Drill Head for Deep-Hole Drilling

Abstract

Provided is a drill head for deep-hole drilling in which a cutting blade tip is mounted to face a cutting chip discharge port opened at a head distal end surface and a hollow inside is made into a cutting chip discharge passage communicating with the cutting chip discharge port, wherein high cutting efficiency based on good cutting chip dischargeability can be achieved and the cutting blade itself is also easily processed in terms of form. The drill head for deep-hole drilling is configured such that an inner end 20a of a blade edge 20 of a center cutting blade tip 2A is spaced apart from a head shaft center axis O and forms a non-cutting zone Z in the vicinity of the head shaft center axis O, an inner side surface of the cutting blade tip 2A constitutes an axially rearwardly inclined side surface 21 inclined from an inner end side to the head shaft center axis O side, an uncut core C of a work material W generated in the non-cutting zone Z is broken off by press-contact of the inclined side surface 21 of the cutting blade tip 2A during deep-hole drilling work.

Description

RELATED APPLICATIONS[0001]This is a continuation-in-part of international application no. PCT / JP2008 / 072627, filed 12 Dec. 2008, which published as WO 2009 / 128183A1 and claims priority to JP2008-104474, filed 14 Apr. 2008. The contents of the aforementioned applications are incorporated by reference in their entirety.FIELD OF THE INVENTION[0002]The present invention relates to a drill head for deep-hole drilling in which a cutting blade tip is mounted to face a cutting chip discharge port opened on a head distal end surface and in which a hollow inside is made into a cutting chip discharge passage communicating with the cutting chip discharge port.BACKGROUND[0003]As this kind of drill head for deep-hole drilling, ones as shown in FIG. 9 and FIG. 10 have been widely used conventionally. A drill head 50A in FIG. 9 has a substantially cylindrical head main body 51 with a hollow portion 52 opened at a proximal end side and a head distal end surface 51a in a substantially obtuse conical ...

AI Technical Summary

Benefits of technology

[0008]The present invention was made in view of the foregoing circumstances, and accordingly it is an object of the present invention to provide a drill head for deep-hole drilling in which a cutting blade tip is mounted to face a cutting chip discharge port opened on a head distal end surface and a hollow inside is made into a cutting chip discharge passage communicating with the cutting chip discharge port, wherein high cutting efficiency based on good cutting chip dischargeability can be achieved and the cutting blade itself is also easily processed in terms of form.

[0015]Effects of the present invention will be described with reference numerals of the drawings. First, in the drill head for deep-hole drilling D1, D2 according to the first aspect of the present invention, the inner end 20a, 30a of the blade edge 20, 30 of the cutting blade tip 2A, 3 is spaced apart from the head shaft center axis O. Consequently, a non-cutting zone Z is formed in the vicinity of the head shaft center axis O and an uncut core C of a work material W is generated in the non-cutting zone Z during deep-hole drilling work. However, at least the inner end side on the inner side surface of the cutting blade tip 2A, 3 constitutes an inclined side surface 21, 31 inclined from the inner end of the blade edge to the head shaft center axis O side. Therefore, the generated uncut core C is forcibly pushed away laterally by press-contact of the inclined side surface 21, 31 and is broken off in such a manner as being twisted in line with rotation of the drill head D1, D2. Thus, the inclination of the inclined side surface 21, 31 increases the degree of lateral displacement from the head shaft center axis O as the uncut core C becomes longer. As a result, the uncut core C is efficiently fragmented little by little without growing long, whereupon excellent cutting chip dischargeability is secured, and high cutting efficiency is attained in cooperation with an elimination of the chisel edge in the shaft center position. On the other hand, as for the cutting blade tip 2A, 3, itself, at least the inner end side on the inner side surface thereof has only to be a simple axially rearwardly inclined surface, so that its manufacturing can be carried out easily and at a low cost.

[0016]According to the second aspect of the present invention, the inclined side surface 21, 31 of the center cutting blade tip 2A, 3 forms an angle in a specific range with respect to the tip front surface 22, 32. Consequently, lateral displacement of the uncut core C by press-contact of the inclined side surface 21, 31 becomes larger, and fragmentation performance of the uncut core C is increased accordingly, while strength of a blade point at the inner end 20a, 30a side of the blade edge 20, 30 is increased and the blade point resists chipping, whereupon durability of the cutting blade tip 2A, 3 is improved.

[0018]According to the fourth aspect of the present invention, the blade edge 20, 30 of the center cutting blade tip 2A, 3 is arranged in an appropriate center-raised position, so that the little by little break-off of the uncut core C is carried out more reliably.

[0019]According to the fifth aspect of the present invention, the cutting blade tips 2A to 2C are brazed to the recessed portions 15a to 15c provided to the head main body 1, but the blade edge 20 of the center cutting blade tip 2A does not need to be made in agreement with the radial line R passing through the head shaft center axis O. Additionally, the inner end 20a of the blade edge 20 has only to be spaced apart appropriately from the head shaft center axis O, too. Therefore, exact positional accuracy at the time of brazing the cutting blade tip 2A is not required, and the manufacturing of the drill head D1 is facilitated accordingly.

[0020]According to the sixth aspect of the present invention, the whole of the blade edge 20, 30 of the center cutting blade tip 2A, 3 is inclined in a radially inward and axially forward direction towards the head shaft center axis O side, and also a guide pad 6A, 7A is provided in a position on the opposite side of the mounting side of the cutting blade tip 2A, 3 on the head outer circumferential surface 1b, so that the radial force of the cutting reaction force is directed to the opposite side of the cutting blade tip 2A, 3 and acts in such a manner as pressing the guide pad 6A, 7A on the opposite side of the cutting blade tip 2A, 3 against a cutting hole H inner circumference. Thus, drilling accuracy of the cutting hole H is improved.

Problems solved by technology

As a result, this has been a factor that cutting efficiency cannot be enhanced.

Further, in a configuration such as the drill head 50A that the cutting blade tip is brazed to a recessed portion of a head main body side, a brazing material intervenes at a fitting portion of the both, so that high precision assembly has been difficult.

However, when a sinking portion is provided to the cutting blade side surface and the inner end of the cutting blade is arranged spaced apart from the head shaft center axis O as in the afore-proposed throwaway tip, there is a concern that the uncut core generated in the shaft center position easily grows linearly to a position of contacting with the inclined step, whereupon a break-off size is enlarged and cutting chip dischargeability is reduced.

Moreover, the cutting blade itself disadvantageously involves a great deal of trouble in processing and its manufacturing costs become expensive due to forming of the sinking portion on the side surface and the inclined step.

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