JPH07195223A - End mill - Google Patents

Abstract

PURPOSE:To provide an end mill having high-performance and high-rigidity, even both in gash-cutting and in couterboring work, by enhancing the rigidity of the end mill, and improving the dischargeability of chips. CONSTITUTION:In an end mill in which a plurality of gashes 5 and cutting edges 1 are formed on the outer circumference of a tool body, the gash 5 whose length is shorter than the gash 5 of the end mill and whose depth is deeper than the depth of the gash 5 is additionally formed from the end part of the tool toward the edge root part of the tool, so that the rigidity is enhanced, and the dischargeability of chips is improved, and high-performance and high- efficiency working can be enabled in various cutting works.

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 machine tools such as milling machines and machining centers.

[0002]

2. Description of the Related Art In recent years, the efficiency of cutting has advanced, and in order to cope with this, end mills have been devised such that the core thickness is set larger than before and the rake angle of the outer peripheral cutting edge is set to a negative angle. Came. As a result, high-speed, high-feed cutting is possible mainly for light side cutting, enabling high-efficiency cutting. In addition, it has become possible to handle cutting of high hardness materials such as hardened steel.

[0003]

However, these effects are obtained by light cutting, and in the case of cutting with a large cutting amount such as groove cutting and counter boring, the chip pocket is narrow and Debris clogging occurred and cutting was impossible. Since the ordinary end mill lacks the rigidity of the tool and the rigidity of the cutting edge, not only high efficiency cutting is not possible but also chipping may occur due to vibration, chattering, etc., which may cause breakage, and there is a problem in stability. Although an attempt was made to obtain tool rigidity by providing the core thickness in a taper shape in the shape of an ordinary end mill, it was not sufficient for high-efficiency cutting and there was a problem in chip discharge.

[0004]

The object of the present invention is to improve the rigidity of the end mill, to improve the chip discharge property, and to achieve high performance in various cutting processes by examining various blade shapes in order to solve the above problems. It is intended to provide an end mill.

[0005]

In order to achieve the above object, the present invention provides an end mill having a plurality of blade grooves and cutting edges formed on the outer periphery of a tool body, from a tool tip portion to a tool blade base portion. On the other hand, a blade groove shorter than the end groove length of the end mill and deeper than the blade groove depth is additionally provided. The core thickness of the tool tip is 70 with respect to the tool blade diameter.
%, The core thickness near the tool blade root may be set in the 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 edge to be more than -30 ° and 0 ° or less, the cutting edge rigidity of the cutting edge can be obtained. By setting the twist angle of the blade within the range of 20 ° to 65 °, the sharpness can be improved and the fracture resistance can be remarkably improved.

Here, as the coating, Al, Si, which is excellent in crater wear, carbides, nitrides, oxides, borides, boron carbide, and hard boron nitride of Group 4a, 5a, and 6a transition metals of the Periodic Table. , Hard carbon, or one or two selected from the group consisting of solid solutions or mixtures thereof.
0.2 or more of one or more hard materials of one or more layers
If it is coated with a thickness of up to 20 μm, a further effect can be obtained.

[0008]

According to the present invention, the rigidity of the tool itself is improved and the chip discharge property is excellent, so that various cutting processes including groove cutting and spot facing can be made more efficient and stable. To do. Therefore, in an end mill in which a plurality of flutes and cutting edges are formed on the outer periphery of the tool body, a flute that is shorter than the flute length of the end mill and deeper than the flute depth from the tool tip toward the tool flute base. Is provided as an additional process.

By additionally machining a blade groove that is shorter than the blade length of the end mill and deeper than the blade groove depth from the tool tip portion toward the tool blade root portion, the clogging of chips is alleviated at that portion. Since it has a function of a chip breaker, cutting such as grooving and spot facing can be performed efficiently and satisfactorily.

In order to obtain a further effect, the core thickness at the tip of the tool may be set to less than 70% of the diameter of the tool blade, and the core thickness near the base of the tool blade may be 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 or spot facing, so the core thickness near the tool tip was set to 70% or less. Further, when the core thickness of the maximum core thickness portion in the vicinity of the tool blade root portion is less than 70%, vibration and chattering are likely to occur, and when it exceeds 90%, sufficient space cannot be secured in the chip pocket, so that it is 70 to 90 %.

Further, the rake angle of the outer peripheral cutting edge is set to be more than -30 ° and not more than 0 ° because the rigidity of the cutting edge is insufficient when the rake angle is a regular angle, and the cutting resistance is less than -30 °. Since it increases, the angle was set to more than -30 ° and 0 ° or less. Furthermore, the reason why the twist angle of the outer peripheral cutting edge is 20 ° to 65 ° is that when 65 ° is exceeded, the number of simultaneous interference blades increases, and when it is less than 20 °, the simultaneous interference blade length increases, and the cutting resistance is increased in both cases. This is because the amount increases and the sharpness tends to be poor. By coating with a hard material, synergistic effect with the above results in higher efficiency and higher performance. .

Here, not only cutting with a large cutting amount such as groove cutting, cutting such as spot facing, but also light cutting such as side cutting and cutting of a high hardness material such as hardened steel are possible. Needless to say. Further, not only the end mill with a square blade, but also various end mills such as a taper end mill, a ball end mill, and a full-shape end mill can be applied.

[0013]

1 and 2 show one embodiment of the present invention, which uses a TiN coating ultrafine particle cemented carbide,
An end mill with a tool blade diameter of 10 mm, 4 blades and a right blade with a right twist. The rake angle of the outer peripheral cutting edge in the cross section perpendicular to the tool axis is -20 °, the flank angle is 10 °, the core thickness of the tool tip is 60% of the tool blade diameter, and the core thickness of the tool blade base is of the tool blade diameter. 80
%, The blade groove is continuous with a smooth curve at the center of the tool blade length, and is approximately 1/4 of the tool blade length from the tool tip.
The change rate of the core thickness is changed at the positions of 1/2 and 1/2. Further, the twist 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 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, for comparison, portions other than the above have the same shape. In the cutting test, the hardness of S50C material is H
The results are obtained by using the RC23 and performing 5 groove cuttings each with a blade feed of 0.1 mm / blade, a tool protrusion amount of 50 mm, and an axial cut of 10 mm up to a cutting length of 2 m.

[0015]

[Table 1]

The evaluation criterion is defined as the defect rate, and the length of the cutting edge chipping or the missing edge is expressed as a percentage of the length of the cutting edge required for cutting. Here, the cutting conditions are conditions in which the amount of tool protrusion and the amount of cutting are large and vibration is likely to occur.

The defect rate of the product of the present invention slightly increases with the cutting length, is less than 1% at the time of 2 m cutting, and the maximum flank wear width of the outer peripheral cutting edge is 0.05 mm, and continuous cutting is possible. Met. The loss rate of Conventional product 1 exceeded 10% on average, many cutting edges were greatly lost, and vibration, chatter and cutting noise during cutting were large, and it was no longer possible to cut at 2 m. Regarding Conventional product 2, chip clogging occurred, and it was broken at the initial stage of cutting and could not be cut.

[0018]

INDUSTRIAL APPLICABILITY By applying the present invention as described above, it is possible to increase the rigidity of the end mill, improve the chip discharge property, and perform high-performance and high-efficiency machining even in groove cutting and counter boring. It has become.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view in a cross section perpendicular to the blade axis near the tip of the tool in FIG.

FIG. 3 is a cross-sectional view in a cross section perpendicular to the axis of the blade portion near the tool blade root portion in FIG. 1.

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

[Explanation of symbols]

 1 Outer peripheral cutting edge 2 Shank part 3 End gash part 4 Up-cutting part 5 Blade groove 6 Core thickness 7 Chip pocket θa Twist angle θb Rake angle θc Long angle

Claims (5)

[Claims] 1. An end mill in which a plurality of blade grooves and cutting edges are formed on the outer periphery of a tool body, the blade length being shorter than the end groove length of the end mill from the tool tip portion toward the tool blade base portion,
An end mill characterized in that a blade groove deeper than the blade groove depth is additionally formed. 2. The end mill according to claim 1, wherein the core thickness in the vicinity of the tool tip is less than 70% of the tool blade diameter, and the core thickness in the vicinity of the tool blade base is set in the range of 70 to 90%. An end mill characterized by. 3. The end mill according to claim 1, wherein the rake angle of the outer peripheral cutting edge in a cross section perpendicular to the axis of the outer peripheral blade is more than −30 ° and 0 ° or less. 4. The end mill according to claim 1, wherein the helix angle of the cutting edge is set in the range of 20 ° to 65 °. 5. The end mill according to any one of claims 1 to 4, wherein Al, Si, carbides, nitrides, oxides, borides, boron carbide, and hard boron nitride of Group 4a, 5a, and 6a transition metals of the periodic table. , Hard carbon, and one or more hard substances selected from the group consisting of solid solutions or mixtures thereof in a single layer or a multilayer of two or more layers.
An end mill coated with a thickness of 20 μm.