Splines are devices used in mechanical drive systems. They are usually seen in most rotating mechanisms that transfer rotary motion from an input to an output via a splined shaft. It typically has teeth around its circumference, which are parallel to the axis of rotation of the shaft. These teeth or grooves are formed in different ways. They can be in involute form, straight sided, or included angle form called serrations. The external splined shaft mates with internal splines which has spaces formed in reverse to that of the shaft’s teeth.
The torque of the splined shaft is being transferred to the internal spline member that is usually a gear. With this type of spline connection, the load is equally distributed along the teeth, providing a longer fatigue life compared to a keyed shaft. The various types of teeth allow for transfer of rotational concentricity, stronger drives, provision for misalignment, ability to slide, and other functions. Both kinds of splines can be machined in almost the same ways, apart from hobbing which is too difficult to do with an internal type. The different methods of machining splines are explained below.
- Hobbing - as mentioned, this process is applicable to external splines. The ratio of the hobbing machine is determined by the number of starts of the hob and the number of spline teeth. The hob machine then rolls along with the spline while the cutting teeth removes the material from the spaces between spline teeth.
- Milling - different types of milling cutters are used to mill different types of spline teeth. A milling cutter with reverse form of the involute is used to machine involute splines. While a double angle milling cutter is designed to machine the spaces between the teeth of a serration of parallel key spline shaft.
- Shaping - this is used to make all types of splined shaft varieties. A shaper cutter is used with a cutting edge at one face, given with specific number of teeth in proportion to that of the number of teeth in the workpiece. Both the cutter and workpiece roll together with the cutter removing the material from the workpiece when in down stroking action.
- Broaching - this is specially designed to produce female splined shafts. The broach tool has the same number and form of the female spline it will produce. It has multiple cutting edges; each has a progressive form of the final spline which permits a specific chip load on every cutting edge as it works through the blank. The last rows of the edges make the final size of the spline upon exiting.
Whether you need small or large volume of splines, either an external or internal splined shaft order, the expertise of True Gear can best serve you. Get in touch with us today to see how we can satisfy your needs.