JP2012171070A - Boring tool - Google Patents

Abstract

Provided is a boring tool capable of improving machining accuracy and suppressing deterioration of machining accuracy due to an external factor.
The rough blades 22, 32, 42 and the rough blades 22, 32, 42 are separated from the rough blades 22, 32, 42 by a predetermined distance in the rearward direction and protrude outward in the radial direction. Finishing blades 23, 33 and 43 determined on the basis of the maximum value of F43, and three chips 20, 30 and 40 are formed, and the rough blades 22, 32 and 42 are formed with respect to the pilot hole W1. In the same posture, they are arranged at equal intervals in the circumferential direction, and are arranged without shifting in the front-rear direction, the length from the processing center C to the radially outer end is the same, and the finishing blade 23. 33 and 43 are arranged in the same posture with respect to the pilot hole W1 at equal intervals in the circumferential direction, and are arranged without being displaced from each other in the traveling direction of the tool body 11, and are radially outward from the machining center C. The length to the end is The same in the stomach.
[Selection] Figure 6

Description

  The present invention relates to a boring tool for machining a prepared hole by entering a prepared hole formed in a work material.

Conventionally, boring is performed on a prepared hole (for example, a cast hole formed by casting or the like) using a boring tool. The boring tool has a tip attached to its tip, and is configured to be rotatable by being mounted on a spindle or the like of a machine tool.
The boring tool enters the pilot hole in a rotated state, and cuts the pilot hole by bringing the tip into contact with the pilot hole. In addition, the pilot hole is cut twice in total with a boring tool corresponding to roughing and a boring tool corresponding to finishing.
In other words, productivity was low because the pilot hole was processed in two steps.

As a boring tool for solving such a problem, a boring cutter (boring tool) disclosed in Patent Document 1 is disclosed.
As shown in FIG. 8A and FIG. 8B, the boring cutter disclosed in Patent Document 1 is shifted to the body (tool body) stepwise by a certain amount in the radial direction and the axial direction of the body. In the state, a plurality of chips are attached. Each tip has a positional relationship such that the tip most attached to the front end side of the body is located on the innermost side in the radial direction of the body, and the tip attached to the rear end side of the body is located on the outermost side in the radial direction of the body. .

In the boring cutter disclosed in Patent Document 1, the tip disposed on the most rear end side of the body functions as a finishing blade (finishing is performed). The maximum value of the machining allowance for such a finishing blade depends on the number of chips, the processing amount of the pilot hole (inner diameter dimension of the pilot hole before and after processing), and the like.
Accordingly, when the prepared amount of the pilot hole is constant, the maximum value of the machining allowance of the finishing blade increases if the number of chips is small. That is, when boring is performed in a state where the machining allowance of the finishing blade is always maximized, the cutting resistance applied to the finishing blade is always maximized (see FIG. 8B). In this case, processing accuracy may be deteriorated.
Further, the cutting balance is deteriorated because the chips are displaced by a predetermined amount in the axial direction of the body. For this reason, processing accuracy will deteriorate.

From the viewpoint of reducing the cutting resistance applied to the finishing blade, as shown in FIGS. 9 (a) and 9 (b), the amount of displacement of the body of each chip in the radial direction is changed, and the maximum machining allowance of the finishing blade is increased. A configuration that reduces the value is conceivable. In such a configuration, a difference occurs in the maximum value of the cutting force applied to each chip (see FIG. 9A).
Therefore, the cutting balance is deteriorated and the processing accuracy is deteriorated.

In the boring process, as shown in FIGS. 10 and 11, the processing amount of the pilot hole may be partially increased (for example, by a certain phase) or decreased.
As such a case, for example, when the machining center (center of rotation of the boring tool) is aligned with the center of the pilot hole, the machining center is displaced from the center of the pilot hole (when the boring tool is misaligned) , See FIG. 10), and there is a case where the prepared hole has uneven thickness (see FIG. 11).
In this case, as shown in FIG. 12, there is a possibility that the boring tool hits against the work piece, and the prepared hole is cut (evenly cut) with the boring tool tilted.

  As described above, in boring, external factors other than the boring tool such as a machine tool and a work material for driving the boring tool are generated, and the machining accuracy may be deteriorated.

  In the boring processing by the boring cutter disclosed in Patent Document 1, when the external factor occurs, in addition to the deterioration of the processing accuracy due to the cutting resistance and the cutting balance applied to the finishing blade, the deterioration of the processing accuracy due to uneven thickness cutting Will be added. In this case, the processing accuracy required for the pilot hole may not be ensured.

JP 2005-186181 A

  The present invention has been made in view of the above situation, and provides a boring tool capable of improving machining accuracy and suppressing deterioration in machining accuracy due to external factors.

  In Claim 1, it is comprised so that rotation is possible, it enters into the pilot hole formed in a work material in the state rotated, and it is a boring tool which performs a boring process with respect to the said pilot hole, Comprising: Three or more chips to be attached are provided, and a first blade part that contacts the pilot hole when the boring tool enters the pilot hole and cuts the pilot hole at the tip of each chip. And spaced apart from the first blade portion by a predetermined distance in the direction opposite to the entry direction, and projecting outward in the radial direction of the boring tool, the projection amount being based on the maximum value of the cutting resistance And when the boring tool enters the pilot hole, a second blade part that contacts the pilot hole and cuts the pilot hole is formed. The boring tool has the same posture with respect to the pilot hole. Are arranged at equal intervals to each other in the direction of travel of the boring tool, and the length from the center of rotation of the boring tool to the radially outer end of the boring tool is mutually The second blade portions are in the same posture with respect to the pilot hole, are arranged at equal intervals in the circumferential direction of the boring tool, and are not displaced from each other in the advancing direction of the boring tool. And the length from the center of rotation of the boring tool to the radially outer end of the boring tool is the same.

  According to a second aspect of the present invention, a contact portion that contacts the inner peripheral surface of the pilot hole is formed on the outer end surface of each chip.

  The present invention can reduce the degree of influence on the machining accuracy due to the cutting resistance applied to the finishing blade and improve the cutting balance, so that the machining accuracy can be improved and the deterioration of the machining accuracy due to external factors can be suppressed. Play.

The figure which shows the structure of a boring tool. (A) Front view. (B) AA sectional view in Drawing 1 (a). Explanatory drawing which shows a chip | tip. Explanatory drawing which shows a contact surface. The figure which shows the positional relationship of a chip | tip. (A) Front view. (B) AA sectional view in Drawing 4 (a). The figure which shows the state in which a rough blade cuts a workpiece. (A) Front view. (B) AA partial expanded sectional view in Drawing 5 (a). The figure which shows the state in which a rough blade and a finishing blade cut a workpiece. (A) Front view. (B) AA partial expanded sectional view in Drawing 6 (a). Sectional drawing which shows the shape of a chip | tip when there is a restriction | limiting in a product shape. (A) A diagram showing a two-stage chip. (B) A diagram showing a three-stage chip. The figure which shows the conventional boring tool in which the space | interval of the radial direction of each chip | tip is not the same. (A) Front view. (B) Explanatory drawing. The figure which shows the boring tool with which the space | interval of the radial direction of the conventional each chip | tip is the same. (A) Front view. (B) Explanatory drawing. Sectional drawing which shows the state in which the boring tool was misaligned. Sectional drawing which shows the work material which has uneven thickness in a pilot hole. Sectional drawing which shows uneven thickness cutting.

  Below, the boring tool 10 of this embodiment is demonstrated with reference to drawings.

As shown in FIG. 1A and FIG. 1B, the boring tool 10 is provided in a pilot hole W1 formed in the work material W (in this embodiment, a cast hole of an HV case manufactured by casting). On the other hand, boring is performed.
The boring tool 10 is configured to be rotatable by mounting a substantially cylindrical tool body 11 on a rotatable main shaft (for example, a main shaft of a machine tool).

  The boring tool 10 is configured to be close to and away from the work material W by a predetermined moving mechanism that moves the spindle, and the machining center C (the rotation center of the tool body 11) is set to the center C1 of the pilot hole. Configured to allow alignment. The boring tool 10 includes three chips 20, 30, and 40.

  In the following, for convenience of explanation, the “front-back direction of the boring tool 10” is defined with the direction in which the boring tool 10 approaches the workpiece W (the left direction in FIG. 1B) as the front direction.

  Each of the chips 20, 30, and 40 is attached to the front end portion (tip portion) of the tool main body 11 through a bolt that is screwed into the bolt holes 25, 35, and 45, and is integrated with the rotation of the tool main body 11. Rotate.

  The chips 20, 30 and 40 all have the same shape. Therefore, the description of the shape of each of the chips 20, 30, and 40 will be given only for the chip 20.

  As shown in FIG. 2, the chip 20 is a substantially triangular member when viewed from the thickness direction. Projections 21, 21, and 21 are formed at the apex portion of the chip 20.

  In addition, each protrusion part 21,21,21 is the same shape altogether. Therefore, description of the shape of each protrusion 21, 21, 21 will be made only for the protrusion 21 (the lower right protrusion 21 in FIG. 2) formed between the front side 20a of the chip and the outer side 20b of the chip. .

The protruding portion 21 is bent toward the one end side of the chip 20 after being bent rearward from one end portion (the right end portion in FIG. 2) of the front side 20a of the chip, and then obliquely rearward (in FIG. 2). It has a staircase shape that bends further toward the left rearward direction.
A rough blade 22, a finishing blade 23, and a contact surface 24 are formed on the protruding portion 21.

The rough blade 22 as the first blade portion is a blade formed at one end of the front side 20a of the chip.
When the rotating tool body 11 enters the pilot hole W1, the rough blade 22 contacts the pilot hole W1 and cuts the pilot hole W1.

Length dimension R22 (FIGS. 1A and 4A) from the processing center C to the outer edge of the rough blade 22 in the radial direction of the tool body 11 (hereinafter simply referred to as “radial direction”). )) Is slightly smaller than the inner diameter of the pilot hole W1 after machining by the boring tool 10 (dimension from the center C1 of the pilot hole to the inner peripheral surface).
The boring tool 10 performs rough machining on the prepared hole W1 by cutting the prepared hole W1 with the rough blade 22.

The finishing blade 23 as the second blade portion is a blade formed at a portion bent toward the one end side of the chip 20 after being bent rearward from one end portion of the rough blade 22.
That is, the finishing blade 23 is spaced apart from the rough blade 22 by a predetermined distance in the rearward direction and protrudes radially outward. When the rotating tool body 11 enters the prepared hole W1, the finishing blade 23 comes into contact with the prepared hole W1 and cuts the prepared hole W1.

The length dimension R23 (see FIGS. 1A and 4A) from the machining center C to the radially outer end of the finishing blade 23 is the inner diameter dimension of the pilot hole W1 after machining by the boring tool 10. It becomes almost the same.
The boring tool 10 performs the finishing process on the prepared hole W1 by cutting the prepared hole W1 with the finishing blade 23.

  That is, the tip 20 has a projecting portion 21 having a stepped shape, so that a blade for cutting the prepared hole W1 is divided into a rough blade 22 and a finishing blade 23, and roughing and finishing are performed on the prepared hole W1. Are integrated (see FIG. 6B).

As shown in FIG. 3, the contact surface 24 is a surface extending from one end portion (right end portion in FIG. 3) of the finishing blade 23 toward the outer side 20 b of the chip in an oblique rearward direction (left oblique rearward direction in FIG. 3). is there.
An angle α1 formed by the front-rear direction (vertical direction in FIG. 3) and the contact surface 24 is smaller than an angle α2 formed by the front-rear direction and the outer side 20b of the chip.

  As shown in FIG. 2, the protrusions 21, 21, 21 are in a positional relationship such that their phases are shifted from each other at equal intervals in the circumferential direction with respect to the center of the bolt hole 25.

A rough blade 22 and a finishing blade 23 of the protrusion 21 (upper protrusion 21 in FIG. 2) formed between the outer side 20b of the chip and the inner side 20c of the chip, and the front side 20a of the chip and the inner side 20c of the chip The rough blade 22 and the finishing blade 23 of the protruding portion 21 (the protruding portion 21 on the lower left side in FIG. 2) formed therebetween do not cut the prepared hole W1.
That is, in FIG. 2, the rough blades 22 and 22 and the finishing blades 23 and 23 formed on the upper and lower left protrusions 21 and 21 are a spare rough blade and a spare finishing blade, respectively.

  When the roughing blade 22 and the finishing blade 23 (that is, the lower right roughing blade 22 and the finishing blade 23 in FIG. 2) are worn, the tip 20 is centered on the center (center of the bolt hole 25). Rotate. Then, the boring tool 10 can easily cope with the wear of the rough blade 22 and the finishing blade 23 by moving the spare rough blade and the spare finishing blade to the positions for cutting.

  As shown in FIGS. 1A and 1B, the tip 20 is attached to the front end portion of the tool main body 11, and the front side 20 a projects forward from the front end portion of the tool main body 11.

  Such chips 20, 30 and 40 have the following positional relationship.

  That is, as shown in FIG. 4A, the chips 20, 30, and 40 are arranged at equal intervals in the circumferential direction of the tool body 11 (hereinafter simply referred to as “circumferential direction”). That is, the respective chips 20, 30 and 40 are in a positional relationship such that their phases are shifted from each other at equal intervals in the circumferential direction with respect to the processing center C (the angles β1, β2,. β3).

Accordingly, the rough blades 22, 32 and 42 are arranged at equal intervals in the circumferential direction (see FIG. 1A).
The finishing blades 23, 33 and 43 are arranged at equal intervals in the circumferential direction (see FIG. 1A).

  Each of the chips 20, 30, 40 has the same length from the processing center C to the radially outer end.

Accordingly, each of the rough blades 22, 32, and 42 has the same length from the processing center C to the radially outer end (see length dimensions R22, R32, and R42 shown in FIG. 4A).
Further, the finishing blades 23, 33, and 43 have the same length from the machining center C to the radially outer end (see length dimensions R23, R33, and R43 shown in FIG. 4A).

  The front sides 20a, 30a, 40a of the chips 20, 30, 40 are parallel to the radial direction. Further, as shown in FIG. 4B, the front sides 20a, 30a, and 40a of the chips are arranged without being displaced from each other in the front-rear direction (see line L1 shown in FIG. 4B).

Accordingly, the rough blades 22, 32, and 42 are arranged in the same posture with respect to the pilot hole W1 without being displaced from each other in the front-rear direction (see line L1 shown in FIG. 6B).
Further, the finishing blades 23, 33, and 43 are arranged in the same posture with respect to the pilot hole W1 without being displaced from each other in the front-rear direction (see the line L2 shown in FIG. 6B).

  Below, the boring process performed with the boring tool 10 is demonstrated.

As shown in FIG. 1B, the boring tool 10 approaches the work material W by a moving mechanism that moves the spindle. And the tool main body 11 starts rotation by rotation of a main axis | shaft.
Thereafter, as shown in FIGS. 5A and 5B, the tool body 11 enters the pilot hole W1 in a rotated state.

  In FIG. 1B, FIG. 5B, and FIG. 6B, no external factor is generated, and the machining amount of the pilot hole W1 (the inner diameter dimension of the pilot hole W1 before and after machining) is a part. The state of the boring tool 10 and the work material W when it does not increase or decrease automatically (by a certain phase) is shown.

  As such an external factor, when the machining center C is aligned with the center C1 of the pilot hole, the machining center C is deviated from the center C1 of the pilot hole (when the boring tool 10 is misaligned, FIG. 10), or when the pilot hole W1 is uneven (see FIG. 11).

  When the tool body 11 enters the prepared hole W1, first, each of the rough blades 22, 32, and 42 comes into contact with the prepared hole W1, and cutting of the prepared hole W1 is started. That is, the boring tool 10 starts roughing.

  As described above, the rough blades 22, 32, and 42 are arranged at equal intervals in the circumferential direction, and the length dimensions R22, R32, and R42 from the processing center C to the radially outer end are the same as each other. (See FIG. 4A). Moreover, each rough blade 22,32,42 is mutually the same attitude | position with respect to the pilot hole W1, as mentioned above.

  For this reason, if no external factor is generated (that is, the boring tool 10 is not misaligned and the pilot hole W1 is not uneven), the machining allowance of each rough blade 22, 32, 42 is always the same. It becomes. In this case, the cutting resistances F22, F32, and F42 applied to the rough blades 22, 32, and 42 are the same.

In such a case, the cutting resistances F22, F32, and F42 act to cancel each other with the same size. Therefore, the boring tool 10 can maintain a good cutting balance when cutting with the rough blades 22, 32, and 42.
Thereby, the boring tool 10 can improve the cutting balance.

  Further, if the external factor occurs (that is, when the boring tool 10 is misaligned or the prepared hole W1 is uneven), the machining amount of the prepared hole W1 is partially increased or decreased.

In this case, for example, when the rough blade 22 cuts a portion where the machining amount is partially increased, the cutting resistance F22 temporarily increases. That is, the cutting resistance F22 is temporarily larger than the other cutting resistances F32 and F42.
Further, when the rough blade 22 cuts a portion where the machining amount is partially reduced, the cutting resistance F22 is temporarily smaller than the other cutting resistances F32 and F42.

In such a case, a boring tool having two tips arranged at equal intervals in the circumferential direction acts so that the cutting forces applied to the two tips cancel each other, but a temporary occurrence occurs between the cutting forces. Such a difference depends on the degree of increase / decrease in the machining amount of the pilot hole W1.
Therefore, when the increase / decrease degree of the machining amount of the pilot hole W1 is large, a temporary difference generated between the respective cutting resistances is increased, and the cutting balance is deteriorated.

On the other hand, in the boring tool 10 including the three chips 20, 30, 40 arranged at equal intervals in the circumferential direction as in the present embodiment, the three cutting resistances F22, F32, F42 act so as to cancel each other. .
In this case, the temporary difference which arises between each cutting resistance F22 * F32 * F42 becomes smaller than the thing according to the increase / decrease degree of the processing amount of the said pilot hole W1.

  Thus, the boring tool 10 can suppress the deterioration of the cutting balance even when the external factor occurs.

  From the above, it is preferable that the number of chips attached to the tool body 11 is three or more. That is, it is preferable that the boring tool 10 has a configuration including three or more chips 20, 30, and 40.

  As shown in FIGS. 6 (a) and 6 (b), after each rough blade 22, 32, 42 comes into contact with the pilot hole W1, the boring tool 10 further enters the pilot hole W1 to finish each finish. The blades 23, 33, and 43 come into contact with the pilot hole W1, and cutting of the pilot hole W1 is started. That is, the boring tool 10 starts finishing.

  As described above, the finishing blades 23, 33, and 43 are arranged at equal intervals in the circumferential direction, and the lengths R23, R33, and R43 from the processing center C to the radially outer end are the same as each other. (See FIG. 4A). Further, as described above, the finishing blades 23, 33, and 43 are in the same posture with respect to the pilot hole W1.

  Therefore, if the external factor is not generated, the cutting resistances F23, F33, and F43 applied to the finishing blades 23, 33, and 43 are the same.

  Therefore, the boring tool 10 can maintain a good cutting balance at the time of cutting by the finishing blades 23, 33, and 43, as in the case of the rough blades 22, 32, and 42. That is, the cutting balance can be improved.

  Further, if the external factor occurs, there is a temporary difference between the cutting forces F23, F33, and F43. However, as in the case of the rough blades 22, 32, and 42, three cutting resistances are used. F23, F33, and F43 act so as to cancel each other.

As described above, in the boring tool 10 of the present embodiment, even when the external factor occurs, the temporary difference generated between the cutting resistances F22, F32, and F42 and the cutting resistances F23, F33, and F43 is eliminated. Since it can be made smaller, deterioration of the cutting balance can be suppressed.
Thereby, the boring tool 10 can suppress the deterioration of the machining accuracy due to the external factor.

  Here, the machining allowance of each finishing blade 23, 33, 43 (the amount by which the finishing blade 23 cuts the pilot hole W1) is the portion cut by each rough blade 22, 32, 42 as shown in FIG. 6B. It becomes the maximum when each finishing blade 23, 33, 43 cuts.

  If the maximum values of the respective cutting resistances F23, F33, and F43 are large, the processing accuracy of the prepared hole W1 may be deteriorated.

  For this reason, in this embodiment, the machining allowances of the finishing blades 23, 33, and 43 are set so that the maximum values of the cutting forces F23, F33, and F43 do not affect the machining accuracy required for the pilot hole W1. The maximum value is set.

  That is, the finishing blades 23, 33 and 43 are projected to the rough blades 22, 32 and 42 according to the processing accuracy required for the pilot hole W1 (length dimensions R22, R32, and the like shown in FIG. 4A). The difference between R42 and the length dimensions R23, R33, and R43) is set as appropriate.

  Thus, the amount of projection of each finishing blade 23, 33, 43 outward in the radial direction with respect to each rough blade 22, 32, 42 is determined based on the maximum value of the cutting resistances F23, F33, F43.

Therefore, even when boring is performed in a state where the cutting forces F23, F33, and F43 are always maximized, the degree of influence on the machining accuracy that the cutting forces F23, F33, and F43 have is reduced.
Thereby, the boring tool 10 can suppress the deterioration of the processing accuracy by each cutting resistance F23 * F33 * F43. That is, the processing accuracy can be improved.

  As described above, the rough blades 22, 32, and 42 and the finishing blades 23, 33, and 43 are arranged without being displaced from each other in the front-rear direction (see lines L1 and L2 shown in FIG. 6B).

For this reason, when the contact part with each rough blade 22,32,42 and each finishing blade 23,33,43 of the pilot hole W1 is flat, each rough blade 22,32,42 and each finishing blade 23,33. 43 is simultaneously in contact with the pilot hole W1.
Accordingly, the cutting forces F22, F32, and F42 are generated simultaneously. Further, the cutting resistances F23, F33, and F43 are also generated at the same time.

  In other words, the boring tool 10 of the present embodiment has the cutting resistances F22, F32, F42 and the cutting resistances only depending on the shape of the contact portion of the pilot hole W1 with the chips 20, 30, 40, which is an external factor. Differences occur in the generation timings of F23, F33, and F43.

  According to this, the difference of the generation timing of each cutting resistance F22 * F32 * F42 and each cutting resistance F23 * F33 * F43 can be made smaller. That is, the boring tool 10 can suppress the deterioration of the cutting balance due to the occurrence of the external factor.

  Further, the cutting forces F22, F32, and F42 and the cutting forces F23, F33, and F43 are generated in a state in which there is no deviation in the front-rear direction, and thus act to more reliably cancel each other. For this reason, the boring tool 10 can further improve the cutting balance.

As described above, the boring tool 10 can reduce the degree of influence on the machining accuracy by the cutting resistances F23, F33, and F43 applied to the finishing blades 23, 33, and 43, and can improve the cutting balance, thereby improving the machining accuracy. .
Even when the external factor occurs, the temporary difference between the cutting resistances F22, F32, and F42 and the cutting resistances F23, F33, and F43 can be further reduced. Deterioration of accuracy can be suppressed.

Therefore, the boring tool 10 can suppress the deterioration of the cutting balance to the minimum even when the external factor occurs. That is, deterioration of processing accuracy can be minimized.
Therefore, even when the external factor occurs, the machining accuracy required for the pilot hole W1 can be ensured.

  During boring, the inner peripheral surface of the pilot hole W1 comes into contact with the outer ends of the contact surfaces 24, 34, and 44. As described above, the angle α1 formed by the front-rear direction and the contact surfaces 24, 34, 44 is smaller than the angle α2 formed by the front-rear direction and the outer sides 20b, 30b, 40b of the chips (see FIG. 3).

  According to this, each chip 20, 30, 40 has a larger contact area between the inner peripheral surface of the pilot hole W1 and each contact surface 24, 34, 44. Therefore, scratches are less likely to occur on the inner peripheral surface of the pilot hole W1. That is, the boring tool 10 can improve processing accuracy.

  As described above, the contact surfaces 24, 34, and 44 that are in contact with the inner peripheral surface of the pilot hole W1 are formed on the end surfaces of the outer sides 20b, 30b, and 40b of the respective chips.

In addition, when performing a boring process to a blind hole (hole which does not penetrate the workpiece W) and a through hole partially (to the middle part of the through hole), the front end W2 (see FIG. 7 (a)) reflects the shapes of the rough blades 22, 32 and 42 and the finishing blades 23, 33 and 43.
That is, the cross-sectional shape along the front-rear direction of the front end W2 of the processed part is a step shape corresponding to the shape of the protrusions 21, 31, 41.

  For this reason, when there is a restriction on the product shape of the pilot hole W1, it is necessary to consider the cross-sectional shape along the front-rear direction of the front end W2 of the processed part.

As such a case, as shown in FIG. 7A, there is a case where a bearing W10 is fitted to the front end W2 of the processed part.
In this case, the cross-sectional shape along the front-rear direction of the front end W2 of the processed part needs to be formed into a shape that does not interfere with the bearing W10.

In the boring tool 10 of this embodiment, the length dimension M1 in the front-rear direction between each rough blade 22, 32, 42 and each finishing blade 23, 33, 43, and each rough of each finishing blade 23, 33, 43. The protrusion dimension M2 with respect to the blades 22, 32, and 42 is set to an appropriate length dimension.
Thereby, the boring tool 10 can shape | mold the front end part W2 of the processed part in the shape which does not interfere with the bearing W10.

  Moreover, you may set arbitrarily the number of the level | step differences (number of blades) formed in each chip | tip 20,30,40. That is, it may have a three-stage shape as shown in FIG. 7B, or may have four or more stages.

  In the case of a three-stage shape as shown in FIG. 7 (b), the blades formed between the rough blades 22, 32 and 42 and the finishing blades 23, 33 and 43 are the intermediate finishing blades 26 and 36, respectively.・ It functions as 46.

In such a configuration, when the product shape of the pilot hole W1 is restricted, the cross-sectional shape along the front-rear direction of the front end portion W2 of the processed portion is considered.
That is, the longitudinal dimension M3 between each rough blade 22, 32, 42 and each intermediate finishing blade 26, 36, 46, and each rough blade 22, 32, 42 of each intermediate finishing blade 26, 36, 46. Projecting dimension M4, longitudinal dimension M5 between each finishing blade 26, 36, 46 and each finishing blade 23, 33, 43, and each finishing blade 26 of each finishing blade 23, 33, 43 -The protrusion dimension M6 with respect to 36 and 46 may be set to an appropriate length dimension.

10 Boring tools 20, 30, 40 Inserts 22, 32, 42 Rough blade (first blade)
23, 33, 43 Finishing blade (second blade)
F23 / F33 / F43 Cutting resistance W Work material W1 Pilot hole

Claims (2)

A boring tool configured to be rotatable, entering a prepared hole formed in a work material in a rotated state, and performing boring processing on the prepared hole,
Comprising three or more chips attached to the tip,
At the tip of each chip,
A first blade portion that contacts the pilot hole when the boring tool enters the pilot hole and cuts the pilot hole;
The first blade portion is spaced apart by a predetermined distance in a direction opposite to the entry direction and protrudes radially outward of the boring tool, and the protrusion amount is determined based on the maximum value of the cutting resistance. And when the boring tool enters the pilot hole, a second blade part that contacts the pilot hole and cuts the pilot hole;
Formed,
Each of the first blade portions is
In the same posture with respect to the pilot hole, arranged at equal intervals in the circumferential direction of the boring tool, arranged without shifting from each other in the advancing direction of the boring tool, from the rotation center of the boring tool, The length to the radially outer end of the boring tool is the same as each other,
Each of the second blade portions is
In the same posture with respect to the pilot hole, arranged at equal intervals in the circumferential direction of the boring tool, arranged without shifting from each other in the advancing direction of the boring tool, from the rotation center of the boring tool, The lengths to the radially outer ends of the boring tools are the same as each other.
Boring tool. On the outer end face of each chip,
A contact portion is formed in contact with the inner peripheral surface of the pilot hole.
The boring tool according to claim 1.

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