End mill.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a tool body having a blade at one end and a shank at the other end, and a plurality of cuts at the end of the blade. The blade is an end mill in which a plurality of twisted cutting edges are formed on an outer peripheral portion, and the cutting edge at the end has a slope of an insole, and is provided at a bottom of a groove through an end gash portion. The core thickness formed by the bottom of the blade groove is provided so that the core thickness of the shank side blade base portion is larger than the core thickness of the tip portion, and the portion where the core thickness changes with a step is defined as the effective blade length. The end mill is characterized in that one or more places are provided between approximately 1/4 to the cut-up portion.

Furthermore, it is preferable that the core thickness at the tool tip is set to less than 70% of the tool blade diameter, and the core thickness near the tool blade base is set to a range of 70 to 90%. Further, by setting the rake angle of the outer peripheral cutting edge in the cross section perpendicular to the axis of the outer peripheral cutting portion to be more than -30 ° and 0 ° or less, the cutting edge rigidity of the cutting edge can be obtained, and furthermore, the twisted cutting edge can be obtained. Torsion angle of 2
When the angle is in the range of 0 ° to 65 °, the sharpness is improved, and the fracture resistance can be significantly improved.

Further, in order to further extend the service life, a coating is applied, and the coating is made of Al, Si, carbides and nitrides of transition metals belonging to Groups 4a, 5a and 6a of the Periodic Table, which are excellent in crater wear resistance. , Oxides, borides, and one or more hard materials selected from the group consisting of boron carbide, hard boron nitride, hard carbon, and solid solutions or mixtures thereof in one or more layers. 0.2-20 μm in multilayer
If the thickness is covered, the life can be further extended.

[0008]

The present invention improves the rigidity of the tool itself and has a configuration excellent in chip dischargeability, in particular, chip discharge in the case of groove cutting and the like, so that groove cutting, spot facing and shoulder cutting can be performed. And various other cutting processes are made more efficient and stable. Therefore, the cutting edge at the end has a slope of the middle bottom, and is continuous with the blade groove bottom through the end gask portion, and the core thickness formed by the blade groove bottom is equal to the shank side blade base. The core thickness is provided to be larger than the core thickness at the tip portion, and a portion where the core thickness changes with a step is provided at one or more locations between approximately 1/4 of the effective blade length and the cut-up portion. is there.

By providing at least one portion where the rate of change of the core thickness changes in the axial direction of the tool, the clogging of chips is reduced at that portion and / or the function of a chip breaker is provided, and the groove cutting is performed. Cutting such as boring and spot facing can be performed efficiently and satisfactorily. Here, it is desirable that the portion where the core thickness changes sequentially has a smooth roundness in the tool axis direction.

In order to obtain the above-mentioned further effect, it is preferable that the core thickness at the tool tip is set to less than 70% of the tool blade diameter, and the core thickness near the tool blade base is set to 70 to 90%. When the core thickness is 70% or more of the tool blade diameter, the chip pocket is narrow in cutting such as groove cutting and spot facing, so the core thickness near the tool tip is set to 70% or less. When the core thickness of the maximum core thickness portion near the tool blade base is less than 70%, vibration, chatter, and the like are liable to occur, and when it exceeds 90%, a sufficient space cannot be obtained in the chip pocket.
0%.

The reason why the rake angle of the outer peripheral cutting edge is set to more than -30 ° and equal to or less than 0 ° is that when the rake angle is a regular angle, the cutting edge rigidity is insufficient. Is increased to more than -30 ° and 0 ° or less. Furthermore, the reason for setting the torsion angle of the outer peripheral cutting edge to 20 ° to 65 ° is that the simultaneous interference blade increases when the angle exceeds 65 °, and the simultaneous interference blade length increases when the angle is less than 20 °, and the cutting resistance is reduced in any case. This is because it increases and the sharpness tends to be inferior. Furthermore, by coating with a hard substance, the synergistic effect with the above-mentioned effect further improved the efficiency and performance.

[0012] Here, not only cutting such as grooving, but also cutting with a large depth of cut, spot facing, etc., as well as light cutting such as side cutting and cutting of a hard material such as hardened steel are possible. Needless to say.

[0013]

1 and 2 show an embodiment of the present invention, in which an ultra-fine-grain cemented carbide coated with TiN is used.
This is an end mill with a tool blade diameter of 10 mm, four blades, right blade, right twist. The rake angle of the outer peripheral cutting edge in the cross section perpendicular to the tool axis is -20 °, the angle of inclination is 10 °, the core thickness at the tool tip is 60% of the tool blade diameter, and the core thickness at the tool blade base is the tool blade diameter. 80
%, And the groove is continuous with a smooth curve at the center of the tool blade length.
The change rate of the core thickness is changed in the お よ び and 部位 portions. Further, the torsion angle of the outer peripheral cutting edge is set to 50 °.

Table 1 shows a comparison of cutting performance between the product of the present invention and the conventional product shown in FIGS. The conventional product has a core thickness of 55% of the tool blade diameter, a rake angle of + 6 ° (conventional product 1), a core thickness of 80% of the tool blade diameter, and a rake angle of −20 ° (conventional product 2). Using. Here, the conventional product 2 has the same shape except for the above. In the cutting test, a work material having a hardness of S50C material of HRC23 was used, and one blade feed was 0.1 mm /
Blade, tool protrusion 50mm, axial cut 10mm
5 shows the results obtained by cutting five grooves each up to a cutting length of 2 m.

[0015]

[Table 1]

In addition, the evaluation is defined as a chipping rate, and the length of the chipping edge of the chipped or chipped portion of the cutting edge is expressed by a value expressed as a percentage of the length of the cutting edge required for cutting. As the cutting condition, a condition in which the tool protrusion amount and the cutting amount were large and vibration easily occurred was selected.

Although the chipping rate of the product of the present invention slightly increases with the cutting length, it is less than 1% when cutting 2 m, and the maximum flank wear width of the outer peripheral cutting edge is 0.05 mm.
And continuous cutting was possible. The chipping rate of the conventional product 1 exceeded 10% on average, there were many cutting edges that were largely cut, and vibration, chatter and cutting noise during cutting were large, and cutting was no longer possible at the time of cutting 2 m. With regard to the conventional product 2, chip clogging occurred, the breakage occurred at the beginning of cutting, and cutting was impossible.

[0018]

As described above, by applying the present invention, the rigidity of the end mill can be increased, the chip discharge property can be improved, and high-performance and high-efficiency machining can be performed even in groove cutting and spot facing. It has become.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the vicinity of the tool tip of FIG.

3 is a cross-sectional view of the vicinity of the tool blade base in FIG. 1 in a cross section perpendicular to the blade axis.

FIG. 4 is a side view showing another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 outer peripheral cutting edge 2 shank part 3 end gash part 4 cut-up part 5 blade groove 6 core thickness 7 chip pocket 8 middle and low gradient θa torsion angle θb rake angle θc angle

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23C 5/10

Claims (5)

(57) [Claims] 1. A mill having a bottom blade cutting edge and the bottom twisted on the outer periphery of the tool body, said end cutting edge has a slope of the insole, it continues into the gullet bottom portion through the end gash section, shank The core thickness of the blade base is provided to be larger than the core thickness of the tip, and one or more locations where the core thickness has changed are provided between approximately 1/4 of the effective blade length and the cut-up portion. An end mill characterized by the following. 2. The end mill according to claim 1, wherein the core thickness at the tool tip is less than 70% with respect to the tool blade diameter, and the core thickness near the tool blade base is 70 to 90%. End mill. 3. The end mill according to claim 1, wherein the rake angle of the outer peripheral cutting edge in the cross section perpendicular to the axis of the outer peripheral cutting portion is more than −30 ° and 0 ° or less. 4. The end mill according to claim 1, wherein the twist angle of the twisted cutting edge is set to 20 ° to 65 °. 5. The end mill according to claim 1, wherein carbides, nitrides, oxides, borides, and boron carbides of Al, Si, and transition metals of Groups 4a, 5a, and 6a of the Periodic Table, and boron carbide and hard boron nitride are provided. Hard carbon and one or more hard materials selected from the group consisting of solid solutions and mixtures thereof in one or more layers of 0.2 to 2
An end mill coated with a thickness of 0 μm.