DIY Network

Maple and Bubinga Treasure-Box: Bending Form and Lid-Core From "Wood Works" episode WWK-505

	The rich contrasting colors, classic design and artistic accents make this treasure box a simple yet elegant showpiece
	The curved top with its majestic maple burl forms the perfect crown for the darker buginga-wood case.

In this episode of DIY Wood Works, host David Marks builds an oblong treasure box, with curved lid, from figured maple and African bubinga.

The curved lid of the box forms the greatest challenge in this piece. It is formed in the vacuum press as multiple layers of bending poplar are veneered with spectacular spalted burl-maple. The top's grain swirls into a curly pattern to create a three-dimensional effect. The four-sided box is built from Bubinga with half-lap joinery and the edges are adorned with brass accents. The accents are the pins that add a decorative touch as they reinforce the joinery. An ebony handle and a tung-oil finish are added as the final touches.

The box is built "from the top down." Two slices of quilted maple will be used to make the top. Once the curved top is made, it will dictate the dimensions of the rest of the design. A special bending form is made from MDF to create the top using a vacuum press.

Materials:

Burl-maple stock
Bending-poplar plywood
MDF for mockup and bending form
Band saw
Table saw
Vacuum press
Hand-held router
Belt sander
Nail gun
Plastic-resin glue
Glue roller
Straight-edge
Carpenter's pencil
Carpenter's tape
Clamps
Safety glasses or goggles

Note: Cut sizes may vary. For exact measurements, please contact David
Marks through his Web site -- information below under Resources.

Safety Alert: Always wear safety goggles or safety glasses when
working with wood, power-tools, saws, drills, routers, etc.

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	Figure A
	Figure B
	Figure C
	Figure E
	Figure F
	Figure G
	Figure H
	Figure I
	Figure J
	Figure K
	Figure L

Bending Form

Steps:

• To begin, sketch a full-scale side view of the top's edge onto some 1/2-inch MDF using a large compass (figure A). The compass helps for drawing the curve, but this is somewhat of a trial-and-error process. Create a pleasing curve that works well with the stock you'll be using.

• The stock for our top is 11-3/4 inches wide. Allowing for the curve, the span of the box from front-to-back is 11 inches (figure B).

• Adjust the setting of the compass 5/8-inch and draw a second curve just below the first one, using the same reference point. These lines outline the thickness of the top. Next, use a straight-edge to draw out the sides and connect the bottom (figure C).

• Now that the basic shape of the box has been determined, a bending form can be created to shape the veneers for the top. The top of the bending form is made with thin layers of special bending plywood (figure D). Stack enough sheets of the plywood to make the top 1/2-inch thick.

• The bent top will attach to a series of ribs that run the length of the form (figure E).

• To make the ribs, use the full-scale profile. Adjust the compass and draw an arc 1/2-inch below the top -- to represent the curve and thickness of the bending form, and to provide the shape of the ribs.

• Next, construct a trammel-arm to hold your hand-router. Using the same reference point, center the router in the trammel-arm so that the bit will follow the curve exactly (figure F). Position the trammel-arm onto a piece of 3/4-inch MDF and rout the arc of the ribbed template. Use the template to batch-cut 13 more ribs using a flush-trim bit.

  Once you have all the ribs cut, glue them onto a piece of 1/2-inch MDF, spacing them evenly (figure G).

• Once each rib is glued in place, secure each to the side with a finishing nail using a pneumatic nail-gun. Next, add the final side -- using glue and nails -- to make the form rigid.

• Next, add the plywood "skins" to the form. We used four sheets of 1/8-inch-thick Italian bending-poplar (a thin, flexible plywood) to finish the form. Each sheet was cut 15" wide by 27" long. First, apply slow-setting resin glue to both faces of each skin using a glue roller.

• Carefully place the "wood sandwich" on top of the form. Once it's in position, tack it in place with the nail gun (figure H).

• Add a caul of bending-plywood covered in plastic, and set the entire assembly into the vacuum press (figure I). Let the form cure inside the press for eight to twelve hours.

• Once the form has cured and the glue has dried, remove any excess hardened glue using a belt sander (figure J).

The Lid-Core

With the bending form finished, the top of the box can be laminated. The top will be 5/8-inch thick, and will be made of four sheets of 1/8-inch bending plywood (figure K) sandwiched between two 1/16-inch-thick maple veneers. Make the top following these steps:

• First, glue the plywood together to make the core of the top. As before, apply slow-setting resin glue evenly to both faces of each plywood sheet using a glue roller.

• Tape the edges of the plywood stack together using carpenter's glue to keep the pieces from slipping.

• Add the plastic-covered caul on top, and set the core and bending-form into the vacuum press (figure L). Seal the bag tightly and turn on the vacuum press. Allow the lid to cure for about 12 hours

Tip: For a good bond, it's a good idea to keep the vacuum press at around 75 degrees. If you're working in a cold environment, you can use an electric blanket to keep the press and wood warm.

In the segment that follows, the curved lid will be covered in burl veneer.

Click here to order your tools and materials for this project from Woodcraft!