How to Bend Wood: The Need-to-Knows
Regardless of which of the following methods you choose, there are a few facts to understand about bending wood. For one, wood fibers are tough and rigid, so wood doesn’t want to bend. For that reason, it’s very easy to break wood while attempting to bend it, so adjust your expectations and don’t get discouraged.
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Also, for bending wood with steam or hot water, as described below, you only have about 30 seconds before the board cools or dries enough to stop being pliable. For that reason, have a form available to which you can quickly clamp the pliable board. You can make a form from standard construction lumber, a jigsaw, and a pattern. If the pattern doesn’t fit on one piece of wood, you can make the form with several pieces screwed to a piece of plywood. Finally, recognize that the thicker a piece of wood is, the harder it will be to bend. If you’re struggling to bend a piece of wood, consider milling it thinner on a bandsaw or table saw. This isn’t always a possibility, like in the case of baseboard trim, but the first tip below will explain how to handle those scenarios.
How to Bend Wood with Kerf Cuts
“Kerf” is the name for the space left in a piece of wood after a saw blade passes through it and cuts away the material. It’s essentially an empty space, and it produces the easiest method for bending wood. This approach to wood bending is best for curved trim pieces or scenarios where only one plane of the wood will be visible. All you need is a table saw, circular saw, or radial arm saw. To bend wood with kerf cuts, adjust the saw blade so that it will cut all but the last ⅛- to 3/16-inch of material. Then, make cut kerfs across the board every ½ inch or so (keep these cuts evenly spaced for best results). The result of all these cuts will be a much more flexible strip of wood that will bend inward and outward. The more closely you cut the kerfs, the tighter you’ll be able to bend the wood, so use a test piece to determine the spacing before moving on to expensive millwork.
Bending Wood with Water
Another method for bending wood involves soaking it in hot water until it becomes pliable. Once pliable, you’ll be able to clamp it to a form and allow it to dry. When it’s cool and dry, it will take the curved shape of the form.
1. Gather the Materials for Bending Wood with Water
A large tub of water Pot for heating water Pre-made form Clamps (squeeze-style clamps are best, but almost any clamp will do) Waterproof and heat-resistant gloves
2. Put the Wood in the Tub
If the boards fit, the best place for soaking wood is a bathtub. A tub limits the mess and can handle the weight of all the water necessary to soak the wood. Be sure to plug the drain so you don’t lose hot water.
3. Heat the Water
Fill the pot with water and heat it on the stove. The hotter the water, the easier the bending will be, but it will also be more dangerous to transport. The amount of water necessary will depend on the size and number of boards, but you want enough to keep the wood submerged. If the wood floats at first, consider placing a heavy rock or similar item on top of it.
4. Add the Water to the Tub
Once hot enough, carefully pour the water into the tub (avoid splashing for safety’s sake). Continue heating water and adding it to the tub. Allow the lumber to soak for at least an hour before removing and clamping it to the form. The longer it soaks in the hottest water possible, the easier it will be to work with but keep in mind that boiling water isn’t vital, so you can supplement with a bit of hot bath water to keep the temperature up.
5. Remove the Board and Clamp it to the Form
Before removing the board from the water, remember that you’re working under a time constraint. With waterproof and heat-resistant gloves, take the wood out of the water. Quickly clamp one end of the board to the form and slowly bend the rest of the board around the form, adding clamps as you go.
6. Allow the Board to Cool
With the board clamped to the form, allow it to cool and dry for a few hours. Remove the clamps and allow the board to continue drying. If it dries and doesn’t quite hold the shape, repeat the process and clamp it to the form again.
Bending Wood with Steam
Steam is by far the most difficult and material-intensive way to bend wood, though it might also be the most effective. The main issue is that this method requires building a long, thin box that you place boards into for steaming. This contraption is known as a “steam box,” and it will have a small hinged door on one end for sliding boards in and out, as well as a port for attaching a hose from a steam cleaner. That might seem like a lot of effort, but steam-bending can be very effective.
1. Gather Steam-Bending Tools and Materials
Start by gathering:
Steam box large enough for the wood Steam cleaner with a hose A pre-made form Clamps (squeeze-style clamps are best) Waterproof and heat-resistant gloves
2. Place the Wood in the Steam Box
Place the wood into the steam box and be sure to close it to prevent steam from escaping. Also, connect the steam cleaner to the steam box with a hose.
3. Turn on the Steam
Turn on the steam cleaner and let it fill the steam box with moisture. A good rule of thumb for timing steam bending is 45 minutes for every 1 inch of thickness, though this can vary depending on the species. Every fifteen minutes or so, be sure to check that the steam cleaner hasn’t run out of water.
4. Remove the Wood and Clamp it to the Board
Wearing heat-resistant gloves, remove the wood from the steam box and clamp one end to the form before bending the rest of the board and adding more clamps. Allow the board to dry and cool for a few hours before removing the clamps. If the board doesn’t hold the shape desired, try placing it back in the box for another 45 minutes. If it’s too curved to fit back in the steam box, you might need to start over with a fresh board.
The Best Types of Wood for Steam and Water Bending
Using just any old wood isn’t going to yield the best results. Certain woods work better than others. Here are the criteria:
The greener, the better. Kiln-dried wood is excellent for building and joinery, but it doesn’t bend as easily as fresh, green wood. Softer woods are easier to bend, so pine, fir, and spruce are prime choices. Straight, vertical grain is far better for bending boards than wood with visible rings or C-shaped patterns in its end grain. Avoid knots as they rarely bend and are the most likely location for snapping wood while bending.
And, with that, you should be able to bend wood for your next project.
