IL177254A - Ballnose end mill - Google Patents

Description

BALLNOSE END MILL m pit»i oi a 177254 'n | 453560 ΤΓΜ Pearl Cohen Zedek Latzer P-8934-IL The present invention relates to tools for the machining of materials by milling.

More particularly, the invention provides an improved end mill having a hemispherical end and a serrated flute body.

End mills are widely used in milling operations due to their versatile range of application and due to the moderate first cost of the tool. End mills are often of cylindrical shape, and may have a hemispherical cutting end, also referred to as ball end or ball nose or ball nose rougher, being particularly useful for CNC work producing complex shapes. An end mill has a number of cutting surface shapes, the nature of which depends on whether it is to be used for hard or soft materials, whether for rough cutting or finishing, the machine tool, and further factors.

An acute problem which has attracted much attention is the clearing away the material produced during machining. Unlike lathe machining, or turning, milled chips are never continuous and if not removed, may again be drawn into the cutting area between the cutting surfaces and the work piece. The result is a degraded surface finish, tool vibrations and increased load on the end mill, the last two ultimately causing it to wear out prematurely.

An additional most important problem is the time factor of performing a given job.

In US Patent No. 6,913,426 to Nobukazu, there is disclosed a throwaway insert having a cutting edge, designed to be mounted onto a tool body. The use of the insert is meant to provide constant cutting efficiency. However, in high volume operations, the disposable nature of using the insert becomes cost-prohibitive.

In attempting to reduce the generation of chips during milling. Japanese Patent No. .IP 2006015419, to Nariyuki, teaches a ball end mill having an arcuate end blade, which further has radial rake angles. The design of the end mill, as well as the inventor' s own admission, testifies to the fact that the problem of chip generation is only partially addressed by the end mill in his invention, and chip removal remains an acute problem.

Shortcomings of the same nature are present in the US Patent 6,953,310 to Iwamoto, wherein a cemented carbide ball end mill has a chip-evacuating flute, which, most prominently, forms an unusual angle to the central axis of the tool, as well as the angle to the rake face. At best, this tool may succeed in keeping fewer chips in the already cut region of the workpiece.

U.S. Patent 6082935 to Nachi describes a ball nose end mill which however does not address the problem of stock removal rate.

U.S. Patent 5562370 to Kennametal refers to a ball nose end mill with an insert, contrary to the present end mill not having an insert.

It is therefore one of the objects of the present invention to obviate the disadvantages of prior art tools and to provide a ball end mill which substantially increases stock removal rate. It is a further object of the present invention to provide a ball end mill that will significantly remove material from cutting surfaces.

The present invention achieves the above objects by providing a ball end mill, or similar configuration, such as a corner radius, preferably coated with a vapor-coated layer to aid in cutting, and utilizes thread-like serrations between flutes.

In a preferred embodiment of the present invention there is provided an improved ball-head end mill or similar configuration having a centerline of rotation and a cutting body, the cutting body being adjacent on first end to a cylindrical gripping section and at the second end terminating in a hemispherical form.

In a preferred embodiment of the present invention there is provided an improved ball-head end mill or similar configuration having a centerline of rotation and a fluted cutting body, the fluted cutting body being adjacent on first end to a cylindrical gripping section and at the second end terminating in a hemispherical form, the end mill comprising teeth formed between the flutes, the teeth being serrated by closely-spaced serrations, the serrations also extending around said hemispherical form; and the fluted cutting body containing 2 to 12 flutes, inclusive.

In a preferred embodiment of the present invention there is provided a ball-head end mill or similar configuration as wherein the serrations extend to the cutting edge of the teeth.

In a preferred embodiment of the present invention there is provided a ball-head end mill or similar configuration wherein the cutting edges are preferably coated with a coating by means of a physical vapor deposition method.

In a further preferred embodiment of the present invention there is provided a ball- head end mill wherein the serrations are generally substantially transverse to the centerline of rotation.

In U.S. Patent No. 6796751 , to Flolo, there is described and claimed an insert for a ball end mill. The insert has a cutting face composed of crest-and-root serrations. In the best-case scenario, a tool may accept no more than two such inserts. The insert disclosed in this patent does not address the task of removing the material during machining.

In contradistinction thereto, the present invention provides a ball end mill comprising serrations preferably but not necessarily throughout the length of the cutting body, including the ball end thereof, the entire surface of the cutting body further preferably coated with a vapor-deposited layer.

It will thus be realized that in operation the cutting edges of the novel cutter of the present invention are in only partial contact with the metal workpiece. Thus, less force is required to at the cutting edges which translates directly into power savings, in comparison with common end mills. More so, less heat is generated and more material can be removed faster.

In operation the cutter according to the invention produces much smaller metal material. These are easily entrained and removed by a normal flow of coolant or air, as is known by those experienced in the operation of machining.

Thus end mills made according to the present invention serve to a) allow for high stock removal rates, thus reducing cycle times and increasing productivity; b) produces chips which due to their small size are efficiently removed by a flow of coolant; c) obtaining an almost finished workpiece, which needs very little finishing.

As with all high performance milling cutters the end mill according to the present invention is advantageously coated with -a thin super-hard coating to increase tool life. However the advantages of the cutter described herein can be gained to a lesser extent also by use of an uncoated cutting tool.

The invention will now be described■■ further with reference to the accompanying drawings, which represent by example preferred embodiments of the invention. Structural details are shown only as far as necessary for a fundamental understanding thereof. The described examples, together with the drawings, will make apparent to those skilled in the ait how further forms of the invention may be realized.

In the drawings: FIG. 1 is a side view of a preferred embodiment of the ball end mill according to the invention.

FIG. 2 is an end view of a preferred embodiment of the ball end mill according to the invention.

There is seen in FIG. 1 a ball end mill 12 having a cylindrical gripping section 80, a cylindrical fluted cutting body 10, and a hemispherical cutting head 20. The cutting body 10 has between 2 - 12 flutes 30, depending primarily on the outer diameter of the end mill. The flutes 30 extend into the hemispherical head. It should be noted that the body could be without said flutes.

Closely spaced, tooth-like serrations 40 are disposed on the teeth 16 remaining between the flutes 30. The serrations 40 extend through the cutting edge 18 of teeth 16. The number of the serrations depend on the size of the tool.

The serrations 40 are preferably longitudinal and are generally transverse to the axis of the ball end mill, according to the most preferred embodiment of the invention.

The serrations 40, according to another embodiment of the invention, may be slightly sloped in relationship to the main axis of the end mill 12.

According to a preferred embodiment of tlie invention, the cylindrical fluted cutting body 10 and the hemispherical cutting head 20 are coated by means of a physical vapor deposition method. The coating layer may contain a material selected from the group including carbide, nitride and oxide of metals in groups TV. sub. A, V.sub.A and VI.sub.A of the Periodic Table.

As seen in FIG. 2, serrations 14 of cutting head 20 extend substantially around the hemispherical form. The serrations 14 are in the present example similar in shape and spacing to the serrations 40, however they could be of different shape and spacing.

The scope of the described invention is intended to include all embodiments coming within the meaning of the following claims. The foregoing examples illustrate useful forms of the invention, but are not to be considered as limiting its scope, as those skilled in the ait will be aware that additional variants and modifications of the invention can readily be formulated without departing from the meaning of the following claims.

Claims (10)

1. A ball end mill having a centerline of rotation, comprising: a cutting body; a hemispherical cutting head adjacent the cutting body and extending to one end of ball end mill; and a plurality of serrations disposed on the hemispherical cutting head.
2. 2. The ball end mill of Claim 1 , wherein the cutting body further comprises a plurality of flutes extending into the hemispherical cutting head, the plurality of flutes forming teeth having cutting edges there between.
3. 3. The ball end mill of Claim 2, further comprising a plurality of serrations disposed on the teeth, the plurality of serrations extending continuously between the cutting edges.
4. 4. The ball end mill of Claim 3, wherein the plurality of serrations are generally transverse to the centerline of rotation of the ball end mill.
5. 5. The ball end mill of Claim 3, wherein the cutting edges are coated using a vapor deposition technique.
6. 6. The ball end mill of Claim 1 , further comprising a gripping section at an opposite end of the ball end mill.
7. 7. The ball end mill of Claim 1 , wherein the serrations are generally transverse to the centerline of rotation of the ball end mill.
8. 8. A ball end mill having a centerline of rotation, comprising: a hemispherical cutting head at one end of the ball end mill; a gripping section at an opposite end of the ball end mill; a cutting body including a plurality of flutes extending into the hemispherical cutting head, the plurality of flutes forming teeth having cutting edges there between; and a plurality of serrations disposed on the hemispherical cutting head and the teeth of the cutting body.
9. 9. The ball end mill of Claim 8, wherein the serrations are generally transverse to the centerline of rotation of the ball end mill.
10. 10. The ball end mill of Claim 8, wherein the cutting edges are coated using a vapor deposition technique. LU22ATT0 & LUZZATTO