JP2003220511A - Gun drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gun drill which is able to drill a hole without vibration even in high speed rotation by increasing stiffness of a pipe of a gun drill. <P>SOLUTION: A flexural vibration of a steel pipe 1 due to centrifugal force is suppressed by shortening the length of a simple steel portion of the steel pipe 1 by inserting a cemented carbide pipe 6 into an internal hollow portion of a circular shape part which has no V flute 4 on its outer periphery. Because the diameter D of the bore of the cemented carbide pipe 6 is formed to be larger than the diameter d of a cutting fluid passage 5 which is opened at the tip end of the gun drill, a flow rate of cutting fluid is secured and dischargeability of chips is maintained. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gun drill used for deep hole drilling. 2. Description of the Related Art In a single-drill gun drill, a V-groove is formed by notching the outer periphery of a pipe and a cutting tip. If the rotation speed is exceeded, the pipe will make a jump rope movement due to the centrifugal force and will bend and vibrate. Therefore, as a measure for preventing vibration, the length of the round portion of the pipe is increased, or Japanese Patent Publication No. 50-20309 or Japanese Utility Model Publication No. 48-2143 is used.
As disclosed in Japanese Unexamined Patent Publication No. 3 (1999), there is an example in which a weight piece is inserted into a pipe so that the center of gravity approaches the rotation axis. [0003] However, even if the length of the round portion of the pipe is increased, there is no significant improvement, and it has been necessary to reduce the number of revolutions. Also,
The method of inserting the weight piece into the pipe has not been put to practical use because the method of inserting and fixing the weight piece is extremely difficult and disadvantageous in manufacturing a tool. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a V-groove formed in an outer peripheral portion of a pipe fixed to a driver, and has a cutting edge at a tip thereof. In a gun drill having a tip joined thereto, a cemented carbide pipe is buried in a round hollow portion of the pipe, and a hole diameter of the cemented carbide pipe is an oil hole opened at a tip of the gun drill. It is characterized by being formed larger than the hole diameter. [0005] The Young's modulus of cemented carbide is three times that of steel.
The bending stiffness is very high because it is nearly double. Then,
The remaining portion of the steel material, in which the cemented carbide is not substantially embedded, serves as a bent portion of the pipe. For example, since the maximum deflection of the beam supported at both ends is increased by the fourth power of the length between the support points, if the length of the bent portion is somewhat shortened, the rigidity is greatly improved. Also, the hole diameter of the cemented carbide pipe is formed larger than the hole diameter of the oil hole opened at the tip of the gun drill so that the flow rate of the cutting fluid ejected from the tip does not decrease. Next, an embodiment of the present invention will be described with reference to the drawings. 1 to 3, a pipe 1 is inserted into a driver 2 and fixed. A cutting edge tip 3 is brazed to the tip of the pipe 1 and a drill blade is formed at the tip. A V-groove 4 is provided on the outer periphery of the pipe 1 and starts from an intermediate portion and communicates with the tip of the cutting edge tip 3 to form a chip discharge groove for allowing chips to flow out together with the cutting fluid. The V groove 4 is manufactured by deforming a round pipe. A cutting fluid is drilled from the rear end of the driver 2 and opened at the tip of the cutting tip 3 by an oil hole 5.
Erupt from A pipe 6 made of cemented carbide is embedded in the hollow portion of the pipe 1. The hole diameter D of the pipe 6 is formed larger than the hole diameter d of the oil hole opened at the tip of the gun drill, so that the flow rate of the cutting fluid is not reduced.
The rigidity of the pipe 6 is determined by its outer diameter, and is hardly affected by the size of the hole diameter D. [0008] By embedding a cemented carbide pipe in the round hollow portion of the pipe, the rigidity of the pipe is increased, and bending vibration due to centrifugal force is suppressed. Drilling can be done by number. The flow rate of the cutting fluid is maintained as before, and the chip dischargeability does not change. [0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a gun drill according to an embodiment of the present invention. FIG. 2 is a front view of FIG. FIG. 3 is a sectional view taken along line AA of FIG. [Description of Signs] 1 Pipe 4 V-groove 5 Oil hole 6 Pipe (made of cemented carbide)

Claims (1)

Claims: 1. A gun drill having a V-groove formed in an outer peripheral portion of a pipe fixed to a driver, and a cutting edge tip joined to a tip of the V-groove. A gun drill wherein a cemented carbide pipe is embedded therein, and a hole diameter of the cemented carbide pipe is formed larger than a hole diameter of an oil hole opened at a tip of the gun drill.