Final answer:
Worm gears primarily exhibit line contact between the worm and worm wheel, allowing for a smooth transmission of motion and high reduction ratios, despite being less efficient due to increased friction.
Step-by-step explanation:
Worm gears are a type of gearing system where the contact between the worm (which is similar to a screw) and the worm wheel (which resembles a traditional gear) is predominantly of the line contact type. Unlike spur gears that exhibit tooth contact, the worm gear's design allows for a gradual engagement between the teeth of the worm wheel and the threads of the worm. This interaction provides a smooth transmission of motion and power.
The worm can have one or more starts (threads), and as it rotates, the worm wheel moves perpendicularly to the axis of the worm, which is due to the sliding contact nature of the gear system. This unique mechanism allows for high reduction ratios and is commonly used in applications where space is limited and large gear reductions are necessary, such as in conveyor systems or tuning instruments.
The line contact between the worm and the wheel leads to increased friction and therefore worm gears are generally less efficient than other gear types. However, their ability to provide high torque at low speeds makes them an invaluable component in many mechanical systems.