DE8809699U1 - Solid carbide end mills - Google Patents

Description

-2- Description

The invention relates to a solid carbide end mill (hereinafter referred to as solid carbide end mill) with at least one tooth that has a chip surface that forms a wedge angle with the associated chip surface.

End mills usually have several teeth

for example three. These run at an angle offset from each other in a spiral shape around the Scha-waxes.

Each chip surface is followed by a clearance surface at a wedge angle. This has a clearance angle relative to the blank's circumference, from which the milling area of the end mill is machined. This means that the individual clearance surfaces are set back relative to the blank's circumference, preferably by relief grinding, so that the end mill does not get stuck in the workpiece to be milled during the milling feed. To ensure this, the clearance surface must have a minimum clearance angle relative to the blank's circumference.

Known solid carbide end mills have a flank in the form of a two-surface relief grinding. Such end mills tend to suffer from relatively severe grain breakouts on the flank in the area where they meet the chip surface. Such grain breakouts lead to premature wear and a correspondingly short service life of the solid carbide end mill.

It is an object of the invention to make available a solid carbide end mill of the type specified at the outset , which leads to significantly reduced wear and a correspondingly increased service life.

The solution to this problem consists in the fact that the flank surface is formed by a conical or eccentric relief surface.

Comparative tests between end mills with conventional two-surface relief grinding and with relief grinding according to the invention show the surprising result that the wear width, which is usually used as a wear measure when evaluating end mills, is reduced by 20 to 50% in otherwise identical solid carbide cutting mills, depending on the milling cutter material and the workpiece material, by the relief grinding surface according to the invention. This means that the relief grinding surface according to the invention has achieved a very considerable reduction in wear and a corresponding increase in service life in solid carbide end mills.

The advantages of an end mill with relief grinding according to the invention are in particular:

1. An end mill with a tapered or eccentric relief grind can be resharpened for at least twice as long as an end mill with a conventional grind.

2. The tapered (eccentric) relief grind significantly expands the application area of the end mill, as each individual tooth has double relief.

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support.

3. Regrinding is much easier for the end mill user than with a conventional tool. This is because the user usually has no way of sharpening the two relief surfaces of the conventional end mill. However, with the end mill according to the invention, it is sufficient to relap the breast or chip surface of the end mill, which the user can do with very simple means.

4. The change in relief grinding according to the invention means that end mills can be used to machine very different materials, from aluminum to gray cast iron to steel.

In many cases where two different solid carbide end mills were previously required, a single end mill is now sufficient.

The cutting geometry of the end mill according to the invention is such that it has the same clearance angle at every point on the relief surface, which brings about a significant improvement in terms of stability and smooth running.

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The invention is illustrated below using an embodiment. The accompanying drawings show:

Fig. 1 is a longitudinal side view of an end mill;

Fig. 2 shows an enlarged view of a face 3π end mill of the type shown in Fig. 1;

Fig. 3 is a partially enlarged view of a solid carbide end mill with conventional two-surface relief grinding; and

Fig. 4 is a partially enlarged view of a solid carbide end mill with a tapered relief grinding according to the invention in the embodiment shown.

In Fig. 1, a solid carbide end mill is shown in approximately natural size. One part of the shaft is used for clamping and is free of milling teeth. The remaining part is provided with, for example, three milling teeth,

which twist in angular displacement to each other

' shape around the shaft axis.

! As the front view in Fig. 2 shows more clearly,

' each chip surface S on the blank circumference RU, which is

the circumference of the clamping shank part of the end mill

From the outer end of each span

The so-called clearance surface FF extends away from the chip surface and is set back from the blank's peripheral surface RU, and forms a wedge angle K with the chip surface. Following the relief surface, the clearance surface merges into a groove A which is also helical and which merges into the adjacent chip surface S at its end remote from the relief surface. The relief surface has a barrel flange FH which extends between the peripheral outer edge of the chip surface S and the groove A. The relief surface forms the so-called clearance angle FW with the tangent of the blank's peripheral surface RU.

The well-known two-surface relief grinding is shown in Fig. 3 i. The clearance surface FF is made up of two surface areas that form an obtuse angle with each other. In order to achieve a certain minimum clearance angle FW, the apex of the two surface parts of the two-surface relief grinding must have a certain minimum distance from the blank circumference RU. This leads to a certain maximum wedge angle K between the chip surface S and the adjacent area of the two-surface relief grinding.

A solid carbide end mill according to the invention as shown in Fig. 4 has a conical or eccentric relief grinding surface, namely eccentric with respect to the shaft axis. This means that the flank surface FF of the solid carbide end mill according to the invention has an arcuate shape.

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Comparative tests between conventional solid carbide end mills | and solid carbide end mills according to the invention show the following values for the wear width V _ß :

First try: Milling length: 10 m Material hardness: . approx. 400 N/kb ² Cooling: Emulsion Conventional solid carbide end mill

of type 21102/12/3: V _ß » 0.07

Solid carbide end mills accordingly Type 21105/12/3, but with

inventive relief grinding: V _£ = 0.049

Result: The relief grinding according to the invention has reduced the wear width by 30%.

Second try: Milling length: 1200 mm Workpiece strength: 1400 N/mm ² Cooling: Emulsion Conventional solid carbide end mill

of type 21102/12/2: V _ß - 0.047

Same end mill, but

with relief grinding according to the invention: V _ß - 0.035

Result: The relief grinding according to the invention leads to a reduction in the wear width by 25t.

-8- Third attempt:

Milling length: 1200

Workpiece strength: 1400 M/am ² Conventional solid carbide end mill

of type 21105 KlO: V _R - 0.04

Same HSS end mill with

inventive relief grinding: V” « 0.025

Result: Improvement of the wear width by 37% due to the relief grinding according to the invention.

Claims (2)

KtUNKER · SCHMTIT-NILSON -HQtSJOH i ^: -''-'·''-'·' PATENT ATTORNEYS .· · . : : *: :.&eacgr;&igr;»&ogr;&rgr;&egr;&agr;&ngr; patent attorneys Hoffmann GmbH Quality Tools Haberlandstrasse 55 8000 Munich 60 ur.Z.: K 32 652S/6 29 July 1988 Solid carbide end mills Protection claims 1. Solid carbide end mill with at least one tooth which has a chip surface (',S) which forms a wedge angle (K) with the associated flank surface (FF), characterized in that the flank surface (FF) is formed by a conical relief surface. 2. Solid carbide end mill according to claim 1, characterized in that three teeth (S) are provided, each with a conical back grinding surface.