花键轴的种类很多，但最常见的是矩形花键轴和渐开线花键轴。然而，矩形花键轴是最广泛使用的，在典型用途中更是如此。渐开线花键轴通常承受较大的载荷，需要较高的定心精度。它们还需要更大的连接尺寸，这使得它们有点复杂。
矩形花键轴常见于飞机、农业机械和汽车。通常还会在机床制造和一般机械传动装置中找到这些轴。从矩形花键轴的设计来看，它们可以使用多个齿。这就是赋予它们高承载能力、良好中性和良好导向型的原因。
花键轴具有广泛的应用，特别是在汽车中。它们可用于汽车中的制动器和转向机构。还有一个伸缩轴，由内管和外管组成。外筒具有内齿，内筒带有外齿，它们套在一起完成机械力矩的传递。伸缩轴在使用时，可在传递旋转扭矩的同时，沿长度方向伸缩。
There are many types of spline shafts, but the most common are rectangular and involute spline shafts. However, rectangular spline shafts are the most widely used, and even more so in typical applications. Involute spline shafts are usually subjected to higher loads and require higher centring accuracy. They also require larger joint sizes, which makes them somewhat more complex.
Rectangular spline shafts are commonly found in aircraft, agricultural machinery and automobiles. These shafts are also usually found in machine tool construction and general mechanical transmissions. The design of rectangular spline shafts shows that they can use multiple teeth. This is what gives them high load carrying capacity, good neutrality and good guiding.
Spline shafts have a wide range of applications, especially in automobiles. They can be used in brakes and steering mechanisms in automobiles. There is also a telescopic shaft that consists of an inner tube and an outer tube. The outer tube has internal teeth and the inner tube has external teeth and they are snapped together to accomplish the transfer of mechanical torque. When in use, the telescopic shaft can expand and contract along its length while transmitting rotational torque.