We have already seen recently how to make a compass for small circles. This time we will see how John Heisz makes a beam compass that can be very useful, since sometimes we need to draw very large circles or arcs, so large that the maximum opening of a normal compass is not enough.
A well-known trick for making circles is to tie a point to one end of a string and a pencil to the other, but this does not make it easy to draw arcs with the exact diameter desired. On the other hand, with a DIY beam compass we can adjust the radius of the circle and draw it quickly and easily. All we need is a couple of strips of wood, two screws with wing nuts and washers and another hex nut. John has a workshop full of woodworking machines that he likes to use, but if we get or buy the two thin strips of wood needed we will only need a drill, a handsaw and a file to make this simple project. Although a grinding machine would also come in handy to sharpen the tip on one of the screws to make the trammel point.
The trick to make this beam compass work easily is the slot between the two strips of wood that allows to slide the trammel point, that serves as the pivot point, to any position to achieve the desired radius of any circle we want to draw. And at one end we regulate, with the other screw, the opening of a slot that divides in two the hole for the pencil. It allows to tighten the pencil firmly while we draw the circle.
On the woodworking projects page you can go to Ibuildit.ca translations and there you have the link in number 4.