Spline shafts can be made from a variety of materials, including aluminum, cast iron, steel, stainless steel and brass. Some spline shafts now incorporate plastic along with the traditional metal composition of the gear, be it part of the spline shaft or the whole thing.
The grooves in spline shafts are created by broaching machines, specifically spline cutting machines. Broaches, or metal tools with a row of successively larger teeth, are used to cut various materials like wood, metal and plastic. They can be used to cut holes or to alter the surface of a product.
In the manufacture of spline shafts, blind broaches, which are also known as external broaches, are used on the material’s surface to cut the furrows along the length of the shaft. As the spline rotates, these grooves interlock with the matching grooves in the mating piece; this connection enables a spline gear to transfer torque.
The production broaching of many spline shafts at once is practiced in certain industries that require these gears in every product they make, such as the automotive industry and certain sports equipment facilities that make bicycles.
Broaching teeth are the ridges on the spline shaft that perform the cutting action. They come in many different sizes and spacing configurations, depending on what generalized spline style they are apart of.
For example, a parallel key spline has parallel, equally spaced groves in both the radial and axial directions, while serrations are spline shafts that have a “V” formed by their equally spaced grooves.
The configuration of the teeth is the main aspect that separates these two shafts. Another common shaft is the involute spline, which works much like an involute gear works, with the uniform pattern of teeth that when rotating, intersect perfectly with each other and cause the torque that powers a vehicle or machine.
Crowned splines are in essence involute splines, except with slightly modified teeth that allow for misalignments. One more well known style is the ball spline, which involves a ball bearing on the end of the teeth for a varied amount of motion.