The free metalworking plan presented here contains drawings with which you can make a trammel, i.e., a beam compass.

Anyone who is at least a little into crafts must have encountered the problem of drawing a larger diameter circle on a workpiece surface. To draw such circles, you can use a piece of rope, with one end fixed to the center of the circle in some way, and a pen attached to the other end. The circle drawn in this way is not very precise and the process itself is quite arduous. If you don't need a precise circle and don't have to draw it too often, this way may be quite useful, though. If, on the other hand, you are in frequent need for a precise large diameter circle, then a quality trammel, whose design plan is offered here, will definitely come in handy! As you can see in the picture, the construction of the trammel is very simple. It is suitable for drawing circles on wood, metal plastic, stone, etc., and its use is also very simple and efficient. To draw circles on metal, a pointed bar with handle is used (as shown in the picture), and to draw on wood or plastic, a pen is fixed to the trammel. Adjust the bar length (Bar – Part 1) to the diameter of the circle(s) you want to draw. 

 

Trammel (beam compass) plan
Project difficulty
Simple, requires precision
Skill level
for DIY enthusiasts
Level of workshop equipment
Basic hand toools
Dimensions

40mm (1.57'') x 124mm (4.9'') x 725mm (28.54'')

 

How to draw a circle using a trammel:

  • Depending on the material on which the circle is to be drawn, fix a pen or fixed holder to the end of the trammel.
  • Change the position of the movable holder until the distance between the points is equal to the radius of the circle you are drawing. Secure the movable holder by tightening the handle. Check again that the distance between the points is equal to the radius of the circle.
  • Place the tip of the movable holder part in the center of the circle you are drawing, keep it pressed at that point, and slowly rotate the opposite end to scribe/mark the circle on the material.

 

Exploded view and parts list
Trammel - Parts list
Assembly drawing
Trammel - Assembly drawing

 

The trammel made according to our plan is primarily intended for amateurs and DIY enthusiasts, but in many cases it can be used by professionals, too.

Study the drawings carefully, adjust the dimensions of the parts to your needs, and feel free to make this simple yet practical hand tool.

 

Download project (high resolution images)