The spline shaft is a kind of mechanical transmission. It has the same function as the flat key, the semicircular key and the oblique key. They all transmit mechanical torque. There are longitudinal keyways on the surface of the shaft. Rotate synchronously with the axis. While rotating, some can also slide longitudinally on the shaft, such as gearbox shifting gears
Here's how lapped bevel gears contribute to the performance of reducers :

Smooth Operation: Lapped bevel gears undergo a finishing process known as lapping, which results in a smoother tooth surface. This smoothness leads to a quieter operation and reduced noise during the meshing of gears in a reducer .

High Precision: The lapping process improves the precision of the gear teeth, which is essential for maintaining the accuracy and efficiency of the power transmission in reducers .
Material and Durability: Lapped bevel gears used in reducers are typically made from high-quality, case-hardened alloy steel. This material provides high strength and durability, which is necessary for the demanding conditions often encountered in agricultural machinery.
Efficiency: The manufacturing process of lapped bevel gears, including case-hardening, quenching, and lapping, ensures high efficiency in power transmission with minimal power loss 
Customization: Lapped bevel gears can be customized to meet specific requirements for different types of reducers, including those used in specialized agricultural applications .
Long Service Life: The combination of high-quality materials and precise c
Versatility: Lapped bevel gears are suitable for use in various types of reducers, providing versatility in design and application. They can be used in both standard and high-performance applications, including those that require high input speeds and low noise levels.