JPH10263929A - Gun reamer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure stable hole accuracy; and prevent a cutting edge from sudden chipping caused by a variation in cutting degree in a diamond sintered body-carried gun reamer. SOLUTION: A finishing cutting edge 4 is formed on an advancing cutting edge 3 in its backward outer peripheral direction. The finishing cutting edge 4 is formed of a diamond sintered body and is to locate at the position, 200 to 290 degrees in the backward rotating direction of the advancing cutting edge 3. In addition, the finishing cutting edge 4 is overhung by the radius difference in 0.003 to 1.0 mm with the advancing cutting edge 3 to form a machining allowance for the finishing cutting edge 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gun reamer, and more particularly to a gun reamer capable of preventing cutting edge chipping and reduction in hole accuracy under high cutting depth and high feed conditions in machining of an aluminum alloy or the like.

[0002]

2. Description of the Related Art A general shape of a gun reamer or the like used for finishing a deep hole is composed of a pipe-shaped shank having an oil hole for supplying cutting oil to a cutting edge and a tip portion 1. The cutting edge portion 10 and several arc-shaped guide pad portions 5 are formed in the portion 1.

FIG. 5 shows a general diamond sintered body reamer, which performs the same cutting action as a conventional cemented carbide gun reamer. The cutting edge portion 10 is formed by joining a diamond sintered body to a notch step provided at the tip of the tip portion 1 made of a cemented carbide by brazing or the like. When viewed from the axial direction, a guide portion called a guide pad portion 5 is provided in a direction facing the cutting edge portion 10. After the inner wall of the processing hole is cut by the cutting edge portion 10, the inner wall is finished by burnishing of the outer peripheral surface of the guide pad portion 5 having the same cutting edge radius as the cutting edge portion 10. However, the burnishing action is caused by the cutting edge 10.
Is performed by pressing the guide pad portion 5 facing the cutting edge portion 10 against the inner wall of the processing hole, and there is a problem that the diameter of the hole is enlarged or reduced depending on the magnitude of the resistance.

Next, FIG. 6 shows one of the prior arts aimed at reducing the burnishing torque. FIG. 6 shows the finish cutting edge 4 formed in the outer peripheral direction rearward of the preceding cutting edge 3 with the opening angle θ in the range of 100 ° to 170 ° around the axis of the gun reamer. The finished cutting edge 4 is slightly overhanged in the outer diameter direction from the preceding cutting edge 3 and is formed to retreat axially rearward from the leading edge of the preceding cutting edge 3. According to this technique, the portion provided with the guide pad portion 5 is replaced with a finishing cutting edge 4 so as to provide a cutting action and reduce burnishing torque, and at the same time, use the finishing cutting edge 4 as a cutting edge of a minute cut. By acting, the hole accuracy and the finished surface roughness are improved.

[0005]

The reaming process is a finishing process for obtaining a correct hole diameter and a finished surface by following a prepared hole previously drilled. The amount fluctuates, and it may not be possible to achieve the desired hole accuracy. The cutting edge portion generates a polygonal hole or enlarges the hole diameter when there is a variation in the cutting depth and thus a variation in the cutting resistance or a large load. The guide pad portion lowers the roughness of the finished surface due to an excessive burnishing effect.

The first prior art is a single-blade gun reamer having a cutting edge only on one radius when the tip portion is viewed from the axial direction, and a relief portion is provided behind the cutting edge in the rotation direction. Subsequently, an arcuate guide pad portion is formed. In the single-blade gun reamer having such a configuration, an appropriate burnishing torque must be present in order to finish the machined surface of the inner wall of the machined hole by the burnishing action of the guide pad portion. In this case, there is no problem when the pilot hole is accurately formed, and a desired hole accuracy can be secured by both the cutting action and the burnishing action. However, when the rotation speed becomes high or the cutting depth increases,
The centrifugal force and cutting resistance increase, and accordingly, an excessive load acts on the guide pad portion, so that the burnishing torque exceeds an appropriate range. In this case, not only the processing accuracy is deteriorated, but also burning and breakage may occur.

In the second prior art, the guide pad having an opening angle with respect to the preceding cutting edge in the range of 100 ° to 170 ° is replaced with a finishing cutting edge, and the guide pad portion is overhanged with respect to the preceding cutting edge. It was arranged by
When the prepared hole is poorly formed or when cutting a hard material, the finished cutting edge tends to bite and induces chattering.As a result, the tool life is shortened by expanding the hole diameter or chipping. Or you may.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a tip portion made of a cemented carbide is joined to a pipe-shaped shank having a fan-shaped irregular cross section. The cutting edge is provided with a cutting edge portion for performing a cutting action and a guide pad portion for performing a burnishing action on the inner wall of the machining hole. The cutting edge portion is separated from the preceding cutting edge and the preceding cutting edge, and has a finish disposed on the outer periphery. In a gun reamer configured to include a cutting edge, the finishing cutting edge is made of a diamond sintered body, and is disposed at a position of 200 ° to 290 ° behind the preceding cutting edge in a rotational direction, and It is characterized by being disposed so as to overhang in the outer diameter direction from the preceding cutting edge.

The radius difference R2−R1 between the cutting edge radius R2 of the finishing cutting edge, the cutting edge radius of the preceding cutting edge, and the radius R1 of the outer peripheral surface of the guide pad portion is 0.003 m.
m to 1.0 mm.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a gun reamer according to the present invention, and show a tip of a gun reamer body. The tip part 1 is made of cemented carbide,
It is joined to one end of a shank portion having a pipe structure of irregular cross section. Chip discharge grooves 2a and 2b are formed in a part of the outer periphery of the chip portion 1 along the direction of the axis o, and serve as a flow path for chip discharge. Chips generated during the gun reamer machining are carried out through this flow path together with the cutting fluid.

The leading end of the tip 1 is provided with a leading cutting edge 3 and a finishing cutting edge 4 for performing a cutting action, and a guide pad section 5 for performing a guiding action. The leading cutting edge 3 and the finishing cutting edge 4 are spaced apart from each other when viewed in the direction of the axis o, and are arranged on the outer edge side on a radius passing through the axis.
The guide pad portion 5 is formed on a part of the side wall on the outer periphery of the tip portion 1, and is formed so as to be connected to the relief portion 6 behind the leading cutting edge 3 in the rotation direction. The relief portion 6 functions to supply a cutting fluid having a cooling action and a lubrication action to the guide pad section 5. It is not formed behind the finishing cutting edge 4 in the rotation direction.

Conventionally, the guide pad portion 5 has a hole with good straightness and a good surface roughness because of both the function of smoothly guiding the gun reamer in the direction of the axis o and the function of burnishing for drilling while sliding on the inner periphery of the hole. Was to get. However, in the present invention, in order to perform machining with stable hole precision, the radius of the outer peripheral surface of the guide pad portion 5 is formed to be equal to the cutting edge radius R1 of the leading cutting edge 3, and in addition, the finishing cutting edge 4 is The portion 5 is overhanged in the outer direction. Guide pad portion 5 configured as above
Can improve the guiding property or the centripetal property, and furthermore, have the effect of preventing vibration. As a result, without being affected by the variation of the prepared hole by drilling,
It is preferable from both sides of the hole accuracy and the tool life without causing the cutting edge chipping.

FIG. 3 shows a leading cutting edge 3 and a finishing cutting edge 4.
FIG. The trajectory circle of the finishing cutting edge 4 is formed slightly larger than the trajectory circle of the preceding cutting edge 3. Cutting edge radius R1 of leading cutting edge 3 and guide pad portion 5
Are formed to have the same radius, and the difference R2-R1 from the cutting edge radius R2 of the finished cutting edge 4 serves as a margin for the finished cutting edge 4. The cutting allowance is 0.003 mm to 1.0 m in consideration of the effect of the finished cutting edge 4 and the balance with the cutting edge strength.
It is preferable to set m. By setting the allowance in this way, stable cutting with a certain amount of minute cut secured is maintained. The leading cutting edge 3 is provided at the leading end so as to slightly protrude ahead of the guide pad portion 5 and the finishing cutting edge 4 when viewed in the cutting feed direction. Contact the inner wall of the hole to be made. As a result, the gun reamer is pushed in the direction facing the leading cutting edge 3, so that the guide pad portion 5 contacts the inner wall of the hole with a large force and receives the force. As a result, since the centering is performed automatically, stable hole accuracy with good centripetality is maintained.

FIG. 4 is a diagram for explaining the force acting on the gun reamer. When viewed in the direction of the axis o, the centrifugal force due to the eccentricity of the center of gravity and the cutting force accompanying the cutting work simultaneously on the gun reamer. The centrifugal force acts in a direction A approximately 135 ° from the tip of the cutting edge, and the cutting force acts as a resultant force of a radial component B1 and a circumferential component B2 in a direction B shown by an arrow in the drawing. Therefore, during gun reamer processing, the total force of centrifugal force and cutting force (hereinafter referred to as
It is called "pressing force". ) Is 90 ° to 1 behind the cutting edge portion 10.
It will work in the direction of 80 °, producing a burnishing effect.

Therefore, as shown in FIG. 5, the conventional gun reamer has a configuration in which stable machining surface roughness and dimensional accuracy of machining holes are ensured by the presence of an appropriate amount of pressing force. However, on the other hand, the pressing force of the guide pad increases due to the reduction of the hole diameter due to wear and chipping of the cutting edge, promoting adhesion, and in high-speed cutting, the cutting fluid flows around the guide pad. And there is a problem that the inner wall surface of the machined hole is brought into a friction welding state.

Further, due to the friction between the inner wall of the hole and the guide pad portion 5, a part of the machined work material is removed from the guide pad portion 5.
Weld to. Due to the welding of the work material, the machining accuracy is no longer maintained, with the result that reliable guidance of the tool in the hole is no longer guaranteed, vibrations are generated, the surface quality is degraded or the roundness or straightness is poor. A hole is formed.

Next, as shown in FIG. 6, in order to reduce the burnishing torque, the one provided with the finishing cutting edge 4 in the direction in which the above-mentioned pressing force acts becomes self-penetrating once it becomes unbalanced, Induce vibration and chatter vibration,
In some cases, chipping of the cutting edge may occur.

Therefore, in the gun reamer having the finished cutting edge 4, the opening angle θ is set to 20 in the direction that is hardly restricted by the pressing force, that is, behind the preceding cutting edge 3 in the rotation direction.
By arranging the finishing cutting edge 4 at a position of 0 ° to 290 °, the problem of the gun reamer having the above configuration can be avoided, and stable hole accuracy can be maintained.

The diamond sintered body is excellent in abrasion resistance and welding resistance, and can maintain a stable surface roughness without forming an altered layer on a processed surface by cutting with a sharp cutting edge. . In addition, high-efficiency machining by high rotation is possible, and the tool life is long. Compared with conventional cemented carbide,
A tool life of about 20 times can be obtained. However, the diamond sintered body has a disadvantage that it is weak to vibration.

In the gun reamer process, it is difficult to realize a straight deep hole because of the asymmetry due to the irregular shape of the axial cross section and the asymmetry of the shape of the cutting edge at the tip. is there. Many of the problems related to tool life such as chipping are caused by the asymmetry described above. According to the present invention, the above problem can be avoided by disposing the finishing cutting edge 4 in a direction in which the pressing force does not work in consideration of the directionality of the force acting on the gun reamer body.

[0021]

As described above, according to the present invention, a stable hole precision and a roughened surface can be obtained by causing the finishing cutting edge to perform a fixed amount of minute cutting. Consequently, by cutting with a sharp cutting edge, welding and the cutting edge can be avoided, and an altered layer is not formed on the processed surface. In addition, sudden chipping of the cutting edge due to variation in the cutting amount can be prevented, and the life of the tool can be extended.

[Brief description of the drawings]

FIG. 1 is a side view of a tip of a gun reamer showing an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is an explanatory diagram showing a rotation locus of a cutting edge.

FIG. 4 is an explanatory diagram showing a force acting on a gun reamer.

FIG. 5 is a side view of a tip of a gun reamer showing a first conventional example.

FIG. 6 is a side view of a tip of a gun reamer showing a second conventional example.

[Explanation of symbols]

 2a, 2b Chip discharge groove 3 Leading cutting edge 4 Finishing cutting edge 5 Guide pad part 6 Relief part R1 Tip radius of leading cutting edge R2 Tip radius of finishing cutting edge

Claims (2)

[Claims] 1. A tip part 1 made of a cemented carbide is joined to a pipe-shaped shank having a fan-shaped irregular cross section, and the tip part 1 is burnished to a cutting edge part 10 for performing a cutting action and an inner wall of a machining hole. It has a guide pad part 5 that works.
In the gun reamer, the cutting edge portion 10 includes a leading cutting edge 3 and a finishing cutting edge 4 disposed on the outer periphery of the leading cutting edge 3 at a distance from the leading cutting edge 3.
Is composed of a diamond sintered body, is disposed at a position of 200 ° to 290 ° behind the preceding cutting edge 3 in the rotation direction, and is disposed so as to overhang in an outer diameter direction from the preceding cutting edge 3. Gun Reamer characterized by having. 2. The radius difference R2−R1 between the cutting edge radius R2 of the finishing cutting edge 4 and the cutting edge radius of the preceding cutting edge 3 and the radius R1 of the outer peripheral surface of the guide pad portion 5 is 0.003.
The gun reamer according to claim 1, wherein the gun reamer is formed to have a thickness of 1.0 mm to 1.0 mm.