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Bent Lamination Made Easy

Master craftsman David J. Marks, host of Wood Works, discusses the advantages of modern glues.

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Bent lamination is an ancient woodworking technique. But today's glues make it a far better tool for craftsmen.

Newer glues make lamination a better option

By David Marks

Bent lamination is a technique of sawing wood into thin slices, coating them with glue and clamping them to a form to create curved pieces. Examples of laminated wood have been found dating from the 15th century, so this is not a new technique. But the old glues weren't reliable.

Modern adhesives developed around World War II eliminated most concerns about delamination, and now we have glues that are as strong as the wood itself.

Here I will describe the process I used to create a mirror image, bent laminated stretcher for a hall table.

My inspiration for the design of this table comes from the work of Edward Barnsley, an English master designer and craftsman. The project begins with full-scale drawings on MDF (medium density fiberboard), indicating front, side and top views. Once I had determined the approximate dimensions, I drew out the footprint for the legs onto a sheet of MDF. This enables you to design the curve of the stretcher.

Thin strips of wood work best to lay out the curve. Next, I marked a centerline between the legs along the length and then set two strips of wood 3/32 of an inch thick on the centerline, clamping them together. I clamped them so that they formed a straight line in the center for a ways and then experimented bending them so that they formed a Y at both ends and met the inside of the legs at a 45-degree angle. After arriving at a pleasing curve, I slid a piece of paper under the laminates and drew the outline onto the paper.

This done, I could now use the drawing to lay out the form.

One of the challenges with bending wood is a tendency for the wood to want to return to its straight form. This is called "spring back" and the best way to minimize it is by cutting the laminations thinner. The thinner the laminates, the less spring back you are likely to have. Knowing from experience that spring back isn't entirely predictable, I usually make the bent laminated components first so that I can adjust the rest of the design accordingly, if necessary.

Begin making the bending form by taping the drawing to a 3/4-inch thick piece of MDF, sliding some carbon paper underneath the drawing and tracing it onto the MDF. Cut out the curve with a band saw or jigsaw and then fare the curve with a pattern makers rasp and smooth it with sandpaper. I usually double-stick tape some 100-grit sandpaper to a thin (3/32-inch) piece of wood. The completed shape is the master template.

To create the opposing side, you'll need to take into consideration the finished thickness of one half of the stretcher, or, in the case, 5/8-inch. And I like to add a layer of cork to aid compression so we add an 1/8-inch for the cork. Now set a compass at 3/4-inch and scribe a parallel curve to the master template onto another sheet of 3/4-inch MDF. Cut it out and smooth its edge.

Once there is an MDF master for each side of the bending form, build the height by cutting, gluing and flush trimming each layer for a total of six layers. The finished form is 4-1/2 inches tall. This form allows us to glue up a 4-1/2 inches tall bent lamination that can be cut in half. Each half will be approximately 2-1/4 inches high and will be mirror images that can be glued and clamped to net a stretcher 1-1/4 inch thick by 2-1/8 inch high. I've had the best success using a slow setting plastic (Urea) resin glue.

(Master craftsman David J. Marks hosts Wood Works on the DIY Network. For more information, visit www.djmarks.com.)

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