You can mark a circle with a compass, a string and pencil, or a trammel, and you can mark a curve with a flexible strip or a template. Choose the method that fits the size of the shape. Small circles are quick, while large arcs need a little more setup.
Small Circles
For circles that fit within the reach of a compass, a compass or divider is the simplest tool.
- Mark the center point with a light pencil dot or a small punch mark.
- Set the compass to the radius, which is half of the width you want across the circle.
- Place the point on the center and hold it steady.
- Swing the pencil around in one smooth motion.
On metal or hard plastic, use a divider with a scribed line. On soft wood, press lightly so the point does not dig a deep hole.
Large Circles
When the radius is too big for a compass, use a length of string or a thin strip of wood.
- String method: Tie a loop at one end for the center pin and another loop for the pencil. Keep the string tight as you swing.
- Strip method: Drill a small hole at the center end and another at the radius. Place a pin through one and the pencil through the other.
- Trammel: A trammel is a bar with two adjustable points that does the same job with better control.
Stretchy string will change the radius as you go, so choose a line that does not stretch.
Gentle Curves
For a freehand curve, mark several points along the path, using a measured offset from a straight edge. Then bend a thin, flexible strip of wood or plastic through the points and trace along it. A helper or a pair of light weights can hold the strip in place. Draw the curve in one pass, then check it by eye from a distance and adjust.
Using Templates
Everyday objects such as plates, lids, and rolls can serve as quick templates for rounds and corners. For repeat shapes, cut a template from thin board, smooth its edge, and trace around it.
| Shape size | Good method | What to watch |
|---|---|---|
| Small circle | Compass or divider | Keep the center point from slipping |
| Large circle | String, strip, or trammel | Avoid stretch and wobble |
| Gentle curve | Flexible strip through points | Hold it steady while tracing |
| Repeated shape | Template | Smooth the template edge first |
FAQ
How do I find the center of a round piece?
Use a center finder, or draw two chords and mark where their right-angle bisectors cross. Check your tool’s manual for specific steps.
Why is my circle not closing?
The center point likely moved or the radius changed. Hold the pin firmly and keep the tension even.
The Short Version
Use a compass for small circles, a string, strip, or trammel for large ones, and a flexible strip or template for curves. Keep the center fixed and the radius steady. Check the shape by eye before you cut.