JP2578251Y2 - Twist drill - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist drill, and more particularly, to improving the shape of a groove to improve chip control.

[0002]

2. Description of the Related Art Conventionally, as an improved technique for chip control in a twist drill, for example, Japanese Utility Model Laid-Open No. 64-1811
Is disclosed in Japanese Unexamined Patent Application Publication No. HEI 9-202, (1994). This is to improve chip discharge in deep hole drilling by uniformly increasing the groove width from an intermediate position in the axial direction.

[0003] As another example, there is a method of changing from a twisted groove to a straight groove at an intermediate position in the axial direction. Further, as another example, there is a method of gradually decreasing the twist angle along the axial direction from the tip end. They are,
This is based on the idea that in deep hole drilling, the chip discharge is improved by shortening the path of the chip from the tip to the exit of the hole being drilled.

[0004]

However, the former two types of drills are made of a material having a relatively low toughness, such as a solid drill made of cemented carbide, because the groove shape changes from an intermediate position in the axial direction. In this case, a sharp decrease in strength is caused, which causes breakage. In the latter,
Due to the gradual change of the torsion angle, the chip is gradually but forcibly deformed in the groove. At this time, the cutting resistance increases due to the deformation resistance due to chip scraping, which may cause an accident such as breakage as described above.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a twist drill provided with a sub-groove at a heel portion. At this time, the sub-groove sets the torsion angle of the intersection formed by the torsion groove and the margin at θ ₁ ,
The torsion angle of the intersection formed by the second cut surface and the sub-groove is θ ₂
Are provided so that the relationship between them satisfies the relationship of θ ₁ / θ ₂ > 1.

[0006]

[Function] As described above, by providing sub-grooves having different twist angles of θ ₁ / θ ₂ > 1 in the heel portion, the groove width is narrowest at the tip end and gradually widens along the axis. Becomes In drilling using such a drill, the chips discharged from the cutting edge at the tip are always smoothly discharged along a groove having a constant helix angle. In addition, since the chip pockets become larger as the process proceeds, good drilling can be performed even in the processing of deep holes where chip clogging is likely to occur.

Further, since such a drill has a continuously changing shape, there is no inflection point relating to the drill stiffness, and a decrease in stiffness due to an increase in groove width is minimized. be able to.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of the entire solid drill according to the present invention. The tip of the drill body 1 has a pair of cutting edges 2, and the outer periphery of the drill body 1 has a pair of twist grooves 3 along the axis of the drill from the tip. Twist angle of the line of intersection formed by the twist groove 3 and the margin 6 is theta _1.

Now, in order to widen the groove width without changing the core thickness of the drill, a sub-groove 5 is provided along the heel 4.
At this time, the sub-groove 5 is provided such that the torsion angle θ _{2 of the} intersection formed by the second cutting surface 7 and the sub-groove 5 satisfies θ ₁ / θ ₂ > 1.

In such a drill, the portion A at the tip has no difference from a very standard cross-sectional shape of a drill as shown in the cross-sectional view of FIG. However, due to the two different torsion angles, the minor groove becomes progressively wider along the axis,
The portion B in the middle has a shape as shown in the sectional view of FIG.

Next, an example will be described. θ ₁ / θ ₂ = 1.
05, θ ₂ = 28.6 degrees for a drill with θ ₁ = 30 degrees. FIG. 4 is a conceptual diagram for explaining the relationship at this time, in which the outer peripheral portion of the drill body is developed. Since the groove width ratio at the tip of the drill is set to 1.0, the groove width ratio at a position separated from the tip by a length of 5 times the drill diameter is 1.5. Usually, it is practical that θ ₁ / θ ₂ is _{1 to} 1.22.

[0013]

[Effect of the Invention] With the drill according to the present invention, the groove width ratio can be continuously increased without changing the core thickness and the torsion angle, so that the reduction in rigidity due to the increased groove width is minimized. In this way, it is possible to improve the discharge of chips particularly in deep hole drilling and prevent breakage.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a twist drill according to the present invention.

FIG. 2 is a sectional view of the drill shown in FIG. 1 taken along line AA.

FIG. 3 is a sectional view of the drill shown in FIG. 1 taken along line BB.

FIG. 4 is a conceptual diagram in which an outer peripheral portion of the drill shown in FIG. 1 is developed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill main body 2 Cutting edge 3 Twisted groove 4 Heel 5 Secondary groove 6 Margin 7 Second cut surface

Claims (1)

(57) [Scope of request for utility model registration] 1. A twist drill having a pair of cutting edges 2 at the tip of a rod-shaped drill body 1 and a pair of twist grooves 3 provided on the outer periphery of the drill body 1 along the axial direction from the tip. , A sub-groove 5 is provided along the heel 4, and the sub-groove 5 has a torsion angle θ _{1 of} an intersection formed by the torsion groove 3 and the margin 6, a secondary cutting surface 7 and the sub-groove 5. the ratio of the twist angle theta ₂ of the intersection line in the formed, θ ₁ / θ
A twist drill characterized in that the groove satisfies the relationship of ₂ > 1.