JPH0313004B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a milling tool such as a drill that performs axial cutting and an end mill that performs axial cutting and horizontal cutting, and more particularly relates to the tool. This allows for effective axial cutting.

[Prior Art] Conventionally, tools such as drills and end mills that perform axial cutting while rotating on their own axis have a cutting edge configuration in the center portion of the cutting edge that is not necessarily suitable for axial cutting.

In other words, in a drill, a large negative rake angle is formed in the part where the rotation of the center of the shaft is extremely slow, and in an end mill, a straight cutting edge is formed from the center of the tool to the outer periphery. ing.

[Problems with the prior art] The above-mentioned drill has poor biting properties;
There is a problem with centripetal property, making it difficult to obtain highly accurate machined holes, and the thrust load increases significantly during cutting, leading to progressive wear on the central cutting edge of the drill, which significantly shortens the life of the drill.

In addition, in the case of the above-mentioned end mill, since the cutting edge is straight from the center to the outer periphery of the tool, the center cutting edge rotates extremely slowly during cutting, and the outer periphery cutting edge has a high circumferential speed. Cutting is started in such a state that both are in solid contact with the workpiece surface at the same time.

For this reason, chips that are generated at the same time as a large cutting load is applied to the central cutting edge become thicker toward the center of the cutting edge due to high heat, and are more likely to be welded to the cutting edge.

As a result of the above, the wear of the central cutting edge is greatly accelerated and the cutting edge is frequently damaged, thereby hindering effective drilling.

[Object of the Invention] The present invention was made to solve the above-mentioned problems, and it improves the center part of the cutting edge of a tool for cutting in the axial direction, such as a drill or an end mill.
It is an object of the present invention to provide a milling tool that can reduce the thrust load during cutting, increase the centripetal property, and prevent wear or breakage of the cutting edge in the central portion.

[Means for Solving the Problems] The present invention solves the above-mentioned problems by the following configuration.

That is, the tool body is provided with a pair of peripheral cutting edges and a chip discharge groove, and the end face thereof is formed with a clearance face having a predetermined clearance angle. A recessed portion is provided which is inclined toward the shaft center with an interval of The ridgeline formed by the flank and rake faces is the center cutting edge, and the center cutting edge, center side cutting edge, and outer peripheral side cutting edge are continuously formed in a broken line shape.

[Operation of the Invention] With the above-described configuration, the cutting blade (drilling blade) formed on the end face of the tool, which is effective for cutting in the axial direction, has a central cutting blade and a central cutting blade. It has a three-stage cutting edge consisting of a cutting edge and a peripheral cutting edge side cutting edge, and in particular, the rake angle of the axial rake face of the center cutting edge and the center side cutting edge is zero, positive, or gently negative.

By making the center cutting edge and the center cutting edge as described above, the biting ability of this tool to the workpiece material during initial cutting is greatly improved, and subsequent hole drilling can be performed with high precision. It also prevents the continuous "squeezing" and "rubbing breakage" that occur with conventional drills, and reduces the thrust load significantly, reducing wear and breakage of the cutting edge while reducing load. Cut.

In addition, the effective cutting edge is long and the cutting edge is formed into a three-stage broken line that extends to the center of the tool, so chips generated during drilling are easily broken and ejected along the cutting edge. As a result, the occurrence of welding of chips to the center cutting edge or the center side cutting edge is extremely reduced, and the problems caused by this are also eliminated.

[Example] Hereinafter, an example of the present invention will be described based on the attached drawings.

The figures all show a milling tool according to the present invention, and Figure 1 shows one applied to a drill, in which a is a bottom view of the central part, and b is a side view of a in the direction of arrow A. Figures 2 and 3 are a side view of a as viewed from arrow B, Figures 2 and 3 are applied to a drill with a cutting edge made of hard alloy, Figure 2 is a front view of the main parts, and Figure 3 is a 2 is a bottom view, and FIG. 4 is a detailed view of FIG. 3, in which a is a bottom view, b is a side view of a as seen from arrow A, c is a side view of a as seen from arrow B, and d is a A is a side view taken from the direction of arrow C, FIG. 5 is another embodiment, a is a bottom view of the main part of the cutting blade, b is a side view of a, and FIG. 6 is another embodiment. A is a bottom view of the main part of the cutting blade, b is a side view of a, etc.

In FIG. 1, the drill body 1 has a pair of outer cutting edges 11, 11a and chip discharge grooves 12, 12a.
Relief surfaces 13, 13a are formed on the end face with a predetermined relief angle.

Then, with the center 10 of the tool as a reference, as shown in Figure c, the angle of inclination θ (5 degrees to 175
(120 degrees in the example), and the inclined surface 1 on the rear side of the tool rotation direction R of this recess.
5, 15a and rake face 1 on the front side in the tool rotation direction R
6, 16a is the center cutting edge 14, 1
4a, and the ridgeline formed by the above-mentioned flank surfaces 13, 13a and rake surfaces 16, 16a is the central cutting edge 1.
7, 17a, and the outer peripheral side cutting edge 11, 1 described above.
1a and the center cutting edge 17, 17a and the center cutting edge 1
4 and 14a are continuously formed in three steps in a broken line shape.

As described above, since the central cutting edges 14, 14a are recessed by the inclined surfaces 15, 15a and the rake surfaces 16, 16a, the cutting edges can be formed up to the tool center 10, and the rake surfaces The rake angle can be set to any desired rake angle depending on the cutting conditions, such as zero, plus, or a gentle negative angle in the axial direction of the tool, making it possible to efficiently cut the center of the tool, which has traditionally been a problem. Moreover, as mentioned above, an effective three-stage cutting edge can be formed from the center to the outer periphery, and the chips generated during cutting are wide, thin, and easily broken, greatly improving chip evacuation. This solves the problem caused by

Next, as shown in FIGS. 2 and 3, a pair of hard metal chips 2, 2 are mounted on the chip seat at a predetermined position at the tip of the shank 1a formed from a metal other than hard metal.
An application of the present invention to a milling tool in which a is brazed or mechanically fixed will be described.

An arcuate cutting edge 100, 100a protruding forward in the tool rotation direction Ra with respect to the tool center 10a is continuous with an arcuate or wavy cutting edge 200, 200a having a straight line or a smaller curvature than the arcuate cutting edge. In the circular cutting blades 100, 100a, inclined surfaces 150, 150a having the same spacing S and the same angle of inclination θ as in the above-mentioned embodiment are recessed from approximately the center of the cutting edges 100, 100a. The ridgeline formed by the face and the rake face 160, 160a is the center cutting edge 140, 140a, and this, the center side cutting edge 170, 170a, and the outer peripheral side cutting edge 110, 110a.
It has the same function and effect as the milling tool of the above-described embodiment as a three-stage cutting blade in which
In addition, since the chip pockets 300, 300a can be formed to be large, chip evacuation during cutting is further improved.

Next, an example in which the present invention is applied to an end mill will be described with reference to FIGS. 5a and 5b.

The figure shows the main parts of the cutting blade, in which a is a bottom view and b is a side view of a.

A central cutting edge that is convex toward the front side in the tool rotation direction Rb is composed of a main chip 2b having a cutting edge starting end at the tool center 10b, and an auxiliary chip 2c having a cutting edge starting edge located away from the tool center. A linear outer peripheral cutting edge is provided, and inclined surfaces 150b and 150c are provided with the same spacing S and an inclination angle θ as in the previously described embodiments based on the tool center 10b. The ridgeline formed by the face and the rake face 160b (one omitted) is the center cutting edge 140b, 140c, and this, the center side cutting edge 170b, 170c, and the outer peripheral side cutting edge 110b, 110c are continuously formed. This configuration also provides an end mill that can perform both axial cutting and radial cutting very well while having the above-mentioned effects.

Moreover, what is shown in FIGS. 6a and 6b shows the main part of the cutting blade of a drill in which the starting end of a pair of cutting blades is spaced a predetermined distance from the center of the tool, and its configuration is as described above. Similar to the embodiment described above, an inclined surface 150 is provided with an interval S and an inclination angle θ based on the tool center 10c.
d, 150e are recessed, and this inclined surface and rake surface 1
60c (one omitted) and the ridgeline formed by the central cutting edges 140d and 140e, and the central cutting edges 170d and 170e and the outer peripheral cutting edges 110d and 11.
Even if 0e is continuously formed, the same operation and effect as in the above-mentioned embodiments can be obtained.

[Operation of the Invention] A drill according to the present invention and a conventional drill for comparison were prepared and the following tests were conducted.

The drill diameter is 20 mm in both cases. The machine used is a vertical milling machine with a horsepower of 7.5KW.
The workpiece material is S55C (HB170-200), and its thickness is 50mm.

The cutting conditions were: rotation speed 850 rpm, feed rate per rotation 0.3 mm/rev, cutting method wet, emulsion type water-soluble cutting oil (diluted 4 times).
was used, and the lubrication method was forced lubrication from inside the drill.

The above test results show that the drill of the present invention is 15
The second wear width of the central cutting edge after m-cutting was approximately 1/5 of that of the conventional drill.

In addition, as a result of measuring the thrust resistance during cutting,
The drill of the present invention was about 85% of the conventional drill.

As described above, the present invention dents the center of the cutting edge of a milling tool, makes one side of this dented part the cutting edge, and divides this into the center cutting edge and the outer peripheral cutting edge.
By forming the step continuously, an effective cutting edge can be formed all the way to the center of the tool, allowing smooth drilling and cutting.This reduces cutting resistance and prevents wear and tear on the cutting edge. In addition to preventing chipping, it is now possible to form the cutting edge all the way to the center of the tool, increasing centripetal properties during initial cutting.
Center run-out during machining is extremely reduced, making it possible to obtain highly accurate machined holes.

[Brief explanation of the drawing]

The figures all show a milling tool according to the present invention, and Figure 1 shows one applied to a drill, in which a is a bottom view of the central part, and b is a side view of a in the direction of arrow A. Figures c and c are side views taken from arrow B in a, Figures 2 and 3 are applied to a drill with a hard metal cutting edge, Figure 2 is a front view of the main parts, Figure 3
The figure is a bottom view of FIG. 2, and FIG. 4 is a detailed view of FIG. , d is a side view of a as viewed from arrow C, FIG. 5 is another embodiment, a is a bottom view of the main part of the cutting blade, b is a side view of a, and FIG. 6 is yet another embodiment. It shows
A is a bottom view of the main part of the cutting blade, b is a side view of a, etc. 1, 1a...Main body, 11, 11a, 110, 1
10a, 110b, 110c, 110d, 110
e... Outer cutting edge, 13, 13a... Relief surface, 1
4, 14a, 140, 140a, 140b, 14
0c, 140d, 140e...Central cutting edge, 1
5, 15a, 150, 150a, 150b, 15
0c, 150d, 150e, ... inclined surface, 16,
16a, 160, 160a, 160b, 160c
...Rake face, 17, 17a, 170, 170
a, 170b, 170c, 170d, 170e...
...Central cutting edge, R, Ra, Rb...Tool rotation direction.

Claims (1)

[Claims] 1 A pair of peripheral cutting edges and a chip discharge groove are formed on the main body, and a clearance surface is formed on the end face with a predetermined clearance angle, and the end face has a predetermined interval with respect to the axial center of the main body. A recessed portion is provided which is inclined toward the shaft center, and the ridgeline formed by the sloped surface of the recessed portion on the rear side of the tool rotation and the rake surface on the front side of the tool rotation is the center cutting edge of the tool. A milling tool characterized in that the ridgeline formed by the face and the rake face is used as a center cutting edge, and the center cutting edge, the center cutting edge, and the outer peripheral cutting edge are continuously formed in a broken line shape.