JP2012011481A - Deep hole drilling drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve breakage strength by increasing core thickness while securing prescribed cutting chip discharge performance, and to perform stable drilling from the beginning of the working.SOLUTION: Because a bottom part 36 of gash 34 formed when applying thinning is provided with roundness of a radius R in a range of 0.03D to 0.05D, cutting chips are easily curled to improve cutting chip discharge performance. By increasing the core thickness W1 in a range of 0.30D to 0.40D, breakage strength is improved while preventing the clogging of the cutting chips. Because a pair of lands are provided with a second margin 56 at a position where a second margin angle α is in a range of 35-45°, support action by the second margin 56 is obtained immediately after the start of the drilling to stabilize the drilling posture. Accordingly, the practical tool lifetime is obtained in the deep hole drilling drill 10 having a long groove length L.

Description

  The present invention relates to a drill, and more particularly to improvement of a deep hole drill having a groove length of 10 times or more of a drill diameter.

  (a) a plurality of chip discharge grooves provided on the outer peripheral surface at a predetermined twist angle, and (b) a plurality of drill blades provided at a portion where the chip discharge grooves are open at the tool tip, and (c) A thinning blade formed by thinning a grinding wheel on an inner end portion close to the axis O of the drill blade; and (d) the chip discharge groove continuously from the outer end portion of the drill blade. And (e) a drill for deep hole drilling in which the groove length L provided with the chip discharge groove is 10 times or more the drill diameter D (patent) Reference 1). Further, Patent Document 2 describes a technique for stabilizing the attitude of the drill by providing a second margin at an intermediate position in the circumferential direction of the land in addition to the margin.

JP 2004-122288 A JP 2008-194774 A

  However, in such a conventional drill for deep hole drilling, if the core thickness is increased to increase the breakage strength for high-speed machining, etc., chip clogging is likely to occur, and on the other hand, breakage is liable to occur. Satisfactory durability was not obtained and there was still room for improvement. Further, in the drill for deep hole machining described in Patent Document 2 having the second margin, the drill attitude at the beginning of machining until the second margin reaches the machining hole is unstable, and vibration or the like may occur. was there.

  The present invention has been made against the background of the above circumstances, and the purpose of the present invention is to increase the thickness of the core by increasing the core thickness while ensuring the predetermined chip discharge performance, and to stabilize from the beginning of processing. It is to improve the durability of the drill as a whole so that the drilling can be performed.

  In order to achieve such an object, the first invention provides: (a) a plurality of chip discharge grooves provided on the outer peripheral surface at a predetermined twist angle; and (b) a portion where the chip discharge grooves are open at the tool tip. (C) a thinning blade formed by thinning an inner end portion close to the axis O of the drill blade with a grinding wheel; and (d) the drill blade. (E) a groove length L in which the chip discharge groove is provided is 10 times or more of the drill diameter D. In the drill for deep hole machining of (f), the bottom of the gasche formed at the end on the axis O side of the thinning blade by the thinning is within the range of 0.03D to 0.05D. (G) The plurality of chips are removed. The second margin is cut at the intermediate position in the circumferential direction of the plurality of lands between the protruding grooves, where the angle α around the axis O from the leading edge is within the range of 35 ° to 45 °. (H) The core thickness W1, which is the web thickness of the tool tip, is in the range of 0.30D to 0.40D.

  According to a second invention, in the deep hole drill according to the first invention, thinning is performed from the outer end portion of the drill blade by the grinding wheel so that the bottom portion of the gasche is sandwiched to the opposite side of the thinning blade. The angle β around the axis O to the outer end of the ridge line of the grinding surface to be formed is 65 ° or more.

  The third invention is the drill for deep hole drilling according to the first or second invention, wherein the inclination angle γ at which the bottom of the gasche inclines from the direction perpendicular to the axis O toward the axis O is 55 ° to 65 °. It is within the range.

  According to such a deep hole drill, since the round portion having a radius R in the range of 0.03D to 0.05D is provided at the bottom of the gasche formed by thinning, Is easy to curl and chip discharge performance is improved, wear on the thinning surface (rake surface) is suppressed and thrust load is reduced, while the core thickness W1 is within the range of 0.30D to 0.40D. Even if it is increased, chip clogging is suppressed, and the breakage strength can be increased. In addition, a second margin is provided at a position that is an intermediate position in the circumferential direction of a plurality of lands and an angle α from the leading edge is within a range of 35 ° to 45 °, that is, a position relatively close to the leading edge. Therefore, the support action by the second margin can be obtained immediately after the start of drilling, the drill posture is stabilized, vibration is suppressed, and excellent machining accuracy (e.g. drilling of drilled holes) ) Is obtained and the processing load is stabilized. Since the machining load is stabilized in this way, durability is improved in combination with the increase in the breaking strength as described above, and a tool life that is practically satisfactory can be obtained even in a deep hole machining drill having a long groove length L. It becomes like this.

  In the second invention, the angle β from the outer edge of the drill blade to the outer edge of the ridgeline of the grinding surface formed on the opposite side of the thinning blade across the bottom of the gasche is 65 ° or more. The opening angle is reduced, and the chips are appropriately curled by the roundness of the bottom of the gasche having the radius R. As a result, chips are better discharged and the thrust load is reduced.

  In the third aspect of the invention, since the inclination angle γ at which the bottom portion of the gasche inclines from the direction perpendicular to the axis O toward the axis O is within the range of 55 ° to 65 °, the inclination angle γ is too large and the drill itself The chip is discharged well into the chip discharge groove along the inclination while avoiding the reduction of the strength and the difficulty of curling the chip.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the drill for deep hole processing which is one Example of this invention, (a) is a front view, (b) is the longitudinal cross-sectional view which showed the chip discharge groove as a straight groove, (c) is a tool front-end | tip part. (D) is a front end view of the drill viewed from the front end side, and (e) is an enlarged view of the vicinity of the axis O of the front end view of (d). It is sectional drawing which shows the gash part of the drill for deep hole processing of FIG. 1, and is a figure explaining the processing method at the time of giving a thinning using a grinding wheel. It is a figure which shows the 3D model which simplified the gash part in order to evaluate the performance of the drill for deep hole processing of FIG. 1 by CAE analysis. It is a figure which shows the factor at the time of performing L9 row orthogonal arrangement | sequence experiment in order to select the optimal chip room shape of a gash part, and a replacement table. It is a figure which shows the effect graph which calculated | required the average of the thrust load for every level about each factor of FIG. FIG. 2 is a view showing a tip portion of the deep hole drill in FIG. 1 in comparison with a conventional double margin drill in which a second margin is provided at a heel portion of a land. It is a figure explaining the specification and test conditions of the test article used when performing the performance test regarding a processing load. It is a figure which shows the result of having measured the spindle load in the performance test of FIG. It is a figure explaining the performance test regarding processing accuracy (eccentricity), (a) is a specification of a test article, (b) is a test condition, (c) is a figure showing a test result. It is a figure explaining the performance test regarding durability, (a) is a specification of a test article, (b) is a test condition, (c) is a figure showing a test result.

  The drill for deep hole machining of the present invention is preferably applied to a drill having a small diameter of about 2 mm to 12 mm, for example, a drill diameter D, but can also be applied to a drill having a diameter larger than 12 mm. The groove length L is 10D or more, and is applied to long drills such as 10D, 15D, 20D, and 30D, for example.

  As the tool material constituting the drill, super hard tool materials such as cemented carbide, cermet, cubic boron nitride (CBN) sintered body are preferably used, but other tool materials such as high speed tool steel are used. Can also be adopted. It is desirable to coat a hard film such as TiAlN, TiCN, or diamond as necessary.

  The present invention is preferably applied to a two-blade drill, but can also be applied to a three-blade or more drill. Also, an oil hole that opens through the shaft center or twists along the land and opens to the flank of the tip can be provided so that lubricating oil or cooling air can be supplied when drilling. desirable.

  The present invention is preferably applied to a deep hole drill for performing drilling on a relatively low hardness work material of, for example, about 40 HRC or 35 HRC or less, and the chip discharge groove is, for example, about 20 ° to 40 °. Although it is provided with a relatively large helix angle, it is applied to a deep hole drill for drilling high hardness materials of 40 HRC or higher, or a chip discharge groove with a helix angle of 20 ° or less is provided. You can also.

  The outer diameter of the groove portion provided with the chip discharge groove on the outer peripheral surface may be substantially constant (drill diameter D), but a predetermined back taper that gradually decreases in diameter toward the shank side, For example, only a portion of 5D to 10D may be substantially the same as the drill diameter D, and the portion on the shank side may be a stepped shape slightly smaller than the drill diameter D.

  The web thickness, which is the groove bottom diameter of the chip discharge groove, may be constant over the entire length of the groove, that is, the same as the core thickness W1, but may be part of the tip side (for example, in the range of about 3D to 7D) or It is also possible to provide a back taper that gradually decreases in diameter over the entire region, or a reverse taper that gradually increases in diameter.

  Thinning is performed, for example, by cutting while rotating the grinding wheel at the end on the axis O side, and moving the grinding wheel and the drill relative to each other to form an S-shaped thinning blade. On the other hand, it is also possible to form the thinning blade while relatively moving in the direction approaching the axis O. In any case, a gash having a V-shaped cross section is formed at the end on the axis O side of the thinned portion, and a radius within a range of 0.03D to 0.05D is formed at the bottom of the gasche. R roundness should be provided. When the radius R is smaller than 0.03D, the flow of chips becomes poor and clogging tends to occur. On the other hand, when the radius R is larger than 0.05D, the chips become difficult to curl properly.

  The second margin is provided such that the angle α from the leading edge is in the range of 35 ° to 45 °, and this angle α is the front edge of the second margin from the leading edge, that is, the angle on the leading edge side. The angle to the part. If the angle α is smaller than 35 °, the effect of stabilizing the drill posture cannot be sufficiently obtained. On the other hand, if the angle α is larger than 45 °, the distance from the drill tip becomes large, and the drill posture at the beginning of machining starts. Becomes unstable.

  If the core thickness W1 is in the range of 0.30D to 0.40D and is less than 0.30D, sufficient break strength cannot be obtained. On the other hand, if the core thickness W1 is greater than 0.40D, the chip flow becomes poor. Scrap clogging easily occurs.

  Since the angle β from the outer end portion of the drill blade to the outer end portion of the ridge line of the grinding surface formed on the opposite side of the thinning blade across the bottom of the gash is less than 65 °, the thrust load increases. 65 ° or more is desirable. The reason why the thrust load is increased is considered to be that when the angle β is decreased, the opening angle of the gasche is increased and the chips are difficult to curl and the chip dischargeability is deteriorated. The upper limit of the angle β is limited by the shape of the grinding wheel and the shape of the thinning blade. However, if the opening angle of the gash becomes too small, the flow of chips becomes worse. For example, about β = 75 ° or less is appropriate. is there. As the grinding wheel for thinning, a cylindrical grindstone whose outer peripheral corners are substantially right angles is preferably used, but if necessary, a cup-shaped (conical) grindstone whose outer peripheral corners are acute angles is adopted. You can also.

  The inclination angle γ at which the bottom of the gasche inclines in the direction of the axis O from the direction perpendicular to the axis O is preferably in the range of 55 ° to 65 °. When the inclination angle γ exceeds 65 °, the strength of the drill itself is reduced and the chips are difficult to curl. On the other hand, when the inclination angle γ is less than 55 °, the flow of the chips into the chip discharge groove is poor. Become.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A and 1B are diagrams showing a deep hole drill 10 according to an embodiment of the present invention. FIG. 1A is a front view seen from a direction perpendicular to the axis O, and FIG. 1B is a longitudinal section including the axis O. FIG. (C) is an enlarged view of the tool tip, (d) is a tip view seen from the tip side, and (e) is an enlarged view of the vicinity of the axis O of the tip view of (d). The drill 10 for deep hole machining is a two-blade twist drill integrally formed of a cemented carbide, which is a super-hard tool material. The groove 14 is provided with a pair of chip discharge grooves 18 symmetrically with respect to the axis O over the entire length of the groove 14, and the chip discharge grooves 18 are provided concentrically in the axial direction. Drill blades 16 are provided symmetrically with respect to the axis O at the portions opened to the tool tip side. The chip discharge groove 18 is a twist groove twisted clockwise at a twist angle of about 30 ° so as to discharge the chip to the shank 12 side. In FIG. In order to clearly indicate the thickness (diameter dimension) W of the web 20 formed by the bottom, the chip discharge groove 18 is shown as a straight groove parallel to the axis O. In other words, the shape of the web 20 in FIG. 1B corresponds to the shape of the rotation locus of the groove bottom of the chip discharge groove 18. The length dimension of the groove portion 14 provided with the chip discharge groove 18, that is, the groove length L is 10 times or more of the drill diameter D which is the diameter of the drill blade 16, and is 20 times in this embodiment. = 8 mm, groove length L = 160 mm. Note that FIG. 1 does not accurately illustrate the ratios and angles of the dimensions of each part.

  The groove portion 14 is composed of a large-diameter portion 14a on the tip side having substantially the same diameter as the drill diameter D and a small-diameter portion 14b slightly smaller in diameter than the drill diameter D. The axial length L1 of the large-diameter portion 14a is about 8D, that is, 64 mm, and a back taper is provided so that the diameter dimension is slightly reduced toward the small-diameter portion 14b side, while the small-diameter portion 14b has a full length. It is provided with a substantially constant diameter dimension (about 7.7 mm in this embodiment). Moreover, a hard film such as TiAlN is coated in a predetermined range on the tip side including the drill blade 16 in the large diameter portion 14a.

  The web 20 has a back taper portion 20a on the drill tip side provided with a back taper that becomes smaller as the web thickness W goes toward the shank 12 side, and the web thickness W is the same as the minimum thickness in the back taper portion 20a. A parallel portion 20b provided continuously toward the shank 12 with the dimension W2 and continuing to the back taper portion 20a. The axial length L2 of the back taper portion 20a is within a range of 3D to 7D with respect to the drill diameter D, and is about 5D (= 40 mm) in the present embodiment, and the core thickness W1 that is the web thickness of the drill tip. Is in the range of 0.30D to 0.40D, and is about 0.35D (= 2.8 mm) in this embodiment. The web thickness W2 of the parallel portion 20b is within a range of 0.25D to 0.35D, and is about 0.3D (= 2.4 mm) in the present embodiment.

  An S-shaped thinning blade 30 is formed on the inner end portion of the drill blade 16 near the axis O by thinning. In this thinning, for example, as shown in FIG. 2, a cylindrical grinding wheel 32 is rotationally driven around an axis to cut into a predetermined position near the axis O, and the thinning blade 30 to be formed in that state is formed. The deep hole machining drill 10 is moved relative to the grinding wheel 32 along the shape, and the thinning start position, that is, the end of the thinning blade 30 on the side close to the axis O is a cross section. Is formed into a substantially V-shaped gouache 34. FIG. 2 is a cross section perpendicular to the longitudinal direction (gash cutting direction) of the bottom portion 36 of the gash 34. The bottom 36 has a radius in the range of 0.03D to 0.05D with respect to the drill diameter D. A roundness of R (R = 0.04D = 0.32 mm in this embodiment) is provided. 2 is a thinning surface that functions as a rake face of the thinning blade 30, and the other wall surface 40 is a relief surface (bottom edge No. 3) of the drill blade 16 by the outer peripheral surface 42 of the grinding wheel 32. (Surface) 46 is a ground surface that is ground. The gash surface 40 corresponds to a grinding surface according to claim 2. A flank (bottom edge 2) 44 is provided between the drill blade 16 and the flank (bottom edge 3) 46.

  With respect to the gash 34, the gash cutting angle γ shown in FIG. 1C is in the range of 55 ° to 65 °, and is about 60 ° in this embodiment. FIG. 1C is a front view of the deep hole drill 10 in the state shown in FIG. 1D viewed from the left side. The boundary A between the drill blade 16 and the thinning blade 30 and the outer peripheral side of the drill blade 16 are shown. FIG. 5 is a diagram viewed from a direction perpendicular to the straight line connecting the apex B of the convex portion. The gash cut angle γ is a direction in which the bottom portion 36 of the gash 34 is perpendicular to the axis O in the state of FIG. It is an inclination angle which inclines in the direction of the axis O from the center. The bottom portion 36 of the gash 34 is a portion ground by the end portion of the outer peripheral surface 42 of the grinding wheel 32, and strictly corresponds to the outer peripheral shape of the grinding wheel 32 (φ125 × width 14 in this embodiment). Although the arc shape is formed and the inclination angle is slightly changed, the gash cutting angle γ is an inclination angle at the cutting start point, that is, the drill tip side.

  Further, the thinning start angle β shown in FIG. 1D is 65 ° or more, and is about 70 ° in this embodiment. This thinning start angle β is a ridgeline 52 between the outer end of the drill blade 16 (same as the leading edge 50 in FIG. 1 (d)) and the gash face 40 and the flank face (bottom edge third face) 46. The angle around the axis O to the outer end of

  On the other hand, the opening margin of the chip discharge groove 18 continuous to the outer end of the drill blade 16 is provided with a first margin 54 having a diameter substantially the same as the drill diameter D, and a pair of chip discharges. A second margin 56 having a diameter substantially the same as the drill diameter D is provided in parallel with the chip discharge groove 18 at the intermediate position in the circumferential direction between the pair of lands located between the grooves 18. The first margin 54 and the second margin 56 are provided in the large-diameter portion 14a of the groove portion 14, and the second margin extends from the leading edge 50 corresponding to the front end corner portion in the circumferential direction of the first margin 54. The second margin angle α around the axis O up to the 56 front end corners in the circumferential direction is within a range of 35 ° to 45 °, and α = 40 ° in the present embodiment. The diameter of the outer peripheral surface (second surface) other than the margins 54 and 56 of the large diameter portion 14a is about 7.8 mm, and the height of the margins 54 and 56 is about 0.1 mm. The first margin 54 is a normal margin, and the second margin 56 is equivalent to a second margin.

  Each of the pair of lands is provided with an oil hole 24 spirally twisted along the chip discharge groove 18, and one end is opened to a flank (bottom blade third surface) 46 at the tip of the drill, The other end passes through the shank 12 and opens to the end face, so that lubricating oil, cooling air, etc. can be supplied as needed during drilling.

  Here, regarding the deep hole drill 10 of the present embodiment in which the bottom 36 of the gash 34 is rounded with a radius R, as shown in FIG. Computer Aided Engineering) analysis. Although the drill 10 for deep hole machining is rotary cutting, when the chip discharge performance is evaluated approximately by straight cutting, it is better to add a radius R radius (R = 0.32 mm) to the bottom 36. As compared with the case of radius R = 0 mm, the contact area between the thinning surface 38 and the chips becomes small. From this, it can be expected that the wear of the thinning surface 38 is suppressed.

  In addition, an L9 row orthogonal array experiment was performed in order to select the optimum chip room shape of the gasche 34 portion. In Fig. 4, (a) shows three types of factors and levels, and (b) shows a replacement table. Then, CAE analysis was performed using the thrust load as an evaluation value, and the average of the thrust load was obtained for each level for each factor. As a result, the effect graph shown in FIG. 5 was obtained. From this result, it is appropriate that the gash cut angle γ is about 60 °, and the rounding radius R of the bottom 38 of the gash 34 is about 0.3 mm (0.0375D with respect to the drill diameter D), and thinning is started. It has been found that an angle β of 65 ° or more is appropriate.

  If the gash cut angle γ is too small, the flow of chips generated by the thinning blade 30 is deteriorated, and it is considered that the thrust load increases due to chip clogging. On the other hand, if the gash cut angle γ is too large, the chips cannot be curled and the discharge performance deteriorates, and it is considered that the thrust load increases due to chip clogging. If the bottom rounding radius R is too small, it is considered that the flow of chips deteriorates and clogging easily occurs, and the thrust load increases. On the other hand, if the bottom rounding radius R is too large, the chips cannot be curled and the discharge performance deteriorates, and it is considered that the thrust load increases due to chip clogging. If the thinning start angle β is small, the opening angle θ of the gash 34 (see FIG. 3) becomes large. Therefore, even if the bottom radius R is small, the chips cannot be curled well, and the chip discharge performance deteriorates. It is thought that the thrust load increases due to chip clogging.

  FIG. 6 shows a deep hole drill 10 (FIG. 6 (a)) in which the second margin 56 is provided at the second margin angle α = 40 °, and the deep hole drill 10 of this embodiment. In FIG. 6, only the position of the second margin 56 is changed, and the comparative product drill 70 (FIG. 6B) in which the second margin 72 is provided at the heel portion of the land, the second margin 56 or 72 from the drill shoulder. It is a figure which compares and shows the reverse amounts H1 and H2 until. The retraction amount H1 of the drill 10 for deep hole machining of the present embodiment is small, and after the start of drilling, the second margin 56 is immediately inserted into the machining hole after the first margin 54 so that a support action can be obtained. Therefore, stable drilling can be realized by supporting four points from the beginning of machining. On the other hand, since the amount of retraction H2 of the comparative product drill 70 is relatively large, it takes a long time until the second margin 72 is inserted into the machining hole to obtain a support action, and the drill posture during that time is unstable. May cause vibration. If the second margin angle α is too small, the support action by the four-point support cannot be obtained properly, and the drill posture becomes unstable. Therefore, the second margin angle α is in the range of 35 ° to 45 °. Is appropriate.

  7 and 8 show three types of test products (conventional ones) having different thickness W1, gash cutting angle γ, bottom radius R, and second margin angle α as shown in the test tool specification of FIG. Product, comparative product, product of the present invention), drilling under the test conditions shown in Fig. 7 (b) and examining the spindle load (motor voltage), the result shown in Fig. 8 is obtained. It was. The basic specifications of the test tool (specifications other than those shown in FIG. 7 (a)) are the same as those of the drill 10 for deep hole machining in the above-described embodiment, with a drill diameter D = 8 mm, a groove length L = 160 mm (20D), and two pieces. Blade, thinning start angle β = 70 °. Further, the conventional product has a single margin and does not have the second margin 56. “SCM440” in the column of the work material in FIG. 7B is a chromium molybdenum steel material according to JIS regulations.

  FIG. 8 is a waveform of the spindle load at the time of drilling the 49th to 70th holes. According to the product of the present invention, the spindle load is about 0.7V, which is smaller than the conventional product and the comparative product of about 0.8V, and there is no sudden increase in the load waveform exceeding 1.0V. It can be seen that it is relatively stable. The comparative product is a double margin drill in which the second margin 56 is provided in the middle position of the land. However, since the second margin angle α is as small as 25 °, the support action by the four-point support cannot be obtained sufficiently, and the single margin There was almost no difference with the conventional product of the margin.

  Fig. 9 shows two types of test products (comparison product, product of the present invention) shown in (a) test tool specifications, and drilling is performed under the test conditions shown in (b). When the amount of eccentricity of the openings at both ends of was examined, the result shown in (c) was obtained. The basic specifications of the test tool (specifications other than FIG. 9 (a)) are the same as the drill 10 for deep hole machining in the above embodiment, drill diameter D = 8 mm, groove length L = 160 mm (20D), two pieces It is a blade. The comparative product is a normal double margin drill in which a second margin is provided at the heel portion of the land.

  FIG. 9 (c) shows the results of examining the eccentricity of each of the three holes when the three holes were machined using the comparative product and the product of the present invention. The eccentric amount of the comparative product is about 0.155 mm, while the product of the present invention is about 0.12 mm, which is an improvement of about 0.035 mm when processing a 150 mm through hole.

  Fig. 10 shows four types of test products (conventional product, comparative product 1, comparative product 2, product of the present invention) shown in (a) test tool specifications, and drilled under the test conditions shown in (b). The results shown in (c) were obtained when the durability, that is, the number of holes processed until breakage was examined. The basic specifications of the test tool (specifications other than FIG. 10 (a)) are the same as the drill 10 for deep hole machining in the above embodiment, drill diameter D = 8 mm, groove length L = 160 mm (20D), 2 pieces Blade, thinning start angle β = 70 °. Further, the conventional product has a single margin and does not have the second margin 56.

  As is apparent from the test results of FIG. 10 (c), according to the product of the present invention, it was possible to perform further drilling without breaking even when 200 holes were drilled. On the other hand, the comparative product 2 having a large core thickness W1 of 0.41D was broken at 10 holes due to chip clogging. The comparative product 1 having a small core thickness W2 of 0.28D was broken by about 110 holes, which was about half that of the present invention product, although the number of processed holes was larger than that of the conventional product. From this result, the core thickness W1 is considered to be appropriate within the range of 0.30D to 0.40D.

  Thus, according to the drill 10 for deep hole machining of the present embodiment, the bottom 36 of the gash 34 formed by thinning is rounded with a radius R within a range of 0.03D to 0.05D. Since it is provided, chips generated by the thinning blade 30 are easily curled and chip discharge performance is improved. As a result, wear on the thinning surface (rake surface) 38 is suppressed and the thrust load is reduced. On the other hand, chip clogging occurs even if the core thickness W1 is increased within the range of 0.30D to 0.40D. Is suppressed, breakage strength is increased, and durability is improved.

  Further, at a position that is an intermediate position in the circumferential direction between the pair of lands and the second margin angle α from the leading edge 50 is in the range of 35 ° to 45 °, that is, a position relatively close to the leading edge 50, Since the two margin 56 is provided, the support action by the second margin 56 can be obtained immediately after the start of drilling, the drill posture is stabilized, vibration and the like are suppressed, and excellent machining accuracy (E.g. tilting of machined holes) is obtained and the machining load is stabilized. Since the machining load is stabilized in this way, durability is improved in combination with the increase in break strength as described above, and a tool life that is practically satisfactory can be obtained even in the deep hole machining drill 10 having a long groove length L. Be able to.

  Further, in this embodiment, since the thinning start angle β from the outer end portion of the drill blade 16 to the outer end portion of the ridge line 52 formed when performing the thinning is 65 ° or more, the opening angle of the gash 34 is correspondingly increased. θ is reduced, and the chips are appropriately curled by the roundness of the radius R of the bottom portion 36 of the gash 34. As a result, chips are better discharged and the thrust load is reduced.

  Further, in this embodiment, the gash cutting angle γ, which is an inclination angle at which the bottom portion 36 of the gash 34 is inclined from the direction perpendicular to the axis O to the axis O direction, is in the range of 55 ° to 65 °. While avoiding the fact that the gash cut angle γ is too large and the strength of the drill itself is reduced or the chips are difficult to curl, the chips can be satisfactorily introduced into the chip discharge groove 18 along the inclination. Discharged.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention implements in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

  10: Drill for deep hole machining 16: Drill blade 18: Chip discharge groove 30: Thinning blade 32: Grinding wheel 34: Gash 36: Bottom 40: Gash surface (grind surface) 50: Leading edge 52: Ridge line 54: First Margin (margin) 56: Second margin (second margin) D: Drill diameter O: Center axis L: Groove length R: Bottom round radius α: Second margin angle β: Thinning start angle γ: Gash cut angle ( Inclination angle) W1: Heart thickness

Claims (3)

A plurality of chip discharge grooves provided on the outer peripheral surface at a predetermined twist angle;
A plurality of drill blades provided in a portion where the chip discharge groove is opened at the tip of the tool;
A thinning blade formed by thinning the inner edge of the drill blade near the axis O with a grinding wheel;
A margin provided at an opening edge of the chip discharge groove continuously from the outer end of the drill blade;
In the drill for deep hole drilling, in which the groove length L provided with the chip discharge groove is 10 times or more the drill diameter D,
The bottom portion of the gasche formed at the end of the thinning blade on the axis O side by the thinning is provided with a radius R roundness within a range of 0.03D to 0.05D. ,
A second intermediate position between the plurality of chip discharge grooves in the circumferential direction of the plurality of lands, where the angle α around the axis O from the leading edge is in the range of 35 ° to 45 °, is the second position. Margin is provided in parallel with the chip discharge groove,
A drill for deep hole machining, characterized in that a core thickness W1, which is a web thickness of a tool tip, is within a range of 0.30D to 0.40D. Axial center from the outer end of the drill blade to the outer end of the ridgeline of the grinding surface formed on the opposite side of the thinning blade across the bottom of the gash by being thinned by the grinding wheel The deep hole drill according to claim 1, wherein an angle β around O is 65 ° or more. 3. The deep hole machining according to claim 1, wherein an inclination angle γ at which the bottom portion of the gasche inclines from a direction perpendicular to the axis O toward the axis O is within a range of 55 ° to 65 °. Drill.

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