Patent Description:
For example, <CIT> (Patent Document <NUM>) discloses a drill having a main body portion to and from which an insert is attachable and detachable. An insertion hole is provided in the main body portion of the drill and a clamp screw is disposed in the insertion hole. By fastening the clamp screw, the clamp screw is brought into abutment with a shank portion of the insert, whereby the insert is fixed to the main body portion.

Moreover, a holder of a drill described in <CIT> (Patent Document <NUM>) is provided with: a shank hole into which an insert is insertable; and a bolt hole communicating with the shank hole. The bolt hole extends in a direction inclined relative to the extending direction of the shank hole. A fastening bolt is disposed in the bolt hole and is brought into abutment with an inclined groove of the insert, whereby the insert is fixed to the holder.

Further, <CIT> (Patent Document <NUM>) discloses a rotary tool including: a base provided with a center hole; a loose top having a pin; and a radial screw. The pin of the loose top is inserted into the center hole. The loose top is locked in the axial direction by the radial screw.

Furthermore, <CIT> (Patent Document <NUM>) discloses a drill including: a cutting tip having a shaft foot; a holder provided with a shaft receiving hole and a through hole; and a fixing member. The shaft foot of the cutting tip is inserted in the shaft receiving hole of the holder. The fixing member is inserted in the through hole and is in contact with the shaft foot. <CIT> relates to a rotatable tool for chip removing machining as well as a cutting insert and a basic body therefor. <CIT> relates to a drill and method for manufacturing cut product using same.

A cutting tool according to the present invention is according to claim <NUM>.

In the case of a drill, the head of the drill is fixed to a holder such that the center of the head of the drill coincides with the center of the holder, unlike a case of fixing a general insert for milling or turning using a screw. Further, the drill requires a structure for receiving, by a side surface of the head and a wall portion of the body, cutting force applied in the rotation direction and for bringing the head into close contact with the holder side.

In the drill described in <CIT> (Patent Document <NUM>), when fastening the clamp screw, force in the rotation direction and a drawing direction is applied to the head. Since the clamp screw is in contact with the head only at one point, sufficient clamping force is not obtained, with the result that the head cannot be firmly fixed to the holder.

In the drill described in <CIT> (Patent Document <NUM>), in order to facilitate removal of the head, there is a space between the shank portion of the head and the hole of the holder engaged with the shank portion. Hence, the head can be moved and therefore cannot be precisely fixed to the holder. As a result, the head may be moved during machining, with the result that sufficient performance may not be obtained.

One embodiment of the present invention has been made to solve the problem with regard to clamping of the head of such a drill or the like, and has an object to provide a cutting tool in which a head can be fixed to a holder firmly and precisely.

According to one embodiment of the present invention, there can be provided a cutting tool in which a head can be fixed to a holder firmly and precisely.

First, summary of the present invention will be described.

The following describes an embodiment of the present invention and reference examples with reference to figures. It should be noted that in the below-mentioned figures, the same or corresponding portions are given the same reference characters and are not described repeatedly.

First, the following describes a configuration of a cutting tool <NUM> according to a first embodiment.

As shown in <FIG> and <FIG>, cutting tool <NUM> according to the present embodiment is, for example, an indexable drill, and mainly includes a holder <NUM>, a head <NUM>, and a fastening portion <NUM>. As shown in <FIG>, a first hole H1 and a second hole H2 are provided in holder <NUM>. Second hole H2 extends along a direction parallel to an axis line DA. First hole H1 extends in a direction inclined relative to a direction perpendicular to axis line DA. First hole H1 communicates with second hole H2. Head <NUM> includes a cutting edge portion <NUM> and a shank portion <NUM> configured to hold cutting edge portion <NUM>. Shank portion <NUM> of head <NUM> is disposed inside second hole H2. Holder <NUM> has a first surface <NUM> and a second surface <NUM> provided to be separated from each other to sandwich axis line DA. Cutting edge portion <NUM> of head <NUM> is located between first surface <NUM> and second surface <NUM>. Fastening portion <NUM> is disposed inside first hole H1.

Fastening portion <NUM> fixes head <NUM> to holder <NUM>. At an outer circumferential surface of fastening portion <NUM>, an external screw portion is formed, for example. On the other hand, at a surface defining first hole H1, an internal thread portion that can be engaged with the external screw portion is formed, for example. Fastening portion <NUM> is a clamp screw, for example. Fastening portion <NUM> is rotated using, for example, a driver in a fastening direction, thereby moving fastening portion <NUM> in first hole H1 in the direction toward second hole H2. By pressing the bottom surface of fastening portion <NUM> against a flat surface portion <NUM> provided at shank portion <NUM> of head <NUM>, head <NUM> is fixed to holder <NUM>. As shown in <FIG>, head <NUM> has a tip <NUM> located forwardly of a first tip surface <NUM> of holder <NUM> in a direction parallel to axis line DA. It should be noted that axis line DA represents a rotation axis of the cutting tool when cutting a workpiece.

It should be noted that cutting tool <NUM> is not limited to the drill as long as cutting tool <NUM> is a rotary cutting tool capable of cutting a workpiece while rotating around axis line DA. Cutting tool <NUM> may be an indexable end mill, for example.

Next, the following describes details of a configuration of holder <NUM> according to the first embodiment.

As shown in <FIG>, holder <NUM> mainly includes first surface <NUM>, second surface <NUM>, first tip surface <NUM>, a second tip surface <NUM>, a first inclined surface <NUM>, a second inclined surface <NUM>, a bottom surface <NUM>, a first flute surface <NUM>, a second flute surface <NUM>, a first side surface <NUM>, a second side surface <NUM>, a holding portion <NUM>, a flat portion <NUM>, and a rear end surface <NUM>. As shown in <FIG>, first side surface <NUM> is continuous to both first flute surface <NUM> and second flute surface <NUM>. In other words, first side surface <NUM> is located between first flute surface <NUM> and second flute surface <NUM> to connect first flute surface <NUM> and second flute surface <NUM>. Similarly, second side surface <NUM> is continuous to both first flute surface <NUM> and second flute surface <NUM>. In other words, second side surface <NUM> is located between first flute surface <NUM> and second flute surface <NUM> to connect first flute surface <NUM> and second flute surface <NUM>. In the direction parallel to axis line DA, first tip surface <NUM> and second tip surface <NUM> are located at one side of holder <NUM> and rear end surface <NUM> is located at the other side of holder <NUM>. Holding portion <NUM> is a portion to be engaged with a spindle of a machine tool.

As shown in <FIG> and <FIG>, first tip surface <NUM> is continuous to first surface <NUM>. First inclined surface <NUM> is continuous to both first tip surface <NUM> and first surface <NUM>. First inclined surface <NUM> is inclined relative to both first tip surface <NUM> and first surface <NUM>. First inclined surface <NUM> is continuous to first flute surface <NUM>. Similarly, second tip surface <NUM> is continuous to second surface <NUM>. Second inclined surface <NUM> is continuous to both second tip surface <NUM> and second surface <NUM>. Second inclined surface <NUM> is inclined relative to both second tip surface <NUM> and second surface <NUM>. Second inclined surface <NUM> is continuous to second flute surface <NUM>.

As shown in <FIG> and <FIG>, first tip surface <NUM> is substantially parallel to second tip surface <NUM>. First tip surface <NUM> and second tip surface <NUM> are flat surfaces substantially perpendicular to axis line DA. As shown in <FIG>, first tip surface <NUM> is a surface substantially perpendicular to first surface <NUM>. Similarly, second tip surface <NUM> is a surface substantially perpendicular to second surface <NUM>. When viewed from axis line DA, second side surface <NUM> is located opposite to first side surface <NUM>. First flute surface <NUM> helically extends around axis line DA. Similarly, second flute surface <NUM> helically extends around axis line DA with second flute surface <NUM> being separated from first flute surface <NUM>. When viewed from axis line DA, each of first side surface <NUM> and second side surface <NUM> is a curved surface protruding outwardly. On the other hand, when viewed from axis line DA, each of first flute surface <NUM> and second flute surface <NUM> is a curved surface protruding inwardly. First side surface <NUM> is continuous to first inclined surface <NUM>. Similarly, second side surface <NUM> is continuous to first inclined surface <NUM>.

As shown in <FIG> and <FIG>, first hole H1 is provided in first side surface <NUM> of holder <NUM>. As shown in <FIG>, first hole H1 extends in a first direction D1 inclined by a first angle θ1 in the direction toward cutting edge portion <NUM> (see <FIG>) relative to a direction DR perpendicular to axis line DA. In other words, first direction D1 is inclined by first angle θ1 toward first tip surface <NUM> relative to direction DR perpendicular to axis line DA. First angle θ1 is, for example, more than or equal to <NUM>°, and is preferably more than or equal to <NUM>°. First angle θ1 may be, for example, less than or equal to <NUM>°. First angle θ1 may be more than or equal to <NUM>° and less than or equal to <NUM>°. First direction D1 is also inclined relative to axis line DA. A recess <NUM> may be provided in first side surface <NUM> and first hole H1 may be provided in a bottom portion of recess <NUM>.

As shown in <FIG>, when viewed in the direction parallel to axis line DA, first hole H1 extends in a third direction D3 inclined by a second angle θ2 relative to a second direction D2 extending from second surface <NUM> toward first surface <NUM>. In other words, when viewed in the direction parallel to axis line DA, third direction D3 is inclined by second angle θ2 toward first tip surface <NUM> relative to second direction D2. Preferably, second angle θ2 is more than or equal to <NUM>° and less than or equal to <NUM>°. Second angle θ2 may be more than or equal to <NUM>°. Second angle θ2 may be less than or equal to <NUM>° or may be less than or equal to <NUM>°. When viewed in the direction parallel to axis line DA, first hole H1 is located between first flute surface <NUM> and second flute surface <NUM>.

Next, the following describes details of a configuration of head <NUM> according to the first embodiment.

As shown in <FIG>, head <NUM> includes cutting edge portion <NUM> and shank portion <NUM> configured to hold cutting edge portion <NUM>. As shown in <FIG>, cutting edge portion <NUM> of head <NUM> mainly includes a third surface <NUM>, a fourth surface <NUM>, a first tip surface <NUM>, a second tip surface <NUM>, a third tip surface <NUM>, a fourth tip surface <NUM>, a fifth tip surface <NUM>, a sixth tip surface <NUM>, tip <NUM>, a seating surface <NUM>, a first rake face <NUM>, and a second rake face <NUM>. A ridgeline between first rake face <NUM> and third tip surface <NUM> defines a first cutting edge 27a. Similarly, a ridgeline between second rake face <NUM> and second tip surface <NUM> defines a second cutting edge 27b.

Shank portion <NUM> of head <NUM> mainly has flat surface portion <NUM>, a curved surface portion <NUM>, and a rear end portion <NUM>. Shank portion <NUM> is in contact with cutting edge portion <NUM> at seating surface <NUM>. A cross sectional shape of shank portion <NUM> at seating surface <NUM> is circular, for example. Shank portion <NUM> extends in the direction of axis line DA of head <NUM>. Axis line DA represents the rotation axis of head <NUM>. As shown in <FIG>, when viewed in the direction parallel to flat surface portion <NUM> and perpendicular to axis line DA, flat surface portion <NUM> is inclined by an angle φ relative to axis line DA. Angle φ is substantially the same as first angle θ1. Angle φ is, for example, more than or equal to <NUM>°, and is preferably more than or equal to <NUM>°. Angle φ may be less than or equal to <NUM>°, for example. Angle φ may be more than or equal to <NUM>° and less than or equal to <NUM>°. When head <NUM> is attached to holder <NUM>, flat surface portion <NUM> faces first hole H1 provided in holder <NUM>.

As shown in <FIG>, third surface <NUM> and fourth surface <NUM> are separated from each other to sandwich axis line DA. Third surface <NUM> and fourth surface <NUM> face each other. Third surface <NUM> is substantially parallel to fourth surface <NUM>. As shown in <FIG>, third surface <NUM> is continuous to first tip surface <NUM>, fifth tip surface <NUM>, and first rake face <NUM>. Similarly, fourth surface <NUM> is continuous to fourth tip surface <NUM>, sixth tip surface <NUM>, and second rake face <NUM>. Second tip surface <NUM> is separated from both third surface <NUM> and fourth surface <NUM>. Similarly, third tip surface <NUM> is separated from both third surface <NUM> and fourth surface <NUM>. First tip surface <NUM> extends in a direction crossing both third surface <NUM> and fifth tip surface <NUM>. Similarly, fourth tip surface <NUM> extends in a direction crossing both fourth surface <NUM> and sixth tip surface <NUM>.

Next, the following describes a method of attaching head <NUM> to holder <NUM>.

As shown in <FIG> and <FIG>, shank portion <NUM> of head <NUM> is inserted into second hole H2 of holder <NUM>. Seating surface <NUM> of head <NUM> is in contact with bottom surface <NUM> of holder <NUM>. As shown in <FIG>, third surface <NUM> of head <NUM> faces first surface <NUM> of holder <NUM>. Fourth surface <NUM> of the head faces second surface <NUM> of holder <NUM>. Cutting edge portion <NUM> of head <NUM> is disposed in a space between first surface <NUM> and second surface <NUM>.

As shown in <FIG> and <FIG>, third direction D3 is the direction in which first hole H1 extends. A fourth direction D4 is a direction perpendicular to flat surface portion <NUM> of head <NUM>. In a plane (field of view of <FIG>) perpendicular to axis line DA, a third angle θ3 between second direction D2 and fourth direction D4 perpendicular to flat surface portion <NUM> is larger than second angle θ2 between second direction D2 and third direction D3. Third angle θ3 is less than <NUM>°. Third angle θ3 is more than or equal to <NUM>° and less than or equal to <NUM>°, for example. A value obtained by subtracting second angle θ2 from third angle θ3 is, for example, less than or equal to <NUM>°, and is preferably less than or equal to <NUM>°.

As shown in <FIG>, fastening portion <NUM> mainly includes a main body portion <NUM>, a tip <NUM>, and a contact surface <NUM>. The diameter of main body portion <NUM> is substantially the same as that of first hole H1. An external screw is formed at main body portion <NUM>, for example. Main body portion <NUM> is in contact with the side surface defining first hole H1. Tip <NUM> has a diameter smaller than that of main body portion <NUM>. Tip <NUM> may be separated from the side surface defining first hole H1. Contact surface <NUM> is in contact with flat surface portion <NUM> of head <NUM>. As shown in <FIG>, fastening portion <NUM> is provided inside first hole H1. A portion of tip <NUM> of fastening portion <NUM> may be located inside second hole H2.

When fastening portion <NUM> is moved in a direction toward shank portion <NUM> of head <NUM>, contact surface <NUM> of fastening portion <NUM> is brought into contact with a portion of flat surface portion <NUM> of head <NUM>. When fastening portion <NUM> is further moved in the direction toward head <NUM>, rotation force is exerted to head <NUM>. Head <NUM> is rotated around axis line DA in a rotation direction R1.

As shown in <FIG>, when head <NUM> is rotated in rotation direction R1, third surface <NUM> of head <NUM> is pressed against first surface <NUM> of holder <NUM>. Similarly, fourth surface <NUM> of head <NUM> is pressed against second surface <NUM> of holder <NUM>. Accordingly, head <NUM> is fixed to first surface <NUM>, second surface <NUM>, and bottom surface <NUM> of holder <NUM> while drawing head <NUM> into second hole H2 from first tip surface <NUM> and second tip surface <NUM> toward rear end surface <NUM> of holder <NUM>. In this state, a workpiece is cut. It should be noted that the rotation direction of head <NUM> during the cutting is a direction opposite to rotation direction R1.

As shown in <FIG>, after fixing head <NUM> to holder <NUM> by fastening portion <NUM>, a fourth angle θ4 between second direction D2 and a fifth direction D5 perpendicular to flat surface portion <NUM> of head <NUM> is smaller than third angle θ3 in the plane perpendicular to axis line DA (see <FIG>). After fixing head <NUM> to holder <NUM> by fastening portion <NUM>, first surface <NUM> may be inclined relative to third surface <NUM>. Similarly, second surface <NUM> may be inclined relative to fourth surface <NUM>.

As shown in <FIG>, after completing fastening by fastening portion <NUM>, a portion of contact surface <NUM> may be separated from flat surface portion <NUM>. For example, more than or equal to <NUM>% of the area of contact surface <NUM> may be in contact with flat surface portion <NUM>, more than or equal to <NUM>% of the area of contact surface <NUM> may be in contact with flat surface portion <NUM>, or contact surface <NUM> may be entirely in contact with flat surface portion <NUM>.

Next, the following describes function and effect of the cutting tool according to the first embodiment.

According to cutting tool <NUM> according to the first embodiment, holder <NUM> is provided with first hole H1 extending in first direction D1 inclined by first angle θ1 toward cutting edge portion <NUM> relative to the direction perpendicular to axis line DA. Fastening portion <NUM> is provided inside first hole H1 and is in contact with flat surface portion <NUM> of shank portion <NUM> of head <NUM>. Fastening portion <NUM> presses flat surface portion <NUM> of shank portion <NUM>, thereby drawing shank portion <NUM> into second hole H2 of holder <NUM>. Moreover, when viewed in the direction parallel to axis line DA, the extending direction of first hole H1 is third direction D3 inclined by second angle θ2 relative to second direction D2 extending from first surface <NUM> toward second surface <NUM>, and third angle θ3 between second direction D2 and fourth direction D4 perpendicular to flat surface portion <NUM> is larger than second angle θ2. Accordingly, flat surface portion <NUM> can be provided with torque in the rotation direction with axis line DA serving as the rotation axis. As a result, third surface <NUM> of head <NUM> can be pressed against first surface <NUM> of holder <NUM> and fourth surface <NUM> of head <NUM> can be pressed against second surface <NUM> of holder <NUM>. That is, when aligning head <NUM> with the center of holder <NUM> and fixing head <NUM> to holder <NUM> by fastening portion <NUM>, head <NUM> is rotated by a very small amount, is drawn to the holder <NUM> side and can be fixed to holder <NUM> firmly and precisely using bottom surface <NUM> of fastening portion <NUM>.

Moreover, according to cutting tool <NUM> according to the first embodiment, first angle θ1 is more than or equal to <NUM>°. Accordingly, shank portion <NUM> of head <NUM> can be drawn effectively into second hole H2 of holder <NUM>.

Further, according to cutting tool <NUM> according to the first embodiment, second angle θ2 is more than or equal to <NUM>° and less than or equal to <NUM>°.

Further, according to cutting tool <NUM> according to the first embodiment, the value obtained by subtracting second angle θ2 from third angle θ3 is less than or equal to <NUM>°. Accordingly, when fastening portion <NUM> is fastened, torque in the rotation direction can be applied effectively to flat surface portion <NUM>. As a result, head <NUM> can be fixed to holder <NUM> more firmly and more precisely.

Next, the following describes a configuration of a cutting tool <NUM> according to a second embodiment. The configuration of cutting tool <NUM> according to the second embodiment is different from the configuration of the first embodiment in that a minimum distance from axis line DA to first surface <NUM> is longer than a minimum distance from axis line DA to second surface <NUM>. The other configurations are substantially the same as those of the first embodiment. Hence, in the description below, the difference from the configuration of the first embodiment will be mainly described.

As shown in <FIG>, in head <NUM> according to the second embodiment, in the direction extending from third surface <NUM> toward fourth surface <NUM>, a distance L1 from axis line DA to third surface <NUM> is longer than a distance L2 from axis line DA to fourth surface <NUM>. In holder <NUM> according to the second embodiment, in the direction extending from first surface <NUM> toward second surface <NUM>, a minimum distance L3 between first surface <NUM> and axis line DA may be longer than a minimum distance L4 between second surface <NUM> and axis line DA. That is, when viewed in the direction parallel to axis line DA, minimum distance L3 between first surface <NUM> and axis line DA is longer than minimum distance L4 between second surface <NUM> and axis line DA, and minimum distance L1 between third surface <NUM> and axis line DA may be longer than minimum distance L2 between fourth surface <NUM> and axis line DA. Minimum distance L1 is <NUM>, for example. Minimum distance L2 is <NUM>, for example. Preferably, a value obtained by subtracting minimum distance L2 from minimum distance L1 is less than or equal to <NUM>. Preferably, a value obtained by subtracting minimum distance L4 from minimum distance L3 is less than or equal to <NUM>. First hole H1 is provided in first side surface <NUM>.

As shown in <FIG>, it is assumed that a straight line B1 represents a straight line perpendicular to both second direction D2 and the direction of axis line DA. Straight line B1 is in parallel with both first surface <NUM> and second surface <NUM>, for example. Similarly, straight line B1 is in parallel with both third surface <NUM> and fourth surface <NUM>, for example. In the plane perpendicular to axis line DA, a distance between axis line DA and second side surface <NUM> corresponds to radius R of holder <NUM>. A circle C1 having radius R and centering on axis line DA is assumed. It is assumed that a straight line B2 represents a straight line that connects axis line DA and a contact point C2 between circle C1 and third surface <NUM>. Similarly, it is assumed that a straight line B3 represents a straight line that connects axis line DA and a contact point C3 between circle C1 and first surface <NUM>. Contact point C3 may be a contact point between first surface <NUM> and first side surface <NUM>.

Minimum distance L1 is the same as a minimum distance between contact point C2 and straight line B1. Minimum distance L3 is the same as a minimum distance between contact point C3 and straight line B1. An angle θ11 between straight line B1 and straight line B2 in the plane perpendicular to axis line DA is expressed by the following formula <NUM>. An angle θ12 between straight line B1 and straight line B3 in the plane perpendicular to axis line DA is expressed by the following formula <NUM>. An angle θ13 is expressed by the following formula <NUM>. <MAT> <MAT> <MAT>.

As shown in <FIG>, it is assumed that a straight line B4 represents a straight line that connects axis line DA and a contact point C4 between circle C1 and fourth surface <NUM>. Similarly, it is assumed that a straight line B5 represents a straight line that connects axis line DA and a contact point C5 between circle C1 and second surface <NUM>. Minimum distance L2 is the same as the minimum distance between contact point C4 and straight line B1. Minimum distance L4 is the same as the minimum distance between contact point C5 and straight line B1. An angle θ14 between straight line B1 and straight line B4 in the plane perpendicular to axis line DA is expressed by the following formula <NUM>. An angle θ15 between straight line B1 and straight line B5 in the plane perpendicular to axis line DA is expressed by the following formula <NUM>. An angle θ16 is expressed by the following formula <NUM>. <MAT> <MAT> <MAT>.

A smaller absolute value of the difference between angle θ13 and angle θ16 is more preferable. The absolute value of the difference between angle θ13 and angle θ16 preferably corresponds to less than or equal to <NUM> seconds. It should be noted that <NUM> second corresponds to <NUM>/<NUM>°. Angle θ13 may be smaller than or the same as the value (see <FIG>) obtained by subtracting angle θ2 from angle θ3. Similarly, angle θ16 may be smaller than or the same as the value (see <FIG>) obtained by subtracting angle θ2 from angle θ3.

Next, the following describes function and effect of the cutting tool according to the second embodiment.

According to cutting tool <NUM> according to the second embodiment, cutting edge portion <NUM> includes third surface <NUM> facing first surface <NUM>, and fourth surface <NUM> facing second surface <NUM>. When viewed in the direction parallel to axis line DA, minimum distance L3 between first surface <NUM> and axis line DA is longer than minimum distance L4 between second surface <NUM> and axis line DA, and minimum distance L1 between third surface <NUM> and axis line DA is longer than minimum distance L2 between fourth surface <NUM> and axis line DA. When minimum distance L3 is the same as minimum distance L4 and minimum distance L1 is the same as minimum distance L2, head <NUM> can be fixed to holder <NUM> such that third surface <NUM> of head <NUM> faces first surface <NUM> of holder <NUM> and fourth surface <NUM> of head <NUM> faces second surface <NUM> of holder <NUM>, or conversely, head <NUM> can be fixed to holder <NUM> such that third surface <NUM> of head <NUM> faces second surface <NUM> of holder <NUM> and fourth surface <NUM> of head <NUM> faces first surface <NUM> of holder <NUM>. Meanwhile, since first hole H1 is formed only at the first surface <NUM> side of holder <NUM>, flat surface portion <NUM> of head <NUM> is not in abutment with fastening portion <NUM> if head <NUM> is conversely attached. In particular, head <NUM> may be attached to holder <NUM> under a circumstance involving a difficulty in visual observation thereof. By configuring holder <NUM> and head <NUM> as in the present embodiment, head <NUM> can be prevented from being attached to holder <NUM> in a wrong direction. Moreover, the thickness of the portion of holder <NUM> at the first surface <NUM> side at which first hole H1 is formed is smaller than the thickness of the portion of holder <NUM> at the second surface <NUM> side at which first hole H1 is not formed. Accordingly, the rigidity of the portion of holder <NUM> at the first surface <NUM> side at which first hole H1 is formed can be maintained to be high.

This embodiment being an embodiment according to the invention.

Next, the following describes a configuration of a cutting tool <NUM> according to a third embodiment. The configuration of cutting tool <NUM> according to the third embodiment is different from the configuration of the first embodiment in that a coolant passage groove <NUM> is provided in the cutting edge portion of head <NUM> and a swaging prevention groove <NUM> is provided in the shank portion of head <NUM>. The other configurations are substantially the same as those of the first embodiment. Hence, in the description below, the difference from the configuration of the first embodiment will be mainly described.

As shown in <FIG>, shank portion <NUM> of head <NUM> according to the third embodiment is provided with a contact portion <NUM>, swaging prevention groove <NUM>, and a curved surface portion <NUM>. Contact portion <NUM> is located opposite to flat surface portion <NUM>. Swaging prevention groove <NUM> is located between flat surface portion <NUM> and contact portion <NUM>. Swaging prevention groove <NUM> may be a cutout provided in shank portion <NUM>. Swaging prevention groove <NUM> is a flat surface, for example. Swaging prevention groove <NUM> may extend in the direction parallel to axis line DA. The normal line of swaging prevention groove <NUM> may be substantially perpendicular to axis line DA. Swaging prevention groove <NUM> may extend to rear end portion <NUM>. Contact portion <NUM> is a curved surface, for example. Curved portion <NUM> connects flat surface portion <NUM> and swaging prevention groove <NUM>.

Coolant passage groove <NUM> may be provided in third surface <NUM> of cutting edge portion <NUM>. As shown in <FIG> and <FIG>, coolant passage groove <NUM> extends from seating surface <NUM> to first tip surface <NUM>. Coolant passage groove <NUM> may extend to seating surface <NUM>, first tip surface <NUM>, and fifth tip surface <NUM>. The longitudinal direction of coolant passage groove <NUM> may be the direction parallel to axis line DA. As shown in <FIG>, coolant passage groove <NUM> may be provided also in fourth surface <NUM>. Coolant passage groove <NUM> may extend to fourth tip surface <NUM> and sixth tip surface <NUM>.

As shown in <FIG>, contact portion <NUM> of shank portion <NUM> is in contact with the surface of holder <NUM> defining second hole H2. On the other hand, swaging prevention groove <NUM> is separated from surface H2a of holder <NUM> defining second hole H2. It may be configured to permit the coolant to pass through a space between swaging prevention groove <NUM> and surface H2a. Curved portion <NUM> may be separated from the surface of holder <NUM> defining second hole H2.

As shown in <FIG>, a coolant feed passage H3 may be provided in holder <NUM> according to the third embodiment. Coolant feed passage H3 extends along axis line DA of holder <NUM>. One end of coolant feed passage H3 may be opened at rear end surface <NUM> of holder <NUM>. The other end of coolant feed passage H3 may communicate with second hole H2. That is, second hole H2 is configured to function as a coolant feed passage.

As shown in <FIG>, when viewed in the direction parallel to axis line DA, the area of opening <NUM> of second hole H2 serving as a portion of the coolant feed passage may be larger than the area of the portion of second hole H2 communicating with first hole H1. Opening <NUM> is formed in bottom surface <NUM>. Opening <NUM> may have a straight line portion parallel to first surface <NUM>, and a straight line portion parallel to second surface <NUM>.

As shown in <FIG>, when viewed in the direction parallel to axis line DA, opening <NUM> of coolant feed passage H3 is exposed from coolant passage groove <NUM> provided in head <NUM> when shank portion <NUM> of head <NUM> is inserted into second hole H2 of holder <NUM>. In other words, when viewed in the direction parallel to axis line DA, most of opening <NUM> is overlapped with head <NUM> but a portion of opening <NUM> is not overlapped with head <NUM>. Accordingly, the coolant flows from coolant feed passage H3 into second hole H2, passes through the space between swaging prevention groove <NUM> and surface H2a, and reaches opening <NUM> of second hole H2. Next, the coolant is sent out forwardly of head <NUM> from opening <NUM>, which is exposed from head <NUM>, through coolant passage groove <NUM>.

The following describes function and effect of the cutting tool according to the third embodiment.

According to cutting tool <NUM> according to the third embodiment, shank portion <NUM> has contact portion <NUM> opposite to flat surface portion <NUM>, and is provided with swaging prevention groove <NUM> located between flat surface portion <NUM> and contact portion <NUM>. If the space between shank portion <NUM> and second hole H2 is small, shank portion <NUM> may become unable to be removed from second hole H2 once shank portion <NUM> is inserted in second hole H2. By providing swaging prevention groove <NUM> in shank portion <NUM>, shank portion <NUM> can be prevented from being unable to be removed from second hole H2.

Moreover, according to cutting tool <NUM> according to the third embodiment, coolant feed passage H3 may be provided in holder <NUM>. When viewed in the direction parallel to axis line DA, opening <NUM> of coolant feed passage H3 may be exposed from groove <NUM> provided in cutting edge portion <NUM>. Swarf is normally discharged to outside via the flute portion. Hence, for example, if the opening of coolant feed passage H3 is formed in the flute portion, the coolant sent out from the opening is blocked by the swarf, with the result that the contact portion between the cutting edge portion and the workpiece cannot be cooled effectively. On the other hand, in the case of the third embodiment, the coolant can be supplied forwardly of cutting edge portion <NUM>. Accordingly, the contact portion between the cutting edge portion and the workpiece can be cooled effectively.

Next, the following describes a configuration of a cutting tool <NUM> according to a fourth embodiment. The configuration of cutting tool <NUM> according to the fourth embodiment is different from the configuration of the third embodiment in that a through hole <NUM> is provided instead of coolant passage groove <NUM> and coolant feed passage H3 is branched. The other configurations are substantially the same as those of the third embodiment. Accordingly, in the description below, the difference from the configuration of the third embodiment will be mainly described.

As shown in <FIG>, coolant feed passage H3 is provided in holder <NUM> according to the fourth embodiment, and coolant feed passage H3 may be branched. Coolant feed passage H3 is branched to a first coolant feed passage H3a and a second coolant feed passage H3c, for example. First coolant feed passage H3a may communicate with a third coolant feed passage H3b. Second coolant feed passage H3c may communicate with a fourth coolant feed passage H3d. First coolant feed passage H3a may extend in a direction crossing both coolant feed passage H3 and third coolant feed passage H3b. Similarly, second coolant feed passage H3c may extend in a direction crossing both coolant feed passage H3 and fourth coolant feed passage H3d. Opening H3e of third coolant feed passage H3b may be exposed at bottom surface <NUM> of holder <NUM>. Similarly, opening H3f of fourth coolant feed passage H3d may be exposed at bottom surface <NUM> of holder <NUM>.

As shown in <FIG>, through holes <NUM> may be provided in head <NUM> according to the fourth embodiment. Through holes <NUM> may be provided in first tip surface <NUM> and fourth tip surface <NUM>, for example. When viewed in the direction parallel to axis line DA, openings H3e, H3f of coolant feed passage H3 may be exposed at through holes <NUM>. In other words, through holes <NUM> communicate with openings H3e, H3f. Accordingly, the coolant sent out from openings H3e, H3f passes through through holes <NUM> and is supplied to a workpiece at head <NUM>.

The following describes function and effect of the cutting tool according to the fourth embodiment.

According to cutting tool <NUM> according to the fourth embodiment, coolant feed passage H3 may be provided in holder <NUM>. When viewed in the direction parallel to axis line DA, opening <NUM> of coolant feed passage H3 may be exposed at through hole <NUM> provided in cutting edge portion <NUM>. Accordingly, the coolant can be supplied forwardly of cutting edge portion <NUM>. Hence, the contact portion between the cutting edge portion and the workpiece can be cooled effectively.

First, there were prepared five types of heads <NUM> in which respective inclination angles φ of flat surface portions <NUM> relative to the axis lines of heads <NUM> were different. Five types of holders <NUM> respectively corresponding to the five types of heads <NUM> were prepared. Each holder <NUM> is provided with first hole H1 inclined in the direction of end surface <NUM> relative to the straight line perpendicular to the axis line. First direction D1 in which first hole H1 extends was set to be the same as the normal direction of flat surface portion <NUM> of head <NUM>. Respective inclination angles φ of flat surface portions <NUM> relative to the axis lines were <NUM>°, <NUM>°, <NUM>°, <NUM>° and <NUM>°. Each inclination angle φ is the same as first angle θ1 (see <FIG>) between first direction D1 in which first hole H1 extends and direction DR perpendicular to axis line DA.

First, a portion of shank portion <NUM> of head <NUM> was inserted into second hole H2 of holder <NUM> such that a distance in the axis line direction between end surface <NUM> of holder <NUM> and seating surface <NUM> of cutting edge portion <NUM> of head <NUM> became <NUM> (see a state before clamping in <FIG>). Before the clamping, a distance A1 in <FIG> was set at <NUM>. Next, a clamp screw <NUM> serving as the fastening portion was inserted into first hole H1 of holder <NUM>. Next, by clamping clamp screw <NUM> using, for example, a screwdriver, shank portion <NUM> of head <NUM> was drawn into second hole H2. The lower surface of clamp screw <NUM> was brought into abutment with flat surface portion <NUM> of the shank portion. After completing the clamping of clamp screw <NUM>, a distance A2 between end surface <NUM> of holder <NUM> and seating surface <NUM> of cutting edge portion <NUM> of head <NUM> was measured (see a state before the clamping in <FIG>).

<FIG> shows a relation between distance A2 and inclination angle φ of flat surface portion <NUM> of head <NUM>. When shank portion <NUM> of head <NUM> is not drawn into second hole H2 of holder <NUM> at all, distance A2 is <NUM>. On the other hand, when shank portion <NUM> of head <NUM> is completely drawn into second hole H2 of holder <NUM>, distance A2 is <NUM>. As shown in <FIG>, as inclination angle φ of flat surface portion <NUM> of head <NUM> becomes larger, distance A2 becomes smaller. That is, as inclination angle φ of flat surface portion <NUM> of head <NUM> becomes larger, shank portion <NUM> of head <NUM> is more likely to be drawn into second hole H2 of holder <NUM>. Moreover, when inclination angle φ is more than or equal to <NUM>°, distance A2 becomes <NUM>, with the result that seating surface <NUM> of cutting edge portion <NUM> of head <NUM> is brought into abutment with end surface <NUM> of holder <NUM>. As a result, head <NUM> is firmly fixed to holder <NUM>. Hence, inclination angle φ is desirably more than or equal to <NUM>°. On the other hand, as inclination angle φ becomes larger, first hole H1 becomes longer, with the result that the rigidity of holder <NUM> is decreased. Hence, inclination angle φ is desirably more than or equal to <NUM>° and less than or equal to <NUM>°. By the above experiment, it was confirmed that first angle θ1 (see <FIG>) is desirably more than or equal to <NUM>° and less than or equal to <NUM>°.

The embodiments disclosed herein are illustrative and non-restrictive in any respect.

Claim 1:
A cutting tool (<NUM>) comprising:
a holder (<NUM>) having a first surface (<NUM>) and a second surface (<NUM>) provided to be separated from each other to sandwich an axis line (DA);
a head (<NUM>)including a cutting edge portion (<NUM>) located between the first surface (<NUM>) and the second surface (<NUM>), and a shank portion (<NUM>) configured to hold the cutting edge portion (<NUM>); and
a fastening portion (<NUM>) configured to fix the head (<NUM>) to the holder (<NUM>),
the holder (<NUM>) being provided with a first hole (H1) and a second hole (H2), the first hole (H1) extending in a first direction (D1) and a third direction (D3), the first direction (D1) being inclined by a first angle (Θ1) toward the cutting edge portion (<NUM>) relative to a direction (DR) perpendicular to the axis line (DA), the third direction (D3) being inclined by a second angle (Θ2) relative to a second direction (D2) extending from the second surface (<NUM>) toward the first surface (<NUM>) when viewed in a direction parallel to the axis line (DA), the second hole (H2) communicating with the first hole (H1), the second hole (H2) extending in the direction parallel to the axis line (DA),
the shank portion (<NUM>) having a flat surface portion (<NUM>), the shank portion (<NUM>) being provided inside the second hole (H2),
the fastening portion (<NUM>) being provided inside the first hole (H1), the fastening portion (<NUM>) being in contact with the flat surface portion (<NUM>),
in a plane perpendicular to the axis line (DA), a third angle (Θ3) between the second direction (D2) and a fourth direction (D4) perpendicular to the flat surface portion (<NUM>) being larger than the second angle (Θ2),
the third angle being less than <NUM>°,
characterized in that when viewed in the direction parallel to the flat surface portion (<NUM>) and perpendicular to the axis line (DA), the flat surface portion (<NUM>) is inclined relative to the axis line (DA) by an angle being substantially the same as the first angle (Θ1), and wherein the shank portion (<NUM>) has a contact portion (<NUM>) opposite to the flat surface portion (<NUM>), and is provided with a swaging prevention groove (<NUM>) located between the flat surface portion (<NUM>) and the contact portion (<NUM>).