How do I cut a circle in wood?

Circles are one of the few shapes where a jig is genuinely faster than freehand, because a pivot point turns a difficult cut into a simple one.

Safety

What you'll need

• jigsaw with a fine blade
• router and straight cutter (optional)
• scrap for a trammel arm
• nail or bolt for a pivot
• clamps

Step by step

1. Choose the method by diameter and finish.Under 100mm, a hole saw. Rough circles of any size, a jigsaw. Anything visible or repeated, a router.
2. Mark the centre and the circle.Compasses or a strip of wood with a nail at one end and a pencil hole at the other. Mark the centre clearly — every method needs it.
3. For a jigsaw, make a pivot arm.A strip of thin ply screwed to the jigsaw's baseplate with a small nail or screw through it at the radius distance. The nail goes into the centre point and the saw traces a perfect arc.
4. Use a fine blade and go slowly.A narrow scrolling blade turns a tighter radius. Let the saw follow the arm rather than steering it.
5. For a router, make a trammel.A strip of ply or MDF screwed to the router base with a pivot pin at the radius, measured from the outside edge of the cutter for an outer circle or the inside edge for a hole.
6. Take shallow router passes.Two to three millimetres per pass, going round several times. Trying to cut 18mm ply in one pass will burn the cutter and snatch the router out of your hands.
7. Support the waste.Whether it is the middle or the outside that is waste, it must be supported so it cannot drop and pinch or catch the tool on the final pass.
8. Watch the feed direction with a router.For an external circle, move the router anticlockwise around the work. For an internal hole, clockwise. Wrong direction and the cutter climbs and pulls.
9. Cut slightly oversize then refine.For the best result, jigsaw about 2mm outside the line, then take the last 2mm with the router trammel. The router is doing a light cleaning cut and the finish is excellent.
10. Clean up the edge.A sanding block wrapped round a curved former, or a spindle sander if you have one, removes any facets.

Tips

• The pivot hole in the centre will remain — plan for it to be in waste, or fill it, or hide it under whatever is being fitted.
• Cut slightly proud with the jigsaw and finish with the router. You get speed and finish rather than choosing between them.
• Double check whether your trammel radius is measured to the cutter's inside or outside edge before you cut. It is an easy and expensive mistake.

Common mistakes

• Freehanding a large circle with a jigsaw — The blade wanders and flexes, so the edge is neither round nor square to the face. A pivot arm takes two minutes to make and removes the problem entirely.
• Taking a full-depth router pass — The cutter loads up, burns, and the router snatches. Depth of cut is the main control over how safe and how clean a router cut is.

If it doesn't work

Questions people ask