Marcus Sly - Furniture Making and Design

There's a lot of talk about design in woodworking circles on the 'net at the moment, perhaps related to the recent release of Lie Nielsen's new video Unlocking the Secrets of Traditional Design. So since design is in the air I thought I'd share a little drafting trick to help you quickly and easily draw accurate freehand circles, both in plan and in perspective.

Why is this useful to you? Firstly it is a great thing to have in your toolbag when developing designs by sketching freehand (naturally the technique also gives you the ability to draw semicircles, arches and arcs as well as whole circles). Secondly it allows you to draw accurate circles and arcs in perspective when the skewing of the subject can make drawing by eye extremely unintuitive. It takes a bit of practice, but it will soon comes quickly and naturally. 

So here's how you do it:

	First draw a square with sides the same length of the diameter of the circle you want to draw.  Cross the circle diagonally to find the centre, then divide it into four smaller squares as shown.
	Draw a diagonal line from corner to corner across one of the small squares like this.
	Now draw an arc round point x, whose radius is x-y, so that it crosses the line at A.  With a bit of practice you can eyeball this.
	Draw a vertical line from A to B.  Use this as a basis to make a square within the original square.
	You now have eight points which you can join together freehand to create a circle.

As I mentioned above, the great thing about this technique is that it works just as well in perspective:

NB make sure that the first thing you do after drawing the original square is to draw the diagonals.  These will give you the centre for the horizontal division.  And remember - practice makes perfect!