GB2186220A - Rotary tool - Google Patents

Abstract

The tool, for example a routing or milling tool, has at least two equidistantly spaced helical blades (6) provided in a head portion thereof for contact with a substrate S to remove material. Each blade (6) is offset from but parallel to a diameter of the tool body. An end portion of each blade comprises three cutting edges formed continuously with one another, the outermost cutting edge (8) of each being positioned to form a rake angle of at least 5 DEG with said diameter, and a second edge (10) in a radial plane, i.e. normal to the axis of rotation. The third, innermost, cutting edges (12) of each blade (6) are arranged to confront each other so that a line drawn from one end, e.g. inner end, of the length of one of the cutting edges (12) to the opposite end, e.g. outer end, of the length of the other cutting edge (12) is approximately 15 DEG to 30 DEG to the radial plane. <IMAGE>

Description

SPECIFICATION Tool formation The invention is concerned with improvements in or relating to the formation of tools. More particularly, but not exclusively, the invention may relate to one or more tool blades formed in a tool body for use in a tool hoider in a rotary machine tool for example for routing or milling.

The invention provides a rotary tool body comprising one or more tool blades formed therewith arranged at positions on the body, each blade being helical in form and having an operative end portion arranged in a position offset by a predetermined amount from a diameter and parallel thereto, said blade end portion comprising three cutting edges formed continuously with each other, the outermost cutting edge of each being positioned to form a radial rake angle of at least 5 with said diameter, and a second edge in a plane normal to the axis of rotation, wherein the third, innermost, cutting edges of each blade are arranged to confront each other so that a line drawn from one end of the length of one of said third cutting edges to the opposite end of the length of the other third cutting edge is at least in the approximate region of 15"-30" to said plane.

The invention further provides a method of using a tool body as described in the preceding paragraph in an operation to remove material from the surface of a workpiece comprising the step of introducing the tool blades to the surface, in a manner such that the rotational axis is perpendicular to the surface, along a path inclined to said surface at an angle not substantially less than 15 .

Advantageously, the tool blades are of tungsten carbide or high speed steel and form inserts clamped or bonded into helical channels formed in the tool body.

In examples of the invention, the end portion of each blade comprises an intermediate cutting edge arranged in a radial plane with respect to the rotational axis i.e. parallel in use to the substrate being cut. Each of the two other cutting edges are arranged to lie at an inclined angle to the intermediate edge which they flank, and, as the tool body rotates, cut away material from the substrate in turn.

There will now be described an example of a tool body and blades according to the invention. It will be understood that the description which is intended to be read with reference to the drawings, is given by way of example only and not by way of limitation.

In the drawings: Figure 1 is a side view of a head portion of a tool body; Figure 2 is an end view of the tool body of Fig. 1; Figure 3 is a diagrammatic representation of the cutting action of blades of the tool body; and Figures 4 and 5 show two angles of tool approach.

Fig. 1 shows a tool body head portion 2 having in the present example two diametrically opposed helical channels 4 in each of which is bonded one of two contoured tool blades 6 of tungsten carbide. End portions of each blade are formed into three cutting edges 8,10,12 continuous with one another.

Each set of edges 8,10,12, are arranged at angles to each other as explained below.

It will be observed from Fig. 2 that the two blades 6 are arranged at opposed positions in the head portion 2 and are also arranged to lie so that each intermediate cutting edge 10 lies in a plane parallel to but offset from a diametral plane. The outer cutting edges 8 are arranged to define an angle x" with the diameter as shown. According to the invention, the value of x" is at least 5". Preferably the value will be between 5-15 and in the present example is 11".

Fig. 1 shows the helical configuration of the blade 6 and it will be observed that the helix angle is y", the value of which is not less than 15 , and preferably lies in the range of 25-30". In the present example, the angle is shown as 30".

Fig. 3 shows the manner in which the tool blades 6 operate in the removal of material from a substrate S. The tool body is held perpendicular to the substrate surface and is caused to approach the substrate at an angle, referred to as the ramp angle, in the direction shown by the arrow A. The cutting is effected by the edges marked as X in the Figure, it being understood that the edges 8 act alternately as operating edge X as viewed on the right of the Figure. The intermediate edges 10 which are maintained parallel to the surface substrate S are in virtual constant contact therewith as the edges 8 cut into the material.

The edges 12 also act alternately as operating edges to cut away the ramp of material at 14.

It will be obvious that the more material cut at each rotation of the tool body the more efficient will be the operation.

Since more material is cut at a high ramp angle than at lower angles, it is advantageous to use angles which are not substantially less than 15". However, this can only be achieved if the geometry of the blades is carefully controlled. It will be observed from Fig. 4 that the effective ramp angle is determined by the angle formed with the horizontal by a line drawn from one end of one edge 12 to the opposite end of the other edge 12 i.e. from point B to point C, 15". Should the width of the blade end portions be insufficient as in Fig. 5, the ramp angle defined by the line B'-C' will be only about 10 and the efficiency of the cutting operation is considerably re duced.

Various modifications may be made within the scope of the invention as defined in the following claims.

Claims (9)

1. A rotary tool body comprising one or more tool blades formed therewith arranged at positions on the body, each blade being helical in form and having an operative end portion arranged in a position offset by a predetermined amount from a diameter and parallel thereto, said blade end portion comprising three cutting edges formed continuously with each other, the outermost cutting edge of each being positioned to form a radial rake angle of at least 5 with said diameter, and a second edge in a plane normal to the axis of rotation, wherein the third, innermost, cutting edges of each blade are arranged to confront each other so that a line drawn from one end of the length of one of said third cutting edges to the opposite end of the length of the other third cutting edge is at least in the approximate region of 15 -30 to said plane.

2. A tool body as claimed in claim 1 wherein the blades are selected from tungsten carbide or high speed steel and form inserts secured in helical channels formed in the body.

3. A tool body as claimed in either one of claims 1 and 2, wherein the end portion of each blade comprises an intermediate cutting edge arranged in a radial plane with respect to the rotational axis.

4. A tool body as claimed in claim 3, wherein the two other cutting edges flank the intermediate edge and are arranged to lie at an inclined angle thereto so as to operate in turn to cut away material from the substrate.

5. A tool body as claimed in any one of the preceding claims, wherein the radial rake angle formed between the outermost cutting edge of each blade end portion and said diameter is between 5 and 15 .

6. A tool body as claimed in any one of the preceding claims wherein the helix angle of the blades is not less than 15.

7. A tool body as claimed in claims 6 wherein the helix angle is in the range of 25 to 30 .

8. A method of using a tool as claimed in any one of the preceding claims, in an operation to remove material from the surface of a workpiece to workpiece comprising the step of introducing the tool blades to the surface, in a manner such that the rotational axis is perpendicular to the surface, along a path inclined to said surface at an angle not substantially less than 15".

9. A rotary tool body constructed and arranged substantially as hereinbefore described with reference to and as shown in the drawings.