Make a DIY Compass From a Ray to Draw Large Circles
If you don’t have a compass at hand and need to draw a large circle, you can turn a few clippings into a compass beam.
The speed square can replace the compass for drawing small circles, but the compass beam is the preferred tool for drawing large circles. Attach the ends of the tram to a shop-made beam like a 1×1 piece of wood. This provides unlimited radius lengths for your circle or curve. You can then turn it into a compass with two small clamps, a deck screw, and a small pencil. The size of your circle is limited only by the length of the bar you cut (as well as the wingspan of your hand). Watch the video above for detailed instructions.
Draw large circles or curves without compasses and trams | Do Something (YouTube)