JP4858859B2 - Drill with double margin - Google Patents

Description

  The present invention relates to a two-blade double margin drill capable of forming a hole with high straightness even by deep hole processing or the like, in which two margins are formed in one land portion and the guide effect by the margin is enhanced.

  Patent Document 1 below discloses a double-edged twist drill with a double margin in which a second margin is formed in the middle of the land portion in the circumferential direction and is rotated by 45 ° to 80 ° in the drill reverse direction from the position of the first margin. ing. In Patent Document 1, the width of the second margin is set to 1 to 3 times the width of the first margin for the purpose of obtaining a guide function during drilling while suppressing contact resistance between the margin and the inner surface of the drilled hole. Says. Since the width of the first margin affects the cutting force, it is recommended that the width of the first margin be as small as possible within a range where the strength is not impaired. Generally, a numerical value (for example, 3 to 10% of the drill diameter D) is adopted. Degree).

Patent Document 2 discloses a structure in which the margin width and the inclination angle of the thinning are defined by a single margin drill and the guide performance is improved so that the rear end of the margin drill rotation direction is on the thinning slope. In the drill of Patent Document 2, the margin width is set to 30 to 60% of the drill diameter. The reason is that if the margin width is 20% or less of the drill diameter, the undulation of the processed hole occurs, and the margin width is There is a description that when the drill diameter exceeds 70%, the torque resistance during machining increases rapidly.
JP 2007-15073 A JP 2007-276076 A

  It has been found that the drill with a double margin disclosed in Patent Document 1 cannot obtain good machining accuracy over a long period of time when the prepared hole is drilled in the workpiece. So-called chattering is likely to occur during machining at the pilot hole inlet, and it is difficult to maintain machining accuracy for a long period of time due to the chattering phenomenon that the outer periphery of the cutting edge is chipped.

  On the other hand, the drill of Patent Document 2 has a problem that the supply of lubricant to the interface between the margin and the machining hole becomes insufficient, leading to an increase in cutting resistance and damage to the drill.

  In order to reduce the tool cost occupying the machining cost and to improve the operating rate of the processing machine by reducing the number of tool exchanges, this invention has demonstrated excellent machining accuracy over a long period of time even when drilling the pilot hole. The challenge is to realize and provide a drill with a double margin that can suppress the increase of the drill.

  In order to solve the above-described problem, in the present invention, two land portions along the twisted groove have first margins in front of the forward direction of drilling, respectively, and further than the first margin of each land portion. In a two-edged drill having a second margin behind the drill in the forward direction, the width of the first margin was set to 10 to 20% of the drill diameter.

Further, the angle formed by two straight lines I and II connecting the rotation center O and the front and rear edges of the first margin in the forward rotation direction of the first margin is an area angle A of the first margin, and the forward rotation direction of the rotation center O and the second margin in the forward rotation direction. The angle formed by two straight lines III and IV connecting the front and rear edges is defined as the second margin area angle B, and the total margin at the two land portions is obtained by adding the first and second margin area angles A and B together. The area angle {(A + B) × 2} was set in the range of 100 ° to 140 ° . In addition, at least one of the second margins extends forward in the forward direction of the drill from the heel portion to the position beyond the thinning portion.
The overall performance is obtained by connecting the connecting surfaces from each land part to the leading edge of the second margin in the forward direction of the drill in an obtuse angle with respect to the second margin, and in particular, the connecting angle θ of the connecting surface with respect to the second margin. (Inclination angle of the connecting surface based on the straight line III connecting the rotation center O of the drill and the leading edge of the second margin in the forward direction of the drill) is −10 ° to −60 °, more preferably −20 ° to −60. The one set in the ° range was excellent.

  In the drill according to the present invention, the width of the first margin is set to 10 to 20% of the drill diameter, so that stable guide performance is exhibited even when the pilot hole is widened. Therefore, damage to the cutting edge due to chatter is caused. And excellent machining accuracy is maintained over a long period of time.

  Further, since the width of the first margin is set to 10 to 20% of the drill diameter, the lubricating oil can be sufficiently supplied to the interface between the first margin and the machining hole, and the increase in cutting resistance can be suppressed. It becomes difficult to cause damage. In a drill with a double margin, the main guide is made by the first margin. The second margin only serves as an auxiliary function, and the pressure pressed against the inner surface of the machining hole is smaller than that of the first margin. Accordingly, it was found that the increase in cutting resistance due to the second margin is small, and even if the width of the second margin is large to some extent, poor lubrication of the margin can be prevented by appropriately setting the width of the first margin.

  Although the influence of the second margin on the cutting force is smaller than the influence of the first margin, the total margin area angle including the second margin is set to a range of 100 ° to 140 °. In the evaluation test, it was confirmed that the damage of the margin can be suppressed to be smaller than those of 100 ° or less or 140 ° or more.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a drill according to the present invention will be described below with reference to FIGS. A drill with a double margin (hereinafter simply referred to as a drill) 1 shown in FIGS. 1 to 3 is the one in which the present invention is applied to a two-blade solid twist drill in which a shank 3 is integrally connected to a rear portion of a main body 2. It is. The drill can be made of a coated cemented carbide, an uncoated cemented carbide, a high speed steel, or the like. Further, a tip mud drill whose tip side is formed of a cemented carbide is also included in the application object of the present invention.

  At the tip of the main body 2, there are provided cutting edges 4, 4 that are point-symmetrical with respect to the center of rotation, and a thinning groove 5 attached to each cutting edge. A twist groove 6 is provided. Further, an oil hole 8 that opens to the flank 7 at the tip is provided inside the main body 2.

  Reference numeral 9 denotes a land portion formed between the twist grooves 6 and 6. A first margin 11 and a second margin 12 are provided in parallel at the two land portions 9 located at point-symmetrical positions with respect to the rotation center O, respectively.

  The first margin 11 is provided along the twist groove 6 in front of each land portion 9, 9 in the forward drill direction, and the second margin 12 is behind the first margin 11 in the forward direction of drill { The drill is in the range from the middle in the circumferential direction of the land portion 9 to the trailing edge (heel 10) in the forward direction of the drill.

  The width W (see FIG. 3) of the first margin 11 is set to 10 to 20% of the drill diameter D. Further, an angle formed by two straight lines I and II connecting the rotation center O and the front and rear edges of the first margin 11 in the forward rotation direction of the first margin 11 is the area angle A of the first margin, and the forward rotation of the rotation center O and the second margin is performed. Area angles A and B of the first and second margins 11 and 12 of the two land portions are added up with the angle formed by the two straight lines III and IV connecting the front and rear edges as the second margin area angle B. The total margin area angle {(A + B) × 2} is set in the range of 100 ° to 140 °.

  In addition, a connecting surface 13 that intersects the second margin 12 at an obtuse angle is provided at a portion from the land portion 9 to the leading edge of the second margin 12 in the forward direction of the drill. In a general drill with a double margin, the connection angle θ of the connecting surface 13 with respect to the second margin 12 (inclination angle with respect to the straight line III) is set to 0 °, but the connection angle θ is 0 ° or −10 °. In the following (where the negative value is smaller), the edge formed at the intersection of the connecting surface 13 and the second margin 12 may damage the inner surface of the processing hole. The damage can be suppressed by setting the connection angle θ to −10 ° or more (negative value is increased). In an evaluation test described later, when the connection angle θ was set to −20 °, the inner surface of the processed hole was not damaged at all by the edge.

  Even if the connection angle θ is extremely increased, the effect of preventing damage to the inner surface of the processed hole due to the intersection ridge of the connecting surface 13 and the second margin 12 cannot be expected to be saturated and further increased. It is better to stop the upper limit of about −60 °.

As shown in FIGS. 4 and 5, the area angle A of the first margin 11 provided in the two land portions 9 and the area angle B of the second margin 12 may be different. In the drill of FIG. 4, the area angle A ₁ of the first margin 11 in one land portion (additional symbols are for identification, the same applies hereinafter) is 23 °, and the area angle A ₂ of the first margin 11 in the other land portion is The width of the first margin of the region angle 23 ° calculated by calculating the length of the first margin with the formula for calculating the chord length is 11.5 °, and the width of the first margin is 20% of the drill diameter and the region angle 11.5 The first margin width in degrees is 13% of the drill diameter.

The area angles B ₁ and B ₂ of the second margin 12 of the drill of FIG. 4 are 47 ° and 58.5 °, respectively, and the total area angle of the four margins is 140 °.

Also drill 5, area angle A ₁ of the first margin 11 of one land portion is 23 °, the area angle A ₂ of the first margin 11 of the other land portion is 11.5 °, the first margin The ratio of to the drill diameter is 20% for the former and 13% for the latter as in the drill of FIG. The area angles B ₁ and B ₂ of the second margin 12 of the drill of FIG. 5 are 27 ° and 38.5 °, respectively, and the total area angle of the four margins is 100 °. Thus, even if the sizes of the margins of the two land portions are different, it is possible to perform processing without any trouble.
4 and 5, the second margin 12 is arranged at the rear end of the land portion 9 in the forward direction of the drill, but is shifted from the rear end to the front side in the forward direction (first margin side). You may arrange in. By reducing the circumferential distance between the first margin and the second margin in this way, the guide effect by the second margin can be made to act faster than that with the long distance. Therefore, even when the total margin area is set small, the guide effect can be sufficiently exerted.

The results of the performance evaluation test are shown below. In this performance evaluation test, a diameter D = φ10 mm made of a coated cemented carbide, a flute length L (see FIG. 1) = 80 mm, the width W of the first margin shown in FIG. 3, and the first and second margins An oil hole drill (coating drill) in which the total margin area angle (A + B) × 2 was changed as shown in Table 1 was made as a prototype. Sample No. 15 is a single margin drill, and the other samples are all double margin drills. In the prototype drill with double margin, the connection angles θ of the connecting surfaces 13 in FIG. 3 were all unified to −20 °.
The work material and cutting conditions were as follows.
Work material: SCM420H
Cutting conditions: Cutting speed Vc = 80 m / min, feed f = 0.25 mm / rev, drilling depth H = 40 mm
Machining hole shape: machining the solid part following the opening of the pilot hole 14 with a diameter d = φ8.0 mm in FIG.

  In this evaluation test, the number of drilled holes until the end of the drill's life, the state of the cutting edge at the end of life, the properties of the inner surface of the drilled hole, the cutting resistance in the drilling of the pilot hole, and the cutting resistance in the drilling of the solid part, respectively. Examined. The results are shown in Table 2. In addition, the cutting resistance in Table 2 is represented by the amplitude shown in FIG. In the comprehensive evaluation, ◯ indicates good, Δ indicates slightly good, and X indicates bad.

  From this test result, the drill according to the present invention exhibits a stable guide performance even in the process of expanding the pilot hole. Therefore, the cutting edge damage due to chatter is suppressed, and excellent machining accuracy is achieved over a long period of time. It can be seen that it is maintained. Samples Nos. 1, 2 and 15 have a narrow first margin and the guide effect at the pilot hole entrance is insufficient. In Sample Nos. 11 to 14, the first margin is too wide and the burn-in of the margin occurs. These defects are not observed in the invention products (Sample Nos. 3 to 10).

  FIG. 8 shows the properties of the inner surface of the processed hole by the drill extracted from the samples in Table 1. 8 (a) to 8 (g) are photographs in which the inner surface of the processed hole is photographed. FIG. 8 (a) is a drill for sample No. 1, and FIG. 8 (b) is a sample No. 8 (c) is a drill of sample No. 4, FIG. 8 (d) is a drill of sample No. 5, FIG. 8 (e) is a drill of sample No. 9, and FIG. 8 (f) is a sample. FIG. 8G shows the inner surface of the processed hole by the drill No. 10 (single margin).

  On the inner surface of the hole processed with each of the drills of sample Nos. 1, 2, and 15, chatter marks are formed at the entrance of the hole. On the other hand, good properties are obtained in the processed holes by the drills of sample Nos. 4, 5, 9, and 10.

  This invention is particularly effective when used for drills for steel and casting. However, the invention is expected to be effective when applied to drills that machine other materials such as aluminum. it can.

The side view which shows embodiment of the drill of this invention Enlarged side view of the tip of the drill of FIG. Enlarged front view of the drill in Figure 1 The enlarged front view of other forms of the drill of this invention The enlarged front view of further another form of the drill of this invention Explanatory drawing of hole processing status in performance evaluation test Explanatory drawing of cutting resistance (amplitude) in performance evaluation test (A)-(g): The figure which shows the property of the inner surface of the processing hole by the sample extracted by the performance evaluation test

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill with double margin 2 Body part 3 Shank 4 Cutting edge 5 Thinning groove 6 Torsion groove 7 Flank 8 Oil hole 9 Land part 10 Heel 11 First margin 12 Second margin 13 Connecting surface 14 Pilot hole A First margin area Corner B Second margin area angle W First margin width θ Connection angle of joint surface to second margin O Drill rotation center I Straight line connecting drill rotation center and leading edge of first margin in forward direction of drill
II Straight line connecting the rotation center of the drill and the trailing edge of the first margin in the forward direction of the drill
III Straight line connecting the rotation center of the drill and the leading edge of the second margin in the forward direction of the drill
IV A straight line connecting the center of rotation of the drill and the trailing edge of the second margin in the forward direction of the drill

Claims (2)

The land portions (9, 9) at two locations along the twist groove (6, 6) have first margins (11) in front of the forward direction of drilling, respectively, and each land portion (9) has a first margin. A double-edged drill having a second margin (12) behind the margin (11) in the forward direction of the drill, wherein the width (W) of the first margin is set to 10 to 20% of the drill diameter (D). ,
The angle formed by the two straight lines (I, II) connecting the drill rotation center (O) and the front and rear edges of the first margin (11) in the forward direction of the drill is the first margin area angle A, the drill rotation center ( O) and the angle formed by two straight lines (III, IV) connecting the front and rear edges of the second margin (12) in the forward direction of the drill as a region angle B of the second margin, the first and second margins (11 , 12), the total margin area angle {(A + B) × 2} at the two land portions obtained by adding the area angles (A, B) is set in a range of 100 ° to 140 °.
A drill with a double margin in which at least one of the second margin (12) extends forward in the forward direction of the drill from the heel portion (10) to a position beyond the thinning portion . The drill connecting surface extending in the forward direction the front edge (13) of the second margin from the land portion (9) (12), according to claim 1 which has intersecting an obtuse angle relative to the second margin (12) Drill with double margin.