JPH1158117A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure stable accuracy in a hole diameter and excellent roughness of a machined surface in a diamond sintered body drill, and to prevent unexpected chipping of cutting edges caused by the fluctuation in the machining allowance of finish cutting edges. SOLUTION: A pair of pat parts 9a, 9b opposite to each other in the diameter direction are formed rearward of the rotational direction (x) of finish cutting edges 8a, 8b. The part parts 9a, 9b are retracted in the axial direction of the finish cutting edges 8a, 8b. In addition, the diameter of the pat parts 9a, 9b is set to be between the diameter of preceding cutting edges 7a, 7b and the diameter of the finish cutting edges 8a, 8b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill and other drilling tools for simultaneously performing drilling and reaming of an inner wall surface of a hole.

[0002]

2. Description of the Related Art Reaming is a finishing process in which a desired hole accuracy and a finished surface are obtained by following a prepared hole previously drilled. However, the depth of cut fluctuates depending on the quality of the prepared hole diameter. In addition, there are problems such as poor processing efficiency in two steps of processing by drilling and reaming.

[0003] In order to maintain stable cutting and improve machining efficiency, the following are known tools that can simultaneously perform drilling and reaming.

[0004] The burnishing drill shown in FIG. 6 has a cutting edge 20 opposite to a tip end of a tool body having a deformed cross section connected to a cylindrical shank, a slope 21 in a rotation direction x rearward connected to the cutting edge 20, and a cutting edge 20. A guide surface 22 extending rearward in the axial direction from the edge of the slope 21 is formed. The cutting edge 20 has a constant cutting edge angle that recedes toward the rear end side from the axis of the tip end toward the radially outward side, and the vicinity of the axis of the cutting edge 20 is made of cemented carbide, The outer peripheral side is made of a diamond sintered body fixed by brazing.

[0005] To briefly explain the structure disclosed in Japanese Utility Model Laid-Open Publication No. 2-97510, as shown in FIG. 7, a pair of first cutting blades 30 are provided at the tip end of a blade portion connected to a shank. Another pair of second cutting edges 31 is also provided in the direction intersecting with the cutting edge 30 of the second cutting edge. First cutting edge 30
Is formed integrally with a shank made of cemented carbide, and the second cutting edge 31 is formed by joining a diamond sintered body to the shank by brazing.

The first cutting edge 30 is formed to be inclined at a predetermined cutting edge angle rearward in the axial direction as going radially outward from the axis. Also, the second cutting edge 31
The first cutting edge 30 is located radially outward from the maximum outer diameter of the first cutting edge 30 and is disposed axially rearward. As a result, immediately after the first hole 30 has formed the pilot hole,
The second cutting edge 31 performs cutting with a fixed allowance.

[0007]

Here, the problems of the prior art will be described below.

[0008] In the first prior art, the outer peripheral edge is formed of a diamond sintered body to improve the processing accuracy, but the biting property in the initial stage of cutting is poor.
In some cases, whirling may be induced at the tip of the tool body, the allowance for increasing the hole diameter may be increased, or the roughness of the inner wall surface may be increased. In addition, the processing with an inconsistent finishing margin may cause chipping or chipping, and there is a risk that the cutting becomes impossible. This is because the diamond sintered body itself has a high hardness but is a brittle material.

In the second prior art, the first cutting edge and the second cutting edge are arranged so as to intersect with the same axis of the tool body. The cutting edge is configured to be able to secure a certain amount of allowance. However, since the tool main body is not a completely rigid body, it may bend, run around, or generate vibration due to cutting resistance. When the so-called walking motion in which the rotation center axis of the tool main body is not constant, the first cutting edge, the second cutting edge, or both cutting edges fluctuate. In such a case, if care is not taken to prevent bending or vibration of the tool, the processing hole becomes an elliptical shape, a polygonal shape, or an enlarged hole diameter, and a desired hole diameter accuracy and finish is obtained. The surface roughness cannot be ensured.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a tool body having a rotational axis symmetrical cross section has a cylindrical shank portion and a part of a circle cut out in a fan shape. And a pair of leading cutting edges that are inclined at the tip angle and a pair of blades that retreat in the axial direction from the preceding cutting edge and have a large diameter. In a drill which is provided with the finishing cutting edge of the present invention, at least the finishing cutting edge is formed of a diamond sintered body, and a rear of the finishing cutting edge in the rotation direction is a pair of diametrically opposed ones. A pat portion is formed, and the pat portion is disposed further retreating in the axial direction than the finishing cutting edge, and the diameter of the pat portion is set between the diameter of the preceding cutting edge and the diameter of the finishing cutting edge. In Characterized in that disposed.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 show a drill according to the present invention. The tool body 1 is roughly constituted by a shank portion having a cylindrical shape having a rotational axis symmetrical cross section and a blade portion 2 having a deformed cross section in which a part of a circle is cut out in a fan shape. A pair of drill grooves 4 for taking out chips is provided on the outer circumference of the blade portion 2.
a, 4b and a pair of reamer grooves 5a, 5b are provided along the direction of the axis o. The drill grooves 4a and 4b and the reamer grooves 5a and 5b are used for smoothly removing chips generated during machining through the grooves together with the cutting fluid from the front end side of the tool body 1 to the rear end side. is there. A relief portion 6 for supplying cutting fluid is formed behind the reamer grooves 5a and 5b in the tool rotation direction x.

The leading end of the blade 2 has a leading cutting edge 7a, 7b acting as a drill blade, a pair of finishing cutting edges 8a, 8b acting as a reamer blade brazed and fixed to the tool body 1, and a strip. Pat portions 9a and 9b. As shown in FIG. 1, when viewed from the front, their positional relationship is determined by the leading cutting edges 7a, 7b and the finishing cutting edges 8a, 8
The b · pat portions 9a and 9b are sequentially separated from each other in the rotation direction x rearward. The positional relationship in the radial direction is such that the leading cutting edges 7a, 7b, the pad portions 9a, 9b, and the finishing cutting edges 8a, 8b are located radially outward in this order. As shown in FIG. 2, when viewed from the direction perpendicular to the axis, the positional relationship in the axial direction is such that the leading cutting edges 7a, 7b, the finishing cutting edges 8a, 8b, and the pad portions 9a, 9b are located rearward in the axial direction in this order. It is in.

The leading cutting edges 7a and 7b have cutting edges that are inclined at a predetermined angle α (hereinafter referred to as “tip angle”) in a direction away from the tip. Drilling is a process in which the cutting force in the axial direction of the tool body (hereinafter referred to as “thrust”) and the cutting force in the rotating direction simultaneously act, so that both the rigidity of the tool body itself and the mechanical properties of cutting edge strength are applied. You need to be good. In particular, the vicinity of the axial center of the cutting edge is a place where the thrust acts extremely strongly, so that further consideration for the cutting edge loss is required. Therefore, the leading cutting edges 7a and 7b are advantageously formed integrally from the same material as the shank in terms of strength.

Next, the finished cutting edges 8a, 8b and the leading cutting edges 7a, 7b are formed at an opening angle β (hereinafter referred to as "crossing angle") formed when each cutting edge is connected to the axis o of the tool. )
It is arranged in. The crossing angle β is smaller than 90 °, but the crossing angle β is set to an angle larger than 45 ° in order to smoothly discharge chips in the shallowly formed reamer grooves 5a and 5b. Is good. The finishing cutting edges 8a, 8b are retreated in the axial direction from the preceding cutting edges 7a, 7b and have a diameter greater than their diameter.

Since the machining by the finishing cutting edges 8a and 8b is performed following the preparation of the prepared hole by the preceding cutting edges 7a and 7b, the precision of the predetermined cutting allowance γ is released from the trouble of controlling the prepared hole diameter. Good one-shot processing can be performed. However, consideration must be given to wear and welding of the cutting edge to maintain the desired accuracy.

The finishing cutting edges 8a and 8b are
Since it is located axially rearward from a and 7b, no thrust is applied, and it is sufficient to mainly consider the cutting force in the rotational direction. Further, since it is a cutting edge that performs micro-cutting, a material having high hardness and excellent wear resistance is suitable as a constituent material thereof, rather than a material having high toughness. On the other hand, welding is affected by the type of the workpiece, the constituent material of the cutting edge, and the like. In particular, when an aluminum alloy is used as a workpiece, welding and the formation and detachment of a cutting edge are continuously repeated, so that it is necessary to select a material having excellent welding resistance.

The diamond sintered body is most suitable for cutting an aluminum alloy having a high welding resistance and a high welding property. In addition, the sharp cutting edge shape is maintained because of high wear resistance,
It is also possible to avoid peeling and digging of the finished surface.

Therefore, the present invention has succeeded in obtaining stable reaming and good processing accuracy by forming the finishing cutting edge with a diamond sintered body.

In order to prevent chipping of the cutting edge of the diamond sintered body which is a brittle material while having a high hardness, the cutting allowance γ as the cutting amount is set to 0.02 mm to 0.08 mm.
mm, particularly preferably in the range of 0.03 mm to 0.75 mm.

The pad portions 9a and 9b are provided with a finishing cutting edge 8a,
8b, it is located after the rotation direction x rearward, and is arranged so as to face each other in the diametric direction. Further, from FIG. 3 showing the rotation locus of the blade portion, the pad portions 9a and 9b are disposed further retreating in the axial direction than the finishing cutting edges 8a and 8b. Further, the diameter of the pad portions 9a, 9b is determined by the diameters of the preceding cutting edges 7a, 7b and the finishing cutting edges 8a,
8b. Radius difference R3 between radius R3 of finishing cutting edges 8a and 8b and radius R2 of pad portions 9a and 9b.
R2, that is, the receding amount δ, is preferably set to 0.001 mm to 0.06 mm, particularly preferably 0.002 mm to 0.05 mm, based on the type and processing conditions of the workpiece. Thereby, the finished surface roughness of the inner wall surface of the hole by the finished cutting edges 8a and 8b is maintained, the run-out and vibration of the tool main body 1 are suppressed, and machining with good centripetality by the finished cutting edges 7a and 7b can be performed. .

The outer peripheral side surfaces 10 of the pad portions 9a and 9b are formed in a curved arc shape, and the curvature is formed to be the same as or slightly smaller than the curvature of the inner wall of the machined hole. Thereby, burnishing when the outer peripheral side surfaces 10 of the pad portions 9a and 9b come into contact with the inner wall surface of the processing hole can be suppressed, and good finished surface roughness can be maintained.

Conventionally, to enable the pad portions 9a and 9b to perform a burnishing action, the finishing cutting edges 8a and 8b
And the same outer diameter. For this reason, when the pressing force against the inner wall of the machined hole becomes excessively large, the burnishing may cause problems such as excessive enlargement of the hole diameter and deterioration of the finished surface roughness of the inner wall of the machined hole. For example, in the case of drilling a prepared hole in an aluminum alloy, the hole diameter may show a tendency to decrease, thereby increasing the pressing force of the pad portions 9a and 9b to deteriorate the finished surface roughness, and further, the roundness and straightness. In some cases, a poor hole was formed. Therefore, the present invention is intended to avoid such a problem and obtain a good and stable hole diameter accuracy and a finished surface roughness.
The diameters of a and 9b are set to be between the diameters of the leading cutting edges 7a and 7b and the diameters of the finishing cutting edges 8a and 8b.

FIG. 4 and FIG. 5 show second and third embodiments of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

FIG. 4 shows a structure in which the vicinity of the axis of the leading cutting edges 7a and 7b acting as a drill blade is made of a material resistant to impact, and the outer peripheral side is made of a material resistant to wear. That is, the vicinity of the shaft center is made of a cemented carbide of the same material as the shank, and the outer peripheral side is made of a diamond sintered body or another hard sintered body. This is because the wear resistance is more important than the chipping resistance, especially in the outer peripheral portion of the cutting edge, which is a place where the erosion wear is severe in proportion to the cutting distance.

FIG. 5 is a view showing a structure in which the pad portions 9a and 9b are pressed against the inner wall of the processing hole by the imbalance of the cutting force in the radial direction of the tool body 1 so as not to scratch the inner wall surface. The figure shows that a diamond sintered body that is unlikely to produce a weld or the like is used as a constituent material of the pad portions 9a and 9b.

[0027]

As described above, by simultaneously performing the drilling and the reaming, it is possible to form a highly accurate processed hole in a short time. In addition, stable cutting is performed with a certain amount of allowance by the finishing cutting edge, and expected hole diameter accuracy and finished surface roughness can be maintained. In addition, it is possible to prevent chipping of the finished cutting edge made of a diamond sintered body which is a brittle material while having high hardness.

[Brief description of the drawings]

FIG. 1 is a front view of a drill showing a first embodiment of the present invention.

FIG. 2 is a side view of the drill according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a rotation locus of a blade unit according to the first embodiment.

FIG. 4 is a front view of a drill showing a second embodiment of the present invention.

FIG. 5 is a front view of a drill showing a third embodiment of the present invention.

FIG. 6 is a front view showing an example of a conventional drill having a finishing cutting edge.

FIG. 7 is a front view showing another example of a conventional drill having a finishing cutting edge.

[Explanation of symbols]

 7a, 7b Leading cutting edge 8a, 8b Finishing cutting edge 9a, 9b Pad portion δ Retreat amount R1 Cutting edge radius of leading cutting edge R2 Radius of pad portion R3 Cutting edge radius of finishing cutting edge

Claims (3)

[Claims] 1. A tool body 1 having a rotational axis symmetrical cross section is composed of a cylindrical shank portion and a blade portion 2 of a modified cross section in which a part of a circle is cut out in a fan shape, and the tip of the blade portion 2 In the part, a pair of leading cutting edges 7a inclined at the tip angle α,
7b and the leading cutting edges 7a, 7b are retracted in the axial direction,
Further, in a drill in which a pair of finishing cutting edges 8a and 8b having a large diameter are provided separately from each other, at least the finishing cutting edges 8a and 8b are formed of a diamond sintered body. A pair of diametrically opposed pats 9a and 9b are formed at the rear of the rotation direction x of 8b, and the pats 9a and 9b are
The cutting edges 8a, 8b are further retracted in the axial direction than the finishing cutting edges 8a, 8b, and the diameter of the pad portions 9a, 9b is set to the diameter of the preceding cutting edges 7a, 7b and the finishing cutting edge 8a.
a, drill arranged to be between the diameters of a, 8b. 2. A radius difference R3-R between a radius R3 of the finishing cutting edges 8a, 8b and a radius R2 of the pad portions 9a, 9b.
2, that is, the retreat amount δ of the pad portions 9a and 9b is 0.0
The drill according to claim 1, wherein the drill is formed to have a thickness of from 02 to 0.500 mm. 3. The drill according to claim 1, wherein the pad portions 9a and 9b are formed of a diamond sintered body.