Title

Drill insert and drill bit

Technical Field

The present application relates to a drill insert and a drill bit using the drill insert, which are particularly suitable for drilling a hard material.

Background Art

Drill bits for drilling hard materials, such as rock, typically have forward impact and rotary cutting capacities. For example, Fig. 1 schematically illustrates a conventional drill bit for drilling a hard material, the drill bit comprising a cemented carbide insert 1 and a drill shank 2 holding the insert 1 . A chisel edge 5a is formed in the middle of the front end face of the insert 1 , and a pair of cutting edges 5z are formed on the two main surfaces of the insert 1 . The chisel edge 5a extends between the two main surfaces and is connected between inner ends of the two cutting edges 5z. The chisel edge 5a is mainly used for forward impact, and the two cutting edges 5z are mainly used for rotary cutting. The chisel edge 5a and the two cutting edges 5z are all straight. A significant included angle is formed between the straight chisel edge 5a and each of the two straight cutting edges 5z, resulting in a significant difference and an abrupt change between a cutting angle at the chisel edge 5a and a cutting angle at the cutting edge 5z. The cutting angle at the chisel edge 5a is large, for example, usually about 110°. The cutting angle at the chisel edge 5a is too great, and there is a great difference between the cutting angle at the chisel edge 5a and the cutting angle at the cutting edge 5z, resulting in the formation of a blunt blade portion, which affects the cutting capacity of the drill bit. In addition, the transition parts between the chisel edge 5a and the two cutting edges 5z are easily damaged due to stress concentration during drilling. For the drill bit for drilling a hard material, it is necessary to ensure its machining capacity and also improve the durability of the insert. It is difficult for the drill inserts in the prior art to have excellent performance in both the aspects.

Summary of the Invention

The present application aims to provide a drill insert and a drill bit using the drill insert, which can improve both the machining capacity and the durability.

According to an aspect of the present application, provided is a drill insert for drilling a hard material, the drill insert having a rotation axis in a direction X, two main surfaces opposite to each other in a direction Z, two side surfaces opposite to each other in a direction Y, a front end face, and a rear end face, wherein the front end face is provided with a blade, which comprises a chisel edge in the centre and cutting edges joined to two end points of the chisel edge; wherein a cutting angle of the blade is measured in a datum plane at each point on the blade, the datum plane is perpendicular to a plane YZ, and the projection of the blade in the plane YZ at this point (or a tangent line of the projection of the blade 5 in the plane YZ at this point) is orthogonal to the projection of the datum plane in the plane YZ; and the blade is manufactured such that the difference in cutting angle at various positions on the entire blade is less than 20°, preferably less than 15°, and there is a smooth transition between the cutting angle of the chisel edge and the cutting angle of the cutting edge.

In an embodiment, the cutting angle at the end point of the chisel edge is equal to the cutting angle at a start point of the cutting edge joined thereto.

In an embodiment, the cutting angle at various positions on the blade is selected within the following range: the cutting angle on the chisel edge is in the range from 80° to 95°; and the cutting angle on the cutting edge is in the range from 70° to 85°.

In an embodiment, the chisel edge is in the form of a curve that axially bulges forwards, and the cutting angle on the chisel edge is variable and varies by no more than 10°. In an embodiment, the cutting angle on each of the cutting edges is variable and varies by no more than 15°, preferably no more than 10°.

In an embodiment, each of the cutting edges extends from the corresponding end point of the chisel edge to the corresponding side surface of the insert; and each of the cutting edges is straight, with a cutting angle thereon varying by no more than 5°; or each of the cutting edges is curved, with a cutting angle thereon varying by no more than 10°.

In an embodiment, each of the cutting edges comprises at least two consecutive segments, one of which has a variable cutting angle; and the at least one segment is a straight segment, with a cutting angle thereon varying by no more than 5°; or the at least one segment is a curved segment, with a cutting angle thereon varying by no more than 15°.

In an embodiment, the cutting angle of one segment of each of the cutting edges is substantially constant.

In an embodiment, each of the cutting edges comprises: a first cutting edge segment extending from the corresponding end point of the chisel edge to the corresponding main surface of the insert, and a second cutting edge segment formed by a line of intersection of a portion of the front end face and the corresponding main surface, the cutting angles at the first cutting edge segment and the second cutting edge segment being selected within the following range: the cutting angle on the first cutting edge segment is in the range from 75° to 85°; and the cutting angle on the second cutting edge segment is in the range from 70° to 80°.

In an embodiment, there is a smooth transition between each of the end points of the chisel edge and the start point of the cutting edge joined thereto, so that in the projection in a reference plane containing or parallel to the rotation axis, an included angle between each of the end points of the chisel edge and the start point of the cutting edge joined thereto is less than 10°, preferably less than 5°, and most preferably the tangent lines thereof are the same. In an embodiment, the reference plane is a plane XY, or is a plane perpendicular to the plane YZ and tangent to the chisel edge at the centre of the chisel edge, and the chisel edge is a quadratic curve in the projection in the reference plane.

In another aspect of the present application, provided is a drill bit, comprising a drill shank and a drill insert mounted on the drill shank, the drill insert being a drill insert described above, wherein a blade of the drill insert is preferably formed by means of machining, such as grinding, the drill insert after the drill insert has been mounted to the drill shank, so as to form various features related to the blade.

According to the present application, the blade of the drill insert has a more uniform cutting angle than the prior art in Fig. 1 , which can improve the drilling capacity of the insert; and the wear on all parts of the insert is even, which can improve the durability of the insert.

Brief Description of the Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description in conjunction with the accompanying drawings, in which:

Fig. 1 is a partial schematic diagram of a drill bit in the prior art;

Figs. 2 to 4 are respectively a front view, a top view and a perspective view of a drill insert according to an embodiment of the present application;

Figs. 5 and 6 are respectively a top view and a perspective view illustrating a cutting angle of the drill insert shown in Figs. 2 to 4;

Fig. 7 is a distribution diagram of the cutting angle of the insert of the drill bit according to the embodiment shown in Figs. 2 to 4;

Fig. 8 is a distribution diagram of a cutting angle of the insert of the drill bit in the prior art in Fig. 1 ;

Fig. 9 is a top view of a drill insert according to another embodiment of the present application; and

Fig. 10 is a distribution diagram of a cutting angle of the insert of the drill bit according to the embodiment shown in Fig. 9. Detailed Description of Embodiments

Various feasible implementations of a drill bit and a drill insert according to the present application are described below with reference to the drawings. It should be noted that the drawings herein are intended to show the principles of the present application clearly, so that some details are omitted, and the drawings are not drawn to scale and in actual shape.

The present application generally relates to a drill bit and a drill insert, which are used for drilling a hard material, especially stone.

Figs. 2 to 4 illustrate a drill bit according to an embodiment of the present application.

As shown, the drill bit comprises an insert 1 . The insert 1 is made of cemented carbide, is substantially plate-shaped, and is fixedly mounted (e.g., welded) to a drill shank (not shown).

The insert 1 has a height direction (an axial direction) X, a width direction (a transverse direction) Y and a thickness direction Z. The insert 1 has a rotation axis O in the direction X.

The insert 1 is flat and has two main surfaces 1 a parallel to each other and two side surfaces 1 b parallel to each other. The side surfaces 1 b may be arranged obliquely (not perpendicular) to the main surfaces 1 a as shown, or may be perpendicular to the main surfaces 1 a.

A front end face of the insert 1 (the face that faces the drilled material during drilling) axially bulges forward in the middle in the width direction. A blade 5 (a main edge) is formed on the front end face of the insert 1 . The blade 5 has a substantially 180° rotationally symmetrical shape. Each point on the blade 5 is the axially frontmost point among all the points on the insert at the same widthwise distance from the rotation axis O. The blade 5 extends from one side surface 1 b to the other side surface 1 b. The blade 5 comprises: a chisel edge 5a in the centre and cutting edges 5b respectively extending from end points of the chisel edge 5a.

The chisel edge 5a is a smooth curved segment, the centre of which is preferably on the rotation axis O and forms the axially frontmost point of the entire insert 1 . The chisel edge 5a is substantially inclined relative to the two main surfaces 1 a, viewed in the axial direction. Specifically, the chisel edge 5a has two end points, each of which is offset, relative to the centre of the chisel edge 5a, towards the corresponding main surface 1 a and side surface 1 b, viewed in the axial direction.

Each cutting edge 5b starts from the corresponding end point of the chisel edge 5a and ends at the corresponding side surface 1 b.

The cutting edge 5b is preferably a straight segment, but may also be a curved segment.

A smooth transition is formed between the start point of each cutting edge 5b and the corresponding end point of the chisel edge 5a, so that in the projection in a reference plane containing or parallel to the rotation axis, the start point of the cutting edge 5b and the corresponding end point of the chisel edge 5a have the same tangent line. In this way, no corner is formed between the start point of each cutting edge 5b and the corresponding end point of the chisel edge 5a, viewed from any direction. The reference plane is selected from a plane (the plane XY) which is parallel to the main surface and a plane which contains the rotation axis and is tangent to the chisel edge at the midpoint of the chisel edge.

The blade 5 divides the front end face into two rotationally symmetrical tool faces 7. With respect to the rotation direction, each tool face 7 comprises a front tool face 7a on the front side of the blade 5 and a rear tool face 7b on the rear side of the blade 5.

The line of intersection of each rear tool face 7b and the main surface 1 a adjacent thereto form a rear edge (a secondary edge) 6. The height of each point on each rear edge 6 in the axial direction is less than the height of the corresponding point on the blade 5 to which the rear edge faces in the thickness direction.

Optionally, in the projection in the plane XY as a reference plane (i.e., in the projection in the main surface 1 a), the projection of the chisel edge 5a is a quadratic curved segment, and the projection of each cutting edge 5b is a straight segment smoothly joined to the quadratic curved segment

Measured in another way, an imaginary plane in which the rotation axis O lies and which is tangent to the chisel edge 5a at the midpoint of the chisel edge 5a is taken as the reference plane. In the projection in the imaginary plane, the projection of the chisel edge 5a is a quadratic curved segment, and the projection of each cutting edge 5b is a straight segment smoothly joined to the quadratic curved segment.

The cutting angle of the blade 5 is further illustrated. The cutting angle at a point on the blade 5 is measured in such a manner that a datum plane is taken at this point, and the included angle between the datum plane and the line of intersection of the front tool face 7a and the rear tool face 7b at the front and back of this point on the blade 5 is the cutting angle at this point.

In the present application, the datum plane at any point on the blade 5 satisfies both the following conditions:

(1) the datum plane is perpendicular to the plane YZ, that is, the rotation axis O is parallel to the datum plane (this point is not on the rotation axis O), or the rotation axis O lies within the datum plane (this point is on the rotation axis O); and

(2) the projection of the blade 5 in the plane YZ (or the tangent line to the projection of the blade 5 in the plane YZ at this point) is orthogonal to the projection of the datum plane in the plane YZ at this point.

Referring to Figs. 5 and 6, a datum plane P at a point A on the blade 5 is shown as an example. Referring to Fig. 6, the cross-section of the datum plane P at the point A on the insert 1 is shown in section. A cutting angle 0 at the point A is measured in this section, and is between a line of intersection of the datum plane P at the point A and the front tool face 7a and a line of intersection of the datum plane P and the rear tool face 7b. By means of measuring the cutting angles at all points on the blade 5 in this way, the cutting angle distribution of the entire insert 1 can be obtained.

Fig. 7 shows the cutting angle distribution of an exemplary insert 1 of the present application. In Fig. 7, the abscissa axis represents the distance W in the width direction of the points on the cutter blade 5 from the rotation axis O (see Fig. 5), expressed as a percentage of the distance W to the total width of the insert 1 ; and the coordinate axis represents the cutting angles measured at the points. The curve in the figure represents the cutting angles at various positions on the blade 5.

It can be seen from Fig. 7 that the maximum cutting angle is at the central point (through which the rotation axis O passes) of the chisel edge 5a and is about 86°. As the point on the chisel edge 5a moves away from this central point, the cutting angle gradually decreases in the form of a curve. At the end points on both sides of the chisel edge 5a, the cutting angle decreases to about 81°. The cutting angle at the start point of each cutting edge 5b joined to the end point of the chisel edge 5a is the same as the cutting angle at the end point of the chisel edge 5a. As the point on the cutting edge 5b moves away from the start point, the cutting angle decreases linearly, but only slightly. At the end point of each cutting edge 5b, the cutting angle decreases to about 80°.

The cutting angle of the insert 1 in the prior art shown in Fig. 1 is measured by means of the same method, and the result obtained is shown in Fig. 8. It can be seen that the cutting angle remains about 117° throughout the chisel edge 5a, and the cutting angle remains about 75° at each cutting edge 5z. The cutting angle at the chisel edge 5a is significantly greater than that at the cutting edge 5b, and there is a step change in cutting angle between the cutting edge 5b and the chisel edge 5a, which is not conducive to the rotary cutting capacity of the drill bit. In addition, the presence of the step change in cutting angle on the blade tends to lead to uneven wear at various positions on the blade, which shortens the service life of the insert. It can be seen from Fig. 7 that the cutting angles at the points on the chisel edge 5a of the drill bit of the present application vary smoothly in the form of a curve. The cutting angle at the end point of the chisel edge 5a and the cutting angle at the start point of each cutting edge 5b are equal and are in smooth transition. Moreover, the cutting angles at various positions on the entire blade 5 are in the range from about 80° to about 86°, and there is a small variation between the cutting angles at the chisel edge 5a and at the cutting edge 5b. With such a distribution and variation of cutting angles, there is no blunt part throughout the blade, which is conducive to improving the rotary cutting capacity of the drill bit, especially the hard material crushing capacity during drilling. In addition, the cutting angles in an even distribution in the present application results in more even wear at various positions on the entire blade, which can prolong the service life of the insert.

In addition, according to the present application, there is a smooth transition between the chisel edge and the cutting edge, so that there is no significant geometrical abrupt change (included angle) in the transition part between the chisel edge and the cutting edge, so that the stress concentration at the transition part is alleviated or even eliminated during drilling, and the transition part is not easily damaged, thereby avoiding the fracture of the entire insert so as to prolong the service life of the entire drill bit.

In addition, according to the present application, the chisel edge of the drill insert is in the form of a curve that bulges forwards, and when the drilling of a hard material starts, a point of contact is formed between the chisel edge and the surface of the hard material, so that the pressure applied by the insert to the hard material can be increased, the forward impact fracture capacity of the drill bit can be improved, and the drilling speed can be increased. Moreover, the curved chisel edge makes it easier to accurately centre the insert on the hard material.

The cutting angle at various positions on the blade in the embodiment in Figs. 2 to 4 can be selected within the following range: the cutting angle on the chisel edge 5a is in the range from 80° to 95°; and the cutting angle on the cutting edge 5b is in the range from 75° to 85°. If the cutting edge 5b is straight, the cutting angle on the cutting edge 5b varies by no more than 5°. If the cutting edge 5b is curved, the cutting angle on the cutting edge 5b varies by no more than 10°.

Various modifications can be made to the previously described embodiment of the insert 1 by those skilled in the art. For example, in the modified embodiment shown in Fig. 9, the blade 5 comprises a chisel edge 5a in the centre and cutting edges respectively extending from end points of the chisel edge 5a. Each cutting edge comprises: a first cutting edge segment 5c extending obliquely from the corresponding end point of the chisel edge 5a to the corresponding main surface 1 a, and a second cutting edge segment 5d formed by a line of intersection of the corresponding tool face 7 and the main surface 1 a. Each first cutting edge segment 5c is joined between the corresponding end point of the chisel edge 5a and the second cutting edge segment 5d. Both the first cutting edge segment 5c and the second cutting edge segment 5d are preferably straight segments, but may also be curved segments.

There is a smooth transition between the start point of each first cutting edge segment 5c and the corresponding end point of the chisel edge 5a, so that in the projection in a reference plane containing or parallel to the rotation axis, the start point of the first cutting edge segment 5c and the corresponding end point of the chisel edge 5a have the same tangent line. The reference plane is selected as previously described. In this way, no corner is formed between the start point of each first cutting edge segment 5c and the corresponding end point of the chisel edge 5a, viewed from any direction. Other aspects of the embodiment in Fig. 9 are the same as or similar to the embodiment shown in Figs. 2 to 4, which will not be repeated.

The cutting angle of the insert 1 shown in Fig. 9 is measured by means of the method previously described, and the result obtained is shown in Fig. 10. It can be seen that the maximum cutting angle is at the central point (through which the rotation axis O passes) of the chisel edge 5a and is about 86°. As the point on the chisel edge 5a moves away from this central point, the cutting angle gradually decreases in the form of a curve. At the end points on both sides of the chisel edge 5a, the cutting angle decreases to about 81 °. The cutting angle at the start point of each first cutting edge segment 5c joined to the end point of the chisel edge 5a is the same as the cutting angle at the end point of the chisel edge 5a. The cutting angle decreases linearly as the point on the first cutting edge segment 5c moves away from the start point. At the end point of each first cutting edge segment 5c, the cutting angle decreases to about 75°. At each second cutting edge segment 5d, the cutting angle remains about 75°.

The embodiment in Fig. 9 can achieve the same or similar technical effect as previously described with reference to the embodiment shown in Figs. 2 to 4.

The cutting angle at various positions on the blade in the embodiment in Fig. 9 can be selected within the following range: the cutting angle on the chisel edge 5a is in the range from 80° to 95°; and the cutting angle on the first cutting edge segment 5c is in the range from 75° to 85°; and the cutting angle on the second cutting edge segment 5d is in the range from 70° to 80°.

It should be understood that the cutting edge of the insert 1 may be in other forms, such as three or more segments, to enable the insert 1 to achieve different functions. Each cutting edge of the insert 1 is preferably in the form of a straight line or a curve with a large bending radius, and forms a smooth transition with the chisel edge 5a, so that in the projection in a reference plane containing or parallel to the rotation axis, the included angle between the start point of each cutting edge and the corresponding end point of the chisel edge 5a is less than 10°, preferably less than 5°, and most preferably the tangent lines thereof are the same. The reference plane is selected as previously described. In this way, no significant corner, or even no corner, is formed between each cutting edge and the chisel edge 5a, viewed from any direction. The cutting edges of the insert 1 also preferably have a smooth transition therebetween.

For the cutting edges in various forms, according to the present application, the difference in cutting angle at various positions on the entire blade is less than 20°, preferably less than 15°. The cutting angle at the end point of the chisel edge is equal to the cutting angle at the start point of the cutting edge joined thereto, and there is a smooth transition between the cutting angle of the chisel edge and the cutting angle of the cutting edge. The cutting angle at various positions on the blade may be selected within the following range: the cutting angle on the chisel edge is in the range from 80° to 95°; and the cutting angle on the cutting edge is in the range from 70° to 85°.

The cutting angle on the chisel edge is variable and varies by no more than 10°. The cutting angle on each of the cutting edges is variable and varies by no more than 15°, preferably no more than 10°.

If each cutting edge comprises two or more segments, the cutting angle on at least one of the segments is variable, and varies by no more than 15°, preferably no more than 10°. The cutting angle on the straight segment varies by no more than 5°. The cutting angle on the curved segment varies by no more than 15°, preferably no more than 10°.

Each cutting edge may have a segment where the cutting angle is substantially constant.

With regard to the blade and the tool faces on the insert, the insert can be machined (e.g., ground), after being fixed (e.g., welded) to the drill shank, to form the blade and the tool faces. It is also possible to machine (e.g., grind) the insert to form the blade and the tool faces and then fix the insert to the drill shank.

By means of setting the cutting angles at various positions on the blade in this way, the cutting angles of the blade are relatively even at various positions, which can not only improve the drilling capacity during drilling, but also result in more even wear at various parts of the insert, thereby prolonging the service life of the insert.

In order to obtain the cutting angles defined in the present application, the designer can design the blade on the insert using various popularly used design software, so as to achieve the cutting angles at various parts by the combination of the front tool face and the rear tool face at the front and rear of the blade. It should be noted that although the blade 5 has a cross-section in the form of a sharp corner in the examples as shown, in practical applications, it is impossible to form an absolute sharp corner, but to be in the form of a rounded corner.

Although the present application is described herein with reference to the specific exemplary embodiments, the scope of the present application is not limited to the details as shown. Various modifications can be made to these details without departing from the basic principles of the present application.