Hard material bit

Abstract

A hard material bit for a rotary-percussion tool (2) includes at least one cutting edge (3), a bottom surface (6) located opposite the at least one cutting edge (3), and at least one attachment surface (8) and at least one free surface (10) both extending transverse to the bottom surface (6) and forming, respectively, a piecewise extending first chamfer (9a) and second chamfer (9b), with the second chamfer (9b) having a width greater than a width of the first chamfer (9a).

Description

BRIEF DESCRIPTION OF THE DRAWINGS:

The drawings show:

FIG. 1 a side view of a rotary-percussion tool with a hard material bit according to the present invention;

FIG. 2 a plan view of the tool shown in FIG. 1;

FIG. 3 a cross-sectional view along line III-III in FIG. 1;

FIG. 4 a cross-sectional view along line IV-IV in FIG. 2;

FIG. 5 a cross-sectional view along line V-V in FIG. 2; and

FIG. 6 a detail VI in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A hard material bit 1 according to the present invention and which is shown in its entirety in FIGS. 1-6, is designed for use with only schematically shown rotary-percussion tool 2 formed as a rotary drilling chisel and rotatable about an axis A. The bit 1 has two X-shaped cutting edges 3 and two diametrically opposite main discharge grooves 4. The hard material bit 1 is connected with a shaft end 5 of the rotary-percussion tool 2 at its bottom surface 6 in a material-locking manner, being brazed thereto with a hard solder 7 in the form of bronze. Two concave attachment surfaces 8, which extend transverse to the bottom surface 6, form a first, piecewise circumferentially extending chamfer 9a having a width Ba, and two concave free surfaces 10, which likewise extend transverse to the bottom surface 6, form a second, piecewise circumferentially extending chamfer 9b having a width Bb twice of the width Ba of the first chamber 9a. A chamfer angle α with respect to the axis A is equal to 45°. The X-shaped, hard material bit 1 is brazed in a matching-shaped mortise 11 in the steel shaft end 5 over the two diametrically opposite attachment surfaces 8, the first chamfer 9a, and the bottom surface 6. The hard material bit 1 is also butt-brazed to a base surface 12 of the shaft end 5 which extends radially beyond the bottom surface 6 of the bit 1, along two sectors 4 of both diametrically opposite free surfaces 10 over the bottom surface 6 and the second chamfer 9b.

Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A hard material bit for a rotary-percussion tool (2), comprising at least one cutting edge (3); a bottom surface (6) located opposite the at least one cutting edge (3); at least one attachment surface (8) extending transverse to the bottom surface (6) and forming a piecewise extending first chamfer (9a); and at least one free surface (10) extending likewise transverse to the bottom surface (6) and forming a piecewise extending second chamfer (9b) having a width greater than a width of the first chamfer (9a).

2. A hard material bit according to claim 1, wherein the width (Bb) of the second chamfer (9b) amounts to between a double and five times of the width (Ba) of the first chamfer (9a).

3. A hard material bit according to claim 1, wherein a chamfer angle (α) relative to a tool axis (A) is within a range from 30° to 60°.

4. A hard material bit according to claim 1, having an X-shaped profile, and wherein the first chamfer (9a) is formed by two attachment surfaces (8) located diametrically opposite each other, formed as concave surfaces, and the second chamfer (9b) is formed by two free surfaces (10) located diametrically opposite each other, formed as concave surfaces.

5. A rotary-percussion tool, comprising a shaft end (5) having an X-shaped mortise (11); and a hard material bit (1) having a matching X-shaped profile and connectable with the shaft end (5) in a material-locking manner by brazing, the hard material bit (1) including cutting edge means (3), a bottom surface (6) located opposite the cutting edge means (3), at least two concave attachment surfaces (8) extending transverse to the bottom surface (6), located diametrically opposite each other and forming a first chamfer (9a), and at least two concave free surfaces (10) extending likewise transverse to the bottom surface (6), located opposite each other and forming a second chamfer (9b) having a width greater than a width of the first chamfer (9a), wherein the X-shaped hard material bit (1) is brazed in the X-shaped mortise (11) in the shaft end (5) over the two, diametrically opposite attachment surfaces (8), the first chamfer (9a) and the bottom surface (6), and is butt-brazed to a base surface (12) of the shaft end (5) which extends radially beyond the base surface (6) of the bit (1), along two sectors (4) of the diametrically opposite free surfaces (10) over the bottom surface (6) and the second chamfer (9b).