JP2000158224A - End mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a flank and a concave angle to an internal blade by a simple and low-priced means by forming a sunk hole provided on the extreme end of a cemented carbide multi-blade end mill into a tapaer hole enlarging the diameter from the inlet to the deep side, and forming the internal blades out of crossing ridge of the inner circumferential face of the hole and the groove faces of chip pockets on the extreme end. SOLUTION: A sunk hole 2 is provided on the extreme end face of a shank 1, and center holes 3 are provided on the deep end face of the sunk hole 2 and the rear face of the shank 1. Further, outer circumferential blades 4 with twist angle, bottom blades 5 and internal blades 6 on the extreme end are provided, chip pockets 7 are provided on the extreme end corresponding to the respective bottom blades 5, and twist grooves are provided along the outer circumferential blades 4. Further the flank 9 of the bottom blade 5 is machined into down-slant toward the rear in the rotation direction of an end mill, and a clearance angle α is fitted. By forming the sunk hole 2 into a taper hole slanting in the direction spreading as going to the depth, the internal blade 6 formed out of the crossing ridge of the inner circumferential face of the hole and the groove face of the chip pocket 7 is added with a concave angle κ', to reduce thrust at vertical feed cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid end mill made of a cemented carbide (including one having a hard coating layer on its surface) used for high-speed, high-precision machining of aluminum and cast iron parts in a machining center and the like. More specifically, the present invention relates to an end mill that is improved to cope with re-polishing and to improve the life.

[0002]

2. Description of the Related Art The machining of mass-produced machine parts requiring high precision and high quality requires a machining center having three or more cutting edges in accordance with high speed and high performance of a machining center and high performance of a cemented carbide end mill. High-speed, high-precision machining using a blade end mill is becoming widespread.

A feature of the end mill used for high-speed, high-precision machining is that center holes are provided on both end surfaces. An end mill for the same application has a large number of blades, is built with high precision, and is originally expensive, so that it is desired to increase the number of times of regeneration by repolishing as much as possible. The center hole is provided to support both centers during re-polishing to maintain the same accuracy as that of the new work.

In the end mill having the center hole, a sink hole is provided at the center of the tip in order to prevent the center hole of the bottom blade from disappearing due to re-polishing, and a center hole at the bottom blade side is provided at an inner end face of the sink hole. However, such end mills perform longitudinal feed (axial feed) and then lateral feed in the front-back, left-right, or a combined direction (a direction in which the trajectory becomes an arc), or simultaneously perform vertical feed and horizontal feed. Processing cannot be performed.
This is because the work material is left uncut at the center of rotation without the bottom blade during vertical feed cutting, which enters the sinkhole and hinders the horizontal feed.

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 cutter. The sinkhole 2 at the tip of this end mill is
As shown in FIG. 2 (b), a straight hole parallel to the axis is formed, and therefore, the inner blade 6 is a blade having no watermark angle.

[0006]

The end mill shown in FIG.
Since not only the outer cutter 4 but also the inner cutter 6 are parallel in the axis, the thrust force at the time of longitudinal feed cutting is increased.

[0007] In the horizontal feed cutting after the vertical feed, the inner blade 6
There is no clearance angle, and no clearance is allowed between the work material and the inner peripheral surface of the sink hole 2, so an excessive load is applied.

Therefore, the end mill to be improved has four to four
Of the ten cutting edges, there have been many accidents in which one breaks at the stage when the number of cuts reaches about 300. The breakage occurs near the intersection of the bottom of the sinkhole and the inner peripheral surface,
It is considered that due to the concentration of the load described above, the stress limit was reached and the breakage was reached during processing about 300 of the portion.

Japanese Patent Laid-Open Publication No. 48-38591 discloses a sinkhole for attaching an inner blade (the publication discloses a relief hole).
It is described that the inner peripheral wall is made to escape to the outer peripheral side. However, in order to provide a relief as shown in FIG. It is essential to use a grindstone that is considerably smaller than the diameter of the sinkhole (the smaller the grindstone diameter, the lower the machining efficiency), and make sure that the grindstone does not interfere with the adjacent inner blades, so that a relief is provided for each blade. The processing time is prolonged, which increases the end mill manufacturing cost.

Further, the end mill disclosed in the publication has a problem that the thrust in longitudinal feed cutting is larger than that of the end mill shown in FIG. 2 because the inner cutter is inclined inward.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has a simple method of forming a relief and a watermark angle on an inner blade to reduce manufacturing costs and prevent breakage of a tip. The task is to make it possible.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a sinking hole provided at the tip of a multi-blade end mill made of cemented carbide is formed by a tapered hole which expands in diameter from an inlet to a depth. The inner cutter was formed at the intersection of the inner peripheral surface of the tapered sink hole and the groove surface of the tip pocket at the tip.

The sink 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 mm.
It is preferable to set the angle to 50 to 50 °.

[0014]

[Function] When the sinking hole is formed into a tapered hole that expands to the back, the inner edge is formed at the intersection of the inner peripheral surface of the hole and the groove surface of the tip pocket at the tip, and the inner blade naturally has clearance for clearance and watermark There is a corner. Therefore, the thrust in the vertical feed cutting is reduced, and the load in the horizontal feed after the vertical feed is also reduced, thereby preventing breakage of the tip portion and improving the life of the end mill.

The deeper tapered sunk hole is used to form a hole capable of being die-cut in the powder material compression molding step at the time of manufacturing a blank material (a material obtained by compressing and sintering a powder material). It is made by embossing, and after sintering, for example, at the time of blade cutting, a method of finishing to a target tapered hole using a reverse tapered grindstone having a predetermined taper angle (this may be slightly smaller than the hole diameter). Can be formed. In this case, the method of expanding the hole is to rotate the grindstone at a fixed position and rotate the blank material once around the axis, or to fix the blank material and rotate the grindstone along the inner peripheral surface of the hole while rotating the grindstone. There is a method of making one round, but no matter which method is adopted, there is no need to care that the grindstone does not interfere with other blades, and it is not necessary to reapply the grindstone for each blade. Therefore, the processing efficiency can be increased by using a grindstone having a larger diameter than when a relief is provided for each blade, and the processing time can be reduced, thereby reducing the manufacturing cost.

If the inlet diameter of the sinking hole is too large, it is difficult to secure the strength at the tip end in the case of a small-diameter end mill having a machining diameter of about 10 mm. Conversely, if the inlet diameter is too small, the sinking of the small-diameter end mill will occur. Since it becomes difficult to taper the inner surface of the hole, the entrance diameter of the sinking hole is 1/1 of the end mill diameter.
It is better to set it to 2/3.

If the depth of the sinkhole is too shallow, the re-grinding allowance cannot be sufficiently taken. On the other hand, if the depth is too deep, the strength at the tip side decreases. ing.

Further, when the taper angle of the sunk hole is less than 10 °, the relief of the inner cutter is insufficient and the effect of reducing the load when cutting with the inner cutter is thin. On the other hand, when the taper angle exceeds 50 °,
The taper angle is 10 ° or more because the root side wall thickness of the portion surrounding the sinkhole becomes too small, resulting in insufficient strength at the tip side.
It is preferable to set the angle within a range of 50 °.

[0019]

FIG. 1 shows an embodiment of an end mill according to the present invention. In the figure, 1 is a shank, 2 is a sunk hole provided on the tip end face, 3 is both end faces, that is, a center hole provided on the back end face of the sunk hole 2 and the rear face of the shank 1, 4 is an outer peripheral blade with a twist angle, 5 is a bottom blade at the tip, 6 is an inner blade, 7 is a tip pocket provided at each of the bottom blades, and 8 is a twist groove along the outer blade 4.

Reference numeral 9 denotes a flank of the bottom blade 5. As shown in FIG. 1D, the flank 9 is formed so as to be inclined downward toward the rear in the rotation direction of the end mill, and the flank 9 has a clearance angle α.

In FIG. 1 (b), κ is the watermark angle of the bottom blade 5, which is also attached to a conventional end mill.

The end mill shown in FIG. 1 is different from the end mill shown in FIG. In this manner, by forming the sinking hole 2 as a tapered hole inclined in the direction of the depth, the angle of the inner blade 6 formed by the intersection ridge between the inner peripheral surface of the hole and the groove surface of the chip pocket 7 is formed. κ 'is attached, and the thrust in vertical feed cutting is reduced. Further, as shown in FIG. 1 (c), a clearance t is formed behind the inner cutter 6 in the rotation direction to reduce the load when cutting by the inner cutter 6 is performed. Frequent stress is eliminated.

The inlet diameter d of the sink hole 2 shown in FIG. 1B is set to 1/2 to 1/3 of the end mill diameter D. The depth L of the sink hole 2 is 1 / 5D to 1 / 10D.
The taper angle θ is set in the range of 10 ° to 50 °.

The end mill of the present invention configured as described above has a diameter D of 11.6 mm, a number of blades N of 6, a sink hole entrance diameter d of 5.5 mm, a sink hole depth L of 2.0 mm, and a sink hole. As a result of an evaluation test using a prototype having specifications of a taper angle θ of 20 °, it was found that there was no breakage accident and the life was extended 1.5 to 2 times as compared with the conventional product.

[0025]

As described above, according to the end mill of the present invention, an inner peripheral surface of the sinking hole and a groove surface of the chip pocket are formed by converting a sinking hole, which was conventionally formed into a straight or tapered taper shape, into a deeper tapered hole. The inner edge formed at the intersection of the edge and the clearance is naturally provided with a clearance angle and a clearance, thereby preventing breakage of the tip, improving the life and reducing the cost of the cutting tool.

In addition, it is not necessary to provide a relief for each blade, and the tapering of the sinking hole can be efficiently performed by using a grindstone having a diameter larger than the grindstone used when providing the relief for each blade. Therefore, the manufacturing cost can be reduced, and the cutting tool cost can be reduced.

[Brief description of the drawings]

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 a tip portion of the end mill. FIG. Enlarged sectional view along X-ray

FIG. 2A is a side view of a conventional end mill with a sunk hole. FIG. 2B is an enlarged partial cutaway side view of a tip end of the end mill.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shank 2 Submerged hole 3 Center hole 4 Outer edge 6 Inner blade 7 Tip pocket 8 Twisted groove 9 Bottom blade flank α Bottom blade clearance angle κ Bottom blade watermark angle κ 'Inner blade watermark angle t Inner blade Escape clearance

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshi Miura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. (72) Inventor Shoji Okui 1-1-1-1, Koyokita, Itami-shi Sumitomo Electric (72) Katsuya Nakagihara, 1-1 1-1 Koyokita, Itami F-term in Itami Works, Sumitomo Electric Industries, Ltd. (reference) 3C022 KK03 KK06 KK23 KK26

Claims (2)

[Claims] The present invention has three or more peripheral blades and a bottom blade connected to each peripheral blade, and has a center hole at both ends, and the center hole on the bottom blade side is a deep end face of a sinking hole provided at the center of the tip. The sinking hole is formed by a tapered hole whose diameter increases from the inlet to the back, and an inner peripheral surface of the tapered sinking hole intersects a groove surface of the tip chip pocket at an inner end of the bottom blade. Cemented carbide solid end mill with inner edge formed by ridges. 2. An inlet diameter of the sink hole is set equal to an end mill diameter.
２〜 to ３, depth is 1/5 to 1/1 of end mill diameter
2. The end mill according to claim 1, wherein the taper angle of the hole is set in a range of 10 ° to 50 °.