JPH0666910U - End mill - Google Patents

Abstract

(57) [Summary] [Structure] Outer peripheral blades 6 are formed on the outer periphery of the tool main body 1, and a bottom blade 8 extending from the inner peripheral side to the outer peripheral side and connected to the outer peripheral blades 6 is formed at the tip of the tool main body. ... is formed.
Of the bottom blades 6, the first bottom blade 6a extends from the vicinity of the tool rotation center C at the tip of the tool body 1 toward the outer peripheral side, and at least in the vicinity of the tool rotation center C, 0 ° or a negative radial rake angle α ₁ It is formed so that it is attached to the other second
The fourth bottom blades 6b to 6d extend from the position separated from the tool rotation center C toward the outer peripheral side, and are formed so as to have a positive radial rake angle α _{2 to} α _{4 and} are inclined downward. [Effect] The first bottom blade 6 extending from the vicinity of the tool rotation center C
By giving a high cutting edge strength to a, it is possible to prevent the cutting edge from being damaged or the like against an excessive cutting load even in the case of inclined cutting.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an end mill used for grooving and shoulder milling of metal work materials.

[0002]

[Prior art]

 In this type of cutting, multiple chip discharge grooves are formed on the outer circumference of a shaft-shaped tool body made of a hard material such as cemented carbide, and these chip discharge grooves have a groove wall surface facing the tool rotation direction and a tool. An outer peripheral blade is formed on the ridge line intersecting with the outer peripheral flank of the main body, and at the intersection ridge line between the groove wall surface and the tip flank of the tool main body, it extends from the inner peripheral side to the outer peripheral side of the tool main body. An end mill having a plurality of bottom blades connected to the outer peripheral blade is often used. In such an end mill, the chip discharge grooves are generally formed at equal intervals in the circumferential direction of the tool body and twisted rearward in the tool rotation direction toward the base end side of the tool body. As a result, the outer peripheral blades are also formed at equal intervals in the circumferential direction of the tool body and with positive axial rake angles.

On the other hand, the plurality of bottom blades are generally formed so as to extend from the inner peripheral side to the outer peripheral side of the tip of the tool body so as to be continuous with the outer peripheral blade, and as described above, the outer peripheral blades are arranged at equal intervals in the circumferential direction. As they are formed, these bottom blades are also formed at equal intervals in the circumferential direction. Thus, the end mill having such a configuration is held by a machine tool or the like and is fed in a direction intersecting with the axis while being rotated about the axis thereof, and a peripheral blade is used to machine a wall portion such as a groove and a bottom blade. Finish the bottom of the groove.

[0004]

[Problems to be solved by the device]

 By the way, in machining with such an end mill, in addition to feeding the tool main body in a direction orthogonal to its axis for cutting, at the same time, the tool main body is also fed toward the tip side in the axial direction to form the work material. In some cases, so-called slant cutting is performed to form slanted grooves. In such a case, since cutting must be performed on the entire tip of the tool body, at least one of the above-mentioned bottom blades should be cut from the vicinity of the tool rotation center at the tip of the tool body to the outer circumference. It must be formed so as to extend to the side so that the locus of rotation of the bottom blade around the axis line substantially coincides with the circular surface formed by the outer peripheral end of the bottom blade around the axis line. Otherwise, when the tool body is fed to the tip side in the axial direction, a large uncut portion will be generated in the part to be cut by the bottom edge of the work material, which will hinder smooth cutting or will result in a good machined surface. You will not be able to get it.

On the other hand, when the tool body is also fed in the axial direction as described above, the bottom blade is directed toward the base end side in the axial direction in the same manner as the cutting blade of the blade is acted. Pushing force acts. Here, the pushing force acting on this bottom blade becomes larger toward the inner peripheral side of the tool body, as in the case of the cutting edge of the drill, and near the tool rotation center at the tool body tip. It will be the maximum. The cutting shape of the bottom blade in the vicinity of the center of rotation of the tool is not such that the work material is scraped away, but rather the work shape is such that the work material is crushed by the bottom blade and the tip flanks connected to it. Therefore, it is unavoidable that an excessive cutting load acts on the bottom blade near the center of rotation of the tool. Therefore, when performing inclined cutting with the conventional end mill as described above, there has been a problem that the bottom blade may be damaged due to such an excessive cutting load.

[0006]

[Means for Solving the Problems]

 The present invention has been made to solve such a problem, and a plurality of chip discharge grooves are formed on the outer periphery of a tool body rotated around an axis, and these chip discharge grooves are oriented in the tool rotation direction. An outer peripheral blade is formed at the ridge line intersection between the groove wall surface and the outer peripheral flank of the tool body, and the inner peripheral side of the tool body is formed at the cross ridge line portion between the groove wall surface and the tip flank of the tool body. In the end mill formed by forming a bottom blade extending from the outer peripheral side to the outer peripheral side and extending from the vicinity of the tool rotation center of the tool body tip to the outer peripheral side, Is formed such that a rake angle of 0 ° or a negative radial direction is provided in the vicinity of the tool rotation center, and another bottom blade extends outward from the position separated from the tool rotation center, and at least one of the above Is characterized in that also the bottom edge large radial rake angle in the positive angle direction is form shaped to be subjected.

[0007]

[Action]

 In the end mill having such a configuration, among the bottom blades formed at the tip of the tool body, at least one bottom blade extending from the vicinity of the tool rotation center to the outer peripheral side has 0 ° or a negative radial direction near the tool rotation center. Since it is formed so as to have a rake angle, it is possible to give a high cutting edge strength to this bottom blade in the vicinity of the center of rotation of the tool. Therefore, even when the above-mentioned excessive cutting load is applied to this part during inclined cutting, it is possible to prevent the cutting edge from being damaged, which prolongs the tool life and facilitates smooth cutting work. Can be possible. On the other hand, the other bottom blades are formed so as to extend from the position away from the tool rotation center toward the outer peripheral side, and have a larger radial rake angle on the regular angle side than the bottom blade extending near the tool rotation center. As a result, the sharpness can be improved, and this can prevent the cutting force acting on the entire bottom blade from increasing.

[0008]

【Example】

 1 to 3 show an embodiment of the present invention. In these figures, the tool main body 1 is made of a hard material such as cemented carbide and has a substantially cylindrical shaft shape. A blade portion 2 is formed on the tip side and a shank portion 3 is formed on the base end side. . The blade portion 2 is provided with four chip discharge grooves 4 which are twisted rearward in the tool rotation direction (arrow T direction in the drawing) from the tip toward the base end side in the axis O direction of the tool main body 1. The groove wall surfaces 4a, which are formed at substantially equal intervals in the circumferential direction of the body 1 and face the tool rotation direction of each chip discharge groove 4, and the outer peripheral surface of the blade portion 2, that is, the outer peripheral flank surface 5, intersect the ridge portion. Has an outer peripheral blade 6. Therefore, these outer peripheral blades 6 are arranged at substantially equal intervals in the circumferential direction of the tool body 1 similarly to the chip discharging groove 4, and are twisted in accordance with the twist of the chip discharging groove 4 to be positively axially scooped. It is formed to have corners.

On the other hand, at the tip of the blade portion 2, tip flanks 7 ... Are formed on the rear side of the chip discharge groove 4 in the tool rotation direction, and these tip flanks 7 ... Bottom blades 8 extending from the inner peripheral side to the outer peripheral side of the tool body 1 are formed at the ridges of the discharge groove 4 which intersect the groove wall surface 4a. It should be noted that, in the present embodiment, all of these bottom blades 8 ... Are formed in a linear shape as shown in FIG. Here, these bottom blades 8 are formed such that the first bottom blade 8a thereof extends from the position of the axis O at the tip of the tool body 1, that is, from the vicinity of the tool rotation center C at the tip to the outer peripheral side. The other second, third, and fourth bottom blades 8b, 8c, and 8d are formed so as to extend from positions slightly separated from the tool rotation center C on the outer peripheral side.

Further, each of the bottom blades 8 ... As viewed from the tip side of the tool body 1 as shown in FIG. Straight line L₁~ L_FourIt is formed so as to be parallel to. Then, the first bottom blade 8a has a straight line L₁With respect to the tool rotation direction front side K₁However, the other second to fourth bottom blades 8b to 8d are respectively formed on the straight line L.₂~ L_FourWith respect to the tool rotation direction, the distance K to the rear side₂~ K_FourIt is formed in a retracted position. That is, the first bottom blade 8a is K with respect to the tool rotation center C. ₁ However, the other second to third bottom blades 8b to 8d are formed so as to have a so-called centering up with respect to the tool rotation center C.₂~ K₃Only then will it be formed in a so-called downfall.

Thus, the first bottom blade 8a extending from the vicinity of the tool rotation center C to the outer peripheral side in this way is provided with the virtual straight line L.₁The first bottom blade 8a has a negative radial rake angle .alpha.₁Will be attached. On the other hand, the other second to fourth bottom blades 8b to 8d are respectively the virtual straight lines L. ₂ ~ L_FourSince it is formed in parallel with and descending from the center, the positive radial rake angle α₂~ Α_Four Will be attached. The above virtual straight lines L₂~ L_FourFrom the second to fourth bottom blades 8b to 8d ₂ ~ K_FourThat is, the downfall amounts of the second to fourth bottom blades 8b to 8d are set equal to each other in this embodiment. Also, the virtual straight line L₁To the first bottom blade 8a from the distance K₁In other words, the amount of rise of the first bottom blade 8a is the distance K in this embodiment.₂~ K_Four Is set to the same size as. Further, the first bottom blade 8a has an end portion on the inner peripheral side thereof, as shown in FIG.₂And L_FourIt is extended so as to slightly protrude beyond the third bottom blade 8c.

Each of the bottom blades 8 ... Is formed such that its outer peripheral side end portion is aligned with the tip of each of the outer peripheral blades 6 ... Here, the outer peripheral blades 6 ... Are formed at equal intervals in the circumferential direction of the tool main body 1 as described above, while the bottom blades 8 ... Are arranged at uneven intervals before and after the first bottom blade 8a as shown in FIG. Since it is formed so as to be the same, the tip ends of the groove wall surfaces 4a ... Of the chip discharge grooves 4 ... A groove (gash) extending in the radial direction of the tool body 1 is formed at the tip of each groove wall surface 4a, and the depth of this groove is adjusted appropriately for each groove wall surface 4a, so that each bottom blade 8 ... You may make it the outer peripheral edge part and the front-end | tip part of each outer peripheral blade 6 correspond.

Further, as shown in FIG. 3, the groove wall surfaces 4a of the chip discharge groove 4 ... In the cross section orthogonal to the axis O, the tool rotation direction is temporarily changed from the inner peripheral side to the outer peripheral side of the tool body 1. It is formed in the shape of a concave curved surface that moves backward in the tool rotation direction after retracting to the rear side, whereby a positive radial rake angle θ is attached to each outer peripheral blade 6. Furthermore, among these four outer peripheral blades 6 ..., the radial rake angle θ ₁ attached to the first outer peripheral blade 6a is the same as the other second, third, and fourth outer peripheral blades 6b, 6c, and It is set to be smaller than the radial rake angles θ ₂ , θ ₃ , and θ ₄ attached to 6d. The radial rake angles θ ₂ , θ ₃ , and θ ₄ provided on the second, third, and fourth outer peripheral blades 6b, 6c, and 6d are set to be equal to each other. The outer peripheral blades 6 ... And the bottom blades 8 ... Are formed such that the tip end of the first outer peripheral blade 6a is continuous with the outer peripheral end of the first bottom blade 8a.

In the end mill having such a configuration, the shank portion 3 is attached and held to the end of the main shaft of the machine tool, and is fed around while being rotated around the axis O to be used for cutting. When the tool body 1 is also fed in a direction parallel to the axis O to perform inclined cutting, the tool rotation center C at the tip of the tool body 1 is cut by the inner peripheral side portion of the first bottom blade 8a. The work material portion facing the vicinity of is cut, and the outer peripheral portion of the first bottom blade 8a and the other bottom blades 8b to 8d cut the portion around the work material portion. Here, at the tip of the tool main body 1, the pushing force applied to the bottom blade 8 increases toward the inner peripheral side, and it becomes maximum near the tool rotation center C, and a large cutting load acts on the bottom blade 8. Is as described above. On the other hand, in the end mill having the above-described structure, the first bottom blade 8a extending from the vicinity of the tool rotation center C is formed so as to rise, and the negative radial rake angle α is formed over the entire length thereof. _{Since 1} is added, it becomes possible to give a high cutting edge strength to the first bottom blade 8a even in the vicinity of the tool rotation center C. As a result, even if a large cutting load is applied as described above, this can be resisted and it is possible to prevent the first bottom blade 8a from being damaged or the like.

By the way, in order to improve only the cutting edge strength of the bottom blade 8 in this way, not only the first bottom blade 8a but also the other second to fourth bottom blades 8b to 8d have the same distance K. _It may be formed so that it is raised by ₁ to form a negative radial rake angle. However, when such a configuration is adopted, the cutting resistance that acts on the entire bottom blades 8 ... Remarkably increases, which causes a large twisting moment to act on the tool body 1 to cause cutting damage and the like. There is a possibility that this may occur or that such a large cutting resistance periodically acts to cause chatter vibrations in the tool body 1 and cause deterioration of the machined surface.

On the other hand, in the end mill having the above-mentioned configuration, only the first bottom blade 8a extending from the vicinity of the tool rotation center C is given a negative radial rake angle, and the other second to fourth The bottom blades 8b to 8d extend from the position spaced from the tool rotation center C to the outer peripheral side, and are provided with a positive radial rake angle α _{2 to} α ₄ so as to have a positive angle. An excessive cutting load does not act on the fourth bottom blades 8b to 8d, and the sharpness thereof is improved, so that the cutting resistance can be suppressed low. That is, according to the end mill having the above-described configuration, it is possible to suppress an increase in the cutting resistance that acts on the bottom blade 8 as a whole while giving sufficient edge strength only to the first bottom blade 8a on which an excessive cutting load acts. Therefore, it is possible to prevent a situation in which the tool body 1 is cut and the machining surface is deteriorated due to chatter vibration.

Further, in addition to this, in the end mill having the above-mentioned configuration, the outer peripheral blades 6 ... Are also provided with a positive radial rake angle θ, and the first outer peripheral blades 6a are connected to the first bottom blade 8a. in the is set to be smaller than the radial rake angle theta ₂ through? ₄ in the radial direction rake angle theta ₁ is other second to fourth peripheral cutting edge 6b to 6d. By adopting such a configuration, it is possible to reduce the cutting resistance that acts on the outer peripheral blade 6, and the cutting resistance that acts on the first outer peripheral blade 6a is the same as that of the other second to fourth parts. Since the size is different from the cutting resistance that acts on the outer peripheral blades 6b to 6d, periodic vibration is less likely to occur in the tool body 1. Therefore, according to the present embodiment, in combination with the effects described above, the moment of twist acting on the tool body 1 is further suppressed to reliably prevent cutting damage and the like, and the occurrence of chatter vibration is further effective. It becomes possible to obtain a good machined surface by preventing it.

In this embodiment, the bottom blades 8 ... Are formed so as to extend linearly from the inner peripheral side to the outer peripheral side when viewed from the tip end side of the tool body 1, whereby the first bottom blade 8a has A negative radial rake angle α ₁ is attached over the entire length, and the other second to fourth bottom blades 8b to 8d each have a positive radial rake angle α 1. _{2 to} α ₄ are attached, for example, as shown in FIG. 4, each of the bottom blades 8 is formed so that only the inner peripheral side portion thereof is straight and the outer peripheral side is a tool. It may be formed in a concave curve shape that is recessed rearward in the rotational direction. However, even in this case, at least one bottom blade 8a is formed so as to extend from the tool rotation center C to the outer peripheral side, and the linear portion on the inner peripheral side located near the tool rotation center C is raised. Therefore, a negative or 0 ° radial rake angle must be provided. However, in the case of adopting such a configuration, the radial rake angle is set to the regular angle side on the outer peripheral side of each of the bottom blades 8 ... Is obtained. In FIG. 4, the same parts as those shown in FIG. 2 are designated by the same reference numerals.

Further, in these embodiments, only the first bottom blade 8a of the four bottom blades 8 ... Is extended from the vicinity of the tool rotation center C toward the outer peripheral side, and the negative radial scoop is provided on the inner peripheral side. Although it is formed so as to have a sharp corner, the same configuration may be applied to some other bottom blades 8 ... However, it is not preferable that all the bottom blades 8 ... Have the same configuration as described above. Further, in these examples, the first bottom blade 8a is formed so as to have a negative radial rake angle by raising the center of the first bottom blade 8a, and the second to third bottom blades 8b to 8d are formed. In this case, a positive rake angle in the radial direction was given by lowering this, but the size of these rising or falling, that is, the bottom blades 8 ... And the straight lines L _{1 to} L ₄ The distances K _{1 to} K ₄ are all preferably in the range of 0 mm to 0.3 mm, and more preferably in the range of 0.05 mm to 0.15 mm.

[0020] This is because if the rise of the bottom blade extending from the vicinity of the center of tool rotation is too small, the radial rake angle of this bottom blade will be close to the conformal side, and it will be sufficient on the inner peripheral side of the bottom blade. It may not be possible to secure the strength of the cutting edge. Conversely, if the amount of this rising is too large, the radial rake angle of the bottom edge becomes too large on the negative side and the cutting resistance becomes excessive. This is because there is a risk that Also, when the bottom blade extending from the position away from the tool rotation center has too large a down-center, the radial rake angle on the outer peripheral side of the bottom blade becomes too large toward the right angle side. As shown in the figure, when the outer peripheral side of the bottom blade is formed into a concave curve shape, defects easily occur near the outer peripheral side end. On the contrary, if this downsizing is too small, the entire bottom blade is This is because it may not be possible to reduce the cutting resistance that acts on it.

Furthermore, the outer peripheral edge 6 ... radial rake angle theta of is set to a positive angle side in this embodiment, either Tsu radial rake angle theta ₁ of the first peripheral cutting edge 6a is, other second to It is set to be smaller than the radial rake angles θ _{2 to} θ 4 of the outer peripheral blades 6b to 6d of No. _4, but these radial rake angles θ are within the range of 0 ° to 30 °. It is preferably formed so as to satisfy the above conditions, and more specifically, it is desirable that the angle be in the range of 5 ° to 15 °. This is because if the radial rake angle θ is too small, the cutting resistance acting on the outer peripheral blades 6 becomes too large, and conversely if the radial rake angle θ is too large, the cutting edge angle of the outer peripheral blades 6 becomes small. This is because the cutting edge strength may be impaired.

[0022]

[Effect of device]

 As described above, according to the present invention, at least one bottom blade extending from the vicinity of the tool rotation center to the outer peripheral side is provided with 0 ° or a negative radial rake angle near the tool rotation center. Since it is formed, it is possible to give a high cutting edge strength to this bottom blade. With this, even when performing inclined cutting using the end mill, it is possible to prevent damage to the cutting edge against excessive cutting load, extend tool life, and enable smooth cutting work. Can be In addition, the other bottom blades extend from the position away from the tool rotation center to the outer peripheral side and have a larger radial rake angle on the regular angle side than the bottom blade extending near the tool rotation center. The sharpness is improved, and it becomes possible to prevent the cutting resistance acting on the entire bottom blade from becoming excessive.

[Brief description of drawings]

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

FIG. 2 is an enlarged front view from the tip side of the embodiment shown in FIG.

FIG. 3 is a sectional view taken along line XX of the embodiment shown in FIG.

FIG. 4 is an enlarged front view showing another embodiment of the present invention.

[Explanation of symbols]

1 Tool main body 4 Chip discharge groove 4a Groove wall surface of the chip discharge groove 4 facing the tool rotation direction 6 (6a, 6b, 6c, 6d) Outer peripheral blade 8 (8a, 8b, 8c, 8d) Bottom blade O Rotation of the tool main body 1 Axis C Center of tool rotation at the tip of tool body 1 Tool rotation direction L (L ₁ , L ₂ , L ₃ , L ₄ ) Virtual straight line K (K ₁ , K ₂ , K _3, K ₄₎ upward imaginary straight line L and the end cutting edge 8 ... and the distance (end cutting edge 8 ... heart, heart size of _{drops) α (α 1, α 2} , α 3, α 2) end cutting edge 8 ... Radial rake angle θ (θ ₁ , θ ₂ , θ ₃ , θ ₄ ) radial rake angle of the outer peripheral blade 6 ...

Claims (5)

[Scope of utility model registration request] 1. A plurality of chips discharging grooves are formed on the outer periphery of a tool body rotated around an axis, and a groove wall surface of these chips discharging grooves facing the tool rotation direction intersects with an outer peripheral flank of the tool body. An outer peripheral blade is formed on the ridge portion, and at the ridge portion intersecting the groove wall surface and the tip flank of the tool body,
In an end mill comprising a bottom blade extending from the inner peripheral side to the outer peripheral side of the tool body and connected to the outer peripheral blade, at least one of the bottom blades is a center of tool rotation of the tool body tip. It extends from the vicinity to the outer peripheral side and is formed so as to have a 0 ° or negative radial rake angle near the tool rotation center, and the other bottom blades extend from the position away from the tool rotation center to the outer peripheral side. An end mill that is formed so as to extend and to have a large radial rake angle on the side closer to the right angle than the at least one bottom blade. 2. The end mill according to claim 1, wherein at least one of the outer peripheral blades has a smaller radial rake angle than the other outer peripheral blades. 3. The end mill according to claim 2, wherein the at least one bottom blade is formed so as to be continuous with the at least one outer peripheral blade. 4. The end mill according to claim 1, wherein the bottom blade is formed to extend linearly at least on the inner peripheral side thereof. 5. The bottom blade is formed in a concave curved shape that is recessed toward the rear side in the tool rotation direction on the outer peripheral side thereof, claim 1, claim 2, claim 3, or claim 4. End mill described in.