JPH07115254B2 - End mill - Google Patents

Description

TECHNICAL FIELD The present invention relates to an end mill in which a plurality of cutting blades are formed on the outer periphery of a tip portion of an end mill body in an uneven twist.

[Prior Art] As a conventional end mill of this type, as shown in Japanese Patent Publication No. 305244, a plurality of cutting blades that draw a spiral in the axial direction are provided on the outer circumference of the tip of a large diameter cylindrical end mill body. It is known that they are formed so as to have unequal twists.

In this end mill, since the cutting edges are formed with unequal twist, the cutting force and the action time of these cutting edges differ in the circumferential direction. Therefore, these cutting blades do not cause periodic vibration that resonates with the natural frequency of the end mill body, so that the chattering phenomenon associated with cutting can be prevented and therefore the cutting performance can be improved. The advantage that it can be obtained.

[Problems to be Solved by the Invention] However, in the above-described conventional end mill, since the cutting blades are formed with unequal twists, the intervals between the cutting blades are different from each other over the entire length of the cutting blades. However, when forming the cutting edge on the end mill body, it is difficult to determine the position to be used as a reference for the polishing process, and therefore, there is a drawback that it requires a lot of labor and skill to manufacture it freely.

Further, since the intervals in the circumferential direction of the end portions of these cutting blades on the base end side of the end mill body are also different, the width dimensions of the chip discharge groove formed between these cutting blades are also different. Therefore, the mechanical bending strength becomes uneven in the circumferential direction, particularly in the portion of the end mill main body where the tool rigidity is poor, so that the tool rigidity further decreases.

For this reason, there is no problem for those with a relatively large diameter and a short cutting edge length and light cutting, but with a small diameter and a long cutting edge length, heavy cutting (deep cutting) and high feed. In the case of cutting, there is a problem in that the end mill itself is broken at the base end portion of the end mill body where the end portion of the cutting edge, which is inferior in mechanical bending strength, is located during cutting.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to prevent the occurrence of vibration or the like due to cutting without lowering the tool rigidity, and thus to perform heavy cutting (deep cutting) or high cutting. It is intended to provide an end mill capable of feed cutting.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a plurality of cutting blades having unequal twists at the end of the end mill body at the base end side of the end mill body. It is formed at equal intervals in the circumferential direction.

[Operation] According to the end mill having the above-described configuration, the end portions of the cutting blades formed at equal intervals can be used as a reference when forming the cutting blades, so that these cutting blades can be easily processed.

Further, in the vicinity of the end of the cutting edge on the base end side of the end mill body having the lowest tool rigidity, since these cutting edges are formed at equal intervals in the circumferential direction, it is possible to prevent a decrease in the tool rigidity at the location. .

[Embodiment] FIGS. 1 to 4 show an embodiment of the end mill of the present invention, in which reference numeral 11 denotes an end mill body.

This end mill main body 11 is a substantially cylindrical appearance integrally formed from high speed steel, cemented carbide thermite, etc., and has four cutting edges 1 with an axial twist on the outer periphery of its tip.
2,13,14,15 are formed. And these cutting edges 12,1
Chip discharge grooves 16, 17, 18, and 19 are formed between 3, 14 and 15, respectively. Further, bottom blades 20, 21, 22, 23 extending from the cutting blades 12 to 15 toward the center of rotation are formed on the tip surface of the end mill body 11.

Here, the four cutting edges 12, 13, 14, 15 are formed with different twist angles θ ₁ , θ ₂ , θ ₃ , θ ₄ as shown in FIG. The magnitudes of these angles θ _{1 to} θ ₄ are θ ₁ <θ ₂ <θ ₃ <θ ₄ respectively.

Furthermore, these cutting edges 12 to 16 are used for the end mill body 11
At the end parts 12a to 16a on the base end side of the
They are formed at equal intervals L ... In the circumferential direction of 11. By the way, these cutting blades 12-15 are attached to the end portions 12a-1
6a are formed at equal intervals in the circumferential direction, and the twist angle θ
_{As a result of making 1} , θ ₂ , θ ₃ , θ ₄ different angles from each other, as shown in FIG.
Wideness of width occurs. In this case, if a chip discharge groove having a width that is too narrow is formed, the chip discharge will be hindered. Therefore, the difference between the torsion angles θ ₁ , θ ₂ , θ ₃ , and θ ₄ is as follows: the end mill diameter D is 3 mm to 25 mm and the ratio of the diameter D to the total cutting edge length l (l /
If D) is about 3, it is desirable to set it between 1 and 5 degrees.

In the end mill configured as above, the cutting edge 12-16
Since the end portions 12a to 16a on the base end side of the end mill body 11 are formed at equal intervals L in the circumferential direction of the end mill 11, the end portions 12a to 16a of the cutting blades 12 to 16 are formed. By using as a reference for forming the cutting edge, the polishing process can be easily performed.

Further, in the vicinity of the ends 12a to 16a of the cutting edges 12 to 16 on the base end side of the end mill body 11 having the lowest tool rigidity, these cutting edges 12
Since ~ 16 are formed at equal intervals L in the circumferential direction similarly to a general end mill having a cutting edge of equal twist, the mechanical bending strength in the circumferential direction can be made uniform, so that the end mill body can be made uniform. It is possible to prevent the deterioration of the tool rigidity at the 11 points.

In addition, the cutting blade 12 to the cutting edge 12 to the tip of the end mill body 11 that is most susceptible to vibration and chatter due to the cutting resistance of the bottom blade
Since the difference between the intervals of 16 is the largest, an excellent anti-vibration effect can also be obtained. Therefore, even when applied to a tool having a small diameter and a long cutting edge length, or a tool for performing heavy cutting (deep cutting) or high feed cutting, excellent cutting performance without vibration or chattering can be obtained.

Therefore, in particular, because it has excellent tool rigidity, it can be used for high-speed cutting where vibration and chatter are likely to occur, but on the other hand, when it is applied to a cemented carbide or cermet end mill whose cutting edge is easily chipped, a significant effect Can be obtained.

In addition, in the above-mentioned examples, the solid type made entirely of high speed steel or cemented carbide has been described, but it is a brazing type in which a cutting edge tip having a cutting edge is brazed to the end mill body. May be. Further, in the end mill of the above embodiment, the four cutting edges 12 to 16
Is formed, but if there are multiple cutting edges, 4
It is not limited to articles. Furthermore, 4 cutting edges 12-16
Although all the twist angles θ ₁ , θ ₂ , θ ₃ , and θ ₄ of are set to different angles, only the twist angle of one cutting edge is formed to be different from the twist angle of other cutting edges. Alternatively, two kinds of twist angles θ ₅ and θ ₆ may be alternately formed in the circumferential direction.

Furthermore, the twisting direction of each cutting edge is set so that the rake angle of the cutting edge is a positive rake angle, but the twisting direction may be reversed. In any case, in the present invention, if a plurality of cutting blades that are unequally twisted are formed at equal intervals in the circumferential direction of the end mill body at the end portion on the base end side of the end mill body, the same effect is obtained. The effect can be obtained.

As described above, according to the end mill of the present invention,
Since a plurality of cutting blades that are unequally twisted are formed at equal intervals in the circumferential direction of the end mill body at the end portion on the base end side of the end mill body, the end portions of the cutting blades formed at equal intervals are By using the reference when forming the cutting edge, it is possible to easily process these cutting edges. Further, since these cutting blades are formed at equal intervals in the circumferential direction in the vicinity of the end portion of the cutting edge on the base end side of the end mill body having the poorest tool rigidity,
It is possible to prevent a decrease in tool rigidity at the contact point.
Therefore, even when applied to a tool having a small diameter and a long cutting edge length, or a tool for performing heavy cutting (deep cutting) or high feed cutting, excellent cutting performance without vibration or chattering can be obtained.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a side view, FIG. 2 is a view taken along line II-II of FIG. 1, and FIG. 3 is III of FIG. -III sectional view taken on the line, and FIG. 4 is a development view of the cutting edge. 11 …… End mill body, 12,13,14,15 …… Cutting edge, 12a, 13a, 14a, 15a …… End of cutting edge, θ ₁ , θ ₂ , θ ₃ , θ ₄ …… Twist angle.

Claims (1)

[Claims] 1. An end mill having a plurality of cutting edges formed in a spiral shape and having at least one helix angle different from other helix angles on an outer periphery of a tip end portion of the end mill body. An end mill, which is formed at equal intervals in the circumferential direction of the end mill body at the end portion on the base end side of the.