JPS6246492Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] The present invention relates to a drill made of cemented carbide, and in particular, to improve the cutting oil supply function and chip discharge function as much as possible. This is about a drill that can be done.

[Technical background of the invention and its problems] High-speed steel drills have traditionally been used for drilling in general steel materials, cast iron, etc., but in recent years, there has been a strong demand for higher efficiency in drilling operations. Increasingly, the number of rotational speeds of drills is increased to meet these demands, and as a result, cemented carbide, which has excellent wear resistance, is increasingly being used as a drill material. However, the use of cemented carbide is limited due to the brittleness of the material itself, such as inferior transverse rupture strength compared to high-speed steel, and various efforts have been made to compensate for this brittleness in its shape. As a specific example, the shape of a cutting edge end face of a conventional cemented carbide drill (twist drill) as viewed directly will be described with reference to FIG.

First, the ratio (core thickness) of the diameter C of the core thick portion 1 (indicated by the broken line) to the drill diameter D is set to 25% to 35%, and the groove width ratio (the circumference B of the groove 2 in the gap) is set to 25% to 35%.
The ratio of the circumferential length A of the land portion 3 having the wall thickness) B:A is
Setting from 0.4:1 to 0.8:1 increases the cross-sectional area of the drill itself, increasing the bending stiffness and torsional stiffness. In other words, the transverse rupture strength is increasing.

Next, the rake angle in the radial direction of the cutting edge 4 on the outer circumferential side is set within the range of -5° to positive by at least 2/3 of the drill diameter D, thereby enhancing the sharpness of the drill.

In addition, the point P1 on the outer peripheral edge of the cutting edge 4 and the point P1 on the outer peripheral edge of the cutting edge 4
The outer circumferential edge of the groove wall 5 facing the cutting edge 4, from the upper point to the perpendicular line on the virtual reference line connecting the point P2, which is 2/3 of the radius from the center and closer to the outer circumference, with a straight line, on the point P1. By setting the distance L (relative distance) from point P3 to 47% or less of the drill diameter D, chips are wound with a small curl radius and cut finely, so that the chip discharge function is enhanced.

The effect of this shape is as explained in detail in Japanese Patent Application Laid-Open No. 59-219108 (Japanese Patent Publication No. 61-30845).

By the way, when performing drilling work using a drill, it is usual to supply cutting oil to the cutting edge portion to cool the cutting edge and the workpiece. The conventional refueling method is
A common method is to supply cutting oil from the outside to the cutting edge of a drill immersed in the workpiece through the groove of the drill and the gap between the drill and the hole wall of the workpiece. However, in drilling work using a cemented carbide drill, the drill is rotated at high speed as described above, and the groove of the drill is
Since the drill is formed in a spiral shape that discharges chips to the outside of the hole as it rotates, the cutting oil supplied along this groove is also discharged to the outside of the hole by the action of centrifugal force. Especially in the case of deep holes, the cutting oil cannot reach the cutting edge. As a result, cooling of the cutting edge and workpiece becomes insufficient, and in the case of deep holes, chips are not ejected smoothly, resulting in a significant increase in cutting resistance, which may lead to drill breakage. Ta.

[Purpose of invention]

The present invention was created in view of the above-mentioned circumstances and to effectively solve the problems.

Therefore, an object of the present invention is to provide a drill made of cemented carbide that can improve the cutting oil supply function and the chip discharge function as much as possible.

[Summary of the idea]

The present invention achieves the above object by forming a cutting oil supply hole twisted along a helix angle in the land portion from the rear end to the tip of the drill.

[Example of idea]

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a perspective view showing a drill according to the present invention. As shown in the figure, inside the land portion 3 and the shank 11, which are solid thick portions from the tip to the rear end of the drill, a spiral cut is made along the helix angle of the groove 2. Two oil supply holes 6 are formed. A discharge port 7 of each oil supply hole 6 is opened at a flank surface 8 at the leading end, and an inlet port 9 is opened at a bottom surface 10 at the rear end. The number of oil supply holes 6 is preferably two, but may be one. Further, the diameter of the oil supply hole 6 is desirably several percent to 20% of the drill diameter D in view of the strength of the drill.

Although this oil supply hole reduces the cross-sectional area of the drill and reduces its strength, on the other hand, the larger the oil supply hole, the greater the amount of cutting oil supplied, which is advantageous for the drilling process. In this invention, the core thickness as mentioned above is 25 ~
Since it is as thick as 35% and has a small groove width ratio, the area of the land portion 3 is large, so even if the oil supply hole is enlarged, there is little effect on strength reduction. The superiority of the present invention is highlighted in this respect as well.

The oil supply hole 6 of this drill is formed by forming two holes that will become the oil supply hole 6 along the axial direction in a cemented carbide material formed by sintering a plate-shaped rod member. It can be formed by plastically deforming a rod member by twisting it under high temperature.

When performing drilling work using the drill configured as described above, when cutting oil is press-injected from the suction port 9 of the oil supply hole 6 through the drill holder, the cutting oil passes through the oil supply hole 6 and enters the discharge port 7 at the tip. It is supplied to the cutting edge 4 from above, and the cutting edge can be effectively cooled. Further, the returning cutting oil passes through the groove 2 and is discharged to the outside of the hole, and at this time, it promotes the discharge of chips and also cools the workpiece. Therefore, the cutting resistance (torque/thrust) is stable and breakage accidents can be prevented.

FIG. 3 is a graph showing the changes in torque and thrust when cutting oil is supplied from outside and when it is supplied from inside. Under these conditions, the drill diameter D is 10 mm, the core thickness is 3.0 mm (30%), and the groove width ratio
The thinning shape is cross thinning with a chisel width of 0.1 mm at 0.5:1, the oil hole size is 1.1 mm and 2 threads, and the cutting conditions are work material S50C, H _B 250, thickness 40.
This is a case where a mm plate is penetrated, and the cutting conditions are cutting speed V = 50 m/min, feed rate per rotation f =
It is 0.3mm/rotation. The cutting oil used is an emulsion type diluted 10 times, and the oil pressure is 4 kg/cm ² for both internal and external oil supply. Figure 3 shows a comparison between when lubricating from the inside and when lubricating from the outside using the same drill. As shown, the maximum torque with external lubrication is 142.9
Kgcm compared to 128.6Kg for internal refueling.
cm and the maximum thrust is 408.2 with external lubrication
kg, and 316.3 kg if internally refueled. In either case, the load as cutting resistance is smaller in the case of internal oil supply.

Further, FIG. 4 shows a comparison of the amount of wear on the cutting edge in a graph. The conditions are the same as those described above. The solid line indicates the case of internal lubrication, and the broken line indicates the case of external lubrication. As shown in the figure, it is clear that the amount of wear is smaller in the case of internal oil supply. In other words, it can be seen that the cutting edge is cooled more completely when cutting oil is supplied from inside.

In addition, in the case of external oil supply, drilling work was discontinued because wear exceeded 0.2 mm in 975 holes.

Note that the oil supply hole in the shank 11 of the drill need not be spirally shaped but may be linearly shaped.

By the way, this drill may be made of only cemented carbide, but TiC,
By coating TiCN, TiN, A ₂ O ₃ , etc., the heat resistance of the drill itself can be increased and wear can be further prevented. Also, these coating materials have a small coefficient of friction, so they can reduce thrust and torque. It can be made even smaller.

This matter is reported in detail on pages 89 and 90 of the Proceedings of the 1985 Spring Conference of the Japan Society of Precision Machinery Engineers.

In addition, when the drill wears out, it is re-ground to regenerate the cutting edge, but even if the base material is exposed on the flank 8 of the drill during this regrinding, the outer circumferential surface of the rake face and margin area is coated. The layer remains and the cutting forces can remain small.

[Effect of idea]

As is clear from the above description, the present invention provides the following effects.

In other words, a cutting oil supply hole twisted along the helix angle is formed in the land area from the rear end to the tip of the cemented carbide drill, making the cutting oil supply function and chip discharge function as possible as possible. can be increased to

Furthermore, since the cooling function of the cutting edge is enhanced, wear can be suppressed and the life of the blade can be extended.

An example from an actual field of use is shown below to make the effect clearer. The processing conditions are that the machine
11KW vertical machining center, emulsion type cutting oil, hydraulic pressure 4Kg/cm ² , workpiece
SCM440 (H _B 280), hole diameter is 14 mm, hole depth is 60 mm. The original drill had a diameter of 14 mm and a core thickness of 4.2 mm.
Cross-thinning with a groove width ratio of 0.5:1 and a chisel width of 0.1mm.The material is basically P30 and TiN.
A PVD-coated material was used. Cutting conditions are cutting speed = 60mm/min, feed = 0.3mm/
It was rev. With conventional drills, the hole depth is 50 to 60 mm.
Chips were not ejected between the holes, and the drill sometimes broke. As a countermeasure to this problem, we used the drill of the present invention, which enabled stable cutting and made it possible to replace all drills after regular wear.
During this time, we also tested an internally oiled drill as shown in Figure 5, and obtained almost the same performance results. However, if the oil hole 6 has a shape as shown in Fig. 5, as the oil hole 6 is re-ground, the position of the oil hole 6 becomes closer to the center and there is a limit to the amount of re-grinding, which is uneconomical. Ta. According to the present invention, since the oil supply hole is located at the same position in any cross section, the performance is stable and economical.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the tip of a conventional drill;
Fig. 2 is a perspective view showing an embodiment of the drill according to the present invention, Fig. 3 is a graph showing the difference in cutting resistance due to the difference in lubrication conditions between the drill according to the present invention and a conventional drill, and Fig. 4 is a graph comparing the wear amount of the cutting edge between the drill according to the present invention and the conventional drill,
FIG. 5 is a partial longitudinal sectional view of a drill for performance comparison with the drill according to the present invention. In addition, in the figure, 1 is the core thickness part, 2 is the groove, 3 is the land part, and 4
is a cutting blade, and 6 is an oil supply hole.

Claims (1)

[Scope of claim for utility model registration] (1) The core thickness is set to 25% to 35% of the drill diameter, the groove width ratio is set within the range of 0.4:1 to 0.8:1, and at least 2/3 of the drill diameter. The rake angle in the radial direction is -5
゜ ~ exactly configured, and a point on the outer peripheral edge of the cutting blade in the shape viewed directly from the cutting edge end surface, and a point on the cutting blade that is a radius from the center.
A groove wall facing the cutting blade across a groove gap with respect to a perpendicular line established through a point at the outer peripheral end of the cutting blade to a virtual reference line connecting a point near the outer periphery of 2/3 of the length with a straight line. In a drill made of an ultra-hard material, the distance from the outer peripheral end of the drill is set to 47% or less of the diameter of the drill, the cutting is twisted along the helix angle in the land area from the rear end to the tip of the drill. A drill characterized by being equipped with an oil supply hole. (2) The drill according to claim 1, wherein the drill surface is coated with one or a combination of two or more selected from the group consisting of TiC, TiCN, TiN, and A ₂ O ₃ . .