JPS62203709A - Ball end mill - Google Patents

Abstract

PURPOSE:To allow smooth relief of chips so as to improve cutting performance by forming an obtuse angle, between a rake face formed along a cutting blade roughly in an axial center direction and a chip relief face near the center. CONSTITUTION:Rake faces 22, 32, extending roughly in a axial direction, are respectively formed on respective cutting blades 2, 3 of a ball end mill. Said rake faces 22, 32 are respectively provided with chip relief faces 20, 30 near the center on the upper end parts, and also with chip relief faces 21, 31 on the part facing to outside rake blades. An angle, formed between the rake faces 22, 32 and the chip relief faces 20, 30, is made to be the obtuse one. Therefore, produced chip grows along rake faces and moved along chip relief faces in order to be discharged, so that cutting performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is directed to improving the shape of the chip release section of a ball end mill.

(Prior art) In cutting with a ball end mill, chips generated by the cutting edge near the center of the bottom shape of the ball end mill grow along the rake surface extending in the axial direction of the shank, and after hitting the chip relief surface. It is ejected by moving along that surface.

In the process of ejecting the chips mentioned above, the chips grow along the rake face and are temporarily stopped when they hit the relief surface, thus providing a large amount of resistance to the moving (rotating) cutting blade. . In other words, if the chips generated by the movement of the cutting blade are ejected as they are, the cutting resistance of the cutting blade only needs to generate (cut) chips from the rigid material. When the chips hit and are stopped, the chips become connected between the chip relief surface and the workpiece, which limits the movement of the cutting edge and also prevents the cutting of chips from the rigid workpiece. Therefore, the cutting performance of the ball end mill is hindered. Conventionally, no consideration was given to the machinability of the cutting edge near the center.

(Purpose of the Invention) The present invention has been made in order to eliminate such conventional drawbacks, and provides a ball that improves machinability by smoothly releasing chips near the center of the bottom shape. It provides end mills.

(Structure of the Invention) The present invention has a bottom shape in which a rake face is formed approximately in the axial direction along a cutting edge that is formed almost continuously from near the center of the shank to the outer peripheral end, and a chip relief surface near the center. The angle formed with the rake face is an obtuse angle.

In the above configuration, the generated chips grow along the rake face, and even when they hit the chip relief surface, they move along the chip relief surface without being stopped and are discharged, so that the cutting edge moves and There is no resistance to the cutting action, and therefore the machinability of the ball end mill can be improved.

(Example) In FIGS. 1 to 4, the head 1 of the ball end mill is attached to the tip of the shank 4 by the brazing part 5,
A pair of cutting edges 2゜3 are formed at the hemispherical tip,
The starting end 4 of each cutting edge has a bottom shape and is located approximately at the center. Each cutting edge 2.3 is curved in a convex shape in the direction of rotation near the center, and is formed into a substantially straight line outside the center. The shape of this cutting edge is not limited to the one shown in the figure, and may be arbitrarily set, and the entire cutting edge may be formed into a curved line, or the area near the center may also be formed into a straight line, so that the entire cutting edge has a broken line shape. Further, although the illustrated example shows a pair of cutting edges formed symmetrically with each other, the pair of cutting edges may be formed asymmetrically, or only one cutting edge may be formed.

Each of the cutting edges 2 and 3 has a rake face 22 extending approximately in the axial direction.
．． 32 are respectively formed, and chip relief surfaces 20 and 30 are formed near the center at the upper end of the rake faces 22 and 32, respectively.
Further, chip relief surfaces 21 and 31 are respectively formed in portions corresponding to the cutting edges on the outside thereof. Chip relief surface 20
．． 30 and the chip release surface 21.31 form a constant angle in the illustrated example for ease of machining, but they may be continuous with a gently curved surface.

As shown in FIG. 4, the chip relief surface 30 is set so that the angle θ1 formed between it and the corresponding rake surface 32 is an obtuse angle. Similarly, the angle θ2 between the chip relief surface 20 and the rake surface 22, and the angle θ2 between the chip relief surface 30 and the rake surface 32 in the horizontal cross section shown in FIG. 5 is also formed to be an obtuse angle. These angles θ1 and θ2 are preferably as large as possible in order to facilitate the escape of chips, and are preferably as small as possible in terms of the strength of the head 1, but are usually 110° to 150°.
A range of is preferred. Also, the chip relief surface 20 and the rake surface 20
The angle θ1 between the two is also set to be an obtuse angle. Although the example shown in the figure shows an example in which the intersection of the rake face 32 and the chip relief surface 30 is a broken line, it is also possible to configure the two to form a continuous curve, that is, to form a curved surface as a whole. .

In the above configuration, the chips generated by the cutting edge 2.3 near the center grow along the rake face 22.32, and the tip thereof hits the chip relief surface 20.30;
2.32, the chips are moved along the chip release surface 20.30 and discharged without hindering the movement of the chips. Therefore, the chips are removed from the chip relief surface 20.3.
Even when it hits zero, no resistance is generated on the cutting blades 2 and 3.

Note that the chip relief surface that is continuous with the rake face in conventional ball end mills is formed at a right angle to the rake face or at a smaller angle (acute angle), as shown by the imaginary line 60 in FIGS. 4 and 5. . For this reason, the chips that have grown along the rake face 22, 32 are stopped by hitting the chip relief surface 60 (further movement is once prevented), giving great resistance to the cutting edge 2.3. There is also a problem in that the portion 5 is damaged during brazing due to the force of the chips hitting the chip relief surface 60 at this time, which causes the portion to be gouged out or by providing a large resistance to the head 1.

Note that the chips generated by the cutting edges 2°3 outside the center of the bottom shape also grow in the axial direction along the rake faces 22°32, but since the outside rake faces are set sufficiently large. , usually .

The chips will strike the chip relief surface 21.31 in a curved manner, so that this surface does not have to be formed at an obtuse angle to the rake surface.

(Effect of the invention in Song Dynasty) As explained above, in the bottom shape of the present invention, a rake face is formed approximately in the axial direction along the cutting edge that is formed almost continuously from near the center of the shank to the outer peripheral edge, and The angle between the nearby chip relief surface and the above rake surface is formed into an obtuse angle, and the generated chips grow along the rake surface and are released without being stopped even when they hit the chip relief surface. Since it moves along the surface and is discharged, it does not create resistance to the movement of the cutting blade and the cutting action, and therefore the cutting performance of the ball end mill can be improved. In addition, since the resistance during cutting is reduced, problems such as gouging of the chip relief surface and damage to the brazed shank and head can be prevented, increasing the life of the ball end mill. You can also do it.

[Brief explanation of drawings]

Fig. 1 is a bottom view showing an embodiment of the present invention, Fig. 2 is a front view thereof, Fig. 3 is a side view thereof, and Fig. 4 is an I of Fig. 1.
FIG. 5 is a sectional view taken along the line V--IV in FIG. 2. 1... Head of ball end mill, 2.3... Cutting blade,
4...Shank, 20.30...Chip relief surface near center Eq, 22.32...Rake face, θ1. θ2...
・The angle between the rake face and the chip release face.

Claims (1)

[Claims] 1. In the bottom shape, a rake face is formed approximately in the axial direction along the cutting edge that is formed almost continuously from near the center of the shank to the outer peripheral edge, and the angle formed by the chip release surface near the center and the above rake face. A ball end mill characterized by being formed at an obtuse angle.