Gear Shaping is a machinery process that involves continuous, same-plane rotational cutting. It is an accurate cutting process that produces a high surface finish on both external and internal teeth. Shaping can generate many gear types including spurs, involute splines, helical, herringbones, and racks. In addition to the versatility of gear types produced, gear shaping also has the advantage of generating teeth close to shoulders, whereas hobbing cannot. Similar to hobbing, gear shaping is considered a generating process, but shaping is based upon the action of a cutter mounted on a cutter-spindle and a gear blank held on an arbor or fixture on the work-spindle. The cutter and work spindle, while driven by independent worm and worm wheels, are tied together by change gears in order to keep the proper relation between cutter and work. Synchronized as such, the cutter makes successive passes through the blank generating a series of closely-spaced individual cuts. These rapidly reciprocating successive passes by the cutter involve a downward ‘cutting’ and upward ‘relieving’ action. Each downward stroke is a cutting motion in which the cutter and work are in mesh at the established infeed depth. On the return upward stroke of the cutting tool, the work and shaper cutter are relieved to avoid rubbing the work on a non-cutting surface of the shaper cutter.
This generating process continues until the work piece has rotated 360 degrees at the established infeed depth. At this point, another 360-degree rotation of the work piece begins when a new infeed depth of cut is taken radially into the work piece. When the cutter reaches the full depth for the given pitch required the desired tooth form will have been produced.
Shaper cutters are essentially gears with relieved cutting edges that provide clearance during the cutting process. Special features such as chamfering, topping, protuberance, full radius, etc. can also be added into the tooth form of the cutter. These special features will be directly dictated by what the work piece requires.