GEAR CUTTING

Gear machining methods include milling, hobbing, shaping, and broaching, Shaving, grinding,
lapping, and burnishing are used to improve accuracy and surface i nish. Sufi cient strength and machinability are the most important prerequisites of machined gears. The high machinability ratings make it easier to achieve precise machining and smooth surface finishes. Other requirements include corrosion resistance, dimensional stability, wear resistance, natural lubricity, noise damping properties, and low cost. Machined gears are most frequently made from steel, which has a high strength and low cost. Carbon steel, which is low in cost, is satisfactory for machining and case hardening, and is very commonly used for commercial gears. Alloy steels have the advantages of strength, heat treatment, and corrosion and wear resistance. However, they also have poor machinability and are higher in cost compared to plain carbon steels. Leaded and resulfurized (free-machining) steels should be used for machined gear whenever possible; however, they have low impact strength and less suitable for high-power applications. Stainless steels are only used when corrosion resistance is essential. They are more expensive, difi cult to machine, have low wear resistance, and are not heat-treatable. CIs have good machinability, are low in cost, and have vibration damping characteristics. Apart from malleable CI, they have low shock resistance. Cast steels have better physical properties than CI but are more expensive, less machinable, and lack good damping characteristics. Bronze is a superior gear material that has excellent machinability
and wear and corrosion resistance. However, its material cost is high. Aluminum is suitable for
lightly loaded gears. It is machinable and provides good surface i nish and corrosion resistance.