For me, one of the most enjoyable times in math class was always when the class got to break out those funny looking folding plasticy things. Those were fun days... except when the compasses wouldn't stay locked at the correct measurement... or when they weren't made to make the circle size I wanted... or, perhaps worst of all, when the pencil would slide around because the cheap plastic piece wouldn't hold it securely in place.
As it turns out, virtually whenever a circle is needed to be drawn, I've found it ridiculously convenient to have a compass. But the thing is, I don't always have one at my disposal, and in all sincerity, the common plastic variety aren't really that good.
To fix this, I've found a simple way to make a compass almost immediately that can accommodate a pencil or pen and always stays locked at the same measurements.
Step 1: Determine the Radius
Assuming you have a circle in mind that you want to draw/copy, it's best to begin by finding its radius. The radius can be found by measuring the length from the center of a circle to the edge, dividing the diameter of the circle by 2, or dividing the circumference by 2π.
Step 2: Cardboard
After you've determined the radius for the circle you want, begin with a piece of cardboard. Cardboard of any sort should work.
Cut the cardboard to about 1 centimeter in width and at least two centimeters longer than the radius for the circle you want to draw. If you are simply making this compass for future use and don't have a specific circle size in mind, just make a guess as to the largest radius you'll want and use that. If you are using corrugated cardboard, I'd suggest cutting with the grain (refer to the picture above).
Step 3: Punching Holes
After you have the rectangle of cardboard cut out, it's a good idea to pencil a line down the center longways using a ruler. Then, make a small tick mark on that line about 1 cm from one end. This will be the hole used for the center of the circle.
After that, proceed to make a tick mark on the center line however far away from the first mark the radius of the intended circle is. If you want to be able to draw circles with different radii, measure different distances from the first and mark accordingly.
Using a skewer, needle, or even the tip of a pen or pencil, carefully punch holes through the cardboard where the tick marks are. Ideally, the holes will be large enough for pencil lead/a pen tip to pass through, but not much larger, as that might impact the perfection of the circle. I find it easiest to accomplish this by beginning the hole with a sharp needle and widening it slightly with the tip of a pen.
Step 4: Draw Circles
At this point, the compass should be complete. To use it, insert the tip of a pen or pencil into the hole closest to the end and place it where you want the center of your circle to be. Then, take another pen or pencil, insert it into the hole the desired distance from the first and slowly revolve the second around the the first until you have a circle. This process seems to be easier if you have a friend hold down the paper while you draw the circle.
If you don't want a mark in the center of the circle, try using a bamboo skewer or a pen that has run out of ink. A needle will also work for this but make poke a hole in the surface.
I hope you found this instructable useful. If you did, it would really mean a lot to me if you would favorite it and share it with your friends. Feel free to ask any questions or give any ideas you might have in the comments below. Lastly, I've entered this into some contests and I'd really appreciate it if you would vote for it!
If you liked this instructable, you might also like some of my others:
- Toothpick Tops:
- Paper Bow Tie: