Richard Findley shares a simple technique for turning a perfect sphere. Turned wooden spheres hold a certain fascination. It is almost the perfect shape. A continual and constant curve that must surely be one of the most challenging objects to craft by hand. They demand to be picked up and rolled in the hand, they show off the figure of the timber and they also hold a mystery to turners and non-turners alike: just how do you turn this perfectly symmetrical shape without marking it? It’s actually not that difficult to do, but there are several stages involved. The method I will show in this article is the simplest way that I have found, but it is by no means the only way. I’ve seen lots of variations, some involve some very careful marking out, some involve some mathematical formulae or the use of jigs. The beauty of the way I do it is that it is pretty much foolproof!
The blank
The first stage with any turning is sorting out the timber. The spheres I show being turned in this article were for a customer who specified softwood spheres, 110mm in diameter with a 16mm hole drilled through the centre. The hole needed drilling first, but isn’t relevant to making a sphere, so I need not go into any details about that, suffice it to say, the holes make no difference to the making of a sphere. To achieve 110mm, I laminated two pieces of 65mm European redwood (Pinus sylvestris) together, to give me a blank of around 130mm thick, and cut it around 150mm long. The beauty of this project is that you can make your sphere from literally any wood, to any size you like and the technique to create the spheres will be just the same as I show here.
Templates
The next step is to make a template. It is quite possible to make a sphere without a template, but to minimise the work later on, a template will make life much easier. I use an offcut of MDF and draw a curve with a radius to match the sphere, in this case 55mm. The beauty of a sphere is that it should be the same in every direction, so I only make about a quarter of a circle, but you can make as much of the curve as you like.
First stages of turning
With the blank held between centres and roughed to a cylinder of the correct diameter, the next stage is to mark out the sphere. In this case I drew two lines to mark the 110mm sphere and a centre line at 55mm, simply marking them with a pencil and ruler. Using my 10mm beading and parting tool, I then turned down the waste at each end, leaving enough solid timber to give a positive drive, but not so much as to get in the way when shaping the ball.
Marking out the sphere
Using my 12mm spindle gouge I then began to shape the block into a ball. I find it best to do this gradually, first rounding off the corners, then, with each cut, increasing the curve. It is important here to keep an eye on the overall shape; to do this I will tend to work on one side until it begins to resemble a sphere, then go to the other side and balance out the shape. It is important to realise when turning a sphere, that the curve begins on the central line – or the equator if you like. There are no flats on a sphere – just curves, so make sure you cut right from the line.
Start checking
As the globe shape emerges from your blank you can bring the template into play. As long as you paid close attention to making the template and did it accurately, you can trust the template. If you are not going to believe what it’s telling you, there was no point in making it! By now your orb should be looking quite spherical, but the chances are your template will tell you it isn’t. Take the blank out of the lathe and turn it on its end so the poles are top and bottom. It is often surprising how this will show you how spherical your ball isn’t… yet! Little by little, cut by cut, remove small amounts of timber as your template guides you and soon enough, you should have a nearly perfect sphere with a relatively small block of waste at each end. With the shaping process, the waste blocks will naturally reduce in size, to the point where they are greatly reduced but still securely driving the blank.
Removing the waste
There are several ways that you could remove the waste, but the safest way is to saw it off with a hand saw. Parting on the lathe would only remove the waste from one end so you would still need to saw off the other waste block anyway and using a bandsaw could potentially be dangerous – if the blade grabbed the wood and spun the sphere it could endanger your fingers. With the waste removed, all that is left to do is to tidy up the cut mark. Potentially the sphere might not be 100% perfect, so you may need to remount the ball on the lathe in such a way that it would allow the removal of the cut areas and to correct any imperfections. There is a way. The beauty of this method of making spheres and the part that makes it foolproof. In addition, it is an easy method to follow as well as inexpensive to create the parts to make it work.
Now you should have the basis of a sphere. The next stage is creating wooden mounting cups that enable the sphere to be turned from different directions. Be doing this, we are able to remove any remanent of waste wood, and sand all the surfaces to achieve a good finish. I will cover these in part two of the series.