How to Cut a Foam Board into Small Circles
When using foam board for crafting purposes, it is often necessary to cut non-square shapes. Tracing and cutting out square or rectangular shapes is fairly straightforward because you only have to run the blade along a line. Circles pose a bit of a problem, especially if they have to be perfectly cut or very small.
Cutting Small Circles in Foam Board
Depending on who you talk to, you might hear several different ways to cut circles in foam board. Among them are to use a hot knife or a dremel tool. However, without resorting to these methods, it is possible to use only a sharp X-acto knife. Start by tracing a perfect circle on the foam board with either a compass or a stencil. Next, very carefully (and lightly) score around the circle with the X-acto knife. Go slowly and try not to let your hand jump. If it helps and if you are able, turn the board as you score rather than the knife.
Getting through the Foam
After making the first light score, go over it again, only a little deeper. The third cut should be straight down into the foam board. Puncture the board all the way to the bottom layer of paper. The final cut will be made through the bottom layer of paper. Take care not to tear the paper away from the cutting line. If you used a compass to trace the line, set the needle point all the way through the foam board. Trace an identical circle on the backside using the same hold and score the paper along the back. This will help prevent tearing.
The danger of using a hot knife to cut foam board is that it could begin to melt the polystyrene core. With a steady hand, a sharp X-acto knife is all you need.