JP2005186181A - Boring cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boring cutter, preventing the occurrence of a "chattering phenomenon" and enabled reducing cutting resistance. <P>SOLUTION: The respective tips 7A to 7F are disposed so that the cutting blades 17 of the tips 7A to 7F are shifted gradually by predetermined amount each both in the radial direction and in the axial direction of a body 2. The gradual shifting amount (a) of each tip 7A to 7F in the axial direction of the body 2 is set larger than the gradual shifting amount (b) or (c) of each tip 7A to 7F in the radial direction of the body 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in a boring cutter in the form of a so-called multi-blade cutting tool in which a plurality of chips having cutting edges are arranged on the outer periphery of a tip portion of a cutter body.

  As this type of boring cutter, for example, as described in Patent Document 1, there is known one in which about seven cutting edge tips are arranged at the same position in the axial direction and in the radial direction on the outer periphery of the front end of the body. .

The boring cutter described in Patent Document 1 assumes so-called full-blade cutting in which cutting is performed by applying an axial feed while all cutting blades are in contact with a surface to be cut, but is represented by a machining center. With the spread of such multi-degree-of-freedom machine tools, as described in Patent Document 2, in order to perform cutting by so-called single point helical feed, the positions of a plurality of cutting edge tips are positive in the axial direction of the body. Something has been proposed.
Japanese Patent Laid-Open No. 10-146712 (FIG. 1) Japanese Patent Laid-Open No. 11-156616 (FIG. 2)

  According to the conventional boring cutter described in Patent Document 1, the cutting load is large and the “chatter phenomenon” tends to occur as a special feature of the multi-blade cutting tool. In particular, when roughing the bore of a cylinder block (so-called rough boring), since the machining is performed from the casting surface, which is a rough material, the radial direction in which one cutting blade bears during one rotation of the cutter. Since the cutting allowance changes, the above-mentioned “chatter phenomenon” tends to occur. In addition, it is possible to reduce the cutting load by reducing the number of cutting edges, but this is not preferable because the tool life is shortened and the number of times of tool replacement is increased.

  On the other hand, according to the boring cutter described in Patent Document 2, when performing cutting by so-called single point helical feed, the number of simultaneous cutting blades is small and the cutting resistance can be equalized. Although it is possible to improve the accuracy of roundness and shorten the machining time, in the case of the so-called full-blade cutting as described above, the front blade runout is large even though all the cutting edges are cut simultaneously. In addition to the fact that the cutting force of each cutting edge is not equalized, the back force cannot be canceled out, so high-precision drilling cannot be expected, and so-called full-blade cutting can be handled. I could not.

  The present invention has been made paying attention to such problems, and on the premise of boring in the form of so-called full-blade cutting, in particular, there is no occurrence of “chatter phenomenon” and reduction of cutting resistance. It is intended to provide a boring cutter that has been made possible.

  According to the first aspect of the present invention, a plurality of chips having cutting edges are arranged on the outer periphery of the tip of the body, and the hole is machined by applying a feed in the axial direction of the body while rotating the body. Assuming the above-described boring cutter, each tip is arranged so that the cutting edge of each tip is shifted by a predetermined amount in both the radial direction and the axial direction of the body. It is characterized in that the stepwise displacement amount of each chip in the axial direction of the body is set larger than the stepwise displacement amount of the chip.

  Moreover, in order to cancel the back force between the cutting edges, the next chip having a cutting edge that causes a shift of one stage relative to the cutting edge of the specific chip as described in claim 2. Is preferably disposed at a position shifted by about 90 to 180 ° in the circumferential direction of the body with respect to the specific chip.

  Therefore, according to the first aspect of the present invention, the cutting edge of each chip is offset by a predetermined amount in both the radial direction and the axial direction of the body, and the feed amount per blade is larger than the cutting amount. By increasing the diameter, it is possible to realize boring processing with substantially low cutting and high speed feed. However, the so-called work amount per blade obtained by multiplying the cutting amount by the feed amount per blade is basically set to the same level as the conventional one. This is advantageous in reducing the feed shaft load and the spindle load associated with the reduction in specific cutting resistance.

  According to the first aspect of the present invention, boring with a substantially low cutting depth and high speed feed can be realized, so that the cutting resistance and thus the specific cutting resistance is reduced, thereby improving the machining accuracy by preventing the occurrence of “chatter phenomenon”. As a result, the tool life can be extended.

  FIGS. 1 to 3 are views showing a preferred embodiment of a boring cutter according to the present invention, FIG. 1 is a front view thereof, FIG. 2 is an explanatory sectional view thereof, and FIG. 3 is an enlarged view of a main part of FIG. Show.

  As shown in FIGS. 1 and 2, the body 2 of the boring cutter 1 includes a tapered shank portion 3. The tapered shank portion 3 is attached to an arbor (not shown) and is driven to rotate around an axis. A coolant supply passage 5 closed by a set screw 4 is formed in the center of the body 2.

  A plurality of chip pockets 6, 6... Having a substantially triangular shape when viewed from the front are formed in the outer periphery of the front end portion of the body 2, and the tip pockets 6, 6. In this case, throwaway chips (hereinafter simply referred to as chips) 7A to 7F each having a substantially square shape are attached to the mounting seat surface 6a in a so-called vertical position with a set screw 8. And while the chips 7A to 7E are one each, only two chips 7F are arranged at almost symmetrical positions, and the cutting edges 17 of these chips 7A to 7F are the cylindrical outer periphery of the body 2 It faces the surface.

  In addition, although the total number of the chips 7A to 7F in the vertically placed posture in FIG. 1 is seven, separately from this, two types of throw-away chips (hereinafter referred to as the flat type) are disposed on the front end surface (front surface) of the body 2. A pair of 9 and 10 is simply mounted.

  In machining using such a boring cutter 1, for example, all the chips on the outer periphery of the front end of the body 2 are fed by feeding the cutter 1 as a whole to the bore hole of the cylinder block while rotating the entire cutter 1. By engaging 7A-7F into the work surface, all the chips 7A-7F perform internal cutting in the form of so-called full-blade cutting that expands the bore pilot hole while simultaneously cutting, for example, roughing of cylinder bores. Will be done. In this case, as will be described later, the pair of chips 7F and 7F is located on the outermost peripheral side among the total of seven chips 7A to 7F, and performs so-called finish cutting.

  In addition to the chip pockets 6, 6..., Coolant supply ports 11, 12, 13 branched from the coolant supply passage 5 are opened in the chip pockets that receive the chips 9, 10. , 12 and 13, the coolant is discharged while the chips generated with the cutting are blown away forward in the feed direction. Further, the front chips 9 and 10 other than the chips 7A to 7F facing the cylindrical outer peripheral surface of the body 2 are not directly involved in the above-described inner surface cutting.

  Here, paying attention to the arrangement relationship of a total of seven chips 7A to 7F facing the cylindrical outer peripheral surface of the body 2, the chips 7A to 7F are not in the same position in the axial direction and the radial direction of the body 2. The chips 7A to 7F are arranged so that the cutting edges 17 of the chips 7A to 7F cause a stepwise offset (offset) by a predetermined amount in both the axial direction and the radial direction of the body 2. . However, since the two chips 7F and 7F both function as finish cutting chips as described above, these chips 7F and 7F are exceptionally the axial direction and the radial direction of the body 2. Are set to be located at the same position.

  More specifically, as shown in FIG. 3 in addition to FIGS. 1 and 2, a total of seven chips 7A to 7F of six types have the cutting edge 17 of the chip 7A at the most distal side in the axial direction of the body 2 and the chip. The positions of the chips 7A to 7F are shifted by a predetermined amount step by step so that the 7F cutting edge 17 is located at the rearmost end side. At the same time, a total of seven chips 7A to 7F in six types are arranged so that the cutting edge 17 of the chip 7A is the innermost side in the radial direction of the body 2 and the cutting edge 17 of the chip 7F is the outermost side. The positions of the chips 7A to 7F are shifted by a predetermined amount step by step.

  The amount of displacement between the cutting edges 17 and 17 of the chips 7A to 7F adjacent to each other in the axial direction of the body 2, that is, the amount of displacement a for one step is, for example, about 1.6 mm, and is equal to each step. It is set. This means that the axial feed amount per rotation is equivalent to 1.6 mm / rev. That is, as apparent from FIG. 3, if the cutting edge 17 of the chip 7A is located at a position shifted from the tip 9 by the dimension H to the rear side, the cutting edge 17 of the chip 7B is separated from the chip 9 by the dimension H + a. In addition, the cutting edge 17 of the tip 7C is located at the position of the dimension H + 2a from the tip 9, and similarly, the tips 7D to 7F are sequentially located at positions shifted backward by a shift amount a for one step. Will be.

  On the other hand, the amount of displacement between the cutting edges 17 and 17 of the chips 7A to 7F adjacent in the radial direction of the body 2, that is, the amount of displacement b for one step is equal, for example, b = 0.35 mm between the chips 7A to 7E. In addition, the shift amount c for one step is set as large as c = 0.5 mm only between the chips 7E and 7F, and as a result, the cutting edges 17 and 7A of the chips 7F and 7A 17 has a relatively large step of 4b + c (in the above example, 4 × 0.35 mm + 0.5 mm = 1.9 mm) as the amount of deviation.

  That is, if the cutting diameter of the tip 7A is φD, the cutting diameter of the tip 7B is φD + 2b obtained by adding a multiple of the shift amount b for one step to the cutting diameter φD of the tip 7A, and the cutting diameter of the tip 7C is the tip 7B. ΦD + 4b obtained by adding a multiple of the shift amount b for one step to the cutting diameter φD + 2b, and the chips 7D to 7E are successively enlarged by a multiple of the shift amount b for one step. However, since the cutting amount c of the tip 7F is set so that the shift amount c for one step is set as c> b, the cutting diameter of the tip 7F is set to the cutting amount φD + 8b of the tip 7E by the shift amount c of one step. ΦD + 8b + 2c obtained by adding a multiple of.

  In this way, the amount of deviation b or c of the cutting edge 17 is also set stepwise in the radial direction because the cutting margin on one side in the radial direction of the workpiece is about 1.6 mm. This is to prevent an excessive load from being applied to the tip 7A that is initially engaged with the work surface in consideration of the positional accuracy of the hole, misalignment between the boring cutter 1 and the bore pilot hole, and the like. Needless to say, the cutting allowance on one side in the radial direction of the workpiece varies depending on the casting method of the workpiece itself, the diameter of the cylinder bore liner, and the like. That is, the amount of deviation b and c for one step between the cutting edges 17 and 17 in the radial direction of the body 2 has a size that is obtained by dividing the cutting allowance when the body 2 makes one revolution by the total number of steps. It is set as. As is apparent from the above relationship, the stepwise shift amounts a of the chips 7A to 7F in the axial direction of the body 2 are larger than the stepwise shift amounts b and c of the chips 7A to 7F in the radial direction of the body 2. Is set to be larger.

  Further, as is apparent from FIG. 1, as the arrangement of the chips 7A to 7F in the circumferential direction of the body 2, the shift amount a, b or a, c for one step with respect to the cutting edge 17 of any chip. Is set so that the next chip having the cutting edge 17 that will cause a lag is positioned with a phase shift of about 90 to 180 ° in the circumferential direction of the body 2, so that each chip 7 A to 7 F bites into the work surface. Consideration is given so that the back force between the chips 7A to 7F can be almost canceled out over time.

  In other words, each of the chips having the cutting edge 17 that causes one-step deviation a, b or a, c with respect to the cutting edge 17 of any one of the chips faces each other in the diameter direction of the body 2. Although it is ideal to arrange the chips 7A to 7F, the arrangement is as described above because the arrangement is not ideal because of the total number of the chips 7A to 7F. In FIG. 1, the chip 7A and the chip 7B face each other in the diameter direction of the body 2, the chip 7B and the chip 7C are arranged with a phase shift of about 90 to 100 °, and the chip 7C and the chip 7D are disposed on the body 2. The tip 7D and the tip 7E are also substantially opposite in the diameter direction of the body 2, and the tip 7E and the two tips 7F are each about 90 to 100 ° out of phase. It is arranged with.

  Therefore, according to the boring cutter 1 of the present embodiment, as described above, while the entire cutter 1 is rotationally driven with respect to the bore pilot hole of the cylinder block, the feed is given in the axial direction, and the body 2. A so-called full-blade cutting configuration in which all the tips 7A to 7F on the outer periphery of the tip end portion 2 are bitten into the work surface, and the bore pilot hole diameter is expanded while simultaneously performing cutting with all the tips 7A to 7F. Thus, rough machining of the cylinder bore is performed.

  At this time, the stepwise displacement amount a of each of the chips 7A to 7F in the axial direction of the body 2 is larger than the stepwise displacement amount b or c of each of the chips 7A to 7F in the radial direction of the body 2. Therefore, it is possible to perform boring with a low amount of cutting and high speed feed. However, the so-called work amount per blade, which is obtained by multiplying the cutting amount by the feed amount per blade, is set to be equivalent to the conventional one, so that the feed shaft load can be significantly reduced without reducing the work efficiency. As a result of experiments conducted by the present inventor, it has been found that the feed shaft load can be reduced by about 40% compared to the prior art.

  In addition, since the feed per blade is set to a high speed feed as described above, the spindle load is reduced as the cutting resistance and thus the specific cutting resistance is reduced. It has been found that the spindle load can be reduced to an extent. In addition, the reduction in cutting resistance is extremely advantageous in preventing the occurrence of the so-called “chatter phenomenon”.

  In addition, the cutting force of not only the cutting edges 17 of the chips 7F and 7F at the outermost peripheral position but also all of the chips 7A to 7F is reduced in combination with the reduction of the feed force as the cutting resistance is reduced. When the chips 7A to 7F are removed from the workpiece, so-called chipping or flashing at the lower end of the cylinder bore is less likely to occur, and the life of the chips 7A to 7F can be expected to be extended. In other words, according to the present embodiment, since the high-speed feed can be realized, the feed force can be reduced without reducing the feed itself as compared with the conventional case, so that the feed force becomes small. Nevertheless, there is no influence that leads to a reduction in the lifetime of the chips 7A to 7F.

  By the way, in the past, when a chip of a workpiece has occurred, the tool life is shortened as a whole because the chip has been replaced even if the chip itself has no problem. In general, since tool wear is proportional to the abrasion length of the tool, high feed cutting is possible in the present embodiment. The extension can be expected further.

  Here, among the plurality of tips 7A to 7F, the cutting edge 17 bites in order from the cutting edge 17 of the tip 7A on the most distal end side and the innermost peripheral side, so that it is a so-called multi-blade cutting tool. However, the resistance at the time of biting is small, and as described above, the back force can be erased as each chip 7A to 7C bites into the work surface. It is difficult to occur.

  The effect of suppressing the “chatter phenomenon” is set not only to cancel the back component force as described above, but also to (1) the tip located in the front side in the axial direction of the body 2 is set to have a smaller diameter. (2) The shift amount a for one step between the cutting edges 17 and 17 in the axial direction of the body 2 is set to be equal to or larger than the feed amount per rotation of the cutter 1 itself. (3) The amount of displacement b or c for one step between the cutting blades 17 and 17 in the radial direction of the body 2 is substantially equal to the cutting allowance when the body 2 makes one revolution in the total number of steps. It depends on that the size is set.

  This is because when the so-called misalignment occurs between the bore prepared hole which is the work surface and the boring cutter 1, the cutting amount of each of the chips 7A to 7F is between the cutting edges 17 and 17 in the radial direction. Therefore, the cutting resistance of most of the cutting edges 17 does not change during one rotation (however, the cutting of the chips 7A and 7B that hit the work surface at a relatively early time). Since the blade 17 may be cut or not cut during one rotation due to the amount of misalignment, the cutting resistance fluctuates.) As a result, the cutting resistance does not fluctuate, and so-called “chatter phenomenon” occurs. It becomes difficult to do.

  Further, when paying attention to the above-mentioned back force, the back force itself tends to be larger than before, but as described above, each chip 7A to 7F has a specific arrangement. The back force between the chips 7A to 7F can be almost canceled. This is because of the arrangement of the chips 7A to 7F as shown in FIGS. 1 and 3, the cutting allowance in the cutting direction of each of the chips 7A to 7F is uniquely determined by the specifications on the cutter 1 side regardless of the material shape. Is based on that.

The front view which shows embodiment of the boring cutter which concerns on this invention. Sectional explanatory drawing of the boring cutter shown in FIG. The principal part enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Boring cutter 2 ... Body 6 ... Tip pocket 7A-7F ... Throw away tip 17 ... Cutting blade a ... Amount of deviation | shift for one step in axial direction b, c ... Gap amount for one step in radial direction

Claims (6)

In a boring cutter in which a plurality of chips having cutting edges are arranged on the outer periphery of the front end of the body, and hole machining is performed by giving a feed in the axial direction of the body while rotating the body,
Each tip is disposed so that the cutting edge of each tip is shifted stepwise by a predetermined amount in both the radial direction and the axial direction of the body,
A boring cutter characterized in that the stepwise shift amount of each chip in the axial direction of the body is set larger than the stepwise shift amount of each chip in the radial direction of the body.   The next chip having a cutting edge that causes a shift of one stage relative to the cutting edge of the specific chip is arranged at a position shifted by 90 to 180 ° in the circumferential direction of the body with respect to the specific chip. The boring cutter according to claim 1, wherein:   The amount of deviation for one step between the cutting blades in the radial direction of the body is set to have a size that is obtained by dividing the cutting allowance when the body makes one revolution by the total number of steps. 2. A boring cutter according to 2.   The plurality of inserts that cause a stepwise shift between cutting edges in the axial direction of the body are set such that the diameter of the cutting edge circle decreases stepwise toward the tip of the body. The boring cutter according to any one of Items 1 to 3.   The amount of deviation for one step between the cutting edges in the axial direction of the body is set equal to or greater than the axial feed amount per rotation of the body. A boring cutter according to any one of the above.   The boring cutter according to any one of claims 1 to 5, wherein each chip having a cutting edge is a throw-away chip.

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