Types of Splines and Common Machining Methods

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Types of Splines and Common Machining Methods

Last updated on Jan 01, 2026

Splines are familiar to most mechanical professionals. Compared with key connections in transmission systems, splines offer advantages such as more teeth, high load-bearing capacity, easy self-centering, and high installation accuracy, making them widely used in various fields.

There are three common types of splines: rectangular splines, involute splines, and triangular splines. Similar to gears, splines can also be designed with crowned teeth or helical teeth, which will not be elaborated on here.

Rectangular Splines

Rectangular splines excel in high centering precision and stability. Heat treatment deformation can be eliminated through grinding, allowing for high accuracy in both the dimensional tolerance and positional tolerance of the centering diameter. According to GB/T 1144 (Chinese national standard), the centering method for rectangular splines is minor diameter centering. They are mostly used for fixed or sliding connections under medium and light loads.

Involute Splines

Involute splines offer multiple centering methods, including tooth flank centering (commonly used), major diameter centering, and minor diameter centering (rarely used). When loaded, radial forces act on the teeth, enabling self-centering that helps distribute forces evenly across all teeth. The tooth root is designed with a transition fillet, ensuring high strength and long service life. They are suitable for connections with heavy loads, high centering precision requirements, and large dimensions.

Triangular Splines

Triangular splines are easy to machine, featuring small and numerous teeth that facilitate mechanism adjustment and assembly. They cause minimal weakening to the shaft and hub. They are mostly used for static connections under light loads and small diameters, especially for connecting shafts with thin-walled parts and for disassembly tools.

For spline machining methods, the common ones are broaching or shaping for internal splines, and hobbing or milling for external splines, as shown in the figures below.

All the above are material removal machining methods. In addition, splines can also be manufactured through extrusion, including tooth extrusion and tooth rolling. Below are some reference images.

(Rolling dies (3 units), base, rear drive mandrel, guide seat, fixed end, sliding block)

Extrusion utilizes the plastic deformation of materials to form teeth. It ensures a uniform profile through molds and minimizes material waste to the greatest extent. It is a cost-effective and ideal choice for mass production of spline shafts. It should be noted that the area to be extruded must be pre-machined to the pre-rolling dimension (which can be calculated based on the principle of constant volume), so that the final desired size can be obtained after extrusion.

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Types of Splines and Common Machining Methods

Rectangular Splines

Involute Splines

Triangular Splines