JPH0440122B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to improvement of an end mill, and more specifically, the present invention relates to the improvement of an end mill, and more specifically, the present invention relates to the improvement of an end mill, and more specifically, to the honing of the cutting edge as disclosed in Utility Model Registration Application No. 57-143897 (Utility Model Application No. 59-50621). This invention relates to an improvement in which an end mill with a strengthened cutting edge is further coated with a hard material having wear resistance. [Prior art] Conventional end mills are classified into three types based on the structure that holds the tool material that makes up the cutting edge: solid type, brazed type, and T type.
Brazed end mills are used with sharp cutting edges. These are used for small diameters. The reason why these solid-type and brazed-type end mills are used with sharp cutting edges is that, firstly, when the peripheral cutting edge, which is the main cutting edge, bites into the workpiece material or separates from the workpiece material, it prevents top-slip phenomenon. This is to reduce burrs etc.
This is to reduce cutting resistance as much as possible since the cutting edge and chuck are separated from each other. [Problems to be Solved by the Invention] Despite the demand for sharp cutting edges for end mills, conventional end mills have had the following drawbacks. In other words, in end mills using high-speed steel as the tool material, burrs tend to remain on the cutting edge, depending on the grinding conditions of the cutting edge during manufacture, and this affects the sharpness during use. Furthermore, with the improvement of cemented carbide, especially the development of ultrafine grained cemented carbide, end mills made of cemented carbide have come to play an important role in practical use. Cemented carbide end mills are generally used for cutting cast iron in most cases, but they are rarely used for cutting steel, except in areas where high-hardness steel is essentially impossible. It has not been. Furthermore, even if it is used, there are restrictions on its use, such as requiring a relatively high outer circumferential speed. This is because, as is well known, although cemented carbide has superior wear resistance compared to high-speed steel, it still has inferior toughness, and is therefore prone to chipping and breakage of the cutting edge when cutting ordinary steel. . When observing the state of damage to the cutting edge after cutting, it is normal that when cutting steel, there are mainly fine chippings accumulated, and there are very few areas of normal wear (or rubbing wear). It is no exaggeration to say that the cutting edge of a carbide end mill, which is originally required to be sharp, is sharp only during final use after grinding.As soon as cutting begins, the cutting edge may chip, resulting in sharpness of several tens of centimeters depending on the conditions. It could not be scraped and chattering and breakage occurred. Conventionally, among cutting tools, throw-away tips have been honed to prevent chipping of the cutting edge, etc., but end mills targeted by the present invention, especially solid or brazed types, are too honed. The term "sharp cutting edge" has never been accepted or applied. [Means for Solving the Problems] In view of the above points, the present applicant had provided an end mill in the previous application which had been honed to a degree that could be put to practical use. The cutting blade is mainly coated with a hard material that has properties such as hardness and welding resistance, in order to further improve performance. That is, the present invention provides an end mill that has a spiral or straight cutting blade on a cylindrical or conical surface centered on a rotation axis, and the cutting blade portion where the rake face and flank intersect is chamfered into a curved shape. Then, the amount of chamfering in the rake face direction is 0.003 to 0.05 mm, the amount of chamfering in the flank direction is 0.002 to 0.05 mm, and the chamfer ratio is rake face / flank face = 1/2 to 6/1, It is characterized by at least the cutting edge portion being coated with a hard substance, and in solid end mills, the cutting edge portion where the rake face and flank intersect is chamfered into a curved shape, and the chamfering in the direction of the rake face is performed. The amount of chamfering is 0.003 to 0.03mm, the amount of chamfering in the flank direction is 0.002 to 0.02mm, the ratio of chamfering amount is rake face / flank face = 1/2 to 6/1, and the coating layer is according to the periodicity table. Group 4a transition metal or A
one or more layers of one or more hard substances selected from the group consisting of carbides, nitrides, oxides, hard boron nitride, hard carbon, and solid substances or mixtures thereof; It is coated with multiple layers of 0.2 to 0 μm in thickness. Furthermore, although the present invention is most effective for solid or brazed end mills made of cemented carbide, high-speed steel end mills can also be used after grinding the cutting edge.
By honing with ~3000 abrasive grains, burrs and low-hardness parts of the cutting edge due to grinding heat are removed, and then a wear-resistant hard material is coated.The present invention does not perform conventional honing, and therefore It shows superior cutting performance compared to end mills whose cutting edges are coated with harmful conditions such as fine burrs, chips, grinding marks, and low hardness areas. [Operations and Examples] The limited scope of the claims will be described in detail below along with Examples. Since the present invention is coated with a hard material, the honing shape and amount of the cutting edge can be applied in a wider range than when the cutting edge is not coated. Figure 1 shows
It is an enlarged view of the cutting edge honing part of the end mill.
1 is the end mill, 2 is the rake face, 3 is the flank face, 4
indicates a honed surface, A indicates a curved surface chamfered, B indicates a straight chamfered surface, 2 and 4
And the connecting portion between 3 and 4 is chamfered into a curved surface. The chamfering amount a in the direction of the rake face and the chamfering amount b in the flank direction were studied. It is effective if the amount of chamfering in the flank direction is up to twice the amount of chamfering in the direction of the rake face, but if it exceeds this, damage to the flank will be significant. In other words, the angle made with the rake face in linear chamfering is effective up to about 10°, but beyond this the cutting edge is less effective and tends to chip. The amount of chamfering is 1/2 to 6 times the amount of chamfering in the flank direction. Furthermore, in the above ratio, if the amount of chamfering in the direction of the rake face is less than 0.003 mm, there will be no honing effect and chipping will occur easily.
Even if it is 0.05mm or more, large diameter end mills are partially effective, but in general, due to increased cutting force,
The amount of chamfering in the direction of the rake face should be set at 0.003 to 0.03 for solids, as chatter and surface defects are likely to occur.
mm, and 0.003 to 0.05 mm for large diameter brazing. Also, the amount of chamfering in the direction of the flank face is the same as that of the rake face.
If the honing is less than 0.002mm, the honing effect will be less and chipping will occur, and if the honing is more than 0.05mm, although it is partially effective with large diameter end mills, in general,
The amount of chamfering in the direction of the flank should not be made with solids, as this will increase the amount of wear and make it more likely that the finished surface will be defective.
0.002~0.022mm, 0.002~ for large diameter brazing
The diameter shall be 0.05mm. Al is used for purposes such as improving wear resistance, preventing the formation of built-up edges during low-speed cutting, and preventing rake face crater damage caused by non-linear cutting edges such as ball end mills that tend to concentrate. Known coatings such as ₂ O ₃ , Si ₃ N ₄ , TiC, TiN, TiCN (titanium carbonitride) Cr carbide, CBN, and diamond can be applied to the present invention as hard materials for coating. The coating layer structure at this time may be one coated with one type selected from the above-mentioned hard substance group, a two-layer structure coated with TiN as the first layer and Al ₂ O ₃ as the second layer, or even A three-layer structure in which a solid solution layer is provided between the first layer and the second layer to further improve the adhesion between the two layers is effective as the present invention, but the overall thickness of the coating layer is 0.2μ. If it is less than 20 μm, the effect will be small, and if it is more than 20 μm, the coating layer will easily peel off. In particular, it is desirable that the coating thickness be 0.3 to 2μ for small-diameter end mills that mainly make minute cuts. [Example 1] Two-flute square-shaped twisted end mills (made of ultra-fine cemented carbide) with outer diameters of 4 and 16 mm were chamfered into a curved surface using the bracket method so that a/b = 2/1 when using a φ4 end mill. However, for φ16 end mills, a/b = 2/1 is chamfered into a curved surface using the same brush method, and a/b = 6/1 is chamfered into a straight shape using a grinding jig with blades and a universal tool grinder. After chamfering, a curved surface was created using the brush method. Next, these end mills and the end mill without honing were coated with TiN to a thickness of 1.2 μm (flank surface) by ion plating. Shoulder milling and down cut cutting tests were conducted using cutting oil under the conditions shown in Table 1 with workpiece material S50C (HRC23). The results are shown in FIG. The chipping rate in FIG. 2 uses the total length of chipped or chipped cutting edges, and is expressed as a percentage of the total length of the cutting blade.

[Example 2]

Using a two-flute square helical end mill with an outer diameter of 12 mm, various honing shapes and amounts were prepared in the same manner as in Example 1, and Al ₂ O ₃ was prepared using an ion plating method different from that in Example 1. Samples coated with and uncoated with a thickness of 0.7 to 1μ were prepared. These were shoulder milled at S50℃ (HRC23) and a down cut cutting test was conducted using cutting oil under the following conditions. Feed = 0.036 mm / axial depth of cut = 12 mm Radial depth of cut = 6 mm Cutting length = 3000 mm The results are shown in Figure 3. The symbols in the figure are as shown in the table below.

[Table] By appropriate combination of a/b ratio and amount of rake face honing, cutting edge damage can be significantly reduced. For uncoated end mills, a/b=1/1 and a=
For 10μm and a/b≒5.5/1, a=
Two types of 50μm were performed, but the former had a wear amount of 0.13mm,
The latter is 0.15mm, and both are when coated.
It was inferior to 0.05 mm or less. [Effects of the Invention] As described above, the present invention removes the harmful state of the cutting blade by applying appropriate honing to the cutting blade, strengthens the cutting blade, and then coats the cutting blade with a hard material. It has a particularly large effect of increasing the lifespan when cutting steel. When cutting steel, there were very few places where normal wear occurred due to the accumulation of fine chippings, but since chipping is less likely to occur, cutting can be performed with normal wear and exhibits excellent cutting performance. be.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a cutting edge portion of an end mill that has been honed, with A showing curved honing and B showing straight honing. FIG. 2 and FIG. 3 are diagrams showing the results of Example 1 and Example 2, respectively.

Claims (1)

[Claims] 1. In an end mill having a spiral or straight cutting blade on a cylindrical or conical surface centered on a rotation axis, the cutting blade portion where the rake face and flank face intersect is curved. Chamfer the amount of chamfering in the direction of the rake face by 0.003 to 0.05mm, and the amount of chamfering in the flank direction.
An end mill with a reinforced coated cutting edge, characterized in that the chamfer is 0.002 to 0.05 mm, the ratio of chamfering amount is rake face/flank face = 1/2 to 6/1, and at least the cutting edge portion is coated with a hard material. . 2. In a solid end mill in which the blade part and base of the end mill are made of carbide, the cutting edge part where the rake face and flank face intersect is chamfered into a curved shape, and the amount of chamfering in the direction of the rake face is 0.003 to 0.03 mm, and the clearance is The coating according to claim 1, wherein the amount of chamfering in the surface direction is 0.002 to 0.02 mm, and the ratio of the amount of chamfering is rake face/flank face = 1/2 to 6/1. End mill with reinforced cutting edge. 3 The coating layer is a transition metal of Group 4a of the periodic table or A
One layer or two or more layers of one or more hard substances selected from the group consisting of carbides, nitrides, oxides, hard boron nitride, hard carbon, and solid bodies or mixtures thereof. An end mill with a reinforced coated cutting edge as claimed in claim 1, characterized in that the end mill is coated with a multi-layer coating with a thickness of 0.2 to 20 μm.