What structural feature of gears helps prevent tooth-to-tooth contact?

The structural feature of gears that helps prevent tooth-to-tooth contact is the fillet. A fillet is a concave curve that is used at the root of the gear teeth where they meet the base circle. This design consideration helps to create a smooth transition between the tooth and its root, reducing stress concentrations that can occur at sharp corners. By allowing for a smoother engagement and disengagement of the gear teeth during rotation, the fillet aids in preventing jarring impacts that might occur if the teeth were to contact each other directly.

Additionally, the fillet helps in distributing forces more evenly across the tooth, which contributes to both improved performance and longevity of the gear. Therefore, its presence is crucial in preventing unwanted tooth-to-tooth contact that could lead to wear, noise, or potential failure of the gear mechanism.