Method of grinding a parting/grooving insert and a parting/grooving insert

Abstract

A parting/grooving insert and a method of grinding a parting/grooving insert including rotating a plane grinding surface having a normal vector parallel to the axis of rotation and a tangential direction of rotation; providing a parting/grooving insert including a rake surface, a main clearance surface, and a main cutting edge formed between the rake and main clearance surfaces; orienting/positioning the insert relative to the grinding surface, such that the main clearance surface is parallel to the grinding surface, the normal vector of the main cutting edge being in the plane of the main clearance surface and with a vector component in the direction of rotation forming an angle to the tangential direction of rotation at the insert of at least 20 degrees from parallel orientation; and grinding the main clearance surface to provide grinding marks having an angle to the normal vector of the main cutting edge corresponding to the angle to the tangential direction of rotation.

Claims

1. A parting/grooving insert comprising: a rake surface; a left side clearance surface; a right side clearance surface; a main clearance surface having a plane; a main cutting edge formed between the rake surface and the main clearance surface, wherein the main cutting edge has a normal vector in the plane of the main clearance surface, and wherein the main clearance surface includes grinding marks having an orientation of at least 20 degrees to the normal vector of the main cutting edge, wherein the grinding marks have an orientation of less than 70 degrees to the normal vector of the main cutting edge; and a cutting edge including the main cutting edge, a left side cutting edge formed between the rake surface and the left side clearance surface, and a right side cutting edge formed between the rake surface and the right side clearance surface, the cutting edge being arranged to perform a parting/grooving operation, wherein the respective left and right side clearance surface each include grinding marks having an angle to the normal vector of at least 20 degrees.

2. The parting/grooving insert according to claim 1, wherein the grinding marks have an orientation of at least 30 degrees to the normal vector of the main cutting edge.

3. The parting/grooving insert according to claim 1, wherein the grinding marks have an orientation of less than 60 degrees to the normal vector of the main cutting edge.

4. The parting/grooving insert according to claim 1, wherein the left and right side clearance surfaces are formed in a shape of a shelf that protrudes from a respective left and right side of the insert.

5. The parting/grooving insert according to claim 4, wherein a rearward extension of the shelf from the main clearance surface, and thus the left and right side clearance surfaces, is greatest close to the respective left and right side cutting edge and wherein the rearward extension of the shelf decreases when moving in a direction downwards from the respective left and right cutting edges.

6. The parting/grooving insert according to claim 1, wherein an angle between the main clearance surface and the left side clearance surface and an angle between the main front clearance surface and the right side clearance surface is each is less than 90 degrees.

7. The parting/grooving insert according to claim 6, wherein an angle between the main clearance surface and the left side clearance surface and main front clearance surface and the right side clearance surface, respectively, is in the range of 85-89 degrees.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention is now described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows grinding of a parting/grooving insert according to prior art.

(3) FIG. 2 shows a parting/grooving insert according to an embodiment of the present invention.

(4) FIG. 3 shows positions of grinding the main clearance surface according to an embodiment of the present invention.

(5) FIG. 4 shows positions of grinding the left and right side clearance surfaces according to an embodiment of the present invention.

(6) FIG. 5 shows a slot milling tool according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

(7) In the following, a detailed description of a method of grinding a parting/grooving insert and a parting/grooving insert according to various embodiments of the invention is presented.

(8) First, in FIG. 1, a conventional method of grinding a parting/grooving insert 1 is illustrated. A grinding disc is provided, having a radially outer curved grinding surface around the circumference of the disc. The insert is brought towards this radially outer grinding surface to finish the main clearance surface of the insert. Thereby a main clearance surface is obtained having a slightly concave shape and provided with grinding marks extending straight from the lower portion of the surface to the upper portion of the clearance surface, at the cutting edge.

(9) A parting/grooving insert according to an embodiment of the invention is shown in FIG. 2. The insert comprises a body of cemented carbide, or other hard/wear resistant material, such as high speed steel or ceramics. The insert comprises a rake surface 3 and a main clearance surface 4. Between the rake surface 3 and the main clearance surface 4 a main cutting edge 5 is formed. An insert according to the invention has a plane main clearance surface 4 obtained during grinding, which will be explained in detail below.

(10) From the left and right hand sides of the body of the insert, a shelf 14 protrude to form a left and right side clearance surface 7 and 8, respectively (only the left side visible in FIG. 2). Between the left side clearance surface 7 and the rake surface 3, a left side cutting edge 9 is formed, and a right side cutting edge 10 is formed between the rake surface 3 and the right side clearance surface 8. The rearward extension of the shelf 14 from the main clearance surface 4 is greatest close to the respective left and right side cutting edge 9 and 10 and decreases with distance below the respective left and right side cutting edge. Thereby the width of the left and right side clearance surfaces 7 and 8, defined by the extension of the shelf, decreases when moving from the cutting edge and downwards. As will be seen later on the shape of the side clearance surfaces are relevant to the method of grinding of the insert.

(11) Between the left and right side clearance surfaces 7 and 8 and the main clearance surface 4, a respective left and right corner radius surface 11 and 12 is formed. Each corner radius surface is formed as a rounded transition surface between the main clearance surface and the right/left clearance surface extending along the side of the insert. Between the corner radius surface and the rake surface a corner radius cutting edge is formed having a rounded shape.

(12) A normal vector of the main cutting edge is defined as a vector which extends perpendicularly to the main cutting edge 5, and lies in the plane of the planar main clearance surface 4. Thus the normal vector of the main cutting edge may extend in the direction N shown in FIG. 2, or in the opposite direction.

(13) The main clearance surface 4 is provided with grinding marks illustrated as lines 6, covering the surface. These grinding marks are slanted in respect to the normal vector as defined above. An angle between the normal vector N and the grinding marks is at least 20 degrees. Preferably the angle is also less than 70 degrees and most preferably within the range of 30-60 degrees. The grinding marks are visible as scratches in the surface of the clearance face.

(14) Also the left and right side clearance surfaces are provided with slanted grinding marks 13 (left side shown). Similarly the grinding marks on the left and right side clearance surfaces are angled to the normal vector N as defined for the main clearance surface. The grinding marks have an angle to the normal vector N of at least 20 degrees. The grinding marks are oriented such that they incline forwards when moving downward from the cutting edge along the sides of the clearance surfaces. Thus the grinding marks essentially follow the shape of the shelf 14 defining the respective left and right side clearance surface 7 and 8.

(15) FIG. 3 illustrates a method of grinding the main clearance surface of a parting/grooving insert. A rotatable grinding wheel or disc having a plane grinding surface 2 is provided and rotated around a rotational axis X. A parting/grooving insert 1 is provided and oriented with the main clearance surface facing the grinding surface and being parallel to the plane grinding surface. A normal vector N of the main cutting edge is defined as above, situated in the plane of the main clearance surface 4 of the insert. The insert is positioned on the grinding surface such that the normal vector N of the main cutting edge, as seen in the plane of the main clearance surface and in the direction of rotation, at this position, forms an angle of at least 20 degrees to the tangential direction of rotation R, at the same position.

(16) In FIG. 3, four sectors A, B, C and D on the grinding surface are illustrated which fulfill the requirement above. Starting with sector A the main clearance surface 4 of the parting/grooving insert is illustrated as a square and the normal vector of the main cutting edge N.sub.A extends in the plane of the grinding surface. In the same point, the tangential direction of rotation is R.sub.A. Between the normal vector N.sub.A and the tangential direction of rotation R.sub.A there is an angle .sub.A. The normal vector is seen or oriented in the direction of rotation in this case (the angle .sub.A is sharper than 90 degrees). This does not necessarily mean that the insert must be turned upside-down in the grinding position. Instead the normal vector is defined in the direction of rotation to specify the specific angles and sectors A, B, C and D on the grinding wheel, and irrespective of the insert rake surface facing the direction of rotation or facing away from the direction of rotation. The insert is positioned on the grinding surface such that the angle .sub.A is at least 20 degrees from parallel orientation. Preferably the angle .sub.A is also less than 70 degrees from parallel orientation. This range is indicated by the outer dotted lines (- - -) surrounding the sector A. Also a preferred range of 30<.sub.A<60 degrees is indicated by the inner dotted lines (- . - . -).

(17) Also in sector B, C and D the requirements that the insert is positioned on the grinding surface such that the angle .sub.B, C, and D is at least 20 degrees from parallel orientation. In each case the normal vector shown (N.sub.B, N.sub.C, N.sub.D) has a vector component in the direction of rotation in the respective position (R.sub.B, R.sub.C, R.sub.D).

(18) Thus by positioning the cutting insert in any of the indicated sectors A, B, C or D, grinding marks are obtained from the rotating grinding surface having an angle of at least 20 degrees from the normal vector defined for the clearance face.

(19) In FIG. 4 the grinding of the left and right side clearance surfaces are shown. The left side clearance surface is grinded in position A and the right side clearance surface is grinded in position B. The shelf 14 on the respective side of the body of the cutting insert, defining the side clearance surfaces, is positioned close to the edge of the rotating grinding surface. Thus the edge of the rotating grinding surface follows the shape of the shelf.

(20) Thus by positioning the sides of the parting/grooving insert in the indicated sectors A or B (or similarly C or D), slanted grinding marks are obtained from the rotating grinding surface having an angle of at least 20 degrees from the normal vector defined for the clearance face.

(21) To grind both side clearance surfaces and the main clearance surface, the insert is moved between the positions indicated in FIG. 4 and one of the positions A or B indicated in FIG. 3. During moving the insert from the position of grinding a side clearance surface to grinding the main clearance surface, the corner radius region between these surfaces is grinded. The movement of the insert is decreased with respect to prior art and thus the throughput during the process of grinding parting/grooving inserts may be increased.

(22) In FIG. 5 a slot milling disc is shown provided with a number of parting/grooving inserts as disclosed herein. The milling disc comprises a thin and flat disc body with a centre axis having a first side with a bearing surface adapted to bear against a mounting surface on the end surface of the shaft, and a second surface adapted to be facing away from the shaft in the mounted state. The disc has an overall circular shape with a sawtooth-like outer peripheral surface having a number of sawtooth-like projections. Each sawtooth-like projection is in the vicinity of its tip provided with a recess in which is mounted a cutting insert in the form of a parting and/or grooving insert, each having a cutting edge, used for cutting off or making grooves in a work piece. The insert is mounted in a seat with a clamping finger for securing it in the seat of the slot milling disc. These inserts are provided with a width of 1.5-10 mm, preferably 2-8 mm, and designed for cutting action in the feed direction. The cutting edge of the insert is however somewhat wider than the width of the slot milling disc in order to ensure clearance of the disc from the work piece in the slot during cutting. Such inserts may also be used for parting and/or grooving when turning. Between each two adjacent sawtooth-like projections is formed a concaveness which is utilized as a chip space in which cut chips are allowed to be formed/collected during cutting operation. The milling disc is also provided with a centre hole and attachment means in form of four screw holes distributed around the centre hole.