What type of gears will be noisier in operation, but they create no axial thrust?

What type of gears will be noisier in operation, but they create no axial thrust?

• A. Bevel-cut
• B. Helical-cut
• C. Spur-cut
• D. Spiral-bevel cut

Answer: (C)

Spur gears have straight teeth that mesh directly and transmit force radially, so the contact force has essentially no component along the gear axis. That means no axial thrust is produced. The downside is that the engagement between straight teeth happens abruptly, especially at higher speeds or under heavy loads, which leads to more noise and vibration. In contrast, gears with angled teeth—helical or spiral bevel gears—spread the load over several teeth as they mesh, reducing noise, but they generate axial thrust that must be managed by bearings. So the gear type described—no axial thrust and higher noise due to direct tooth contact—is spur gears.

Spur gears have straight teeth that mesh directly and transmit force radially, so the contact force has essentially no component along the gear axis. That means no axial thrust is produced. The downside is that the engagement between straight teeth happens abruptly, especially at higher speeds or under heavy loads, which leads to more noise and vibration. In contrast, gears with angled teeth—helical or spiral bevel gears—spread the load over several teeth as they mesh, reducing noise, but they generate axial thrust that must be managed by bearings. So the gear type described—no axial thrust and higher noise due to direct tooth contact—is spur gears.