Patent Application
20160236282
The present invention relates to a cutting tool holder that has a shaft hole and is used for inner diameter processing by turning or the like, and a cutting tool formed by inserting a boring bar (a bar-shaped cutting tool having a cutting edge formed at one side of one end thereof or at one side of each of both ends thereof) into the shaft hole of the cutting tool holder and screwing a setscrew into a fixing screw hole, which is provided so as to penetrate from the outer peripheral surface of the cutting tool holder toward the shaft hole, thereby to fix (cramp) the boring bar.
Conventionally, of inner diameter processing (hole processing) of a workpiece (to-be cut object), in boring in which the inner peripheral surface of a pilot hole is processed by turning or the like, a cutting tool may be used which is formed by: inserting a boring bar having a cutting edge (knife edge) at one side of a front end thereof into a shaft hole of a sleeve-shaped holder such that a rear end of the boring bar initially enters the shaft hole; and screwing a setscrew into a screw hole provided in the outer peripheral surface of the cutting tool holder (hereinafter, also referred to merely as holder), thereby to fix the boring bar. Such a cutting tool is inserted into a holder mount hole that is provided in a tool rest of a lathe and extends in a main shaft (rotation shaft) direction, the holder of the cutting tool is fixed by screwing a fixing bolt into a screw hole provided in the outer peripheral surface of the tool rest, and the cutting tool is used for processing with the lathe. As such a cutting tool, in the case where the diameter of a hole to be processed is small and the boring bar is thin, there is a cutting tool in which a coolant is not supplied from the outside, and a flow path provided in the holder itself along a direction in which the shaft hole extends is opened in a front end surface of the holder to form an ejection port (discharge port) (Patent Document 1). As shown in
In inner diameter (inner peripheral surface) processing of a hole with such a cutting tool 400, if the inner diameter is small (e.g., Ø10 mm), the gap between the outer peripheral surface of the boring bar 200 and the inner peripheral surface of the hole becomes small due to a demand for ensuring a desired thickness of the bar, and thus dischargeability of swarf deteriorates. Still, as shown in
Under such a circumstance, an invention is known in which, in order to enhance the dischargeability of swarf even in such inner diameter processing of a blind hole, the coolant ejection port is opened not at the cutting edge side (flank), but at the side opposite to the cutting edge (at the back surface side), when the cutting tool is seen from the front end side (when the cutting tool is seen from a rotation shaft direction of the workpiece) (Patent Document 2). In this invention, as shown in
Incidentally, in the cutting tool 400 including the holder 500 shown in
Meanwhile, in the holder 500 of the above conventional cutting tool 400, screw holes 135 into which the setscrews 130 for fixing the boring bar 200 are screwed are provided in one side surface of the outer peripheral surface of a shank portion of the boring bar 200 (see
Patent Document 1: Japanese Utility Model Publication Laid-Open (kokai) No. H05-85535
Patent Document 2: Japanese Patent Publication Laid-Open (kokai) No. 2007-185765
As is obvious from the above, in the cutting tool 400, when the holder 500 is rotated relative to the boring bar 200 in order to shift to the back surface supply, the setscrews 130 do not press the surface facing in the same direction as the rake face 205 of the cutting edge 203 of the boring bar 200 but press a surface opposite to this surface, as shown in
Furthermore, originally, settings are made in which the holder 500 is fixed to the tool rest H such that, in the set-up operation including such an operation of screwing the setscrews 130 and the like, an operator is allowed to screw the setscrews 130 and the like while seeing the holder 500 from above, in order to be able to visually recognize the setscrews 130 and the like. On the other hand, in changing to the back surface supply as described above, the holder 500 is rotated in the mount hole of the tool rest H by 180 degrees, and thus the operation of screwing the setscrews 130 becomes an operation in which the setscrews 130 are screwed at the lower surface of the holder 500. Therefore, there is also a problem that the operability deteriorates. If the boring bar 200 is rotated by 180 degrees without rotating the holder 500, to be disposed in the reverse direction (configured as a so-called reverse cutting tool), and inner diameter processing is performed, such a problem in the screwing operation is eliminated. However, in this case as well, the setscrews 130 press the surface facing in the direction opposite to the rake face 205 side, and thus the fixed state becomes inappropriate. In addition, in the case of being configured as a reverse cutting tool, a difference occurs in a position such as the edge position of the cutting edge 203. Thus, for example, another program needs to be created in an NC lathe, and there is also a problem that the settings of the NC lathe need to be changed.
For these reasons, conventionally, two types of holders between which the position of the coolant ejection port 120 and the positions of the screw holes 135 are different need to be prepared in order that pressing of the boring bar 200 by the setscrews 130 can be performed at the surface facing in the same direction as the rake face 205 of the cutting edge 203 in any of the “knife edge supply” and the “back surface supply”. Therefore, since the number of holders is doubled, there is a remarkable difficulty in terms of stock of the cutting tool and control thereof on a site for such a type of machining, and this causes an increase in the processing cost.
The present invention has been made in view of the above-described problems in the cutting tool for inner diameter processing, and an object of the present invention is to allow a single holder to handle a difference in the position of an ejection port between knife edge supply and back surface supply of a coolant without causing the problems regarding fixing of a boring bar.
The invention according to claim 1 is a cutting tool holder including: a shaft hole into which a boring bar having a cutting edge at one side of a front end thereof can be inserted; one or a plurality of screw holes for fixing the inserted boring bar by screwing setscrews thereinto, the one or the plurality of screw holes being provided at one side of an outer peripheral surface of the cutting tool holder so as to penetrate toward the shaft hole; and an ejection port formed such that a coolant can be ejected therefrom toward the front end of the boring bar inserted in the shaft hole and fixed by screwing in the setscrews, the ejection port being opened in a front end surface of the cutting tool holder, wherein a screw hole for fixing the inserted boring bar by screwing a setscrew thereinto is provided also at a side opposite to the screw holes in a radial direction of the shaft hole, so as to penetrate from the outer peripheral surface of the cutting tool holder toward the shaft hole.
The invention according to claim 2 is a cutting tool holder according to claim 1, wherein, when the cutting tool holder is seen from the front end surface, the ejection port is provided so as to be present on a straight line that is drawn so as to be perpendicular to a center line of the screw hole and pass through a center of the shaft hole.
The invention according to claim 3 is a cutting tool holder according to claim 1, wherein, when the cutting tool holder is seen from the front end surface, the ejection port is provided so as not to be present on a straight line that is drawn so as to be perpendicular to a center line of the screw hole and pass through a center of the shaft hole.
The invention according to claim 4 is a cutting tool holder according to any one of claims 1 to 3, wherein the ejection port is opened in the front end surface so as to be recessed in an inner peripheral surface of the shaft hole.
The invention according to claim 5 is a cutting tool holder according to any one of claims 1 to 3, wherein the ejection port is opened in the front end surface as an independent hole near the shaft hole via a flow path provided within the cutting tool holder without communicating with the shaft hole.
The invention according to claim 6 is a cutting tool holder according to any one of claims 1 to 5, wherein the setscrews 130 are screwed in all the screw holes.
The invention according to claim 7 is a cutting tool including: the cutting tool holder according to claim 6; a boring bar being inserted into a shaft hole of the cutting tool holder; and the setscrew screwed with the screw hole located at a position where a surface facing in the same direction as a rake face, of the setscrews, thereby to fix the boring bar.
With the cutting tool holder according to the present invention, because of the above configuration, particular complication of the structure is not caused, and pressing for fixing the boring bar by means of the setscrews can be performed at the surface facing in the same direction as the rake face of the cutting edge, even in any of knife edge supply and back surface supply. Thus, it is not necessary to prepare two types of holders between which the positions of the screw holes are different as in the conventional art, in order to be able to handle a difference in the position of the coolant ejection port. Therefore, a remarkable merit is obtained for the effect on stock of the cutting tool and control thereof. As described above, with the cutting tool holder according to the present invention, because of the above configuration, the following remarkably excellent effects are obtained: there is no problem in pressing by screwing in the setscrews for fixing the boring bar; a convenient holder can be configured as a single holder allowed to handle a change in the position of the ejection port between the knife edge supply and the back surface supply of the coolant; and the processing cost can also be reduced. In the present invention, the ejection port is formed so as to be opened in the front end surface of the holder itself and only needs to allow a selection to be made between the knife edge supply and the back surface supply. Therefore, the ejection port itself suffices to be opened as one port in the front end surface and at one side of the shaft hole, but a plurality of ports may be opened.
As recited in claim 2, the ejection port is preferably provided such that the center thereof is present on a straight line that is drawn so as to be perpendicular to the center line of the screw hole and pass through the center of the shaft hole, when the holder is seen from the front end surface. However, as recited in claim 3, the ejection port may be provided so as not to be present on the straight line that is drawn so as to perpendicular to the center line of the screw hole and pass through the center of the shaft hole, when the holder is seen form the front end surface.
In the present invention, the ejection port may be recessed in the inner peripheral surface of the shaft hole as recited in claim 4, or may be provided as a separate hole independently of the shaft hole as recited in claim 5. If the ejection port is provided as recited in claim 4, the ejection port can be recessed in the inner peripheral surface of the shaft hole so as to be cut thereinto. Thus, it is easy to form the ejection port, and the coolant can be effectively supplied even when the hole diameter is small and the gap between the inner peripheral surface of the hole and the outer peripheral surface of the boring bar is narrow. On the other hand, if the ejection port is provided in this manner, there is a problem regarding airtightness such as a possibility that the coolant flows around into the gap between the inner peripheral surface of the shaft hole and the outer peripheral surface of the boring bar, or the coolant leaks through the screwed face of the setscrew. In contrast, in the invention according to claim 5, such a problem can be eliminated.
In the holder of the present invention, as in the invention according to claim 6, the setscrews may be screwed in all the screw holes. This is because the setscrews are less likely to be scattered or lost, and the cutting tool can be promptly adapted to any of the knife edge supply or the back surface supply.
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An embodiment of the cutting tool holder of the present invention will be described in detail based on
Meanwhile, in an outer peripheral surface 102 of the holder 100, flat surfaces (even surfaces) 106 having a certain width are formed at both sides in the same manner so as to be parallel to each other and extend in a front-rear direction. In this example, in a portion of each flat surface 106 which portion is present at the front end surface 103 side of the holder 100 and corresponds to the above-described shaft hole 110, screw holes 135 for screwing fixing setscrews 130 therein are provided so as to penetrate in a radial direction of the holder 100 toward the shaft hole 110. In this example, the screw holes 135 are provided at two locations on each side spaced apart from each other in the front-rear direction, namely, at four locations in total, and each screw hole 135 is set such that the setscrew 130 (e.g., a setscrew 130 with a hexagon socket) can be screwed thereinto. Each flat surface 106 is a surface pressed by screwing in a fixing bolt after a cutting tool including the holder 100 is inserted into a mount hole of a tool rest of a lathe. That is, the holder 100 has a transverse cross-section that can rotate in a slide contact state within a mount (hole) having a circular transverse cross-section in the tool rest of the lathe, and is configured such that the rotation is stopped when the holder 100 is fixed.
Meanwhile, the shaft hole 110 is formed as a circular hole into which an intermediate portion (shank portion) 207 between cutting edges 203 provided at one sides of front and rear ends, respectively, as in a boring bar 200 shown in the lower drawing in
In such a holder 100 of this example, the predetermined boring bar 200, as shown in the lower drawing in
Thus, in the cutting tool 300, if a coolant supply pipe is connected to the connection portion (thread for pipe) 114 of the rear end 105 of the flow path 113 for coolant supply at the rear end surface 105 of the holder 100 and a coolant (e.g., a cutting fluid) is supplied under high pressure, the coolant is poured as a jet flow from the ejection port 120, which is opened in the front end surface 103 of the holder 100, toward the cutting edge 203. Accordingly, when the cutting tool 300 of this example is inserted into a mount hole of a tool rest H of a predetermined lathe with the rake face 205 facing upward and is fixed by means of a fixing bolt Vo as shown in
Meanwhile, in such a cutting tool 300 using the holder 100 of this case, at the time of set-up for changing the cutting tool 300 to “back surface supply” in order to allow for inner diameter processing of a blind hole, the fixing bolt Vo fixing the holder 100 in the tool rest H and all the setscrews 130 screwed into the holder 100 are screwed back to be loosened, and, for example, the holder 100 is inverted (by 180 degrees) around the boring bar 200 while the attitude of the boring bar 200 is maintained as it is. By so doing, as shown in
That is, as described above, for example, when the holder 100 is inverted about the axial line of the boring bar 200 without rotating the boring bar 200, the coolant ejection port 120 is located at the side opposite to the cutting edge 203 side. At this time, the setscrews 130 that are present at the rake face 205 side of the boring bar 200 and have not played a role of fixing before the inversion come to the same position as the setscrews 130 that have performed fixing at the surface facing in the same direction as the rake face 205 before the inversion. Therefore, the boring bar 200 can be cramped again as if by screwing again the setscrews 130 that have played a role of fixing before the inversion. As described above, with the holder 100 according to this example, even in a use mode of the back surface supply, instability of fixing of the boring bar 200 by means of the setscrews 130 is not caused, and the screwing operation can be performed in an attitude in which the operator looks down from above similarly as described above. Thus, for the operator, the operation can be simplified and sped up. As a matter of course, also in the case of returning to the knife edge supply later, the operation can be performed in the exactly same manner. The operation of changing between the knife edge supply and the back surface supply can be performed naturally after the cutting tool 300 is removed from the tool rest H. In this case as well, the same advantageous effects can be obviously obtained.
In the above example, the ejection port 120 is provided by recessing the inner peripheral surface of the shaft hole 110 and the shape of the ejection port 120 is a circular arc shape (crescent shape). Thus, in any of the knife edge supply and the back surface supply, the coolant can be supplied toward the front end of the boring bar 200 along the boring bar 200, efficiently even if the gap with the inner peripheral surface of a machined hole is small. However, even when the ejection port 120 is provided (opened) by recessing the inner peripheral surface of the shaft hole 110, the flow path cross-section of the ejection port 120 is not limited to the circular arc shape (crescent shape), and the ejection port 120 may have an appropriate cross-sectional shape such as a rectangular shape. In addition, in the above example, the case where the coolant is supplied from the rear end surface 105 of the holder 100 via the flow path 113 provided coaxially with the shaft hole 110 has been described. However, for supply of the coolant from a pressure feed source (pump), a connection port (screwing portion) for a supply pipe may be provided, for example, at a portion that does not interfere with fixing to the tool rest and is close to the front end, of the outer peripheral surface 102 of the holder 100, and the flow path 113 may be provided so as to be connected to the ejection port 120.
As shown in
The cutting tool holder 100 of the above example is based on a round bar having a circular transverse cross-section and provided with the flat surfaces 106, which are parallel to each other, on the outer peripheral surface. The shape of the outer peripheral surface of the cutting tool holder 100 itself may be appropriate one. The outer peripheral surface may be, for example, smaller in diameter at a portion close to the front end and connected to the front end surface 103 than at the other portion continuous rearward therefrom (a portion mounted to the tool rest). In addition, the shaft hole 110 only needs to allow the position of the ejection port 120 to be selectable from a position for the knife edge supply or a position for the back surface supply in accordance with the boring bar. Therefore, the transverse cross-sectional shape of the shaft hole 110 is also not limited to a circle.
In the above example, the case has been described in which the center of the recessed groove 116, connected to the ejection port 120, in the groove width direction thereof when the holder 100 is seen from the front end surface 103 side (see
In
Even with the “knife edge supply”, this is suitable for the case where supply of the coolant to the rake face 205 side in a large amount is demanded. In the holder 100, in the case of shifting to the “back surface supply”, even at the back surface side, the ejection port 120 is located in a portion close to the side opposite to the rake face 205. Thus, in processing of a blind hole, when the coolant makes a U turn to be returned, an effect of causing generated swarf to rise from the rake face 205 by the flow of the coolant is obtained. Thus, the dischargeability of swarf also can be enhanced depending on a processing condition. That is, even in any of the “knife edge supply” and the “back surface supply”, a portion surrounding the shaft hole 110 at which portion the coolant should be ejected to the front end side depends on a processing condition. In accordance with this, the position of the ejection port 120 (the position of the ejection port around the shaft hole 110 relative to the axial line of the screw hole 135) may be set, and, therefore, the above angle α may be set as appropriate. In
In the above example, when seen from the front end surface 103 of the holder 100, the ejection port 120, which should achieve either the “knife edge supply” or the “back surface supply”, is composed of a single port. However, for example, even in the case where the ejection port 120 is provided in the inner peripheral surface of the shaft hole 110, the ejection port 120 may be divided into two or more ports, and may be divided into two ejection ports 120 as shown in
Regarding the holder according to the present invention, as long as the boring bar can be fixed at a fixed part thereof on the surface facing in the same direction as the rake face side, by means of the setscrews, and the single holder can handle the difference in the position of the ejection port between the “knife edge supply” and the “back surface supply” of the coolant, there are no limitations on the other structure and shape of the holder itself. Regarding fixing of the boring bar, the “surface facing in the same direction as the rake face” at which surface the fixing by means of the setscrews is performed includes, in addition to the surface parallel to the rake face, a surface that is not parallel to the rake face and has an inclination angle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-217676 | Oct 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/004852 | 9/22/2014 | WO | 00 |
