Ball-making jigs – By Brian Mills

There are many ways of producing balls on a lathe, with practice perfect spheres can be made ‘free hand’ between centres. However, it is difficult to produce an ‘exact size’ in this way, as the ball must be turned several times and re-turned until any ghost image is removed.

For precision ball turning a jig is required. These can be constructed from wood, but again greater precision comes if metal is used.

One reason for turning a precise sized ball is so that it can then be processed further, for instance to produce a pierced product, a series of concentric ‘Chinese’ balls, or to produce a hollow ball with a ‘surprising’ insert – for instance a lidded pot from the same piece of wood.

To do this it is necessary to produce a suitable hollow ‘cup’ to hold the ball. One way to achieve this is to rough out the cup, slightly over size, then cover the inside with a thin layer of wood filler, wrap the pre-turned ball in cling-film and push it into the ‘cup’ allowing the filler to set. The ball may then be removed, unwrapped and re-inserted for further work.

I have constructed two jigs to enable a ball and matchning cup to be turned with great accuracy. The ball jig is as shown in the following picture.

The concave, or cup making jig is shown in the second picture

 

The following pictures show these in use

 

 

 

The precise size and finish can be judged from the following picture

Fitting the ball and cup