GB2308325A

GB2308325A - Rotary cutting tools

Info

Publication number: GB2308325A
Application number: GB9623170A
Authority: GB
Inventors: Clive Harper; John Yates
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 1995-12-21
Filing date: 1996-11-06
Publication date: 1997-06-25
Anticipated expiration: 2016-11-06
Also published as: GB9623170D0; GB2308325B; GB9526197D0

Abstract

A routing cutter has a tool body 2 carrying replaceable cutting inserts which include side inserts 14 with cutting edges 22 projecting radially from the periphery of the body and end inserts 28 with cutting edges 38 projecting forwards from the body. The cutting edges of the side inserts have inward extensions 24 to define a cutting envelope that intersects or overlaps the cutting envelope of the end inserts. Each side insert is secured by clamping means 20 extending substantially radially into the tool body, rearwards of the insert cutting edge. This arrangement of the clamping means allows the body to be formed with relatively shallow seating recesses (12, Fig.2) for the side inserts with substantially tangential locating faces (16, Fig.2) against which the inserts are clamped for precise radial location.

Description

ROTARY CUTTING TOOLS This invention relates to rotary cutting tools such as routing cutters and end mills, intended to be used to machine slots and/or recesses in a workpiece.

GB 2186220 shows a routing tool in which, typically, a pair of cutter blades are mounted at diametrically opposed positions of a rotary body in flutes formed in the sides of the body, each blade having a cutting edge that extends along the flute over its radially outer edge and continues inwards and rearwards over end portions of the blades that project forwards from the axial end of the tool body. In a routing operation in which the cutter moves along the workpiece in a direction perpendicular to its rotary ax.s, only the radially outer cutting edge is employed. The inward and rearward continuation of the cutting edge at the end of the tool body is necessary to permit the tool to be given an axial feed movement into the workpiece at the same time as it moves along the workpiece.During such a ramping movement the end portions of the blades then act to remove a core of material that is left projecting above the instantaneous depth reached by the outer part of the cutting edge.

For this reason, routing cutters and like rotary tools which are required to perform a ramping motion have relatively large and complex cutter blades and the cost of production is consequently relatively high even if, as in the example already mentioned, the cutter blades are formed separately from the body of the tool.

According to one aspect of the present invention a routing cutter is provided comprising a rotatable body having a plurality of cutting inserts, said inserts comprising at least one side element providing a cutting edge that projects radially from the periphery of the body, and at least one end element that projects from a forward axial end of the body having a cutting edge inclined radially inwardly and rearwardly of the body, said two elements being located in positions that are angularly spaced about a central rotary axis of the body and describing cutting envelopes that intersect or overlap in the rotation of the body about said axis, said at least one side element being secured to the cutter body by clamping means that extend inwardly through a radially outer face of the element rearwardly of its cutting edge.

Preferably there are at least two of each of said elements, symmetrically spaced about the central axis of the body and in corresponding axial and radial positions.

The cutting elements may conveniently be in the form of replaceable inserts and in the application of the invention it is possible to arrange that the inserts are held against respective faces of the cutter body that lie at least approximately tangential to their direction of rotation, thereby to fix them more securely.

In the angular spacing of the respective cutting elements of said plurality of elements, preferably a flute or other radially outer recess in the tool body lies between successively spaced elements.

It is also preferred to provide said at least one side cutting element with a cutting edge that acts over a radially outer region of the forward axial end of the cutter body. Continuing from the radially inner end, said end cutting edge of the element may have a rearwardly directed edge having an envelope of rotation which overlaps with the envelope of rotation of a cutting edge of said at least one end element.

The inserts may be of elongate form with a substantially uniform cross-section, said at least one side element having its longitudinal axis parallel to the rotary axis of the tool and said at least one end element having its longitudinal axis inclined obliquely upwards toward the centre of the tool.

According to another aspect of the invention, there is provided a cutter comprising a tool body rotatable about a longitudinal axis and carrying at least one group of at least two replaceable cutting inserts, a first insert of the or each said group at the outer periphery of the body having a cutting edge that projects radially and axially of the body, said first insert being secured to the tool body by clamping means extending inwardly into said body from an aperture in the insert spaced rearwardly from a leading face of the insert, said first insert projecting radially outwardly further than a second insert of the group at the forward end of the body, said second insert having a cutting edge that projects forwardly from the body and is inclined rearwardly towards the axis of rotation, said second insert extending radially inwards beyond said first insert cutting edge, said first and second inserts of the or each group being angularly spaced from each other with respect to the axis of rotation of the tool.

An example of a tool according to the invention is illustrated in the accompanying drawings, in which: Figs. 1 and 2 are oblique views of a routing cutter according to the invention, the cutting inserts of the tool being absent in Fig. 2, Fig. 3 is an oblique view to a larger scale of one of the inserts of the cutter, and Fig. 4 is a diagrammatic view of the routing cutter illustrating its cutting action.

Referring to the drawings, the routing cutter is symmetrical about a central axis on which it rotates in the arrowed direction and comprises a generally cylindrical body 2 having a pair of diametrically opposed flutes 4 extending rearwards from a forward end of the body. A diametrically opposed pair of shorter hollows 6 are formed in the forward end of the body, between the flutes 4. The flutes and hollows may be directed axially or helically to the rotary axis. Between the flutes 4 and hollows 6 the forward end of the body is formed by facets 8 that are inclined axially rearwards from their radially outward ends.

At the outer side region of the trailing face of each flute a recess provides a seating 12 for an elongate first cutting insert 14 of generally uniform cross-section which projects from the periphery of the body and also from its forward end. The bottom or inner face 16 of the seating lies substantially tangentially to the direction of rotation of the cutter and has a tapped hole 18 extending substantially radially into the body to receive a clamping screw 20 passing through bore 21 in the insert. The insert thus. secured against. the face 16 on the body can have a considerable thickness in the circumferential direction, so that adequate support can be provided for the cutting edge even if a cutting edge profile is chosen that results in the insert projecting further than shown from the body. At the same time, the insert can be kept compact in the radial direction so that the seating recesses 12 can be relatively shallow, limiting their effect on the strength of the body.

The insert 14 is secured in the seating with its major axis and an outer cutting edge 22 parallel to the body rotary axis. The cutting edge 22 extends the length of the insert and at the projecting forward end of the insert it joins a radial end cutting edge 24 running at right-angles to it, the cutting edges 22,24 defining the leading face of the insert. At the inner corner of the edge 24 a stepped recess is formed with an axially extending clearance face 36 having chamfers at its upper and lower edges. The clearance face 37 extending from the cutting edge 24 is inclined rearwardly therefrom.

At the trailing face of each hollow 6 there is a further recess in the leading end of the body providing a seating 26 for a second uniform cross-section cutting insert 28. The bottom or inner face 30 of the seating 26 has a tapped hole 32 for the insert clamping screw 34. The second insert 28 is also elongate and is essentially rectangular in form. The insert 38 has longer cutting edge 38 spaced forwards from the tool body and inclined axially rearwardly from its radially outer end. As can best be seen in Fig. 4, the radially outer end of the second insert cutting edge 38 lies at a greater radius than the inner radius of the end cutting edge 24 of the first insert. The second insert cutting edge 38 also continues radially inwards further than the edge 24 of the first insert.

The radially outer end of the end element cutting edge 38 does not project forwards of the outer element cutting edge 24, and can lie slightly behind it. The stepped recess formed in the outer element with the axial face 36 allows the tool to be fed axially into the workpiece without interference from the inner region of the insert 14. The paths of rotation of the inner element cutting edge 38 and the radially outer edge of the recess about the tool longitudinal axis intersect each other.

The two inserts 14,28 act in a complementary manner in that when they rotate about the tool axis they describe cutting envelopes that intersect or overlap. The inserts can therefore cut a recess in the same manner as a unitary routing cutting edge of the kind shown in GB 2186220. Fig. 4 illustrates how, when the routing cutter is being fed obliquely into a workpiece W, it cuts a ramped recess. The first outer cutting inserts 14 leave an upstanding core or "cherry" C as the cutter advances into the material, the size of which depends upon the angle of feed of the cutter. This is removed by the end inserts 28 as the tool moves across the workpiece in a routing operation. By staggering the angular positions of the side and end inserts, it is possible to obtain the overlap of their cutting envelopes to give this result.It will be noted that each cutting insert 14,28 is associated with a respective flute 4 or hollow 6, providing a passage for the escape of the cuttings from that insert.

The arrangement of separate inserts allows smaller size cutter elements to be used, which is more economical, in particular if the inserts are arranged to be indexable, as the illustrated inserts are by rotation through 1800. Both inserts are reversible to present alternative cutting edges for an extended working life. It is also possible within the scope of the invention to employ permanently fixed, eg. brazed inserts. Furthermore, by employing multiple cutting inserts, it is also possible to select different materials for the inserts so as to optimise their operation under different conditions, in particular to allow for the slower cutting speed at which the axial end inserts operate.

Another advantage of the illustrated arrangement of the inserts is that because each insert is clamped against a face that is substantially tangential to the direction of rotation it can be secured in a precise manner that facilitates the rotational balancing of the tool, a factor of some importance for the high-speed routing of light alloys.

Claims

1. A routing cutter comprising a rotatable body provided with a plurality of cutting inserts, said inserts comprising at least one side element having a cutting edge that projects radially from the periphery of the body, and at least one end element that projects from a forward axial end of the body having a cutting edge inclined radially inwardly and rearwardly of the body, said two elements being located in positions that are angularly spaced about a central rotary axis of the body and describing cutting envelopes that intersect or overlap in the rotation of the body about said axis, said at least one side element being secured to the cutter body by clamping means that extend inwardly through a radially outer face of the element rearwardly of its cutting edge.

2. A cutter according to claim 1 wherein said at least one side cutting element is provided with a cutting edge that acts over a radially outer region of the forward axial end of the cutter body.

3. A cutter according to claim 2 wherein said end cutting edge has a rearwardly directed edge continuing from its radially inner end, said rearwardly directed edge having an overlapping envelope of rotation with a cutting edge of said at least one end element.

4. A cutter according to any one of claims 1 to 3 wherein the inserts are held against respective faces of the cutter body that lie at least approximately tangential to their direction of rotation.

5. A cutter according to any one of the preceding claims wherein the cutting elements are replaceable and indexable.

6. A cutter according to any one of the preceding claims wherein the inserts are of elongate form with a substantially uniform cross-section, said at least one side element having its longitudinal axis parallel to the rotary axis of the tool and said at least one end element having its longitudinal axis inclined obliquely upwards toward the centre of the tool.

7. A cutter according to any one of the preceding claims wherein said first and second inserts of the or each group are located at the trailing sides of respective radially outer recesses in the tool body.

8. A cutter according to any one of the preceding claims having a plurality of said side elements equiangularly spaced about the central rotary axis and in corresponding axial and radial positions.

9. A cutter comprising a tool body rotatable about a longitudinal axis and carrying at least one group of at least two replaceable cutting inserts, a first insert of the or each said group at the outer periphery of the body having a cutting edge that projects radially and axially of the body, said first insert being secured to the tool body by clamping means extending inwardly into said body from an aperture in the insert spaced rearwardly from a leading face of the insert, said first insert projecting radially outwardly further than a second insert of the group at the forward end of the body, said second insert having a cutting edge that projects forwardly from the body and is inclined rearwardly towards the axis of rotation, said second insert extending radially inwards beyond said first insert cutting edge, said first and second inserts of the or each said group of inserts being angularly spaced from each other with respect to the axis of rotation of the tool.

10. A cutter according to claim 9 wherein there are a plurality of said groups of cutting inserts, said groups being mounted on the tool body in a rotationally symmetrical arrangement relative to said axis of rotation of the body.

11. A routing cutter constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.