GB2163377A

GB2163377A - A metal-cutting tool

Info

Publication number: GB2163377A
Application number: GB08424065A
Authority: GB
Inventors: Manfred Szwajor
Original assignee: Linsinger Ernst & Co GmbH; Dr Techn Linsinger and Co GmbH
Current assignee: Linsinger Ernst & Co GmbH; Dr Techn Linsinger and Co GmbH
Priority date: 1984-07-12
Filing date: 1984-09-24
Publication date: 1986-02-26
Also published as: JPS6125710A; GB8424065D0; DE3425699A1

Abstract

In order to eliminate the high risk of breaking extra-long hard-metal cutters during three-dimensional milling, without reducing the effective number of cutters with regard to the high rate of advance, at least two suitably-shaped cutting elements (2), more particularly turn-over cutting plates of hard metal, are disposed side by side with or without a gap to form a cutter combination on a base member of a tool or on a cutting-element holder (15). The cutter combinations or cutting- element holders may also (to avoid long shut-downs) be disposed on an intermediate ring which is secured to the cutter head and can be quickly and easily replaced. <IMAGE>

Description

SPECIFICATION A metal-cutting tool The invention relates to a metal-cutting tool, more particularly for milling at high rates of advance, e.g.

three-dimensional milling, comprising a base member (cutter head) fitted with exchangeable cutting elements, e.g. hard-metal cutters or turnover cutting plates, and securing means for the cutting elements.

Prior-art tools of this kind have a base member or cutter head fitted with replaceable cutting elements, more particularly extra-long turn-over plates with clamping devices such as covers or wedges or clamping shoes. When wide working surfaces are being milled by methods such as conical orthreedimensional or peripheral milling, the cutter axis is inclined in the advance direction and during the engagement period the work surface moves along the cutting edge. The cutting elements must have a certain length (extra length) in order to distribute the cutting work over the relatively great cutting length.

Since hard metal is very brittle, there is a serious dangerthan long or extra-long cutters will break if locally stressed. To reduce or prevent this danger, the base members must be given a corresponding surface hardness. These base members, however, are very expensive to manufacture and themselves present problems of brittleness of the hard surface.

To reduce or prevent the risk of breakage when using these massive (large cross-section) hardmetal tools or cutting elements, the cutting element will have to be unusually thick, is extremely difficult to manufacture, and will be very uneconomic owing to the high costs relative to the weight of hard metal.

One possibility of avoiding the use of extra-long cutting elements would be to dispose short turnover plates in a number of overlapping tracks in known manner. This distribution, however, reduces the effective cutter number and thus drastically reduces the attainable rate of advance in the case of methods of milling where a high advance speed is very important, particularly in three-dimensional milling.

The object of the invention therefore is to devise a tool, more particularlyforthree-dimensional milling, which does not reduce the effective cutter number with regard to the speed of advance and eliminates the high risk of breakage of extra-long hard-metal cutters.

To this end, substantialiy according to the invention, in the case of a tool of the previouslydescribed kind, at least two suitably-shaped cutting elements, more particularly hard-metal turn-over cutting plates, are provided on a cutting element holder and are disposed at or in the base member or holder side by side with or without a gap to form a cutter combination.

According to a particularly advantageous feature, the base member (cutter head) is a conical milling cutter head, preferably having a large vertex angle between 150 and 1800. This advantageous embodiment of the base member gives very high rates of advance, the milling tool being inclined forwards in the direction of advance.

According to another particularly advantageous feature, turn-over cutting plates having a square base are disposed side by side to form a cutter combination and the square cutting plates, suitably shaped, have up to 8 teeth and can be used correspondingly often.

According to another advantageous feature, the cutter combination consists of turn-over cutting plates having a triangular or approximately triangular base, the base member or holder being formed with correspondingly-shaped seats to receive the cutting forces.

In the case of milling tools or cutter heads for three-dimensional milling it is advantageous (e.g. to make use of the full travel of a conical milling head as closely as possible above the workpiece surface) to secure the cutting plate e.g. by a countersunk screw in the aforementioned seats, which have corresponding bearing or abutment surfaces for receiving the cutting forces.

In order to replace cutter combinations or turnover cutting plates or cutting-element holders together and avoid prolonged shut-downs, according to a specially advantageous feature the cutter combinations or turn-over cutting plates are secured directly or via the cutting-element holders to an intermediate ring which is attached to the base member and can be quickly and easily replaced so that the cutter head adjustment can be retained without need for subsequent or re-adjustment.

According to another feature of the invention the cutter combinations are triangular turn-over cutting plates having bevelled or rounded corners, to prevent the gap between cutting plates becoming excessively large even when there is very little wear of exposed surfaces.

According to another advantageous feature of the invention, the cutter combination consists of turnover cutting plates having triangular and square bases disposed in alternation.

Advantageously, when there are more than two, more particularly square, plates, an e.g. sheet-metal spacer is inserted between the cutting elements and the cutters or cutter combinations are laterally clamped. This prevents the individual hard-metal plates from oscillating backwards and forwards and prevents direct contact between brittle hard metals.

According to another feature of the invention, the cutting elements are radially or tangentially disposed in or on the cutting element holder or on the base member or intermediate ring. If cuttingelement holders are used they can be radially or tangentially disposed on the base member or on the intermediate ring if required.

According to a particularly advantageous feature, the cutting-element surfaces are offset relatively to one another so that chips of considerable length, e.g. in three-dimensional milling, which are difficult to remove, are broken into two or more pieces.

Other advantages and features of the invention will be explained in detail with reference to the drawings which show diagrammatic embodiments and in which: Fig. 1 shows an extra-long turn-over cutting plate secured by a clamping wedge; Fig. 2 shows an extra-long turn-over cutting plate secured by screws; Fig. 3 shows part of a tool according to the invention in which a number of square cutting elements or turn-over cutting plates are disposed side by side; Fig. 4 shows a tool in which triangular cutting elements are disposed side by side; Fig. 5 shows a tool in which triangular cutting elements with bevelled corners are disposed side by side; Figs. 6 and 7 show triangular cutting elements with bevelled or rounded corners; Fig. 8 shows cutting elements in which the cutting surfaces are offset from one another.

Fig. 9 shows part of an intermediate ring with cutting element holders and cutting elements disposed therein and Fig. 10 is a cross-section of Fig. 9.

The device in Fig. 1 illustrates the prior art. A base member 1 of a milling tool has a radially-disposed turn-over cutting plate 2 clamped to member 1 by a wedge 3 secured by screws 4.

Fig. 2 is a perspective oblique view of an extralong turn-over cutting plate 2 secured by screws 4 to member 1.

In the embodiment in Fig. 3, plates 2 having a square base 16 are disposed side by side with a gap 5 preventing direct contact between plates 2. Gap 5 can be defined by inserting a spacer 13, more particularly so as exactly to secure the central plate and prevent the plates from oscillating backwards and forwards. Plates 2 are secured e.g. by screws 4 to member 1 or to a cutting-element holder 15 or an intermediate ring 14.

Fig. 4 shows triangular sheets formed in e.g. base 1 with bearing surfaces 6 and abutment surfaces 7 for receiving the cutting forces.

Fig. 5 shows turn-over cutting plates 2 with a triangular base and bevelled corners. Plates 2, like those shown in Fig. 3, are separated by a small gap 5 (less than 1.5 mm). After the cutter combination has come into action, a narrow web equal in width to the gap is left on the working surface. In the case of the aforementioned milling process for which the tool is designed, the motion of the cutter as seen vertically on the working plane, is not identical with the direction of advance and the web is cut away when the tool next engages, thus producing a clean working surface or plane. The webs can also be removed by a laterally offset device 8 as described in Figs. 6 and 7. In these devices the successive cutter combinations are each offset from one another by a lateral amount 8.As a result of the bevelling 11 of the approximately triangular plates 2 shown in Fig. 6, the length of exposed surface at gap 5 is relatively large, instead of being very short as in Fig. 4. Fig. 7 shows a solution in which the round parts 12 counteract any wear of exposed surfaces.

Fig. 8 shows plates 2 having an offset cutting surface 10 and/or a vertical offset 9.

Figs. 1 to 5 show tangentially disposed cutters.

However, the cutting elements shown in Figs. 6 and 7 can be used tangentially or radially with or without a holder 15, e.g. on an intermediate ring 14, more particularly for quick and easy replacement without altering the adjustment of the cutter head or the manner of operation.

The invention is not restricted to the embodiments described and illustrated but includes all routine modifications and partial and subcombinations of the described and/or illustrated features.

Claims

1. A metal-cutting tool, more particularly for milling at high rates of advance, e.g. threedimensional milling, comprising a base member (cutter head) fitted with exchangeable cutting elements, e.g. hard-metal cutters orturn-over cutting plates, and securing means for the cutting elements, characterised in that at least two suitablyshaped cutting elements, more particularly hardmetal turn-over cutting plates, are provided on a cutting-element holder and are disposed at or in the base member or holder side by side with or without a gap to form a cutter combination.

2. A tool according to claim 1, characterised in that the base member is a conical milling cutter head, preferably having a large vertex angle between 150 and 1800.

3. A tool according to claim 1 or 2, characterised in that turn-over cutting plates having a square base are disposed side by side to form a cutter combination.

4. Atool according to claim 1 or 2, characterised in that the cutter combination consists of turn-over cutting plates having a triangular or approximately triangular base, the base member or holder being formed with correspondingly-shaped seats to receive the cutting forces.

5. A tool according to one or more of claims 1 to 4, characterised in that the cutter combination or turnover cutting plates or the cutting-element holder is disposed in or on an intermediate ring secured to the base member.

6. A tool according to claim 1 or 2, characterised in that the cutter combination consists of triangular turn-over cutting plates having bevelled corners.

7. Atool according to claim 1 or 2, characterised in that the cutter combination consists of triangular turn-over cutting plates having rounded corners.

8. A tool according to claims 1 or 2, characterised in that the cutter combination consists of tu rn-over cutting plates having triangular and square bases disposed in alternation.

9. A tool according to anyone of the preceding claims, characterised in that a spacer is disposed between the cutting elements.

10. Atool according to claim 9, characterised in that the cutter or cutter combination is laterally clamped together.

11. A tool according to anyone of the preceding claims, characterised in that the cutting elements are disposed tangentially or radially in or on the base member on the cutting-element holder or in or on the intermediate ring.

12. A tool according to anyone of claims 1 to 8, characterised in that the cutting-elment holder or holders are tangentially or radially disposed in or on the base member or on the intermediate ring.

13. A tool according to anyone of the preceding claims, characterised in that the cutting elements are offset from one another laterally and/or vertically.

14. A metal-cutting tool substantially as hereinbefore with reference to anyone of the embodiments shown in Figures 1-10.