Although both splines and gears have teeth, their fundamental purpose, operating principles and design standard within mechanical systems are different.
Simply speaking:
- Gears are for power transmission. They change speed, torque, or direction of rotation. Splines are for connection. They couple two parts rigidly to transmit torque without changing the form of motion.
- Gears allow for relative motion; meshing gears can rotate at different speeds or in opposite directions. Splines, in contrast, lock a shaft and a hub together, forcing them to rotate synchronously at the exact same speed and direction.
- Gears transfer loads tooth by tooth during rotation, whereas splines utilize teeth distributed along their entire length for engagement; with all teeth remaining in constant contact, the load is distributed evenly.
- Gear teeth are relatively short and come in various forms (such as spur, helical) to meet diverse power transmission requirements. Splines feature elongated longitudinal teeth designed to create robust, precise connections—often allowing for axial sliding—such as when mounting a gear onto a shaft.