GB2199058A

GB2199058A - Tool Holder

Info

Publication number: GB2199058A
Application number: GB08726837A
Authority: GB
Inventors: Ernst Heiderich
Original assignee: Boart HWF GmbH and Co KG Hartmetallwerkzeugfabrik
Current assignee: Boart Longyear GmbH and Co KG
Priority date: 1986-11-20
Filing date: 1987-11-17
Publication date: 1988-06-29
Also published as: ATA247087A; AT387426B; GB8726837D0; DE8631103U1

Abstract

A tool holder (1) has a seating (2) for the shank of a cutting tool, with a bearing shell (3) for the shank formed as a hard-metal sleeve, to reduce wear and distortion, leading to extended lifespans for the tool holder and the cutting tool, and the hard-metal sleeve (3) may have a collar (4) covering at least part of the leading endface (5) of the holder (1) so that local wear is also reduced. <IMAGE>

Description

TOOL HOLDER This invention relates to a tool holder having a seating for the shank of a cutting tool, more particularly a round chisel, in which a bearing shell for the tool shank is inserted into the seating.

There are known tool holders of this type in which the bearing shell is formed as a surface- or through-hardened sleeve. Bearing shells of this type usually have a Rockwell hardness of 5 to 6 HRC on the outside and 4 to 5 HRC on the inside. It has been found that when tool holders with bearing shells of this type are used in mining and tunnelling operations serious wear and distortion develops on the inside face, concentrated more particularly in the upper and lower thirds of the shank seating or bearing shell. This leads to unsatisfactory lifespans for the tool holder and consequently for the cutting tool.

The object of the invention is to provide a tool holder of the type initially described which is characterised by substantially reduced wear and distortion, so that optimised mounting of the cutting tool leads to extended lifespans for the tool holder an the cutting tool.

According to the present invention, in a tool holder of the type initially described the bearing shell is formed as a hard-metal sleeve. The invention arises from the realisation that a hard-metal sleeve of this nature has outstandingly high inner and outer hardnesses and thus ensures optimal tool holding without premature wear or distortion damage. In this- way, the wear race of the assembly, including the cutting tool itself, is substantialy reduced, thereby extending the lifespans of both the tool holder and the cutting tool.

The hard-metal sleeve preferably extends over the entire length of the shank seating, though it is also advantageous to confine the hard-metal sleeve or two hardmetal sleeves to the upper third and/or the lower third of the shank seating. The hard-metal sleeve may have a collar covering at least part of the leading endface of the holder, so that local wear is also reduced. The hard-metal sleeve of the invention preferably has a Rockwell hardness of 84 to 93 HRA both inside and outside. A Rockwell hardness of this magnitude is preferably attained by using a hard-metal sleeve containing 6 to 25% cobalt, preferably 15% cobalt, as a binder, the remainder consisting of tungsten carbide. The hard-metal sleeve performs satisfactorily when it is shrunk into or brazed in the shank seating.

Two embodiments of the invention will now be described purely by way of examples with reference to the accompanying drawings in which: Figure 1 is an axial section through a tool holder in accordance with the invention; Figure 2 is a plan view of the tool holder of Figure 1; and Figure 3 corresponds Figure 1 but shows a modified version of tool holder in accordance with the invention.

Figures 1 and 2 show a tool holder 1 having a seating 2 for the shank of a cutting tool, more particularly a round chisel, not in itself shown. The tool holder 1 and cutting tool form a tool unit intended more particularly for use in mining and tunnelling machines. A bearing shell 3 for the tool shank is inset in the seating 2. The bearing shell is formed as a hard-metal sleeve, and it extends over the entire length of the shank seating 2. It is alternatively possible to confine the hard-metal sleeve 3 or two such sleeves to the upper third and/or the lower third of the shank seating 2.

In the modified embodiment of Figure 3, the hard-metal sleeve 3 has a collar 4 covering part of the leading endface 5 of the holder.

The hard-metal sleeve 3 preferbly has a Rockwell hardness of 84 to 93 HRA both inside and outside. It contains 6 to 25% cobalt, preferably 15% cobalt, as a binder, the remainder consisting of tungsten carbide. The hard-metal sleeve 3 may be shrunk into the shank seating 2, but it can alternatively be brazed in positon.

Claims

1. A tool holder having a seating for the shank of a cutting tool, in which a bearing shell for the tool shank is inserted into the seating, and wherein the bearing shell is formed as a hard-metal sleeve.

2. A tool holder as in Claim 1, wherein the hardmetal sleeve or two hard metal sleeves extends or extend over the upper third and/or the lower third of the shank seating.

3. A tool holder as in Claim 1 or Claim 2, wherein the hard-metal sleeve has a collar covering at least part of the leading endface of the holder.

4. A tool holder as in any one of Claims 1 to 3, wherein the hard-metal sleeve has a Rockwell hardness of 84 to 93 HRA both inside and outside.

5. A tool holder as in any one of Claims 1 to 4, wherein the hard-metal sleve contains 6 to 25% cobalt, preferably 15% cobalt, as a binder, the remainder consisting of tungsten carbide.

6. A tool holder as in Claim 5, wherein the hardmetal sleeve contains 15% cobalt.

7. A tool holder as in any one of Claims 1 to 5, wherein the hard-metal sleeve is shrunk into the shank seating.

8. A tool holder as in any one of Claims 1 to 5, wherein the hard-metal sleeve is brazed in the shank seating.

9. A tool holder having a seating for the shank of a cutting tool substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.