JPS5835366Y2 - rotary cutting tool - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in the shape of a cutting edge of a rotary cutting tool such as an end mill or a drill.

Conventional end mills have two cutting blades with straight or spiral outer peripheries, and are configured so that they intersect at the center toward the tip, and the curve when viewed from the bottom of the blade at the tip is approximately It's in a straight line.

Therefore, when cutting with the rotation of an end mill, the parts 1 from the center of the blade to the outer periphery come into contact with the workpiece material almost simultaneously, which increases the impact force during cutting and easily damages the cutting edge. Heavy cutting was impossible.

In recent years, work materials such as shapes have become increasingly hard and difficult to cut, so it has become necessary to use cemented carbide for end milling. There is a problem that the cutting edge will break when cutting with.

For this reason, if cemented carbide is used for the end mill, even if the mill rotates at high speed, the cutting speed near the center will be slow.
Breakage of the cutting edge near the center is unavoidable.

Furthermore, the conventional cutting edge shape has the disadvantage that chips generated during cutting are pressed against the rake face, making it difficult to discharge the chips smoothly.

Almost the same problem exists with old conventional drills.

In view of these points, the present invention aims to provide a rotary cutting tool that reduces impact force during cutting, smoothly discharges chips, and can withstand heavy cutting for an extremely long period of time. .

Hereinafter, the present invention will be explained with reference to drawings of embodiments.

1 is an end mill body, and tips 2 and 3 are attached to the tip thereof.

The chip 2 is formed into a flat plate shape and has a main cutting edge 4 formed therein.

The starting end 6 of this main cutting edge 4 is located at the axial center of the end mill body 1, and the shape of the main cutting edge 4 is a curve that is convex in the rotation direction when viewed from the bottom of the mill, and has a large curvature near the center.
It is almost straight at the outer periphery.

The angle θ between the tangent to the cutting edge at the center point and the tangent to the cutting edge at the outer periphery is 90°.

Further, a rising portion 60 is formed at the starting end 6 of the main cutting edge.

The insert 3 is configured to have almost the same shape as the insert 2, but the starting end 7 of the auxiliary cutting edge 5 is slightly eccentric from the axial center of the end mill body 1, so that the auxiliary cutting edge 5 traces the same trajectory as the main cutting edge 4. I have to.

70 is its rising portion.

Further, the main cutting edge 4 has a notch 13 and a notch 17 formed therein.

The notch 13 is for cutting chips at this portion, and the notch portion is extended to the side surface of the chip so that a cutting edge is formed also in this portion and a burnt surface is formed.

The chipped notch 17 is used to leave this portion uncut and use another cutting blade (auxiliary cutting blade 5) to scrape that portion to generate thin chips corresponding to the width of the notch 17.

A required number of such notches may be formed on the main cutting edge 4 and the auxiliary cutting edge 5 as necessary to adjust the amount of chips.

The advantage of adjusting the size of chips by forming such notches is particularly great when drilling deep holes with a drill.

In other words, in deep hole machining, if the chips are large, they will rub against the inner circumferential surface of the hole as they ascend through the hole, damaging the inner circumferential surface of the hole and impeding the evacuation of the chips themselves due to frictional resistance. However, this inconvenience can be overcome by adjusting the size of the chips using the notches.

The mounting position of the chips 2 and 3 is not limited to the case where they are mounted in the axial direction of the main body as shown in the illustration, but it is also possible to mount one or both chips at an angle with respect to the axial direction of the main body 1. Furthermore, the cutting edge curves on the bottom crosspieces of the main cutting edge 4 and the auxiliary cutting edge 5 may be made different.

Further, in the illustrated example, the locus drawn by the cutting edge is hemispherical, but it may also be configured to draw a conical shape with various apex angles.

When cutting is performed using the end mill configured as described above, cutting first starts from the starting end 6 of the main cutting edge, and the cutting point gradually moves toward the outer periphery.

Even if the auxiliary cutting edge 5 is bent, the depth of cut starts from the starting end 7 and the cutting point gradually moves to the outer periphery.

In this way, each cutting edge has a large curvature near the center, so the cutting position gradually moves outward from the middle to the top, and at the same time the cutting edge has a force that pushes chips outward from the center at the beginning of cutting. This prevents the top-slipping phenomenon that occurs in conventional products, and also prevents the application of an impact load due to gradual cutting from the center.

In addition, due to the force that pushes the chips outward near the center, the chips are not pressed against the rake surface b, and as the cutting point moves outward, the chips also move outward, ensuring that they are separated and discharged. Ru.

In addition, the force that pushes the chips that have broken into the center of the cutting edge outward generates frictional heat on the cutting edge, which reduces the temperature difference between the cutting edge and the outer periphery, reducing thermal stress on the chip and preventing chips from adhering. .

These effects have made it possible to use cemented carbide in Bo) C end mills, which was previously considered impossible, and thereby made it possible to process difficult-to-cut materials.

In other words, materials with high hardness and toughness such as die steel, materials with high ductility such as copper and SS materials, materials with high work hardenability such as stainless steel, materials with hard fine particles such as FC, and materials with high hardness such as FC. This invention exhibits amazing cutting performance for heavy cutting of materials such as stainless steel and titanium, which have an affinity for hard metals.

In the present invention, since an auxiliary cutting edge is provided outside the main cutting edge, there is an advantage that a cutting reaction force is applied symmetrically to the axis of the tool during cutting, thereby preventing axial runout.

In addition, with the above configuration, since the auxiliary cutting edge is located eccentrically from the shaft center, when grinding the cutting edge near the center, the machining becomes easier than when the auxiliary cutting edge and the main cutting edge are continuous at the center. Easy and i! Since the main cutting edge and the auxiliary cutting edge are asymmetrically formed, there is an advantage that sudden loads during machining can be relieved and stress is not placed on the tool.

Moreover, the present invention can also be applied to a drill, and when applied to a drill, the main body 1 is
A spiral groove may be provided above the terminal end of the cutting blade, or the diameter of the main body 1 above the terminal end of the cutting blade may be made thinner.

The cutting mechanism of drills is almost the same as above, and the cutting resistance near the center is small and the chips are sent out sequentially toward the outer circumference so that the next chip can be cut smoothly. Even if an alloy is used, there will be no chipping.

Furthermore, by using cemented carbide, it becomes possible to cut difficult-to-cut materials and high-hardness materials, and the machinability is also improved, making it possible to significantly increase the rotational speed and perform high-speed machining.

Further, in a drill, especially when drilling a deep hole, the present invention is preferable because the auxiliary cutting edge is provided as described above to prevent shaft runout.

The above effects are achieved by making the curvature of the cutting edge larger toward the center than the outer periphery, and the curvature at the center is significantly larger than that of conventional products. This is a basic feature of the present invention, but the optimal degree to which this curvature should be set varies depending on the material of the rigid material, cutting conditions, etc.

According to the inventor's experiments, the tangent line at the starting end (6 and 7) of the cutting edge curve in bottom view and 0.7R (
If the angle θ between the point (R is the radius of the main body 1) and the tangent to the button (10 and 11) is 35° or more, the effect of the present invention will appear, and under normal conditions, the larger the angle, the more effective it will be. becomes noticeable.

[Brief explanation of the drawing]

FIG. 1 is a bottom view showing an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a side view rotated by 90 degrees from the state shown in FIG. 2. 1...Main body, 2, 3...Chip, 4...Main cutting edge, 5...Auxiliary cutting edge, 7...Starting end of the cutting edge.

Claims (1)

[Scope of utility model registration request] A rotary cutting tool such as an end mill or a drill, which has a main cutting edge whose starting end is located at the center of the axis of the tool, and an auxiliary cutting edge whose starting end is located eccentrically from the axial center of the tool, and A rising part is provided at the starting end of each cutting edge, and when viewed from the bottom of the tool, each cutting edge forms a curve that is convex in the direction of rotation, and the cutting edge curve at the center has a larger curvature than the cutting edge curve at the outer periphery. A rotary cutting tool characterized in that the main cutting edge and the auxiliary cutting edge are formed asymmetrically with respect to the shaft center.