GB923087A - Improvements in or relating to hobs - Google Patents

Abstract

923,087. Milling-cutters. HERBERT LINDNER G.m.b.H. April 9, 1959 [April 9, 1958], No. 12093/59. Class 83 (3). [Also in Group XXIII] A hob comprises teeth which have relieved flanks formed by involute surfaces, the pitch of which differs from that of the flanks of teeth of an unrelieved hob, the cutting edges being formed by a generatrix of the flanks, the generatrix being tangential to a base circle different from that of an unrelieved hob, the pitch angle of the basic circle of the unrelieved cutter being maintained. Thus the cutting edges of the teeth are located for one tooth flank on a basic circle of greater diameter than that of the basic circle of the unrelieved cutter while for the opposite flank it is of lesser diameter. In Fig. 2, the flutes are axial, the cutting edges 1a-4a cut one flank and the edges 1b-4b cut the other flank. Alternatively, the hob may be formed as in Fig. 4, to cut one flank as it rotates in one direction and is then rotated in the opposite direction to cut the other flank, the flutes then being helical. If all the teeth of the hob are undercut, the teeth all have the same length Z3, Fig. 5, so that more teeth can be provided than in a hob which cuts both flanks simultaneously. The flutes are produced by end mills, or sintered multi-grain diamond cones, St, Fig. 6, the cone being pivoted so that the generating line coincides with the generatrix E of the hob. The teeth Z4, Z5, Z6 may be mounted on strips LK sliding into grooves in the body HK. The flanks of the teeth are first ground without relief. All the teeth are then removed except for those on one strip which are then relieved.