JPS6144728Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a carbide drill in which two cutting blade chips made of cemented carbide having cutting blades are provided at the tip of the drill body, and more specifically, the inside of the two cutting blades is This invention relates to a carbide drill whose end edge is spaced 0.1 mm to 1.25 mm from the center axis of rotation.

Generally, in this type of carbide drill, the cutting edge is made of cemented carbide, and the inner edge of the cutting edge is spaced apart from the rotation center axis of the drill to reduce the thrust load. Because of this, it is possible to perform high-speed, high-feed drilling.
This provides the advantage of improving the efficiency of drilling.

However, when using such a carbide drill to drill a deep hole, for example, about five times the diameter of the drill, there is a problem in that the above-mentioned advantages cannot be fully exhibited. That is, in a drill for drilling deep holes, the length of the drill body increases depending on the depth of the hole. As a result, the rigidity of the drill body, particularly the torsional rigidity, decreases, and chatter vibration occurs when high-speed, high-feed drilling is attempted. Furthermore, the chips generated by high-speed, high-feed drilling are thick and in large quantities, so in the case of deep hole drilling, there is a risk that the chips will become clogged in the middle of the hole. From the above points, in the case of deep hole machining, high speed,
High feed machining cannot be performed.

This invention was made in consideration of the above circumstances, and aims to provide a carbide drill that can perform high-speed, high-feed drilling even in deep hole drilling.

This invention reduces the web thickness to 25% to 45% of the drill diameter.
%, the helix angle of the chip evacuation groove is set at 0° to 30°, and the heel part is cut off along the chip evacuation groove.The combination of these features enables high-speed, deep hole machining. This enables high-feed machining.

Hereinafter, one embodiment of this invention will be described with reference to the attached FIGS. 1 and 2. In addition, FIG. 1 is an axial tip end view of the carbide drill according to this invention, and FIG. 2 is a partially omitted side view thereof.
In the figure, the two-dot chain line indicates the heel portion of the conventional drill and its vicinity.

In FIGS. 1 and 2, reference numeral 1 indicates a drill body made of steel. Chip discharge grooves 2, 2 are provided on the outer periphery of the tip of the drill body 1. A cutting blade tip 3 made of cemented carbide is fixed by brazing to the tip of the wall surface of the chip discharge groove 2 facing the direction of rotation. A cutting edge 4 is formed at the tip of this cutting edge tip 3. The two cutting blades 4, 4 are arranged point-symmetrically with respect to the rotational center axis 0, and the inner edge 4a of the cutting blade 4 is provided at a distance of 0.1 mm to 1.25 mm from the rotational center axis 0.

The above configuration is similar to the conventional carbide drill, but in the carbide drill of this invention, by setting the web thickness W to 25% to 45% of the drill diameter D, the rigidity of the drill body 1, especially Efforts are being made to improve torsional rigidity. However, when set in this way, the cross-sectional area of the chip discharge groove 2 is reduced, and it is undeniable that the chip discharge performance is deteriorated. Therefore, in the carbide drill of this invention, the heel part A of the conventional drill shown by the two-dot chain line in FIG.
The convex curved surface portion 5 is formed there by cutting off along the line. This was done by focusing on the fact that the heel part A has almost no effect on torsional rigidity, and by cutting off the heel part A, the groove width ratio is increased and the cross-sectional area of the chip discharge groove 2 is reduced. It is possible to improve chip evacuation by increasing the amount of chips. Moreover, since the heel portion A has almost no contribution to the torsional rigidity, even if it is cut off, the torsional rigidity of the drill body 1 will hardly decrease. In addition, in the carbide drill of this invention, the rotation center side portion of the wall surface of the chip discharge groove 2 following the convex curved surface portion 5, that is, the rotation center side portion of the wall surface facing in the opposite direction to the rotation direction of the wall surface of the chip discharge groove 2. is formed by a concave curved surface portion 6 in contact with a convex curved surface portion 5. When this concave curved surface portion 6 is formed, chips generated by the cutting blade 4 collide with the concave curved surface portion 6 and are curled along the concave curved surface portion 6, thereby being divided into pieces. Therefore, the chip discharge performance can be further improved.

Further, in the carbide drill of this invention, the helix angle of the chip discharge groove 2 is set at 0° to 30°, thereby improving the rigidity of the drill body 1 and improving the chip discharge performance. That is, in general, if the flute length of the chip discharge groove is l and its helix angle is β, then
The length L along the twist of the chip discharge groove is L=l/
It is expressed as cosβ. Therefore, if the helix angle is set small, the length L of the chip discharge groove along the torsion becomes shorter. If this length L is shortened, the amount of cutout of the drill body is reduced by forming the chip discharge groove, thereby improving the rigidity of the drill body. Therefore, in this invention, the chip discharge groove 2
By setting the helix angle between 0° and 30°,
The rigidity of the drill body 1 is improved. Furthermore, for the same reason, by reducing the helix angle, the cross-sectional area of the chip discharge groove 2 perpendicular to the helix can be increased, thereby improving chip discharge performance. Moreover, as mentioned above, the chip discharge groove 2
Because the length along the torsion of the chip is short, the length from when chips are generated by the cutting edge until they are discharged to the outside of the hole is short, and the wall surface facing in the opposite direction to the rotation direction of the chip evacuation groove is short. Since the portion on the rotation center side is formed by a concave curved surface, chips can be separated, thereby further improving chip evacuation performance. Further, by improving the rigidity of the drill body 1 as described above, damage to the inner edge 4a can be reduced. That is,
The inner edge 4a functions to thread the core, which is the uncut portion of the workpiece located at the center of the drill, but when chatter vibration occurs in the drill, the inner edge 4a
A repeatedly comes into contact with and separates from the core, so there is a risk of early chipping. In this regard, in the above-mentioned drill, the rigidity of the drill body 1 is improved, and chatter vibration can be prevented from occurring. As a result, the inner edge 4a is always in contact with the core, and does not repeatedly separate from and come into contact with the core. Therefore, damage to the inner edge 4a can be prevented.

As explained above, according to the carbide drill of this invention, the web thickness can be set to 25% to 45% of the drill diameter.
Since the helix angle of the chip evacuation groove is set at 0° to 30°, and the heel part is cut off along the chip evacuation groove, both the rigidity of the drill and the chip evacuation performance can be improved at the same time. Therefore, high-speed, high-feed opening machining can be performed even in deep hole machining. In addition, when drilling holes at normal depths, it is possible to perform drilling at higher speeds and higher feed rates, further improving processing accuracy, and preventing damage to the inner edge of the cutting edge. Effects such as being able to do the following can be obtained.

[Brief explanation of the drawing]

The attached drawings show an embodiment of this invention, with FIG. 1 being a front end view in the axial direction, and FIG. 2 being a partially omitted side view. 1... Drill body, 2... Chip discharge groove, 3...
Cutting blade tip, 4... Cutting blade, 4a... Inner edge, 5...
...Convex curved surface part, 6...Concave curved surface part, A...Heel part,
O...Rotation center axis.

Claims (1)

[Scope of utility model registration request] Two chip evacuation grooves are provided on the outer periphery of the tip of the drill body, and a cemented carbide cutting tip is formed at the tip of the wall surface facing the rotation direction of each chip evacuation groove. In a carbide drill in which the cutting blade is fixed so as to be positioned 0.1 to 1.25 mm away from the rotation center axis of the drill body and point-symmetrically, the web thickness is set to 25% to 45% of the drill diameter, and the A helix angle of the chip discharge groove is set to 0° to 30°, the heel portion is formed by a convex curved surface extending along the chip discharge groove, and a wall face facing in a direction opposite to the rotational direction of the chip discharge groove. A carbide drill characterized in that a rotation center side portion of the carbide drill is formed by a concave curved surface in contact with the convex curved surface.