Working with plywood can be a little tricky, but it does have the advantage of being more flexible than some other wooden materials. Plywood is a synthetic material made by gluing thin layers of wood veneer with each other. It is widely used in many wood-related applications such as construction, aircraft-building, and furniture-making.
Let’s look at some of the common ways to bend plywood for construction or furniture making purposes.
What Is the Best Type of Plywood for Bending?
Hardwood plywood made from dicot trees is generally suited to creating bent or warped shapes. This includes white oak, red oak, elm, hickory, ash, beech, birch, maple, walnut, mahogany, sweetgum, and poplar. Hardwood plywoods consist of a close-grained hardwood face which reduces chances of splintering and breakage when bending.
In contrast to hardwood plywoods, softwood plywoods made from coniferous trees are not ideal for bending. This includes douglas fir, pines, spruce, larch, red cedar, hemlock, and yew. This is because fibers in softwoods are more brittle and likely to separate easily. Softwoods are also less dense than hardwoods and are more likely to tear and break while bending. They are more suited to creating straight surfaces such as doors, chipboards, and panels.
How to Bend Plywood: 4 Common Methods
Without further ado, let’s jump into the four most common ways used when bending plywood.
Method #1: Clamping
To bend plywood using the clamping method, follow the process below:
- Step 1 – Build a form for the bend that you need. The form should be made of a hard material so that it does not change shape when pressure is applied. You can build your form using MDF (medium-density fibreboard). Alternatively, you can also use a metal rod or cylinder which matches the shape.
- Step 2 – Take a sheet of plywood and wrap it around the form. For best results, ensure that the plywood is 1/5 to 1/4 of an inch thick. The plywood may not curve if it is too thick, or it may require much longer to curve.
- Step 3 – Clamp the plywood sheet to the form. Apply the clamps starting with the middle of the corner, to the center of the arch, and to the opposite corner. Apply more clamps to ensure there is no space between the form and the plywood. You should make sure that the pressure applied is even across the form, as there are no dents along the plywood surface. Leave the clamps on for 24 hours.
- Step 4 – After 24 hours, unclamp the plywood and remove it from the form.
- Step 5 – Use your hands to check if the plywood retains shape. Turn the shape upside down and apply pressure on the curved edges to open them up. After that, flip it back and apply pressure on the arch to flatten it. If the plywood loses its curve then clamp to the form for another 24 hours.
Method #2: Soaking
To bend plywood using the soaking method, follow the process below:
- Step 1 – Build a form for the bend that you desire.
- Step 2 – Collect water in a bathtub or water tank large enough to submerge the plywood. Soak the plywood in the container of water, and let it rest for around 2 hours. This will allow water to penetrate the wood and soften the fibers.
- Step 3 – Like in the previous method, clamp the wet plywood on the form, ensuring that there are no spaces between the wood and the form. Make sure that the plywood is wet when you do this. If it feels drier, use a wet rag of cloth to soak the wood.
- Step 4 – Keep the clamps on for four to six hours. Making the wood wet reduces the time required for keeping the plywood clamped to the form as wood becomes softer and more malleable.
- Step 5 – After four to six hours, unclamp the wood and remove it from the form.
Method #3: Kerfing / Notching
To bend plywood using the kerfing or notching method, follow the process below:
- Step 1 – Take the piece of plywood that needs to be bent and lay it out flat on a surface.
- Step 2 – Mark the crease where the bend needs to be made. Make thin lines around the crease using a pencil and ruler. These should be roughly 1/5 of an inch apart from each other. The lines will guide you when you start cutting your notches which are also called kerfs.
- Step 3 – Take a circular saw and calibrate to one-half or one-third of the thickness of the plywood.
- Step 4 – Using your penciled lines, cut grooves into the plywood with the circular saw.
- Step 5 – Fill the grooves with wood bonding glue. The glue should preferably be a strong and slow setting glue for maximum strength.
- Step 6 – Bend the plywood till the grooves join together and hold it in place using clamps. The clamps can be attached directly to the plywood where considered necessary to keep it in a folded position.
- Step 7 – Allow the glue to dry for around six to seven hours. The time may vary slightly depending on the type of glue being used.
- Step 8 – Remove the clamps from the plywood. The surface should be curved and able to retain its shape.
Method #4: Steaming
Finally, to bend plywood using the steaming method, follow the process below:
- Step 1 – Prepare a steam box using a rectangular wooden box large enough to hold the piece of wood that needs to be bent. The box should be open on one side and closed on the other. Add wires inside the box to support the plywood when you put it in. The plywood should be suspended in the middle of the box and not touching the sides, to increase surface area for the steam to work on. The bottom of the close-ended side of the box should have a hole that connects to an electric or gas stove.
- Step 2 – Put a cooking pot, filled 2/3 with water on the stove, and let it boil. When the water starts boiling, steam will form within the box. Once there is a steady flow of steam coming from the open side of the box, add your plywood and cover the open end with a towel. Make sure you do not seal the box with a hard cover, as that might cause build-up of steam and an explosion.
- Step 3 – Keep the wood inside the box for one hour for every inch of plywood that needs to be bent. While the wood is steaming, prepare a form for bending. As mentioned earlier, this could be made of any hard material that does not lose shape easily.
- Step 4 – Take the wood out of the box and bend it with your hands while wearing heat gloves. If the piece is large and difficult to bend, feel free to use a helper for assistance in applying pressure. This should be done as soon as the wood is removed, as the wood is most bendable at this time.
- Step 5 – Secure the bent plywood with clamps to maintain the shape. This should feel more effortless than bending without steaming, due to the heat and water treatment. If you feel resistance in the wood here, put it back in the steamer for an additional 15 to 30 minutes.
- Step 6 – Let the wood cool for an hour, and you should have your curved plywood. For thicker plywoods, you can attach the sheet to a mold or form for drying. This will ensure that the fibers do not contract when cooled. Allow the plywood to dry in the mold or form for 24 hours
- Step 7 – Remove the wood from the mold in 24 hours. The wood should be completely cool and dry. If it is still wet, wait for it to dry before removing the wood.
Mistakes to Avoid, Tips & Tricks
Here are some useful insights and tips that will help you achieve the perfect shape with your plywood.
The first thing to keep in mind is that not all plywoods bend the same way using the same method. While woods like oak are likely to produce good results using steam bending, maple and poplar are less likely to retain shape after steaming.
Before using any wood, it is important to check for any knots or cross-grain. Straight-grained wood is more likely to bend than cross-grained. Knots form on the wood where the grain is distorted. The knots resist compression and make bending difficult, increasing the chances of the plywood breaking. Therefore, you should only use high-quality straight-grained plywood sheets.
In addition, the thickness and type of the workpiece can greatly affect the time required to create a perfect bend. The thicker the plywood, the longer it takes to bend. However, thicker plywood is more likely to retain its shape once bent. It is advised that you use multiple thin plywood sheets glued together, rather than a single sheet to improve the sturdiness and the overall look of the finished product. Though bending will take much longer, the finished result will be more refined and durable.
Regardless of the method you choose, checking your plywood for knots and cross-grain is the first step to ensure that you get the result you want.
When using the soaking or steaming method make sure that the wood is allowed to dry completely while secured to a mold or form. This will reduce springback by allowing the wood fibers to take the shape of the form as they cool. When using the kerfing method, you should make sure that the plywood used is not too thin. The thinner the plywood the greater the chances of breaking the wood when bending at the kerfs.
Finally, make sure that the type of wood used is suitable for the curved structure that you want to create. While you can use softer and thinner plywoods for creating frames and ornamental pieces, thicker plywoods are needed to make furniture pieces that are sturdy and able to carry weight.