JP2006281360A - Tool holder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply achieve centering of a tool with high accuracy without resorting to troublesome adjusting work and without making any alteration to a basic structure. <P>SOLUTION: This tool holder 10 includes: a holder body 11 having a tool insert hole 15 at the shaft center part, in which a straight shank part T1 of the tool T is inserted and having a taper hole 16 concentric with the tool insert hole 15 at the tip part; a collet 20 having an outer peripheral taper part fitted to the taper hole 16 of the holder body 11; and a fastening nut 26 engaged with the tip of the holder body 11 to force the collet 20 in the taper hole 16 to be reduced in diameter. In the tool holder, a bush 30 for guiding the straight shank part T1 of the tool T with a very small clearance is fitted in the tool insert hole 15 of the holder body, thereby holding the tool T at two points of the collet 20 and the bush 30 to achieve centering of the tool T with high accuracy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tool holder for gripping a rod-shaped tool such as a drill, a reamer, or an end mill, and more particularly to a tool holder including a collet that grips a straight shank portion of a tool.

  This type of tool holder generally has a holder body having a tool insertion hole into which a straight shank portion of a tool is inserted in an axial center portion and a tapered hole concentric with the tool insertion hole in a tip portion, and the holder The collet has an outer peripheral tapered portion that is fitted into the tapered hole of the main body, and a tightening nut that is screwed into the tip of the holder main body and pushes the collet into the tapered hole to reduce the diameter. (For example, refer to Patent Document 1).

  By the way, in drilling with a drill or reamer or grooving with an end mill, the length of a tool to be used naturally increases as the depth of the hole or groove to be machined increases. However, according to the general tool holder described above, since the grip allowance of the collet is small (about 15 mm), when gripping a long tool, a so-called long tool, the tool is likely to shake. There has been a problem that it is difficult to ensure desired processing accuracy.

In some cases, the holder body is divided into a collet holder that holds the collet and a tapered shank attached to the spindle (spindle) of the machine tool, and the center of the tool is formed by a jack bolt interposed between the joints. A tool holder that can correct the deviation has been developed (Patent Document 2). However, in such a tool holder, in addition to the troublesome adjustment work of operating the jack bolt while measuring the deflection of the tool tip, an increase in the manufacturing cost of the holder body due to the split structure is avoided. Therefore, problems are left in terms of operability and cost.
JP 2004-255474 A Japanese Utility Model Publication No. 6-50712

  The present invention has been made in view of the above-described technical background, and the object of the present invention is to easily and accurately perform the tool without relying on troublesome adjustment work and without changing the basic structure. An object of the present invention is to provide a tool holder that can perform centering and is useful for high-precision machining with a long tool.

  In order to solve the above problems, the present invention includes a holder body having a tool insertion hole into which a straight shank portion of a tool is inserted in an axial center portion and a tapered hole concentric with the tool insertion hole in a tip portion; A tool comprising: a collet having an outer peripheral tapered portion that is fitted into the tapered hole of the holder body; and a tightening nut that is screwed into the tip end portion of the holder body and pushes the collet into the tapered hole to reduce the diameter. In the holder, a bush for guiding the straight shank portion of the tool with a slight clearance is fitted into the tool insertion hole of the holder main body so as to be separated from the collet toward the rear end side.

  In the tool holder configured as described above, the tool is supported at two places (two points), that is, a grip part by the collet and a guide part by the bush, so that a special operation or structure for centering the tool is required. No improvement is needed.

  In the present invention, if the clearance between the straight shank portion of the tool and the bush is too small, it becomes difficult to insert the tool into the bush. Conversely, if the clearance is too large, the centering accuracy of the tool by the two-point support is lowered. It is desirable to set the dimensional tolerance of the inner diameter of the bush to +0.03 to +0.08 mm with respect to the dimensional tolerance h8 of the fit of the shank diameter.

  In the present invention, the bush preferably has a chamfered inner peripheral edge at the tool insertion side end, so that the tool can be smoothly inserted into the bush.

  According to the tool holder of the present invention, the tool is centered with high accuracy by the two-point support by the collet and the bush, so that it is extremely useful for high-accuracy machining with a long tool. In addition, no troublesome adjustment work is required, and there is no need to change the basic structure, so that the burden on operability and cost is not increased, and the utility value is great.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a tool holder as one embodiment of the present invention. The tool holder 10 according to the present embodiment is used by being mounted on a machining center, and the holder main body 11 is a main spindle (spindle) of the machining center on the rear end side of the large-diameter gripped portion 12 used for tool replacement. 1 is provided with a shank portion 13 that is coupled to the distal end portion, and a collet holder portion 14 that holds a collet 20 described later on the distal end side of the gripped portion 12. Here, the shank portion 13 has a bifurcated shape, and a plurality of recesses 13a are formed on the inner surface of the shank portion to engage with the ball 2 provided in a retracting device (not shown) extending in the main shaft 1. ing. The ball 2 is movable in the radial direction, and the holder main body 11 is drawn into the main shaft 1 by receiving the ball 2 in a recess 13 a formed in the shank portion 13, and is coaxial with the main shaft 1. Is fixed to the position.

  On the other hand, a tool insertion hole 15 into which the straight shank portion T1 of the tool T is inserted is provided through the gripped portion 12 of the holder body 11 and the shaft center portion of the collet holder portion 14, and the collet holder portion 14 is provided. A tapered hole 16 connected to the tool insertion hole 15 with a diameter gradually reduced from the distal end side is provided at the distal end portion.

  A female screw portion 17 is formed over a predetermined length at a rear end portion of the tool insertion hole 15 located in the gripped portion 12, and a shaft member inserted into the tool insertion hole 15 is formed in the female screw portion 17. A male screw portion 19 formed on the outer periphery of the rear end portion of the (tool driver) 18 is screwed. At the rear end portion of the tool driver 18, a socket portion 18a for receiving a tip portion of a screw jig (not shown) inserted from the shank portion 13 side is provided. The tool driver 18 is attached to the socket portion 18a. The inside of the tool insertion hole 15 is screwed back and forth along the female screw portion 17 in accordance with the rotation of the engaged screw jig. The tool driver 18 serves to adjust the protruding margin of the blade portion T2 of the tool T from the tool holder 10, and the rear end of the straight shank portion T1 of the tool T is brought into contact with the tip portion thereof. A stopper portion 18b is provided.

  As shown well in FIG. 2, the collet 20 includes a head portion 22 having an annular groove 21 on the outer peripheral surface, and an outer peripheral taper portion 23 extending rearward from the head portion 22. The collet 20 includes a plurality (six in this case) of first slits 24 extending in the axial direction from the end face of the head portion 22 to the vicinity of the end face of the outer peripheral tapered portion 23 and the end face of the outer peripheral tapered portion 23 to the vicinity of the head portion 22. A plurality (six in this case) of second slits 25 extending in the axial direction are formed alternately and equally in the circumferential direction. The inclination angle of the outer peripheral taper portion 23 is set to be the same as the inclination angle of the taper hole 16 of the collet holder portion 14, and the outer peripheral taper portion 23 of the collet 20 is tapered by a tightening nut 26 described later. By being pushed into the hole 16, the diameter is reduced.

  The tightening nut 26 has, on one end side of the inner peripheral surface thereof, an internal thread portion 28 that engages with an external thread portion 27 formed on the outer periphery of the tip end portion of the collet holder portion 14 of the holder body 11. An annular protrusion 29 that engages with an annular groove 21 formed in the head portion 22 of the collet 20 is provided at an intermediate portion. As shown in FIG. 3, the contour of the annular protrusion 29 is set so that an elliptical opening S is formed therein. The annular protrusion 29 is formed in an annular shape over the shoulder of the collet 20 by appropriately tilting the tightening nut 26 with respect to the collet 20 by using the opening on the long axis side of the oval opening S. The collet 20 and the tightening nut 26 can be sub-assembled.

  In the present embodiment, a bush 30 is fitted into the tool insertion hole 15 of the holder body 11. The bush 30 is disposed away from the collet 20 toward the rear end side at a portion outside the moving range of the tool driver 18. The inner diameter of the bush 30 is formed to a dimension that ensures a slight clearance with the straight shank portion T1 of the tool T. This clearance is desirably set to such a size that the dimensional tolerance of the inner diameter of the bush 30 is set to +0.03 to +0.08 mm when the dimensional tolerance of the fitting of the shank diameter of the tool T is h8. Thus, the straight shank portion T1 of the tool T is guided to the bush 30 with almost no play. As shown in FIG. 4, the bush 30 is also provided with a chamfered slope 31 at the inner peripheral edge of the tool insertion side end.

  The bush 30 is fixed to the tool insertion hole 15 of the holder body 11 in any manner, and may be fixed using an adhesive, press-fitted, or screwed through a screw portion. Moreover, the material type of this bush 30 is also arbitrary, and can be made of metal, ceramics, resin, or the like. However, in consideration of wear resistance and cost, it is desirable to use metal, particularly steel (heat treated product). Further, it is desirable that the inner peripheral surface of the bush 30 has as fine a surface roughness as possible in order to facilitate the insertion of the tool T.

  In order to cause the tool holder 10 configured as described above to grip the tool T, first, the straight shank T1 of the tool T is inserted into the tool insertion hole 15 of the holder body 11 through the collet 20 and the bush 30, and the straight shank. The tool T is pushed in until the rear end of the portion T1 contacts the stopper portion 18b at the tip of the tool driver 18. At this time, the tool driver 18 is rotated by a spiral jig to adjust the protruding length of the tool T from the tool holder 10. Next, the tightening nut 26 is screwed into the male screw portion 27 at the tip of the collet holder portion 14. Then, the collet 20 is pushed into the tapered hole 16 of the collet holder portion 14 by being pushed by the annular protrusion 29 of the tightening nut 26, whereby the collet 20 is reduced in diameter and the tool T is passed through the collet 20 to the tool holder. 10 to be gripped.

  Thus, when the tool T is gripped by the tool holder 10, a part of the straight shank T 1 of the tool T is guided by the bush 30, so that the tool T includes a gripping portion by the collet 20 and a guide portion by the bush 30. Are supported at two locations (2 points), and thereby the tool T is centered with high accuracy. Therefore, even when the tool T is a long tool and the protruding length from the tool holder 10 is long, the deflection of the tip of the blade portion T2 of the tool T is suppressed, and as a result, the deep hole can be processed with high accuracy. become able to. In particular, in the present embodiment, the collet 20 has a structure in which the first slits 25 and the second slits 26 that reverse the slitting direction are alternately arranged, so that the collet 20 is pushed into the tapered hole 16. The diameter is reduced on average, so that the tool T is centered with higher accuracy.

  Incidentally, a drill having a straight shank portion T1 with a diameter of 5 mm is used as the tool T, and the tool holder 10 of the above embodiment is caused to hold the drill with a projecting allowance of 100 mm so that the drill tip (tool tip) can be swung. When measured, it was 0.01 mm or less. This value is remarkably small as compared with the fact that the deflection of a general tool holder is about 0.03 mm per 100 mm of the projection allowance, and it is clear that the tool holder 10 is extremely useful for high-precision machining with a long tool. It is.

  Here, the coupling structure of the tool holder 10 to the spindle 1 of the machining center is arbitrary. For example, as shown in FIG. 5, a pull stud 40 is provided at one end with respect to the large-diameter gripped portion 12 of the holder body 11. The pull shank 41 is connected to the main shaft 1, the pull stud 40 is engaged with a pulling device (not shown) extending in the main shaft 1, the holder body 11 is pulled into the main shaft 1, and the tapered shank 41 is inserted into the tapered hole 3 of the main shaft 1. A structure for fitting may be used. In this case, a through hole 42 communicating with the tool insertion hole 15 in the gripped portion 12 is formed in the axial center portion of the taper shank 41, and the socket portion 18 a at the rear end of the tool driver 18 is passed through the through hole 42. The screw jig is engaged. In this embodiment, since there is no change in the collet holder part 14 of the holder main body 11 and the structure inside thereof, the same parts as those shown in FIG.

  In the above embodiment, the tool holder 10 has been described as being used by being mounted on the spindle 1 of the machining center. However, the tool holder 10 is used by being mounted on a general-purpose machine tool such as a drilling machine or a milling machine. Of course, it is good also as a structure.

It is sectional drawing which shows the whole structure of the tool holder as one Embodiment of this invention. The structure of the collet with which this tool holder is equipped is shown, (a) is sectional drawing, (b) is a front view. It is a front view which shows the structure of the clamping nut with which this tool holder is equipped. It is sectional drawing which shows the structure of the bush with which this tool holder is equipped. It is sectional drawing which shows the whole structure of the tool holder as other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main spindle of machining center 10 Tool holder 11 Holder main body 14 Collet holder part 15 Tool insertion hole 16 Tapered hole 20 Collet 21 Outer peripheral taper part 26 Tightening nut 30 Bushing T Tool T1 Straight shank part T2 Blade part

Claims (3)

  A holder main body having a tool insertion hole into which the straight shank portion of the tool is inserted at the shaft center portion and a tapered hole concentric with the tool insertion hole at the tip portion, and fitted into the taper hole of the holder main body. In a tool holder comprising a collet having an outer peripheral taper portion and a tightening nut screwed into the tip end portion of the holder main body to push the collet into the taper hole to reduce the diameter, the tool insertion hole of the holder main body A tool holder characterized in that a bush for guiding a straight shank portion of a tool with a slight clearance is fitted away from the collet to the rear end side.   2. The tool holder according to claim 1, wherein the dimensional tolerance of the inner diameter of the bush is set to +0.03 to +0.08 mm with respect to the dimensional tolerance h8 of the fitting of the tool shank diameter. The tool holder according to claim 1 or 2, wherein the inner peripheral edge portion of the end portion on the tool insertion side of the bush is chamfered into a tapered shape.

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