How to Bend Wood Molding
Make Wood Crown Molding, Baseboard, and Wood Window Frames Conform.
Mar 26, 2008
In a perfect world, wood molding would always follow a straight wall. But at times, especially with wood framed home walls, the wall isn't quite straight. At other times, it needs to follow a predetermined curve or radius. Perhaps it's being nailed to the railing on a circular staircase, framing an ornamental mirror, or trimming out wood window frames. When any of these things happen, the wood must adapt. Read on to learn how to bend wood molding.
Wood has been shaped for many architectural purposes since building with wood began. At one time it wasn't bent, but just cut in the proper shape. The downside of this is that the integrity of the wood grain is compromised and the result is a total loss of the strength of the timber. However, when the wood is bent, maintaining wood structure and grain continuity, the strength is actually increased in most situations.
How to Steam Wood Molding for Shaping
A very effective way to bend wood is to apply steam to it. This is called the steam bending method. Wood is more flexible when it's subjected to a fog of moisture. The concept is to apply steam to the wood until it's pliable, then remove it from the steam heat chamber. Next, it's clamped into the finish shape, and then it's dried to ambient humidity conditions.
This is easy with modern materials. What's needed is a length of PVC drain pipe long enough and of the right diameter to accommodate the length of wood. Allow about a foot extra for the length. Also needed are two PVC pipe caps. This is assembled into a steam chamber. A tiny hole is drilled in the center of each pipe cap.
Applying the Steam Heat
Insert the molding into the steam chamber. Attach a steam source to one cap. This can be as basic as a length of surgical tubing attached to a tea kettle and the chamber. The opening on the far end of the chamber should be isolated until the steam chamber is fully saturated. Then, some steam may be released to the atmosphere to allow new, hot steam to fill the gap.
When the molding will is pliable enough, remove it, bend it into the desired shape, and clamp. An alternative to clamps is to secure the molding in place using screws or clamps. But only do this if the moisture won't affect the rest of the project. This is the best solution because the molding will dry fit itself as it dries.
The Back-Cutting Method of Bending Molding
Sometimes the molding's back side will not be visible on the finished woodworking project. Back cutting is a good solution here. This involves cutting many small V-shapes into the molding stock using a coping saw. This allows the stock to gradually conform to the correct shape. The notches should be equally spaced apart. The tighter the curve is, the closer the notches must be to each other.
The critical things to keep in mind when bending molding is to maintain patience and persuade the wood, not force it.
 |
