JP2001198725A - Ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loosening preventing structure for a tightening screw in which friction holding force between a male screw and a female screw of the tightening screw is maintained for strongly centering a plate tip to a holder main body even when cutting load fluctuates by change of a processing margin in a workpiece during cutting or fine vibration of a cutting edge of the plate tip or the like. SOLUTION: In this ball end mill in which a plate tip 13 is inserted into a split groove 2 crossing a tip center part of a holder main body 1, and in which the split groove 2 is closed with a tightening screw 4 to hold and fix the plate tip 13, a conical receiving surface 8 with which a head part 5 of the tightening screw 4 matches is provided on one half-split part 3, a female screw 10b of the tightening screw 4 is provided on the other half-split part 9, an abutment surface 13b in a truncated chevron shape is provided in the plate tip 13, and a receiving surface 15 for a split groove bottom part 11 is provided, thereby a trunk part 7 of the tightening screw 4 is inserted into a through-hole 13a in the plate tip 13 for fixing the plate tip 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type ball end mill used for machining a free-form surface such as a ball groove of a constant velocity ball joint at high speed and high precision. Related to a structure for fixing to a holder main body.

[0002]

2. Description of the Related Art Conventionally, when machining precision is required for cutting a ball groove or the like, a solid ball end mill in which a holder body and a cutting blade are integrated or a bladed ball end mill in which the cutting blade is fixed by brazing or the like is used. Was used. However, if the cutting speed is increased and emphasis is placed on the cutting efficiency, abrasion and chipping of the cutting edge increase, and the frequency of re-polishing and replacement of the end mill body increases, which is uneconomical.

Therefore, a throw-away type ball end mill in which a plate-shaped tip is provided with a cutting blade has been frequently used. The ball end mill inserts a plate-shaped chip into the split groove at the tip of the holder body, closes the split groove with one tightening screw, and abuts the bottom of the split groove with the end face of the plate-shaped chip, This is to stop the mechanical rotation of the plate-shaped chip and integrate it with the holder main body.

[0004] Therefore, in this aspect, it is intended to fix the central portion of the plate-shaped chip with the tightening screw so that the bottom of the split groove and the end face of the plate-shaped chip are in contact with each other to restrain the plate-shaped chip. Things. It is necessary to improve the accuracy of the tightening screw and maintain a tightening force that does not lose the friction holding force between the male screw and the female screw due to the tensile stress of the tightening screw even if the load during cutting changes periodically. is there.

For this purpose, various devices have been devised for the shape of the restraining means and the split groove around the tightening screw. JP-A-8-
Japanese Patent No. 252714 discloses a technical idea in which a rear end surface of a plate-like chip is formed in an arc shape. FIG. 5 is a plan view, and FIG. 6 is a cross-sectional view of a plate-like chip constrained by a split groove.

In FIG. 5, a plate-like chip 3 having a cutting edge
1 is inserted into a single groove formed so as to cross the center of the front end of the holder body 30, and a tightening screw 3
It is fixed by closing the split groove at 2. Plate chip 3
If the rear end face 31a is formed to have a radius of curvature equal to or larger than the radius of curvature of the bottom 33 of the split groove, the center of the plate-shaped chip 31 automatically overlaps with the center of the holder body 30. And can be aligned.

In FIG. 6, a rear end portion 31 of a plate-like chip 31 inserted into a split groove 34 at the front end of a holder body 30 is shown.
a is that the head of the tightening screw 32 is in contact with the conical receiving surface 36 eccentric with respect to the female screw 35 so that the split groove 34 is formed.
Moves in the direction of the bottom 33 and comes into close contact therewith. According to this prior art, the center of the plate-shaped chip 31 can be automatically matched with the center of the holder main body 30 by the configuration of FIGS. 5 and 6, and the conical receiving surface 36 which is eccentric with the head of the tightening screw 32 can be used. It is described that the plate-like chip 31 can be firmly restrained by the action.

However, in order to satisfy the condition, the fitting accuracy between the neck diameter of the tightening screw 32 and the plate-like chip 31, the position of the female screw 35 of the holder body 30 and the plate-like chip 3
All of them, including the relationship between the rear end face 31a and the arc-shaped abutment face of the bottom 33 of the split groove, must be aligned.
Regardless of the actual combination such as the selective assembly, in the random combination of the plate-like chip 31, the holder body 30, and the tightening screw 32, the precision of each part must be maintained extremely high. In addition, since the bottom 33 of the split groove is formed in an arc shape, it is considerably difficult to improve the processing accuracy of this portion. In addition, the rear end face 3 of the plate-like chip 31
There is also a known technique in which the 1a shape is not a curved surface but a V-shaped surface. In this case, the same problems as those in the related art remain.

[0009]

In ball end milling, fluctuations in the cutting load due to a change in the machining allowance of the workpiece during cutting and a slight run-out of the cutting edge of the plate-like tip cannot be avoided. Absent. Therefore, the plate-shaped chip, the split groove and the tightening screw are preferably as tight as possible so that the frictional holding force of the male screw and the female screw, which is maintained by the tensile stress of the tightening screw, is not lost by the vibration caused by the variation of the cutting load. It is desirable to be tense with an appropriate pre-pressure. Further, it is preferable that the plate-like chip is sandwiched so as to be centered by the holder body. The present invention proposes a tightening screw loosening prevention structure that satisfies the above-mentioned requirements.

Another object is to provide a structure for accurately and firmly fixing a plate-like chip to a holder body. For this purpose, the positional accuracy of the plate-shaped chip, the holder body, and the tightening holes must be extremely precise. It is not practical if the cost required for improving the accuracy increases. The present invention compensates for the deficiency in dimensional accuracy of such component parts and the like by the plate-shaped chip fastening structure. Specifically, it is to make the shape of the component part easily attain the processing accuracy.

[0011]

According to a first aspect of the present invention, a plate-like chip having a through hole is inserted into a single split groove crossing the center of the front end of a holder body, and the split groove is closed with a tightening screw to close the split groove. In a ball end mill for pinching and fixing a chip-shaped chip, a cone receiving surface on which the head of the tightening screw is aligned is provided in one half and a female screw of the screw is provided in the other half, and a rear end of the plate-shaped chip is provided. And a receiving surface with which the C-shaped abutment surface of the plate-shaped chip abuts at the bottom of the split groove, and tightens into the through hole of the plate-shaped chip. The plate tip is fixed by inserting the body of the screw. Preferably, a tapered portion that tapers toward the screw side is formed between the body portion and the female portion of the tightening screw to guide the plate-like chip to the through hole.

According to a second aspect of the present invention, a plate-like chip having a through-hole is inserted into a single split groove crossing the center of the front end of the holder body, and the split groove is closed with a tightening screw to clamp and fix the plate-like chip. In the ball end mill, one half of the half is provided with a seat hole in which the head of the tightening screw is aligned, and the other half is provided with a female screw of the tightening screw. A tapered ring that matches the tapered shape with the disc spring is installed under the head of the screw, and a C-shaped contact surface that spreads rearward is provided at the rear end of the plate-shaped chip, and at the bottom of the split groove A receiving surface is provided on which the C-shaped contact surface of the plate-shaped chip comes into contact, and the body of the fastening screw is inserted into the through hole of the plate-shaped chip to fix the plate-shaped chip.

A hole is provided at a receiving surface at the bottom of the split groove, at one position away from the axis of the holder body, to allow a locking pin in a direction parallel to the tightening screw to enter the split groove,
On one of the U-shaped contact surfaces of the plate-shaped chip, a concave portion for engaging with the locking pin is provided so that the insertion direction of the plate-shaped chip is specified, and the C-shaped contact surface and the receiving surface are formed. Fix the combination.

[0014] A screw reinforcing member is screwed to the female screw of the other half part to strengthen the friction holding force between the tightening screw and the male screw.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1, which is a preferred embodiment 1 embodying the present invention, will be described in detail with reference to an enlarged sectional view of the vicinity of a split groove 2 of a holder body 1. FIG. In FIG.
One half part 3 is provided with a conical receiving surface 8 on which the head 5 of the tightening screw 4 is aligned, and the other half part 9 is provided with a female screw 10. The plate-like chip 13 inserted into the split groove 2 is tightened and fixed by the tightening screw 4 in a direction to close the split groove 2. A slit 12 may be provided in the bottom portion 11 of the split groove 2 at a position biased toward the one half split portion 3 side.

When a tightening force acts on the XX line of the tightening screw 4, the split groove 2 bends so that the width of the split groove 2 becomes narrow as a cantilever starting from the bottom A of the slit 12. Span L from starting point A of slit 12 to XX line
In the case of the cantilever having the above, when the slit 12 is provided so as to be biased toward the half part 3, the second moment of area of the half part 9 becomes larger. Therefore, the bending on the half-split portion 3 side becomes larger, and the female screw 10 provided on the other half-split portion 9 side
Center line XX directly faces the tightening screw 4 without tilting.

In general, loosening of a screw is due to a decrease in friction holding force generated on a slope of a screw thread of a male screw and a female screw due to a tensile stress of a male screw. Therefore, it is preferable that the slopes of the thread of the male screw and the female screw be as close as possible. More preferably, the tightening screw 4 can be screwed into a place where the helical lock helicert 14, which is a screw reinforcing member corresponding to the size of the female female, is screwed in advance, so that the degree of tightness can be further improved. In addition, since the center axis XX of the female screw 10 is screwed together without tilting by the action of the slit 12, a friction holding force faithful to the precision of the screw is obtained.

As shown in a cross-sectional view taken along the line YY which crosses the plate chip 13 and the tightening screw 4, the center point O2 of the through hole 13a of the plate chip 13 and the center point O1 of the tightening screw 4 are shown.
Are mounted so as to be eccentric by S, and the plate-like chip 13 is moved in the direction of arrow B by the screwing of the tightening screw 4 into the body 7.
To move. As shown in FIG. 2, the plate-shaped chip 13 has a C-shaped abutting surface 13b which spreads rearward at the rear end.
Is pressed against the receiving surface 15 provided on the bottom 11 of the split groove 2 to be positioned. Further, a tapered portion 6 tapering toward the female screw 10 is provided on the male screw side of the body 7 of the tightening screw 4 to guide the body 7 to the through hole 13a.

FIG. 2 is a plan view of the ball end mill according to the first embodiment of the present invention as viewed from one of the half portions 3. The plate-like chip 13 is held between the split grooves, and is fixed by screwing the tightening screw 4 to the other half part 9. At this time, as shown in the YY sectional view of FIG.
Is moved in the direction B by the action of the eccentricity S between the center point O2 of the plate-shaped chip 13 and the center point O1 of the tightening screw 4. As a result, the rear end of the plate-like chip 13 is pressed against the receiving surface 15 provided on the bottom 11 of the split groove 2 with the C-shaped contact surface 13b spreading rearward.

FIG. 3 shows a plan view of the plate-like chip 13.
The plate-like chip 13 is made of an alloy steel, a cemented carbide, a cubic boron nitride sintered body or a diamond sintered body, and is formed with a uniform thickness. A through-hole 13a is provided at the center thereof, and the body 7 of the tightening screw 4 is inserted into the through-hole 13a, thereby forming a C-shaped contact surface 13b provided at the rear end of the plate-like chip 13. Receiving surface 1 provided on bottom 11 of split groove 2
Pressed to 5. The locking pin 17 is inserted into the hole 16 shown in FIG.
Can be screwed and engaged with the concave portion 13c provided on one of the contact surfaces 13b to specify the insertion direction of the plate-shaped chip 13.

In the present invention, the abutment-shaped contact surface 13b and the receiving surface 15 have a shape that can be easily polished, and can be in close contact with high accuracy. With the V-shaped receiving surface of the prior art, polishing of the bottom side of the split groove is practically impossible. In order to make the combination of the C-shaped contact surface 13b and the receiving surface 15 close to the optimum, in the present invention, the contact surface 13
At the time of polishing b, it is temporarily assembled with a specific holder main body 1 serving as a master, and the C-shaped angle θ and the edge radius R are adjusted. Then, the tolerance of the C-shaped angle θ is set to be slightly larger on the receiving surface 15 side. With this setting, the plate-like chip 13 is held at both ends of the holder main body 1 that are separated from the axis. Conversely, receiving surface 1 of holder body 1
In the case of polishing 5, the specific plate-shaped chip 1 serving as a master
Temporarily assemble with No. 3 and process. It goes without saying that the holder main body 1 and the plate-like chip 13 of the masters are accurately aligned.

Then, as shown in FIG.
A hole 16 in a direction parallel to the tightening screw 4 is provided at one position away from the axis of
To enter. By engaging with the concave portion 13c of the plate-shaped chip 13 and specifying the insertion direction of the plate-shaped chip 13, it is possible to eliminate an error caused by randomly combining the insertion direction of the plate-shaped chip 13.

As another embodiment of the present invention (hereinafter, referred to as Embodiment 2), FIG. 4 is an enlarged sectional view of the periphery of the split groove 2 of the holder body 20. In FIG. 4, one half part 3 is provided with a seat hole 23 in which the head 22 of the tightening screw 21 is aligned, and the other half part 9 is provided with a female screw 10. The bottom portion 11 of the split groove 2 may be provided with a slit 12 for effectively tightening and fixing at a position biased toward the one half split portion 3 side.

When a tightening force acts on the XX line of the tightening screw 21 in the same manner as in FIG. 1, the split groove 2 becomes a cantilever starting from the bottom A of the slit 12, and the width of the split groove 2 becomes narrower. To bend. Since the second moment of area of the other half part 9 is larger, the center axis XX of the female screw 10 provided in the half part 9 is not inclined and the tightening screw 2
1 is the same as that described in the first embodiment.

A disc spring 24 and a tapered ring 25 are rotatably fitted below the neck of the head 22 of the tightening screw 21.
Temporarily assembled with a snap ring 26. And
The side surface 22a of the head 22 of the tightening screw 21 and the wall surface 23a of the seat hole 23 provided in the half part 3 are JIS B 0401.
It is consistent with the accuracy including the clearance zero corresponding to the position (H / h) of the tolerance range specified in “Dimensional tolerance and fitting method”. Further, the half part 9 includes the body 2 of the tightening screw 21.
The guide hole 27 for accommodating 1a is located at the position of the tolerance zone (H / h).
It is matched with an accuracy that includes a considerable gap. Note that H is a symbol indicating a hole, and h is a symbol indicating a shaft tolerance.

A tightening screw 21 is attached to the female screw 10 of the half portion 9.
As the screw is screwed into the plate-shaped chip 13, the inclined surface 25a of the tapered ring 25 comes into contact with the tapered hole 13d of the through hole 13a. Then, the plate-like chip 13 is moved toward the bottom 11 of the split groove 2. Taper ring 25 and tightening screw 2
Since a disc spring 24 is interposed between the heads 22 to apply a preliminary pressure to the tapered ring 25, the plate-shaped chip 13 is always urged toward the bottom 11 of the split groove 2.
Therefore, the contact surface in the shape of a letter C that extends toward the rear of the rear end of the plate-shaped chip 13 is pressed strongly against the receiving surface provided on the bottom 9 of the split groove 2. To facilitate this effect, FIG.
It is important that the slope 25a of the tapered ring 25 is not in contact with the plate-like tip 13 on the tip end side of the cutting blade. Therefore, it is preferable that the through-hole 13a is a long hole.

By tightening the tightening screw 21, the lower surface 22b of the neck of the head 22 comes into contact with the seat surface 23b of the seat hole 23, and the operating load of the disc spring 24 is determined. Then, a bending stress corresponding to the bending stress of the half-split portions 3 and 9 as a cantilever and a compressive stress of the disc spring 24 is generated in the tightening screw 21, and the frictional holding force of the male screw and the female screw is generated by the variation of the cutting load. The plate-like chip 13 can be firmly fixed to the holder body 20 without being lost by vibration. Further, even when a hard structure is unevenly distributed in the composition of the work material, or when the resistance and the direction of the cutting edge such as inclined cutting and spiral cutting are variously changed due to a complicated shape, the plate-like chip 13 is firmly attached to the holder body 20. Can be fixed.

Furthermore, the seat hole 23 of the half part 3, the head side surface 22 a of the tightening screw 21, and the guide hole 27 of the half part 9 are provided.
And the body 21a of the tightening screw 21 are tightly aligned, so that the screw engagement faithful to the precision of the screw is compensated. As in the first embodiment, the helical lock helicert 14 serving as a screw reinforcing member corresponding to the size of the female screw is added to the female screw 10 of the second embodiment.
Is screwed, it is possible to fix the plate-shaped chip 13 more firmly.

[0029]

According to the present invention, the plate-shaped chip is attached to the holder body by providing a U-shaped contact surface at the rear end of the plate-shaped chip and making contact with the receiving surface at the bottom of the split groove. Centered and pinched. In addition, even if the cutting edge of the plate-shaped tip slightly fluctuates or the cutting load fluctuates, lock helicert or taper ring so that the frictional holding force of the male screw and the female screw maintained by the tensile stress of the tightening screw is not lost. The plate-shaped chip can be accurately and firmly fixed to the holder body by the combination of the plate spring and the disc spring.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view around a split groove according to a first embodiment of the present invention.

FIG. 2 is a plan view of a split groove according to the first embodiment of the present invention.

FIG. 3 is a plan view of the plate-shaped chip of the present invention.

FIG. 4 is an enlarged cross-sectional view around a split groove according to a second embodiment of the present invention.

FIG. 5 is a plan view of a conventional split groove.

FIG. 6 is an enlarged cross-sectional view around a split groove according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 20 Holder main body 2 Split groove 3 One half part 4, 21 Tightening screw 5, 22 Head 6 Taper part 7, 21a Body part 8 Conical receiving surface 9 The other half part 10 Female screw 11 Bottom part 12 Slit 13 Plate Shaped tip 13a Through hole 13b Contact surface 13c Recess 13d Tapered hole 14 Lock heli-sert 15 Receiving surface 16 Hole 17 Locking pin 23 Seat hole 24 Disc spring 25 Tapered ring 25a Slope 26 Snap ring 27 Guide hole

Claims (5)

[Claims] 1. A ball end mill for inserting a plate-shaped chip having a through hole into a single split groove crossing the center of the front end of a holder body, closing the split groove with a tightening screw, and clamping and fixing the plate-shaped chip. In one of the halves, a conical receiving surface on which the head of the tightening screw is aligned is provided, and the other half of the halves is provided with a female screw of the tightening screw. An abutting surface in the shape of a U-shape that spreads is provided, and a receiving surface is provided at the bottom of the split groove with which the abutting surface in a U-shape of the plate-shaped chip abuts. A ball end mill, wherein the plate-shaped chip is fixed by inserting the body portion of the ball end mill. 2. The ball end mill according to claim 1, wherein a tapered portion tapering toward the screw side is formed between the body and the screw portion of the tightening screw. 3. A ball end mill for inserting a plate-shaped chip having a through hole into a single split groove crossing the center of the tip of the holder body, closing the split groove with a tightening screw, and clamping and fixing the plate-shaped chip. In one of the halves, a seat hole for matching the head of the tightening screw is provided, and the other half of the halves is provided with a female screw of the tightening screw. A conical spring and a tapered ring that matches the tapered shape are mounted under the head neck of the tightening screw, and a C-shaped contact surface that extends rearward at the rear end of the plate-shaped chip is provided, At the bottom of the split groove, a receiving surface with which the abutment-shaped contact surface of the plate-shaped chip comes in contact is provided, and the body of the fastening screw is inserted into a through hole of the plate-shaped chip to fix the plate-shaped chip. A ball end mill characterized by: 4. A hole for allowing a locking pin in a direction parallel to the tightening screw to enter the split groove at a position on the receiving surface at the bottom of the split groove at a position away from the axis of the holder body. The ball end mill according to any one of claims 1 to 3, wherein a concave portion for engaging with the locking pin is provided on one of the C-shaped contact surfaces of the plate-shaped chip. 5. The ball end mill according to claim 1, wherein a screw reinforcing member is screwed to the female screw of the other half portion.