JP2005205526A - Deep hole boring tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an inside cutting edge for reducing cutting resistance, since the cutting quality is not yet better to an outer peripheral side cutting edge 4 having a large positive rake angle γ, since a rake angle β of the inside cutting edge formed by cross-thinning is normally the 0° vicinity to the drill axis. <P>SOLUTION: In a twist drill 1 of applying the cross-thinning 3, this boring tool is set at 115 to 125° in an angle α formed by the inside cutting edge front edge formed by the cross-thinning, to a straight line passing through the tool axis 7, in parallel to a line for connecting the outer peripheral side cutting edge 4 front edge or the outer peripheral side cutting edge 41, 42 both ends 9 and 10, when viewed from the cutting edge front in the tool axis 7 direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a drilling tool that contributes to a reduction in drilling cost by improving the life of a deep hole drill.

  Conventionally, in deep hole machining of steel materials with a drilling tool having a twist groove, it is necessary to enlarge the groove area compared to shallow hole machining for smooth chip discharge, and the groove width ratio is designed in terms of design. Enlarge. However, this leads to a reduction in tool rigidity, and usually the core thickness W is increased simultaneously to improve the rigidity. However, since the length of the chisel 2 that is extremely sharp at the center is increased because the increase in the core thickness W is increased, the thrust that is the axial load is increased, the wear due to the increased load on the cutting edge, and the drill due to buckling. Invited a bend.

Various thinning methods have been proposed in order to reduce the sharpness of the chisel. Among them, cross thinning or X-type thinning is widely used, and there are many patent documents related to it. For example, in Patent Document 1, the width of the chisel is regulated to 0.1 to 0.25 mm, in Patent Document 2, the chisel length is regulated to 0.02 to 0.05 times the drill diameter, and in Patent Document 3, the drill is regulated. The rake angle β on the drill center side of the secondary cutting edge formed at the tip is set to −50 to −2 degrees. In Patent Document 4, the center is shaped like a bowl, and in Patent Document 5, thinning is performed. A curve is provided at the intersection of the blade and the cutting blade, and the radius of curvature is 0.05 to 0.15 times the drill diameter.
JP 2003-39220 A JP-A-5-253719 Japanese Patent Laid-Open No. 10-315021 Japanese Patent No. 3162309 Japanese Patent No. 2674123

  An object of the present invention is to improve cross-thinning in a twist drill by changing a part other than these parts. By applying cross thinning, the cutting thrust is greatly reduced as compared to the case without thinning, but the rake angle β of the inner cutting edge formed by cross thinning is usually around 0 ° with respect to the drill center axis, so it is large. The sharpness of the outer peripheral cutting edge 4 having a positive rake angle γ is still not good. In order to reduce cutting resistance, it is necessary to improve the inner cutting edge.

  Therefore, the present invention relates to a cross drilled twist drill that is parallel to a line connecting the leading edge of the outer peripheral edge or both ends of the outer peripheral edge when viewed from the front of the cutting edge in the tool axis direction, and the tool axis. The above-mentioned problems have been solved by a drilling tool characterized in that the angle α formed by the inner edge of the inner cutting edge formed by cross thinning is 115 to 125 ° with respect to a straight line passing through the center.

  The present invention relates to a deep hole twist drill in which the core thickness W must be increased to improve rigidity, and the inner cutting edge formed on the drill center side by cross thinning is the outer cutting edge leading edge or the outer cutting edge. The angle α formed with the line connecting both ends of the blade is that the conventional product is approximately 130 to 140 ° when viewed from the front of the drill tip, but the present invention product forms a blade edge in the range of 115 to 125 °. . As a result, the rake angle β with respect to the center axis of the drill is usually around 0 °, so that the length of the inner cutting edge with poor sharpness is shortened, and a drilling tool with reduced cutting resistance is provided.

  When the angle α formed between the inner cutting edge and the line connecting the leading edge of the outer peripheral side or both ends of the outer peripheral cutting edge is less than 115 °, the chip flows if the work material is alloy steel or carbon steel. If the direction is biased toward the outer periphery of the drill and the discharge performance is deteriorated, and the angle α exceeds 125 °, the shortening of the length of the inner cutting edge with poor sharpness becomes insufficient, and the effect of the present invention becomes insufficient. Therefore, the angle α was limited to 115 to 125 °.

Preferably, when viewed from the front of the cutting edge, the front side of the inner cutting edge formed by cross thinning with respect to a straight line parallel to a line connecting the leading edge of the outer peripheral side or both ends of the outer peripheral cutting edge and passing through the tool axis. The effect of the present invention is more exhibited when the angle α formed by the edge is 115 to 120 °. More preferably, in the deep hole twist drill, the groove core thickness is extremely important, and when the diameter of the drilling tool is D, the groove core thickness is preferably 0.35 to 0.45D. This is because if the groove core thickness is less than 0.35D, the rigidity is insufficient, and if it exceeds 0.45D, the groove becomes shallow and the chip discharging property deteriorates.
Moreover, it is preferable that the twist angle of a twist groove has 33-42 degrees with respect to the axial center of the said drilling tool. This is because if the twist angle is less than 33 °, the chip discharging property deteriorates, and if it exceeds 42 °, the rigidity is insufficient.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a front view of a twist drill subjected to cross thinning according to the best embodiment of the present invention as viewed from the front of the cutting edge in the tool axis direction. The drilling tool of the present invention is subjected to cross thinning 3. In the twist drill 1, the inner cutting edge formed by the cross thinning 3 with respect to a straight line parallel to the front edge of the cutting edge 4 on the outer peripheral side and passing through the tool axis 7 when viewed from the front of the cutting edge in the direction of the tool axis 7. The drilling tool is characterized in that the angle α formed by the leading edge is 115 to 125 °. 2 is a chisel, 6 is a clearance surface of the outer peripheral cutting edge 4, 8 is a groove, 9 is an outer end face of the outer peripheral cutting edge 4, and 10 is an inner end face of the outer peripheral cutting edge 4.

  FIG. 2 is a side view of the drill 1 of FIG. 1 as viewed from the side of the groove. As shown in FIG. 2, the rake angle β with respect to the drill axis 7 is normally near 0 °, and the sharpness of the inner cutting edge 5 is poor. In the present invention, the angle α formed by the inner cutting edge leading edge formed by cross thinning is 115 to 125 ° with respect to a straight line parallel to the leading edge of the outer cutting edge 4 and passing through the tool axis 7. Thus, the length of the inner cutting edge 5 is shortened, and a drilling tool with reduced cutting resistance is provided. FIG. 3 shows an enlarged side view of the front edge of the outer peripheral cutting edge 5 as viewed from the side of the drill in such a direction as to the front edge of the outer peripheral edge of the drill 1 of FIG. As shown in FIG. 3, the front edge of the cutting edge 4 on the outer peripheral side of the drill 1 of FIG. 1 has a large rake angle γ with respect to the tool axis 7.

  FIG. 4 is a front view of a twist drill 11 subjected to cross thinning according to the preferred embodiment of the present invention, which is different from FIG. 1, as viewed from the front of the cutting edge in the tool axis direction. As shown in FIG. 4, it is formed by cross thinning 3 on a straight line passing through the tool axis 7 in parallel to the line connecting the both ends 9 and 10 of the outer peripheral edge 41 when viewed from the front of the cutting edge in the tool axis direction. The angle α formed with the leading edge of the inner peripheral cutting edge 5 is set to 115 to 125 °. FIG. 5 shows a front view of a twist drill 12 subjected to cross thinning according to a preferred embodiment of the present invention, which is further different from FIGS. 1 and 4, as viewed from the front of the cutting edge in the tool axis direction. As shown in FIG. 5, it is formed by cross thinning 3 on a straight line passing through the tool axis 7 in parallel to the line connecting the both ends 9 and 10 of the outer peripheral edge 42 when viewed from the front of the cutting edge in the tool axis direction. The angle α formed with the leading edge of the inner peripheral cutting edge 5 is set to 115 to 125 °. The cutting edge 41 on the outer peripheral side in FIG. 4 has a curved shape with the center retreating, and the cutting edge 42 on the outer peripheral side in FIG. 5 has a curved shape with the center protruding, both of which are on the linear outer peripheral side in FIG. The same effect of the present invention as that of the leading edge of the cutting edge 4 is obtained.

A deep hole drilling experiment was conducted using a high-shear drill with a TiAlN coating according to the present invention shown in FIG. The drill size is 6.0 mm in diameter, 213 mm in total length, 120 mm in groove length, 40 ° twist angle, and the core thickness W is 45% of the diameter. Using this drill, the angle α formed by the inner thin cutting edge 5 and the outer peripheral cutting edge 4 of the cross thinning was sharpened to 120 ° for the product of the present invention, and the angle α of the comparative conventional product was sharpened to 135 ° for the experiment. . The processing conditions are as follows.
Drill diameter: 6.0mm
Work material: S50C
Hole depth: 100mm
Cutting speed: 15 m / min
Feeding speed: 120mm / min
Cutting fluid: water-soluble

  Table 1 shows measured values of thrust cutting resistance obtained by the cutting test, and Table 2 shows measured values of wear width of the drill in the cutting test. The angle α is an angle formed by cross thinning formed by the inner cutting edge and the outer peripheral cutting edge of the cross thinning. The average thrust cutting resistance of the cutting test was about 30% less than that of the conventional product. The average torque was almost the same. The measured value of the wear width of the drill in the cutting test was 78 holes, and the product of the present invention drastically decreased to about 1/3 or less. The conventional product was determined to have a lifetime at the time of 78 hole machining, but the product of the present invention could be further used continuously.

切削試験のスラスト切削抵抗測定値

切削試験のドリル摩耗幅測定値

〔本発明の最良の実施形態の効果〕

Thrust cutting resistance measurement value of cutting test

Drill wear width measurement value of cutting test

[Effect of Best Embodiment of the Present Invention]

  The above-described drilling tool according to the best embodiment of the present invention is a deep hole twist drill in which the core thickness W has to be increased to improve rigidity, and the inner cutting edge formed on the drill center side by cross thinning is provided. The angle α between the front edge of the outer peripheral cutting edge or the line connecting both ends of the outer peripheral cutting edge is approximately 130 to 140 ° in the conventional product when viewed from the front of the drill tip. The cutting edge is formed in a range of 125 °. As a result, the rake angle β is usually around 0 ° with respect to the center axis of the drill, so the length of the inner cutting edge with poor sharpness is shortened, the cutting thrust is reduced, and the load on the cutting edge is reduced. Surface wear decreased. In addition, drill bending due to buckling was reduced due to lower thrust, and abrasion with the hole wall in the hole was reduced, so that margin wear was significantly reduced and the amount of hole bending was also reduced.

Preferably, when viewed from the front of the cutting edge, the front side of the inner cutting edge formed by cross thinning with respect to a straight line parallel to a line connecting the leading edge of the outer peripheral side or both ends of the outer peripheral cutting edge and passing through the tool axis. The effect of the present invention is more exhibited when the angle α formed by the edge is 115 to 120 °. More preferably, in the deep hole twist drill, the groove core thickness is extremely important, and when the diameter of the drilling tool is D, the groove core thickness is preferably 0.35 to 0.45D. This is because if the groove core thickness is less than 0.35D, the rigidity is insufficient, and if it exceeds 0.45D, the groove becomes shallow and the chip discharging property deteriorates.
Moreover, it is preferable that the twist angle of a twist groove has 33-42 degrees with respect to the said drilling tool axial center. This is because if the twist angle is less than 33 °, the chip discharging property deteriorates, and if it exceeds 42 °, the rigidity is insufficient.

The front view which looked at the twist drill in which the cross thinning of the best embodiment of this invention was given from the cutting-blade front in the tool axis direction. The side view which looked at the drill of FIG. 1 from the groove | channel side. FIG. 2 is an enlarged side view of a cutting edge leading edge on the outer peripheral side viewed from the side of the drill in a direction toward the cutting edge leading edge on the outer peripheral side of the drill of FIG. 1. The front view which looked at the twist drill in which the cross thinning of the best embodiment of this invention different from FIG. 1 was given from the cutting-blade front in the tool axis direction. The front view which looked at the twist drill with which the cross thinning of the best embodiment of this invention different from FIG. 1, FIG. 4 was given from the cutting-blade front in the tool axis direction.

Explanation of symbols

1: Drill groove 2: Chisel 3: Cross thinning 4, 41, 42: Outer peripheral cutting edge 5: Inner cutting edge 6: Drill flank 7: Axis center line W: Center thickness α: Inner cutting edge and outer peripheral cutting edge Angle β: Rake angle of inner cutting edge γ: Rake angle of outer peripheral cutting edge

Claims (6)

  For twist drills with cross thinning, with respect to the straight line passing through the tool axis and parallel to the line connecting the leading edge of the outer peripheral edge or both ends of the outer peripheral edge when viewed from the front of the cutting edge in the tool axis direction An angle α formed by the leading edge of the inner cutting edge formed by cross thinning is 115 to 125 °.   When viewed from the front of the cutting edge, the inner cutting edge leading edge formed by cross thinning is parallel to the line connecting the outer cutting edge leading edge or the outer cutting edge both ends and passing through the tool axis. The drilling tool according to claim 1, wherein the angle α is 115 to 120 °.   3. The drilling tool according to claim 1, wherein a groove core thickness is 0.35 to 0.45 D, where D is a diameter of the drilling tool.   The drilling tool according to any one of claims 1 to 3, wherein a twist angle of the twist groove is 33 to 42 ° with respect to the drilling tool axis.   The drilling tool according to any one of claims 1 to 4, wherein a cutting edge of the drilling tool is high-speed tool steel or cemented carbide.   The drilling tool according to any one of claims 1 to 5, wherein the cutting edge of the drilling tool is coated with a hard coating such as a titanium compound.

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