渐开线花键是键齿在圆柱（或圆锥）面上且齿形为渐开线的花键，它采用齿形定心。渐开线花键和矩形花键的参数区别如下：
• 模数与小径：渐开线花键的模数是重要参数，决定花键尺寸和承载能力，模数越大，齿厚和齿高越大，承载能力越强。矩形花键主要尺寸参数是小径，根据轴的强度和连接要求确定，轻系列多用于静连接和轻载连接，中系列用于中等载荷连接。在相同外形尺寸下，渐开线花键的小径相对较大，有利于增加轴的刚度。
• 齿数：渐开线花键齿数较多，一般根据轴的直径大小、传递扭矩要求以及设备整体结构布局选择，能保证足够承载能力和均匀载荷分布。矩形花键齿数相对较少，需考虑承载能力和结构，一般不少于10。
• 压力角：渐开线花键标准压力角有30°、37.5°和45°等多种，30°压力角的承载能力较高，45°压力角适用于轻载和小尺寸场合。矩形花键通常没有压力角这一参数，其齿形为矩形，齿侧是平行平面。
• 定心方式：渐开线花键定心方式有齿侧定心、大径定心和小径定心。矩形花键一般采用小径定心，定心精度高，稳定性好，能用磨削方法消除热处理引起的变形。
Involute spline is a spline with key teeth on the cylindrical (or conical) surface and tooth shape involute, which uses tooth shape for centering. The difference between the parameters of involute spline and rectangular spline is as follows:
• Module and minor diameter: The module of involute spline is an important parameter, which determines the spline size and load-bearing capacity. The larger the module, the larger the tooth thickness and tooth height, and the stronger the load-bearing capacity. The main size parameter of rectangular spline is the minor diameter, which is determined according to the strength and connection requirements of the shaft. The light series is mostly used for static connection and light load connection, and the medium series is used for medium load connection. Under the same external dimensions, the minor diameter of involute spline is relatively large, which is conducive to increasing the rigidity of the shaft.
• Number of teeth: Involute spline has more teeth, which is generally selected according to the diameter of the shaft, the torque transmission requirements and the overall structural layout of the equipment, which can ensure sufficient load-bearing capacity and uniform load distribution. The number of teeth of rectangular spline is relatively small, and the load-bearing capacity and structure need to be considered, generally not less than 10.
• Pressure angle: The standard pressure angles of involute splines are 30°, 37.5° and 45°. The 30° pressure angle has a higher load-bearing capacity, and the 45° pressure angle is suitable for light loads and small sizes. Rectangular splines usually do not have a pressure angle parameter. Their tooth shape is rectangular and the tooth sides are parallel planes.
• Centering method: The centering methods of involute splines include tooth side centering, large diameter centering and small diameter centering. Rectangular splines generally use small diameter centering, which has high centering accuracy and good stability. The deformation caused by heat treatment can be eliminated by grinding.