METAL-CUTTING TOOLS: SPECIAL HOBS FOR CUTTING GEARS WITH RECESSED BASE OF THE TEETH

摘要

Heavily loaded gears are made with recessing of the teeth (Fig. 1a) in order to avoid the undercutting of the base in the finish grinding operation and the consequent reduction of the bending strength of the teeth. The production of these gears requires the use of a special gear-cutting tool - worm milling cutters (hereafter, the hobs) with protuberances (or with modified teeth), i.e., with thickened segments on the heads of the hob teeth (Fig. 1b). In cutting the gears with a small number of teeth (z ≤ 16), it is very difficult to machine them by the hobs with protuberances on all of the teeth without undercutting the active involute profile. In this case constant-setting hobs (CSHs) are used with protuberances that have in the middle part of the turn of the thread a certain number of teeth (equal to or greater than one) with protuberances - while the remaining teeth are made without protuberances.