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How to Machine External and Internal Splines

January 20, 2021

How to Machine External and Internal Splines

Splines are useful devices used in various mechanical drive systems. They can often be found in most mechanisms that transmit rotary motion from input to output through a splined shaft. The spline has teeth around the shaft which interlocks with other gears. These teeth, also known as grooves are formed in different ways. Generally, they come in involute forms, straight-sided, or serrated. The external spline shafts work with internal splines which have spaces formed in reverse to that of the shaft’s teeth.


Here's how these splines are made.


Torque is transmitted to the internal spline member that is often a gear. In this kind of spline connection, the load is evenly distributed along with the teeth, offering a longer fatigue life compared to a keyed shaft. The different types of teeth allow for the transfer of rotational concentricity, stronger drives, the capacity to slide, provision for misalignment, and other functions. Both the external and internal splines can be shaped in virtually the same ways, apart from hobbing which is quite challenging to do with an internal spline.


There are different methods of machining splines including hobbing, milling, shaping, and broaching. Hobbing is a process applicable to process external splines wherein the hob machine rolls along with the spline while the cutting teeth remove the material from the spaces between spline teeth. Conversely, in milling, different types of cutters are utilized to mill various kinds of spline teeth. On the other hand, shaping is commonly utilized to make both external and internal splines whereas broaching is specially designed to produce the internal spline or female splines of all types.


Whether you need a small or large volume of splines, or other services including gear shaping and gear manufacturing, the expertise of True Gear can best serve you. Get in touch with us today to see how we can satisfy your needs.