JP4136139B2 - End mill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a solid end mill (hereinafter simply referred to as an end mill) made of cemented carbide (including a hard coating layer on the surface) used for high-speed and high-precision machining of aluminum and cast iron parts in a machining center or the like. The present invention relates to end mills that have been improved for polishing and improved service life.
[0002]
[Prior art]
High-precision and high-quality machining of mass-produced machine parts is possible with high-speed, high-performance machining centers, high-performance cemented carbide end mills, and multi-blade end mills with 3 or more cutting edges. High precision machining is becoming popular.
[0003]
The feature of the end mill used for this high-speed, high-precision machining is that center holes are provided on both end faces. The end mill for the same application has a large number of blades and is built with high precision and is originally expensive. Therefore, it is desired to increase the number of times of re-grinding as much as possible. The center hole is provided in order to maintain the same accuracy as that of the new work by supporting both centers during re-polishing.
[0004]
In the end mill having the center hole, a sink hole is provided at the center of the tip in order to prevent the disappearance of the center hole on the bottom blade side due to re-polishing, and a center hole on the bottom blade side is provided on the back end surface of the sink hole. Such end mills can perform longitudinal feed (feeding in the axial direction), transverse feed in the front-rear direction, left and right, or their combined direction (direction in which the locus becomes an arc), and machining that advances vertical feed and transverse feed simultaneously. Absent. This is because the work material is left uncut at the center of rotation where there is no bottom blade during vertical feed cutting, and it enters the sink hole to prevent lateral feed.
[0005]
Therefore, an inner blade is provided on the inner end side of the bottom blade. FIG. 2 shows a conventional example of an end mill having the inner blade. As shown in FIG. 2B, the sink hole 2 at the end of the end mill is a straight hole parallel to the shaft center, and therefore the inner blade 6 is a blade having no corner.
[0006]
[Problems to be solved by the invention]
In the end mill of FIG. 2, not only the outer peripheral blade 4 but also the inner blade 6 are parallel at the axis, so that the thrust force during longitudinal feed cutting becomes large.
[0007]
Further, in the transverse feed cutting after the longitudinal feed, the inner blade 6 has no clearance angle, and a clearance for the relief cannot be formed between the work material and the inner peripheral surface of the sink hole 2, so that an excessive load is applied.
[0008]
Therefore, there are many accidents in which the end mill to be improved breaks when one of the 4 to 10 cutting edges reaches the number of machining of about 300. The breakage occurs near the intersection between the bottom of the sink hole and the inner peripheral surface, and due to the concentration of the load described above, the stress limit is reached and the breakage is reached while about 300 pieces are processed. Conceivable.
[0009]
Japanese Patent Laid-Open No. 48-38591 describes that the inner peripheral wall of a sink hole (referred to as a relief hole in this publication) is escaped to the outer peripheral side in order to attach an inner blade. In order to have a relief as shown in (The inner wall moves closer to the rear in the rotational direction), the outer diameter is considerably smaller than the diameter of the sink hole (the smaller the grinding wheel diameter, the lower the machining efficiency) In other words, it is necessary to provide a relief for each blade so that the grindstone does not interfere with the adjacent inner blade, which increases the processing time and the manufacturing cost of the end mill.
[0010]
Further, the end mill of the publication has a problem that the thrust in the longitudinal feed cutting becomes larger than that of the end mill of FIG. 2 because the inner blade is inclined inward.
[0011]
The present invention has been made in view of the above points, and can reduce the manufacturing cost and prevent the tip portion from being broken by allowing the inner blade to have a relief and a bevel angle by a simple method. The challenge is to do.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, a sink hole provided at the tip of a cemented carbide multi-blade end mill is formed as a tapered hole whose diameter increases from the inlet toward the back, and the inner peripheral surface of the taper sink hole An inner blade was formed at the intersection ridge between the tip and the groove surface of the tip pocket.
[0013]
The end hole of the end mill has an inlet diameter of 1/2 to 1/3 of the end mill diameter, a depth of 1/5 to 1/10 of the end mill diameter, and a taper angle of the hole of 10 ° to 50 °. Is preferable.
[0014]
[Action]
When the inner blade is formed at the intersection of the inner peripheral surface of the hole and the groove surface of the tip chip pocket with the sinking hole being a tapered hole, the inner blade naturally has clearance clearance and a corner angle. . Therefore, the thrust in the longitudinal feed cutting is reduced, the load in the transverse feed after the longitudinal feed is also reduced, the tip portion is prevented from being broken, and the life of the end mill is improved.
[0015]
In addition, the taper sinking hole that spreads out is formed by pressing a hole that can be punched in the compression molding process of the powder raw material at the time of manufacturing the blank material (the material obtained by sintering the powder raw material after compression molding). For example, at the time of blade processing after sintering, it is formed by a method of finishing to the desired tapered hole using a reverse tapered grindstone having a predetermined taper angle (this may be a little smaller than the hole diameter). Can do. In this case, the hole is expanded by rotating the grindstone at a fixed position, rotating the blank material around the axis, and fixing the blank material along the inner peripheral surface of the hole while rotating the grindstone. However, no matter which method is used, there is no need to worry that the grindstone does not interfere with other blades, and there is no need to reapply the grindstone for each blade. Therefore, it is possible to increase the processing efficiency and reduce the labor of processing by using a grindstone having a larger diameter than when a relief is provided for each blade, thereby reducing the manufacturing cost.
[0016]
If the entrance diameter of the sink hole is too large, it is difficult to secure the strength at the tip side in the case of a small diameter end mill with a machining diameter of around 10 mm. Conversely, if the entrance diameter is too small, the inner peripheral surface of the sink hole in the case of a small diameter end mill. Therefore, it is preferable to set the entrance diameter of the sink hole to 1/2 to 1/3 of the end mill diameter.
[0017]
Further, if the depth of the sunk hole is too shallow, a sufficient re-polishing allowance cannot be taken. Conversely, if the depth is too deep, the strength on the tip side decreases, so about 1/5 to 1/10 of the end mill diameter is suitable.
[0018]
Furthermore, if the taper angle of the sunk hole is less than 10 °, the inner blade is not sufficiently escaped and the effect of reducing the load when cutting with the inner blade is thin. On the other hand, if the taper angle exceeds 50 °, the part surrounding the sunk hole Since the thickness of the root side becomes too small and the strength on the tip side is insufficient, the taper angle is preferably set in the range of 10 ° to 50 °.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an end mill of the present invention. In the figure, 1 is a shank, 2 is a sink hole provided in the tip surface, 3 is both end surfaces, that is, a center hole provided in the back end surface of the sink hole 2 and the rear surface of the shank 1, 4 is an outer peripheral blade with a twist angle, Reference numeral 5 is a bottom blade at the tip, 6 is an inner blade, 7 is a tip pocket provided at the tip corresponding to each bottom blade, and 8 is a twist groove along the outer peripheral blade 4.
[0020]
Reference numeral 9 denotes a flank of the bottom blade 5. As shown in FIG. 1 (d), the flank 9 is machined in a downward slope toward the rear in the rotational direction of the end mill, and the bottom blade has a flank angle α.
[0021]
Κ in FIG. 1 (b) is a margin angle of the bottom blade 5, which is also applied to a conventional end mill.
[0022]
The end mill shown in FIG. 1 has a sink hole 2 that is a tapered hole that extends back, and this is different from the end mill shown in FIG. In this way, by forming the sinking hole 2 into a tapered hole inclined in the direction of depth, a corner angle is formed on the inner blade 6 formed by the intersecting ridge between the inner peripheral surface of the hole and the groove surface of the chip pocket 7. With κ ', thrust in vertical feed cutting is reduced. Moreover, as shown in FIG.1 (c), the clearance t of the escape in the rotation direction of the inner blade 6 arises, and the load at the time of cutting with the inner blade 6 is also reduced, and it is unreasonable at the corner portion of the sink hole. Stress is not frequently applied.
[0023]
In addition, the entrance diameter d of the sink hole 2 shown in FIG.1 (b) is set to 1 / 2-1 / 3 of the end mill diameter D. As shown in FIG. Further, the depth L of the sink hole 2 is set to 1 / 5D to 1 / 10D, and the taper angle θ is set to a range of 10 ° to 50 °.
[0024]
The end mill of the present invention configured as described above has a diameter D of 11.6 mm, the number of blades N: 6, sinkhole inlet diameter d: 5.5 mm, sinkhole depth L: 2.0 mm, sinkhole taper angle θ. : As a result of an evaluation test using a prototype of 20 ° specifications, it was found that there was no breakage accident and that the life was 1.5 to 2 times longer than that of the conventional product.
[0025]
【The invention's effect】
As described above, in the end mill of the present invention, the sink hole that has been formed in a straight or tapered shape in the prior art is formed as a taper hole that is widened to the depth, and at the intersection ridge between the inner peripheral surface of the sink hole and the groove surface of the chip pocket. Since the inner blade formed has a natural clearance angle and clearance clearance, breakage of the tip is prevented, the life is improved, and the cutting tool cost is reduced.
[0026]
In addition, it is not necessary to make a relief for each blade, and it is possible to efficiently taper a sunk hole using a grindstone having a diameter larger than that of the grindstone used when making a relief for each blade. Therefore, the manufacturing cost can be reduced and the cutting tool cost can be reduced.
[Brief description of the drawings]
FIG. 1A is a side view showing an embodiment of an end mill of the present invention, FIG. 1B is an enlarged partial cutaway side view of the tip end portion of the end mill, and FIG. [FIG. 2] (a) Side view of a conventional end mill with a sink hole (b) Side view of an enlarged part of the tip of the end mill (c) Same front view [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shank 2 Sink hole 3 Center hole 4 Outer edge blade 6 Inner blade 7 Tip pocket 8 Torsion groove 9 Bottom blade flank α Bottom blade clearance angle κ Bottom blade clearance angle κ 'Inner blade clearance angle t Inner blade Clearance clearance

Claims (2)

It has three or more outer peripheral blades and a bottom blade connected to each outer peripheral blade, and has center holes at both ends, and the center hole on the bottom blade side is provided at the back end surface of the sink hole provided at the center of the tip, The sink hole is formed by a tapered hole that expands from the entrance toward the back, and is formed at the inner end of the bottom blade by an intersection ridge between the inner peripheral surface of the taper sink hole and the groove surface of the tip tip pocket. Solid end mill made of cemented carbide with inner blade. The entrance diameter of the sink hole is set to 1/2 to 1/3 of the end mill diameter, the depth is set to 1/5 to 1/10 of the end mill diameter, and the taper angle of the hole is set in a range of 10 ° to 50 °. 1 is an end mill.

Images