Which gear type typically produces more heat due to sliding contact?

• A. Bevel gears
• B. Spur gears
• C. Helical gears
• D. Worm gears

Answer: (D)

The main idea here is that heat in gears comes from friction at the contact surfaces, and sliding friction tends to generate more heat than rolling friction. In a worm gear, the contact between the worm thread and the worm wheel involves substantial sliding as the worm advances and the wheel teeth mesh along the length of the thread. That extended sliding path causes greater friction losses and lowers efficiency, so more input power is dissipated as heat compared with other gear types. Other gears—spur, helical, and bevel—primarily rely more on rolling contact with less pronounced sliding for the same load, so they typically produce less heat from friction. So, the worm gear is the type that typically generates more heat due to sliding contact.