JP2000263328A - Reamer for cutting sintered metal - Google Patents

Abstract

(57) [Summary] [PROBLEMS] As a reamer for finishing a valve guide made of sintered metal with high accuracy, a form in which a hard cutting blade body with sharpness and high abrasion resistance is firmly joined to the tip part and maintains it. We propose a technology to do the same, a form to discharge chips forward, and a technology to actively support it. SOLUTION: A cutting blade 4 made of a high-hardness sintered body having the same outer diameter as the blade diameter is joined to a tip of a blade diameter portion 3 extending from a cemented carbide or steel shank. A plurality of continuous blade grooves 9 are formed on the outer periphery of the blade diameter portion 3 and the oil hole 5.
Is formed at the center of the shank 2 from the rear end of the shank 2 to just before the joint 7, and the injection hole 6 is formed so that the joint 7 radially extends from the oil hole 5 toward the tip of the shank 2.
The blade groove 9 is formed so as to reach the vicinity of the blade groove 9.
Is formed on the left side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting blade made of a high-hardness sintered body, which is mainly suitable for finishing the inner diameter of a deep hole having a small diameter. The present invention relates to a sintered metal cutting reamer having an oil hole.

[0002]

2. Description of the Related Art With respect to a drill, which is a representative of a rotary tool, a prior art in which a cutting blade body made of cemented carbide is joined to the tip and an oil hole for supplying cutting oil is provided at the center of a steel shank is well known. . Among them, the one devised at the position of the cutting oil injection hole,
Japanese Utility Model Publication No. 61-109612 (Microfilm)
Has been proposed.

FIG. 4 shows a front view thereof. This drill 1
00, a cutting blade 101 made of cemented carbide is joined to the tip, and an oil hole 103 is formed at the center of a steel shank 102 in the cutting blade 1.
The injection hole 105 for the cutting oil extends radially toward the inside of the blade groove 106 by extending to just before the joint 104 of No. 01.

In this prior art, the wear resistance of the cutting blade is improved by joining a cutting blade body made of a cemented carbide to the tip, and an injection hole for cutting oil is provided near the joint of the cutting blade body. In addition to preventing the heat deterioration of the brazing material due to the cutting heat of the portion, the chips are separated by the injected cutting oil, the wall can be prevented from being worn by the chips hitting the blade groove, and the smooth discharge of the chips is possible. It is explained that there is.

Japanese Patent Application Laid-Open No. 59-59309 discloses that
No description about oil holes ゝ Drill 10 in FIG.
A member has been proposed in which the member corresponding to the zero cutting blade 101 is changed to a cutting blade made of a high-hardness sintered body such as diamond or cBN.

FIG. 5 shows a front view thereof. This drill 2
In No. 00, a cylindrical cutting blade 201 made of a high-hardness sintered body is joined to a cutting blade holder 202 made of a cemented carbide, and further joined to a steel shank 203. Shank 203
Examples of the form of the joining portion 204 include a V shape as shown in FIG. 5, a plurality of mountain shapes, a U shape, a stepped parquet shape, and the like. And the cutting blade body 201 and the cutting blade holder 20
No. 2 proposes that it is preferable to join them together by a crystallization bond that sinters both at the same time.

In this prior art, a cylindrical cutting blade made of a high-hardness sintered body is crystallized at the tip and bonded to a shank in an appropriate form, so that the guide is sharp, accurate and vibration-free. And a reliable and durable mounting of the blade tip, which allows for improved cutting performance, service life and surface quality.

The present invention also relates to a rotary tool but relates to a reamer. Further, the present invention relates to a reamer for cutting a sintered metal, wherein a cutting groove is formed in a left-handed spiral to discharge chips to the front. Incidentally, the drill is a rotary tool that discharges chips backward.

[0009]

A separate heat and wear resistant member serving as a valve guide for an intake / exhaust valve is press-fitted into a cylinder block of an automobile engine. Machined to dimensions. Conventionally, cast iron and special cast iron containing Cr have been used for valve guides. In recent years, however, iron-based sintered metals containing Cu, P, and C have been widely used due to their excellent wear resistance. It has become Since hard cementite is dispersed in the composition of this iron-based sintered metal, the wear of the cutting edge is fast if the cutting body is a cemented carbide, and chips are discharged backward during reaming. As a result, the hard cementite bites between the finishing inner wall and the blade groove blade, and deteriorates the finished surface.

Therefore, as a reamer for finishing a valve guide made of an iron-based sintered metal with high precision, a technique in which a hard cutting blade body having sharpness and high abrasion resistance is firmly joined to the tip and maintaining the same is provided. is necessary. In addition, there is a need for a form in which chips are discharged forward and a technique for actively supporting the chips. The present invention seeks to solve these problems.

[0011]

Means for Solving the Problems A cutting blade made of a high-hardness sintered body having the same outer diameter as the blade diameter is joined to the tip of a blade diameter extending from a cemented carbide or steel shank. A plurality of continuous blade grooves are formed on the outer periphery of the blade diameter part, an oil hole is formed in the center of the shank, from the rear end of the shank to immediately before the joint, and the injection hole is formed from the oil hole toward the shank tip. It is formed radially into the blade groove near the joint, and the blade groove is formed to be left-handed to discharge chips forward.

Further, the torsion angle of a plurality of continuously formed blade grooves on the outer peripheral portion of the blade diameter portion including the cutting blade body is 5 to 45 °.
, More preferably 10 to 30 ° to maintain excellent cutting performance and dimensional accuracy.

As a similar means, a cutting blade made of a high-hardness sintered body is formed in a cylindrical shape, and is joined to a stepped small-diameter column formed at the tip of a blade diameter portion extending from a cemented carbide shank,
A plurality of continuous left-hand twisted blade grooves are formed on the outer peripheral portion of the blade diameter portion including the cutting blade body, an oil hole is formed in the center of the shank, from the rear end of the shank to immediately before the joint, and the injection hole is formed. It is formed so as to extend radially from the oil hole toward the shank tip into the blade groove near the joint, and by providing a center hole at the end face of the small-diameter column, the cutting blade at the tip is firmly joined and Make sure to carry out the grinding operation for the diameter.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In FIG.
1 shows an external view of a reamer 1 according to a first embodiment of the present invention. FIG.
(A) is a front view of the tip, and FIG. 1 (b) is a side view. In FIG. 1B, reference numeral 2 denotes a shank made of cemented carbide or steel. The diameter recommended by the present invention is 5 to 10
In the case of a reamer for a deep hole having a small diameter of 1 mm and a total length of the blade groove of 150 to 300 mm, if it is integrally sintered with a cemented carbide from the shank 2 to the blade diameter portion 3, it tends to be distorted. Therefore, the long part of the shank 2 is made of steel, and the blade diameter part 3 made of cemented carbide is joined to the tip by brazing. It is economical to join the cutting blade 4 made of a high-hardness sintered body such as diamond or cBN mixed with a metal binder to the tip.

The blade diameter portion 3 made of a cemented carbide is provided with an oil hole 5 and a radial injection hole 6 inclined toward the tip in a preforming step. A joint 7 between the cutting blade body 4 and the blade diameter portion 3 and a joint 8 between the blade diameter portion 3 and the shank 2 are both V-shaped as shown in FIG.
Butting in the shape of a letter can prevent peeling of the joint 7 due to cutting torque.

A round bar-shaped cutting blade body 4 after the brazing process has been completed,
The blade diameter portion 3 and the shank 2 are provided with a plurality of continuous left-handed screw grooves 9 on the outer peripheral portion from the cutting blade body 4 to the blade diameter portion 3 by electric discharge machining.
Is provided.

The reamer of the present invention can be used for casting iron, ceramics,
It is suitable for cutting a work material in which chips are powdered such as a sintered metal. Especially, when the work material is an iron-based sintered metal, excellent cutting performance is exhibited. In recent years, iron-based sintered metals containing Cu, P, and C have been frequently used for valve guides of intake / exhaust valves of automobile engines that require heat resistance and wear resistance. Since the hard cementite is dispersed in the composition of the iron-based sintered metal, it is necessary that the cutting blade 4 having good sharpness and high wear resistance is joined to the tip. The chips are sheared into fine powder. When the chips are discharged rearward, the hard cementite bites between the finishing inner wall and the blade groove blade 11 and deteriorates the finished surface of the corner.

Therefore, when the reamer rotates forward as shown by the arrow A in FIG. 1, the blade groove 11 is formed in a left-handed twist, and chips are discharged toward the tip. Since the sintered material of the valve guide is hollow, chips do not clog forward. In order to assist the flow of the chips, the oil hole 5 at the center of the reamer 1 is extended to just before the joint 7, and high-pressure cutting oil is injected from the injection hole 6 toward the tip. This cutting oil enhances the lubricity between the finished inner wall and the cutting blade 11 and at the same time has a cooling effect in the vicinity of the joint 7, and can prevent thermal deterioration of the brazing material due to the cutting heat of this portion.

The outer diameter of the reamer is finished to an arbitrary size by polishing using a center hole 12 provided at the tip of the cutting blade body 4 and a center hole (not shown) at the end of the shank 2. The roundness and cylindricity of the finished reamer
It increases as the number of cutting blades 10 increases. In the first embodiment, since the solid cutting blades 4 are joined, the number of cutting blades can be increased much more easily.

FIG. 2 shows a reamer 20 according to a second embodiment of the present invention.
2A is a front view of the tip, and FIG. 2B is a side view. In FIG. 2B, 21 is
It is a shank made of cemented carbide. A stepped small-diameter pillar 22 is integrally formed at the tip, and a reamer 2
A center hole 12 used for polishing and finishing the outer diameter of the zero cutting blade 10 is provided. Center hole 12 of the first embodiment
Is made of a high-hardness sintered body and can be provided only by electric discharge machining. On the other hand, the center hole 12 of the second embodiment can be easily formed at the time of preforming the cemented carbide.

A cylindrical cutting blade 23 made of a high-hardness sintered body such as diamond or cBN is inserted along the outer diameter of the small-diameter column 22, and is brought into contact with a joint 24 and brazed. The radial component force during cutting is received by the central small-diameter column 22, and the brazing area is equal to the outer peripheral portion of the small-diameter column 22 and the joint 24.
Since the end face extends over a wide range, the cutting blade body 23 can be extremely firmly fixed to the shank 21. The small-diameter column 22 may have a rectangular shape. In this case, the fitting shape of the cutting blade 23 is assumed to be suitable.

Thereafter, a plurality of continuous left-hand twisted blade grooves 9 are formed on the outer peripheral portion from the cutting blade body 23 to the shank 21 by electric discharge machining and polishing with a diamond grindstone. Unlike a drill, in a reamer, the amount of chip discharge is small, so that the blade groove 9 may be relatively shallow, and the cylindrical cutting blade body 23 is not divided by the blade groove 9. The reamer 20 configured in this manner can join the cutting blade body 23 made of a high-hardness sintered body to the tip end where the cutting load is the largest, and can form a plurality of cutting blades 10, so that long-term stable cutting performance and Excellent dimensional accuracy can be maintained, and since the brazing is performed over a wide area, peeling of the portion can be prevented.

With respect to the function of the left-hand twisted blade groove 9 and the means for forming the oil hole 5 and the injection hole 6, the same results as those of the reamer 1 of the first embodiment can be obtained.

Next, a comparison of cutting performance between a comparative reamer having the same outer shape as that shown in FIG. 1 and a reamer 1 of the first embodiment having a cutting blade made of a high-hardness sintered body. explain.

As a work material, an iron-based sintered metal containing Cu, P, and C, which is a difficult-to-cut material used as a material for a valve guide of an automobile engine, was selected. The dimensions of the prepared cutting sample are outer diameter = 11 mm, inner diameter = 5.3 mm, and length = 45 mm.

The shape of the reamer 1 is as follows: cutting edge diameter = 6 mm, number of cutting edges = 6, left twisting cutting edge angle = 20 °, cutting edge body length = 5
mm, blade length = 80 mm. The shape of the comparative reamer has the same specifications. The cutting conditions were as follows: rotation speed = 2100 rpm, feed per rotation =
At a setting of 0.42 mm / rev, the width of flank wear of the reamer after machining 200 valve guides, the surface roughness of the inner diameter surface of the valve guides, and the change of the cutting torque for each arbitrary number were recorded.

As a result, the width of the flank wear was 0.08 mm for the reamer of the comparative example, and 1/4 of the reamer 1 for the reamer.
Of 0.02 mm. The surface roughness of the inner diameter surface of the valve guide was Ra 3 μ for the comparative reamer, and 1/10 Ra 0.3 μ for the reamer 1.

The cutting torque was measured by installing a Kistler dynamometer incorporating a strain gauge integrated with a workpiece chuck on a table of a milling machine. FIG. 3 is a graph in which the index is plotted on the vertical axis and the change for every 50 pieces is plotted on the horizontal axis based on the initial cutting torque in the reamer 1.
The cutting torque of the reamer of Comparative Example is slightly increased from the vicinity where the number of processed samples exceeds 50, reflecting the influence of the progress of the flank wear. The increase was only about twice.

Generally, when the helix angle of the reamer blade groove is small, it is difficult to discharge chips in the axial direction. When it increases, the cutting resistance increases and the sharpness deteriorates. The following describes a process in which the twist angle is consciously changed for the reamer 1 of the first embodiment, and a change in the cutting torque accompanying the change is investigated to find a suitable twist angle.

The cutting sample as the work material, the cutting conditions, the specifications of the reamer 1 and the method of measuring the cutting torque were the same as those in the above-mentioned cutting performance comparison test, and only the left-hand twist angle of the blade groove was 10 °.
A reamer 1 set at 20 °, 30 °, and 40 ° was prepared. Table 1 shows the results of recording the cutting torque at each reamer.

[0031]

[Table 1]

According to Table 1, assuming that the cutting torque is 1 when the left helix angle of the blade groove is 10 °, 2.
It was found that the cutting force increased by a factor of 5 and the cutting force increased. Accordingly, it is determined that a more preferable angle range of the left-hand twist angle of the blade groove is desirably a range from 10 ° at which chips are appropriately discharged to 30 ° at which the cutting force does not exceed twice based on 10 °.

[0033]

According to the present invention, a cylindrical cutting blade made of a high-hardness sintered body is joined to the tip of the blade diameter portion extending from the shank where the cutting load is the largest, and a plurality of cutting edges are formed on the outer peripheral portion of the blade diameter portion including the cutting blade body. Since the continuous left-handed kerfs are formed, stable cutting performance is maintained for a long time, and chips are discharged forward, so that excellent surface roughness and dimensional accuracy are maintained.

The oil hole extends from the rear end of the shank to immediately before the joint at the center of the shank, and the cutting oil injection hole is formed so as to be inclined toward the front end and radially reach the inside of the blade groove. The hard cementite in the sintered alloy, which easily bites between the inner wall and the cutting blade, is caused to flow forward, and the cutting heat near the joint of the cutting blade body is cooled to prevent the thermal deterioration of the brazing material.

The cylindrical cutting blade of the second embodiment is inserted along the outer diameter of a stepped small-diameter column formed at the tip of a blade diameter portion extending from a cemented carbide shank, and is inserted into the joint. Since the butting and brazing are performed, the brazing area extends over a wide range of the outer peripheral portion of the small-diameter column and the end face of the joint, and the cutting blade can be extremely firmly fixed to the shank.

[Brief description of the drawings]

FIG. 1 is an external view of a reamer 1 according to a first embodiment of the present invention.

FIG. 2 is an external view of a reamer 20 according to a second embodiment of the present invention.

FIG. 3 is a diagram plotting changes in cutting torque in a cutting test of a reamer according to the first embodiment of the present invention.

FIG. 4 is a front view of a conventional drill having an oil hole for supplying cutting oil.

FIG. 5 is a front view of a conventional drill in which a cutting blade body of a high-hardness sintered body is joined to a tip end.

[Explanation of symbols]

 1: Reamer of the first embodiment 2, 21: Shank 3: Blade diameter part 4, 23: Cutting blade body 5: Oil hole 6: Injection hole 7, 8, 24: Joint part 9: Blade groove 10: Cutting blade 11 : Blade groove blade 12: Center hole 20: Reamer of the second embodiment 22: Small diameter column

Claims (4)

[Claims] 1. A cutting blade made of a high-hardness sintered body having the same outer diameter as the blade diameter is joined to a tip of a blade diameter extending from a cemented carbide or steel shank. A plurality of continuous blade grooves are formed on the outer peripheral portion of the diameter portion, an oil hole is formed in the center of the shank from the rear end of the shank to immediately before the joint, and an injection hole is formed from the oil hole to the shank tip. A reamer for cutting a sintered metal, wherein the reamer is formed so as to radially reach the inside of the blade groove near the joint portion, and the blade groove is formed in a left-handed spiral. 2. The blade according to claim 1, wherein a plurality of blade grooves formed continuously on an outer peripheral portion of the blade diameter portion including the cutting blade body have a twist angle of 5 to 45 °. A reamer for cutting a sintered metal according to item 1. 3. A torsion angle of a plurality of continuously formed blade grooves on an outer peripheral portion of a blade diameter portion including the cutting blade body is 10 to 30 °.
The sintered metal cutting reamer according to claim 1, wherein the reamer is set to: 4. A cutting blade body made of the high-hardness sintered body is formed in a cylindrical shape, and is joined to a stepped small-diameter column body formed at a tip end of a blade diameter portion extending from a cemented carbide shank, and ,
The sintered metal cutting reamer according to any one of claims 1 to 3, wherein a center hole is provided in an end surface of the small-diameter column.