JPH04322909A - Throw-away type ball end mill - Google Patents

Abstract

PURPOSE:To reduce the cutting resistance and the stability of an attaching mechanism and to prevent damage to a cutting blade even during heavy cutting. CONSTITUTION:A plurality of chip seats are formed in a spherical head part 3 of a tool body, being continuous with a chip pocket 6, and a throw-away chip 7 is removably attached to the tool body through the center attaching hole thereof with screws 8. The throw-away chip 7 is basically polygonal, and when it is attached to the tip seat of the spherical body 3, its convex cylindrical side surface serves as a rake surface while its planar upper surface serves as a flank. Further, their crossing lines form cutting ridges. Further, the chips are attached to the spherical head 3, being successively shifted from each other so that the cutting ridges depict a semicircular shape on their rotating loci.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a large-diameter indexable ball end mill used in milling machines and the like for profiling in mold machining.

0002

BACKGROUND OF THE INVENTION Conventionally, ball end mills have been mainly used for machining molds, but as molds have become larger, end mills have also become larger and required heavy cutting. Due to the need to improve the performance of large ball end mills, they have changed from being made of steel to being brazed with cemented carbide. This brazed cemented carbide is expensive, and due to problems such as re-polishing,
As a solution to this problem, an indexable ball end mill has been constructed by removably attaching an indexable tip to a steel main body, but there are still many points that require improvement. (For example, Jikko 02-33
74)

0003

[Problem to be solved by the invention] Under the required heavy cutting conditions, vibration is likely to occur due to large cutting resistance and insufficient mounting strength of the insert, leading to premature wear and damage of the indexable insert. Along with this, there were problems that needed to be resolved, such as damage to the main body chip seat, which is the indexable chip attachment part.

[0004] The present invention has been made in view of the above points.
The purpose of the present invention is to provide a large diameter indexable ball end mill that exhibits stable cutting performance even under heavy cutting conditions and is easy to handle.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following constituent elements. That is, according to the present invention, several indexable inserts are used, the cutting edges are distributed at several locations for partial cutting, and the cutting edge shape is a convex curve, so that the impact when biting into the workpiece is reduced. The cutting force is relaxed and becomes two-dimensional cutting, and since the cutting edge is longer with a convex curve, the cutting resistance per unit length of the cutting edge is also reduced, reducing the burden on the cutting blade and mounting mechanism, resulting in stable weight as a whole. Cutting becomes possible.

[0006] Furthermore, the chamfer provided on the edge of the cutting edge adjacent to the side surface that intersects at an obtuse angle with the rake face increases the strength of the cutting edge at the corner, and even at high feeds, the chamfered portion is provided at the edge of the cutting edge to ensure that the corner is aligned in the longitudinal direction of the chip. Since it is possible to provide a relief angle to the cutting surface, stable cutting can be made more reliable.

Furthermore, since the flank of the chip is spherical, when it is set in the tool body, even if the clearance angle is the lead-like clearance angle, that is, the minimum clearance angle required at the cutting edge, the bottom of the cutting edge (that is, the cutting edge) On the other cutting edge (on the opposite side), the clearance angle gradually increases, and the clearance angle is large to prevent the bottom of the cutting edge from coming into contact with the workpiece, as would be the case when the clearance surface is flat. There is no need to form a corner, and the minimum necessary clearance angle (usually 5° to 8°) is sufficient during cutting, so the strength of the cutting edge is not likely to be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an indexable ball end mill according to the present invention, FIG. 2 is a bottom view thereof, and FIG. 3 is a longitudinal cross-sectional view of a tip attachment portion. In the figure, reference numeral 1 denotes a cylindrical tool body, with a spherical head 3 formed at one end and a shank portion 4 formed at the other end.

The spherical head 3 is provided with a plurality of chip seats 5 connected to the chip pockets 6.
A throw-away tip 7 is removably attached to the tip by a set screw 8 through its central attachment hole. or,
As shown in FIG. 3, the chip seat 5 is machined so that when the indexable chip 7 is set, a clearance angle θ is given to the cutting edge, which is the cutting edge.

Furthermore, this indexable tip 7 is shown in FIG.
~As shown in FIG. 7, the basic shape is a polygon, and has a flat top surface 10, a bottom surface 11, and a convex circular side surface 12 that intersects the top surface 10 at an acute angle. When attached to the chip seat 5, the side surface 12, which is a convex circular surface, forms a cutting rake surface, the upper surface 10 forms a flank surface, and the intersection line of these forms a cutting edge.

Next, in the spherical head 3, the tips are mounted so as to be sequentially shifted in the axial direction or in the axial direction and rotational direction so as to form a hemispherical shape on the rotation locus of each cutting edge. Incidentally, the arrangement angle of each tip in the axial direction for a blade with a cutting edge diameter of 50 mm (rotation radius 25 mm) is α1 = 12° 30', α2 = 4
5°, α3 = 71°, clearance angle θ = 7°, and the ball R1 of the chip used was 25 mm (spherical surface) and R2 = 50 mm.

0012

Effects of the Invention The present invention aims to reduce the cutting resistance of indexable ball end mills, prevent damage to the cutting edges even during heavy cutting, and improve the stability of the mounting mechanism. Throw-away inserts with ridges are distributed vertically to perform three-dimensional partial cutting, and the flank of the chip is spherical, so the cutting edge is smaller than when using a flat clearance angle. The strength can be significantly improved, and the synergistic effect of these makes it possible to provide an indexable ball end mill that can perform stable cutting even under heavy cutting conditions.

[Brief explanation of drawings]

FIG. 1 is a front view of an indexable ball end mill according to the present invention.

FIG. 2 shows a bottom view of FIG. 1;

FIG. 3 shows a longitudinal cross-sectional view of the indexable tip mounting portion.

FIG. 4 shows a front view of the indexable tip incorporated into the ball end mill of the present invention.

FIG. 5 shows a left side view of FIG. 4;

FIG. 6 shows a right side view of FIG. 4;

FIG. 7 shows a bottom view of FIG. 4;

[Explanation of symbols]

1 Tool body 2 Blade part 3. Spherical head 4 Shank part 5 Chip seat 6 Chip pocket part 7 Throwaway tip 8 Set screw

Claims (2)

[Claims] [Claim 1] A spherical head at the tip of a cylindrical tool body is provided with a plurality of chip seats connected to a chip pocket,
In the indexable ball end mill, in which an indexable insert having a center mounting hole is removably arranged on the insert seat using a set screw, and the rotation locus of each cutting edge is formed in a hemispherical shape, the indexable insert has a center mounting hole. The basic shape of the chip is a polygon, and each side of the top surface and the bottom surface, which are flat, and the side surfaces connecting the top surface and the bottom surface, are formed into a cylindrical convex curved surface that intersects the top surface at an acute angle.
In addition, the lines of intersection with the upper surface each constitute a cutting edge edge, and the indexable insert is detachably arranged so as to be sequentially shifted in the axial direction or in the axial direction and rotational direction so as to form a hemispherical shape on the rotation locus. Thumb-away ball end mill. 2. The throw-away ball end mill according to claim 1, wherein a chamfer is provided at the apex portion of the intersection between the side surfaces.