FACING CUTTER

Abstract: The invention relates to a facing cutter for making annular holes. At the lower end of the jacket (2) of the cutter a plurality of cutting teeth (3) are formed, each tooth having an inner cutting edge (4) and an outer cutting edge (5). Adjacent cutting teeth are of alternately different construction, such that adjacent teeth may cut a different portion of the groove to be formed. Since at all cutting teeth the outer end of the inner cutting edge and the inner end of the outer cutting edge are offset a distance with respect to each other it is made possible to cut four different chips of substantially equal size with two adjacent cutting teeth.

Description: The invention relates to a facing cutter for making annular holes, including a substantially cylindrical jacket with a plurality of axial teeth spaced circumferentially at the lower end of the jacket, wherein each cutting tooth has an inner cutting edge extending outwardly from the inner periphery of the jacket and an adjacent outer cutting edge extending inwardly from the outer periphery of the jacket, successive teeth being of alternately different construction, wherein the angle between the inner cutting edge and the outer cutting edge, respectively, and a radial transverse plane of the cutter is different for adjacent cutting teeth, and the axial length for adjacent teeth is also different such that from the groove to be formed by the cutting teeth the cutting teeth with the largest angle between the cutting edges and the radial transverse plane may cut the central portion of this groove, while the adjacent edges may cut the side portions of the groove. In a known embodiment of such cutter the cutting teeth are of such construction that in one half of the number of cutting teeth each tooth cuts one chip from the centre of the groove to be cut, whilst the remaining cutting teeth each form the side portions of the groove by cutting two chips. It is an object of the invention to improve such cutter so as to provide a cutter which produces a very favourable chip geometry. To this end a cutter according to the invention is characterized in that for all cutting teeth the outer end of the inner cutting edge is offset a distance with respect to the inner end of the outer cutting edge. As a consequence of the offset of the cutting edges on the cutting teeth which remove metal from the central portion of the groove, in the cutting operation of these cutting teeth two central chips develop, so that totally four chips are formed at two adjacent cutting teeth. As a consequence of the offset of the cutting edges on the cutting teeth which remove metal from the side portions of the groove, it is made possible to obtain four chips of substantially equal size, so that a very favourable chip geometry is obtained in that the four chips have a small chip slenderness, whereby at equal feed per revolution a lower specific cutting energy is needed compared with the known cutter. As a result thereof it is possible to cut a hole at the same speed with less power supplied to the cutting device. Because of the small width of each chip the gullet can be made correspondingly shallower. In this way the cutter jacket will be stronger, and more rigid, whereby the vibration stability of the cutter and thereby the quality of the cutting operation will be improved. The invention will hereafter be elucidated with reference to the drawing, which shows an embodiment of the facing cutter according to the invention by way of example. Fig. 1 is a side view of a facing cutter according to the invention. Fig. 2 is an enlarged detail of the lower portion of the cutter of fig. 1. Fig. 3 is a bottom view of half of the cutter of fig. 1 on an enlarged scale. Fig. 4 is a section along the line IV-IV in fig. 3. Fig. 5 is a section along the line V-V in fig. 3. Fig. 6 is a schematic illustration of the way of cutting of the cutter according to the invention, wherein two adjacent cutting teeth are projected onto each other in the circumferential direction. The drawing shows a cutter for making annular holes, which is referred to as a facing cutter. This cutter is provided with a coupling portion 1 for the connection to a cutter device (not shown) and with a jacket 2. The jacket 2 is of a cylindrical hollow construction, and at the lower edge thereof a plurality of cutting teeth 3 are formed, which extend axially and which are spaced apart in the circum­ ferential direction. Each cutting tooth 3 has an inner cutting edge 4 extending from the inner periphery of the jacket 2 and has further an associated outer cutting edge 5 extending from the outer periphery of the jacket 2. Between any two successive cutting teeth 3 an outer gullet 6 is formed in the wall 11 of the jacket 2 to extend helically in the axial direction, which gullets are designed to permite the passage of chips during cutting. The chips formed by the outer cutting edges 5 enter directly into these outer gullets 6, whilst the chips formed by the inner cutting edges 4 are led through upwardly and outwardly inclined inner gullets 7 to the respective outer gullets 6. As can be seen from fig. 3 to 6, the successive cutting teeth 3 are of alternately different construction, in such way that adjacent cutting teeth 3 have a different configuration. In the embodiment shown by way of example the cutting teeth 3′ according to fig. 4 have a roof-shaped clearance face 8′, and the clearance face 8″ of the cutting teeth 3″ according to fig. 5 has a flat configuration. The cutting teeth 3′ and the cutting teeth 3″ extend in the axial direction to such extent with respect to each other that the radially central portion of each roof-shaped cutting tooth 3′ projects beyond the central portion of each flat cutting tooth 3″, whilst the radially inner and outer portions of each roof-shaped cutting tooth 3′ projects less in the axial direction than the radially inner and outer portions of each cutting tooth 3″. This can be clearly seen from fig. 6. This feature results in that the roof-shaped cutting teeth 3′ cut the central portion of the groove to be formed, whilst the side portions of the groove to be formed are cut by the flat cutting teeth 3″. Fig. 2 and 3 show that the outer end of the inner cutting edge 4′, 4″ of each cutting tooth 3′, 3″ is offset forwardly in the direction of rotation of the cutter with respect to the inner end of the outer cutting edge 5′, 5″ of the respective cutting tooth 3′, 3″. This is a result of the fact that the inner cutting edge 4′, 4″ of each cutting tooth 3′, 3″ as viewed in the direction of rotation of the cutter lies further forwardly than the outer cutting edge of the same cutting tooth 3′, 3″, so that the clearance face 8′, 8″ of each cutting tooth 3′, 3″ extends further forwardly at the inner cutting edge 4′, 4″ than at the outer cutting edge 5′, 5″. Since the clearance angle of the clearance face 8′, 8″ of each cutting tooth 3′, 3″ has a positive value, the fact that the clearance face 8′, 8″ extends further forwardly at the inner cutting edge 4′, 4″ results in that this inner cutting edge cuts deeper in the axial direction of the cutter than the outer cutting edge 5′, 5″ of the same cutting tooth 3′, 3″. In fig. 4 and 5 the cutting teeth 3′, 3″ respectively are shown in a circumferential view, wherein it can be clearly seen that the outer end of the inner cutting edge 4′, 4″ is offset downwardly with respect to the inner end of the outer cutting edge 5′, 5″. The offset between the inner cutting edge 4′ and the outer cutting edge 5′ of each roof-shaped cutting tooth 3′ causes the central part of the groove cut in the material by this cutting tooth to be separated into two single chips 9, so that at two adjacent teeth totally four different chips 9 are formed. As fig. 6 illustrates, the offset of the inner cutting edge 4″ with respect to the outer cutting edge 5″ of the flat cutting tooth 3″ results in that the four chips 9 formed by two adjacent cutting teeth 3′ and 3″ are substantially of equal size. Hereby the four chips have a small chip width, so that the outer gullets 6 can be constructed radially narrower, i.e. shallower from the outer cutting edges 5 on through an inclined edge 10. The wall 11 of the jacket 2 at the location of the outer gullets 6 can thereby be made correspondingly thicker, which has a positive influence on the vibration stability of the cutter and thereby on the quality of the cutting operation. The invention is not restricted to the embodiment shown in the drawing by way of example, which can be varied in different ways within the scope of the invention.

Claims: 1. Facing cutter for making annular holes, including a substantially cylindrical jacket with a plurality of axial teeth spaced circumferentially at the lower end of the jacket wherein each cutting tooth has an inner cutting edge extending outwardly from the inner periphery of the jacket and an adjacent outer cutting edge extending inwardly from the outer periphery of the jacket, successive teeth being of alternately different construction, wherein the angle between the inner cutting edge and the outer cutting edge, respectively, and a radial transverse plane of the cutter is different for adjacent cutting teeth, and the axial length for adjacent teeth is also different such that from the groove to be formed by the cutting teeth the cutting teeth with the largest angle between the cutting edges and the radial transverse plane may cut the central portion of this groove, while the adjacent edges may cut the side portions of the groove, characterized in that for all cutting teeth the outer end of the inner cutting edge is offset a distance with respect to the inner end of the outer cutting edge. 2. Facing cutter according to claim 1, characterized in that the outer end of the inner cutting edge is offset axially with respect to the inner end of the outer cutting edge when viewed in the circumferential direction of the cutter. 3. Facing cutter according to claim 1 or 2, characterized in that the outer end of the inner cutting edge is offset circumferentially with respect to the inner end of the outer cutting edge. 4. Facing cutter according to claim 3, characterized in that the outer end of the inner cutting edge is offset forwardly in the direction of rotation of the cutter with respect to the inner end of the outer cutting edge. 5. Facing cutter according to one of the preceding claims characterized in that the clearance faces of the successive cutting teeth are alternately of roof-shaped and flat configuration.

Inventors: BIJL, ROY
Applicants: WALKER-HAGOU B.V.
Application year: 1986
Main classification: B23B51
IPC codes: B23B51