Milling machine – how to make – splines

Milling machine – making – splines

A spline is commonly taken to mean a series of grooves cut in a shaft equally spaced around its circumference. A male spline is designed to fit into a female spline.

This has several advantages. There can be negligible play rotationally between the two shafts. This is probably the best method of joining two shafts so as to maximise the power that can be carried from one to the other. The use of splines also allows for one shaft to slide longitudinally against the other.

Examples

Splines are used in transmission systems of cars where, due to the up/down movement of the wheels the distance between two points in the transmission will vary.

fig a spline on a prop shaft

Splines are used to hold handles on leadscrews

fig spline on a leadscrew

Splines are used in gear boxes because the gears can be slid along a spline in order to change gear.

fig splines in a gear box

Making splines

As can be seen in the examples above splines can have grooves of many different forms and sizes.

For any spline there are two parts.. There is the external spline and the internal spline. External spline can often be cut using a milling machine. Internal splines usually need some sort of slottting mechanism.

Two easy examples are where the groove is a rectangular channel and where the groove is a V-shaped cut.

Fig. Spline 367

This spline has parallel sides to each groove. In industry a cutter would be used that gave the groove a round bottom. This would be to make the best use of the material in the shaft.

In the home workshop this is not so important and it is easier to use an ordinary side and face cutter. This gives the groove a flat bottom.

In order to get the best fit between the male and female parts the groove is not cut with an endmill because, with the sizes of grooves involved, a side and face cutter will give a more accurate groove in terms of size and straightness.

Fig.  Spline for stub axle fitted with splined gear 411

A cutter like this can be used on a horizontal arbor or a stub arbor in the vertical socket. Another problem is that there is a limit as to how close to the chuck the cutter can get.

Fig. Cutting a spline on a horizontal milling machine 455

It is also possible to cut the groove using a T-slot or Woodruff cutter held in the vertical socket.

fig cutting a spline on a vertical milling machine

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