Cylindrical gear

helicalprecisioninternal

Internal gearing is important when a high degree of surface space utilization and the exact precision parallel movement of several parts are required. Products which feature internal gearing include drive shafts, planetary (epicyclic) gears, coupling hubs, cylindrical gears, ring gears and internal ring gears. When producing straight or slanted internal gear teeth, the workpieces can be broached, punched, grooved, drawn (pulled) or hobbed. The profile of the internal gear is created in the gear shaping process. Internal gearing having a small diameter can be produced by using profile broaches, a process which is much faster than internal gear shaping. In the internal gear shaping process, the workpiece and the tool form what could be described as kind of internal gear unit. The shaping tool moves like a planet gear inside a ring gear and rotates around its own axis together with the workpiece. The lifting movement of the shaping tool (a pinion with sharp edges) shaves away material from the workpiece step by step and thus creates the desired tooth profile. The tools used to create internal gearing often have disk, bell-type or shaft-type (Morse taper) shapes. The shaping tool for manufacturing must always have a fewer number of teeth than the workpiece, otherwise both could collide and the workpiece could be damaged by the tool. The geometry of the gear workpiece (number of teeth, module, contact angle, profile shift) determines the number of teeth on the tool. Furthermore, the length of the shaping tool must be sufficient for the job – this length is determined in relation to the width of the tooth shaping defined for the workpiece.