Patent GB-1426678-A (GB)
Title: Methods of grinding cutting tools operating by axial thrust and having at least one cutting edge coplanar with the axis and jig for carrying out siad method
IPC: B24B3/24
Filed: 1974-06-05
Abstract: 1426678 Sharpening cutters; drills; end mills M COSTIL 5 June 1974 [20 June 1973] 24953/74 Headings B3D B3C and B3K A method of sharpening a cutting tool which operates by axial thrust and has at least one cutting lip 4 comprises mounting the tool 17 in a holder 16 of a jig, and positioning the tool relative to the flat face of a cup shaped grinding wheel in a first position for grinding a cutting rake plane 3, in a second position for grinding a cutting face plane 5, and in a third position to form a small face 6 intersecting the rake plane along a line forming an angle not in excess of 90 degrees with the cutting tip and having its apex coincident with the tool centre to limit the central portion of the cutting tip. The tool may have two flutes 1, 2, the flute 2 being formed with a cutting tip 4 defined by a cutting rake 3 and a cutting face plane 5. The plane 5 extends beyond the centre line YY<SP>1</SP> of the drill and intersects a plane 6 which intersects the cutting edge 4 at the centre C<SP>1</SP> of the tool. The other cutting edge is defined only by a cutting rake plane and a cutting face plane. A jig for use in positioning the tool for sharpening by a cup-shaped grinding wheel 9 consists of a vertical support 10 carried by a table 8 movable in the direction of the arrows f. The support mounts a horizontal shaft 11 which is rotatable about its axis X, X<SP>1</SP> to positions determined by engagement of a spring- loaded catch 22 mounted on the support with notches 21 1 , 21 2 , 21 3  in an indexing plate secured to one end of the shaft 11. The other end of the shaft has a support 12 for an offset plate 13 provided with a pivot 14 for the head 15 of a tool-holding headstock 16 for the tool 17. The head is adjustable about the pivot 14 to positions determined by a quadrant 18 and has means 19 for indexing the tool. The axes XX<SP>1</SP>, YY<SP>1</SP> and Z, Z<SP>1</SP> of the shaft 11, tool 17 and pivot 14, respectively, intersect at C. A boss 28 having a face in the vertical plane containing axis XX<SP>1</SP> in one position of support 12 is formed on the support and carries a diamond for truing the grinding wheel. In operation, the tool is inserted into the holder so that the position to be ground extends beyond the axis Z, Z<SP>1</SP>. In the first position, the catch 22 is engaged with notch 21, and the head 15 is positioned at the end of the quadrant. Movement of the support 10 engages the tool with the grinding wheel for grinding the cutting rake face 3. In the second position, the catch 22 is engaged with notch 21 2  and the axis YY<SP>1</SP> moved through an angle b of, for example 45 degrees. The axis YY<SP>1</SP> is in a vertical plane and movement of the support engages the tool with the grinding wheel for grinding the cutting face 5. In the third position, the catch is engaged with notch 21 3  and the tool engaged with the grinding wheel to grind the plane L limiting the cutting edge 4 to the centre C<SP>1</SP> of the tool. The other tips of the tool may be ground after indexing of the tool by the device 19 and grinding with the tool moved to the first and second positions only.