JPS637449Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a drilling drill that uses cast iron, steel, etc. as a work material, especially cemented carbide, or a hard coating layer with high wear resistance on its surface. The present invention relates to an improvement in a drill for drilling taper holes, which uses a formed material and has a cutting edge with a predetermined slope.

[Conventional technology and its problems]

Increasingly, drills are responding to demands for higher efficiency in drilling operations by increasing the rotational speed of drills. It has become increasingly common to use materials as drilling materials. However, cemented carbide is not a material with satisfactory strength, as it has inferior resistance compared to high-speed steel, and for this reason,
It was difficult to apply it to drills that have a large cutting load.

For example, the strength of a drill depends on its torsional rigidity and bending rigidity, but the strength is determined by the core thickness and groove width ratio. Figure 7 shows the torsional stiffness value when changing the value, and shows the circular cross section without grooves.
The value and ratio are shown as 100%. As is clear from this, the drill strength improves as the core thickness increases and the groove width ratio decreases. however,
On the other hand, in the case of the conventional drill shape shown in Figure 8, as the core thickness increases and the groove width ratio decreases, the cutting resistance (torque, thrust) increases proportionally, making it difficult to eject chips. Become. For this reason, in high-speed steel drills, the core thickness W is generally set at 15 to 23% of the drill diameter, and the groove width ratio (B:A) is set at 1 to 1.3:1. The strength is insufficient, leading to breakage accidents.

One of the factors that increases the cutting resistance is that the rake angle θ ₁ in the radial direction of the cutting edge 1 is negative at any point. In addition, since the relative distance l ₁ between the groove wall 2, which is in a negative position and faces the flow of chips, becomes large, the ejected chips may not hit the groove wall but directly hit the inner surface of the machined hole. This not only deteriorates the surface roughness of the hole but also increases the cutting resistance.
Of course, the increase in core thickness is also a major factor, but it is difficult to reduce this value when using cemented carbide as a material, so eliminating the first two factors is the key to creating a high-load carbide drill with a good finished surface. This is an important issue in realizing this.

Therefore, the present applicant proposed a basic solution to the above-mentioned problem in Japanese Patent Application No. 58-93098. However, in the tapered drill that is the object of this application, not only the cutting edge at the tip but also the cutting edge along the margin are involved in cutting, so the cutting resistance is much larger than that of a straight drill, and therefore, even stronger strength is required. Atsup is required.

The present invention is based on the technical idea of Japanese Patent Application No. 58-93098 and meets this demand.

[Means for solving problems]

The taper drill of this invention meets the above requirements.
For drills for drilling taper holes made of ultra-hard materials or materials with a hard coating layer with higher wear resistance on the surface, the core thickness at the tip of the taper part with a predetermined slope is 25 to 30% of the drill diameter. Groove width ratio 0.4~
Set it to 0.8:1 and set the radial rake angle of the tip side cutting edge located outside at least 2/3 of the drill diameter to -5° to positive when viewed directly from the end face, and further, set it from 2/3 above. The distance between the imaginary perpendicular from the outer periphery of the groove wall facing the cutting edge perpendicular to the outer cutting edge as a reference line and the imaginary perpendicular from the outer periphery of the cutting edge is set to 47% or less of the drill diameter. shall be.

In other words, by setting the core thickness and groove width ratio to the above values, the strength of the drill can be increased by increasing the cross-sectional area. By limiting the relative distance between the opposing groove wall outer peripheries, an increase in cutting resistance is eliminated.

If the core thickness is less than 25% of the drill diameter, torsional rigidity will be insufficient, and if it exceeds 35%, chip evacuation will be poor. Furthermore, if the groove width ratio and the relative distance from the outer periphery of the groove wall to the outer periphery of the cutting edge are out of the above range, the chips may not curl or break properly, and the ejected chips may directly hit the surface of the machined hole. Furthermore, when the radial rake angle is -5° or less, cutting resistance increases and rigidity is insufficient. A rake angle in the range of 0 to 10 degrees is more desirable because the cutting quality is better.

〔Example〕

Hereinafter, embodiments of this invention will be described based on the accompanying drawings.

1 and 2 show a taper drill according to the first embodiment, in which a predetermined slope α is attached to the range L from the outer periphery of the cutting edge 1 on the distal end side to the middle of the cutting edge 4 along the margin 3. . Further, the cutting edge 1 has a chisel edge of 0 or a dimension close to 0 by providing a thinning groove 5, and furthermore, the edge 1a on the outside of 2/3 of the drill diameter of the cutting edge 1 is as shown in FIG. In order to set the rake angle θ ₂ in the radial direction to be positive in this state, the blade itself is a curved blade, and the cutting blade 1b in the core thickness is connected to the curved cutting blade 1c which is concave in the direction of rotation.

In addition, the core thickness W is 25 to 35% of the drill diameter, the groove width ratio B:A is 0.4 to 0.8:1, and furthermore, the cutting edge 1a is set as a reference line, and the outer periphery of the groove wall 2 facing it is measured from the reference line. The distance l ₂ between the line perpendicular to the line and the line perpendicular to the outer periphery of the cutting edge is set to 47% or less of the drill diameter.

Figure 3 shows the radial rake angle of the cutting edge 1a on the outside of 2/3 set to 0°, and Figure 4 shows the same rake angle θ ₂ set to positive. Blade 1
There is almost no difference from the drill of the first embodiment except that a is a straight line.

On the other hand, Fig. 5 shows that in the case of a taper drill, the centripetality during machining is poor, so as a solution to this problem, a straight part 6 with a length of 20 to 30% of the drill diameter is connected to the tip of the taper part. It is equipped with a cutting edge 1, and has a tapered slope backward from the continuous point C. This diagram exaggerates the taper slope to make it easier to understand.

Note that, in order to ensure rigidity, it is desirable that the cross-sectional shape of the tapered portion at any point from the tip toward the shank portion 7 be made similar to the tip and gradually increase in size.

The results of a comparison of drilling experiments using the drill of the present invention and a conventional drill are shown below.

The drill of the present invention is based on FIG. 5, and the end face shape of the straight portion 6 is the same as that in FIG. 2. In addition, the dimensions shown in Fig. 5 are d = 6 mm, L ₁ = 10
mm, L ₂ = 20 mm, α = 60°. The core thickness is 1.8 mm for the straight part 6, and the tapered part behind it is 30% of the diameter of each part of the tapered part, and the groove width ratio (B:A in Figure 2)
The ratio is 0.5:1, and the tip is cross thinned to make the chisel width 0.1mm. The drill material is based on P30 and its surface is coated with TiN.

On the other hand, the conventional drill has the following features: the end face has the shape shown in Figure 8, the core thickness is 1.2 mm at the tip straight part, 20% of the diameter of each part at the tapered part, and the groove width ratio is 1:
1, which is different from the present drill.

Other conditions are as follows.

Workpiece: Automotive parts, material SCM415, H _RC 20 or less Processing machine: Dedicated machine 11KW Cutting conditions: Cutting speed at straight section V=
35m/min, feed f = 0.04mm/rev, machining depth = straight tip part 8mm, tapered part
10mm (total 18mm) Cutting oil: Emulsion type was used As a result of the above, the drill of this invention was able to stably machine 600 holes. On the other hand, although some conventional drills were capable of drilling 600 holes, most of them broke between 50 and 600 holes, and their lifespans varied greatly.

FIG. 6 shows the measured values of the surface roughness of the tapered hole machined with the drill of the present invention. The numbers in the diagram are 100 in the hole depth direction.
It is enlarged 500 times in the roughness direction,
As described above, according to the present application, the machined surface roughness is sufficiently reduced. In the figure, it falls within a range of approximately 10 μm.

〔effect〕

The taper drill of the present invention constructed as described above has a large core thickness and a small groove width ratio, so that torsional rigidity and bending rigidity are improved.

In addition, since the radial rake angle of the cutting edge outside 2/3 of the drill diameter is in the range of -5° to positive, the torque is lower than that of a conventional drill with the same core thickness and groove width ratio. Thrust is significantly reduced.

Furthermore, since the distance from the outer periphery of the cutting edge to the outer periphery of the opposing groove wall is short, the curling of chips is reduced.
Breakage and evacuation are performed only through the drill groove, thus eliminating problems such as chip clogging, increased chip resistance due to chip contact with the inner surface of the machined hole, and deterioration of the surface roughness of the machined hole.

Furthermore, when the cutting edge in the core thickness part and the cutting edge on the outside of 2/3 are connected by a curve, the cutting edge length becomes longer, so the amount of work per unit length of the cutting edge is reduced, and the cutting edge at the start of the cut is reduced. A further reduction in resistance and higher wear resistance of the cutting edge can be achieved.

[Brief explanation of drawings]

FIG. 1 is a side view showing an example of a taper drill of the present invention, FIG. 2 is a front end view thereof, FIGS. 3 and 4 are front end views of other embodiments, and FIG. 5 is a further example of another embodiment. Fig. 6 is a measurement graph of the surface roughness of the hole surface drilled by the drill of the present invention, Fig. 7 is a correlation graph of core thickness and groove width ratio on torsional rigidity, and Fig. 8 is a graph of the conventional drill. It is a front view of a drill. 1... Cutting edge, 2... Groove wall, 3... Margin, 4
...cutting edge, 5...thinning groove, 6...straight part, 7...shank part.

Claims (1)

[Claims for Utility Model Registration] (1) In a drill for drilling a taper hole made of an ultra-hard material or a material with a hard coating layer with higher wear resistance on its surface, the tip of the taper part with a predetermined slope Set the core thickness to 25 to 30% of the drill diameter, set the groove width ratio to 0.4 to 0.8:1, and look directly at the radial rake angle of the tip side cutting edge located outside at least 2/3 of the drill diameter from the end face. In addition, with the cutting edge outside 2/3 of the above as the reference line, an imaginary perpendicular line from the outer periphery of the groove wall opposite the cutting edge and an imaginary perpendicular line from the outer periphery of the cutting edge. Drill distance between 47% of diameter
A taper drill characterized by the following. (2) Concave this cutting edge and the cutting edge of the thick core part in the direction of rotation when looking directly at the end so that the radial rake angle of the cutting edge outside the above 2/3 becomes 0° to positive when looking directly at the end. 2. A taper drill according to claim (1) of the utility model registration, characterized in that the taper drill is connected with a curved cutting edge. (3) Utility model registration claim (1) characterized in that the cross-sectional shape of any point from the tip of the cutting blade toward the shank portion is made similar to the cross-sectional shape at the tip and gradually increases; or Taper drill described in paragraph (2). (4) Request for registration of a utility model characterized in that a straight cutting edge with a length of 20 to 30% of the drill diameter is connected to the tip of the tapered part, and a cutting edge on the tip side is attached to the tip. Scope of paragraph (1) or (2)
Taper drill as described in section.