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Foam board is a versatile material that can be used for various DIY projects. To cut foam board, follow these simple steps:
1. Measure and mark the desired dimensions on the foam board.
2. Use a straightedge or ruler to guide your cutting tool.
3. Score the foam board along the marked line using a utility knife or box cutter.
4. Apply gentle pressure to break the foam board along the scored line.
5. For more precise cuts, use a hot wire foam cutter or a jigsaw with a fine-toothed blade.
6. Sand the edges of the cut foam board if necessary.
Remember to work in a well-ventilated area and wear safety goggles when cutting foam board.
To cut foam board, whether it’s a thin style used for crafts or the thick insulating type sold in large sheets, you need to be careful and precise. It is essential to have a sharp utility knife or craft knife. If you are new to working with foam board and need to make anything other than a straight cut, it’s a good idea to have some extra board for practice cuts until you become familiar with how the material responds to the knife.
Making Straight Cuts in Thin Foam Board
Thin foam board, also known as foam core board, is commonly used for creating large presentation displays or for mounting photos and artwork. It typically has a thickness of 1/8 to 3/16 inches and consists of a center layer of polystyrene or polyurethane foam sandwiched between sheets of thick paper. Cutting straight lines without specialized tools requires a sharp craft knife or razor knife and a straightedge as a guide.
- Measure and mark the starting and ending points of the desired cut line on the board, similar to sawing wood or cutting a piece of paper.
- Place the straightedge along the marked line, hold it firmly, and poke the tip of the knife through the top layer of paper.
- Once the knife has pierced the surface, adjust its angle to no more than 30 degrees from the foam board’s surface to prevent snags and tears.
- Slide the knife along the straightedge without attempting to cut all the way through the foam.
- It is recommended to make three passes with the knife to ensure a clean and thorough cut. After completing the cut, you can use scissors or a knife to trim any stray bits of paper or foam.
Using a Mat Cutter for Thin Foam Board
A mat cutter, commonly used for cutting straight lines in art mats, can also be used for cutting thin foam core boards. Before purchasing a mat cutter, read the instruction manual to ensure that it can handle the specific foam board you are using. This type of cutter has a slicing device that slides along a rod and is designed for cutting only straight lines. Align the foam board at the desired slicing location, similar to using a paper cutter. Hold the board firmly in place with one hand while sliding the cutting tool from one end of the rod to the other.
Tip
If possible, test the cutter on a scrap piece of foam board to determine if it can cut all the way through or if multiple passes are needed for a clean cut.
Creating Circles and Curves
To cut a circle or arc in foam without a specialized circle cutter, you can use a sharp craft knife. Begin by marking the center of the hole and then use a compass to draw the circle on one side of the board. Insert a needle or nail through the center hole and recreate the circle on the other side using the compass. Carefully follow the pencil line with the craft knife, cutting through the paper to create a clean edge. Repeat the process for the circle on the other side and then cut through the foam using the knife.
A foam-board circle cutter is equipped with a device similar to a compass, but with a small blade instead of a pencil tip. Adjust the cutting tool so that its pivot point is at the center of the circle, with the outer blade along the marked circle. Hold the pivot point in place and rotate the blade along the perimeter of the circle. You may need to make multiple passes with the blade to complete the circle. If necessary, repeat the process on the other side of the board until the cuts meet in the center and the cutout is complete.
Cutting Rigid, Thick Foam Board
Thick foam panels, such as those used for insulation, can be cut using a regular handsaw.
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inga/iStock/GettyImages
A thick foam board, like the type used for insulation, can be snapped in a straight line once it has been properly scored. Similar to cutting a small foam board, mark the starting and ending points for your cut line.
- Place a long straightedge on the starting and ending marks and secure it with clamps near each end. Make sure the straightedge is aligned on the side of the board that will be used for your project, not on the scrap section. This will protect the piece as you score it.
- Use a marker and the straightedge as a guide to draw the cut line.
- Score along the line using a sharp utility knife.
- Remove the straightedge and clamps, hold the board upright, and apply pressure along the back side behind the cut line. The board should snap along the line.
- If the board is too thick to snap easily, use a hacksaw or foam saw to cut it. Even a regular carpenter’s cross-cut saw can be used for cutting thick rigid foam panels.
Making Cutouts and Curves
In certain situations, such as when insulating a foundation wall around an electrical outlet box, you may need to create a cutout in the foam board. To make this type of cutout, press the board against the installed outlet box to create an impression on the back of the foam panel. Alternatively, you can measure the location and use an unattached box to make an impression on the panel. Then, use a sharp utility knife for thin panels or a drywall saw for thicker panels to cut out the desired shape in the foam.
Cutting shapes or curves on thick foam board can be more challenging. It may be difficult to cut out small shapes, but creating a slightly curved edge along the board’s edge is not as difficult. To achieve the best results, follow these steps:
1. Use a marker to draw the desired shape on the foam board.
2. Score the outline using a small craft knife.
3. Sharpen one of the long edges of a narrow putty knife blade and use it to slice slight curves in the foam.
4. For clean cuts, use a forceful pulling motion of the blade, similar to how you cut with a utility knife. This method tends to work better than using a sawing motion.
