Woodworker's Journal 1993-17-1, страница 29

Special Techniques

When most woodworkers think of woodworking materials and construction methods, they think of solid wood or plywood, using terms like mortise-and-tenon. frame-and-panel, apron, rail, or carcass But solid wood isn't always the best choice, and even with adequate supporting framework, table or workbench tops made from solid wood can twist and bow. For some applications, there is another choice: The torsion box, "T-box " for short. The T-bo.x is ideal for surfaces where stability is important, and contrary to what you may at first think, they aren't really complicated or difficult to build. The T-box that we show being constructed here is the bench top for the T-box workbench project on page 44. The entire workbench is constructed from just two 4 by S sheets of medium density fiberboard (MDF).

A T-Box is a mostly hollow-core structure that has a skin male-rial attached to each side. A hollow core door, and an airplane wing are two good examples. The T-Bo\ gives you a strong and stable panel, as thick as you like, without adding excess weight or expense to the project.

A T Box can be used for any vertical or horizontal panel where extra strength and stability are required. A few of its many uses include doors, shelving, desk and table tops, cabinets, benches, and work surfaces.

For furniture, the corc is usually made of a man-made sheet material iMSM). Plywood, or medium density fiberboard (MDF), are the best choice. The skins are also made of MSM. Plywood, MDF, or particleboard all work well. The choice is determined by what type of finish covering you will be applying to the skins: veneer, leather, plastic lami-

January/February l^lW

Make a Torsion Box

The High Strength!Lightweight Alternative to Solid Wood

by Ed Speas

ANATOMY OF A TORSION BOX

nate, paint, etc. In most cases, your best choice for the skins is also MDF. Il is the best substrate tor veneer, and also accepts paint very well.

It is very important to understand that a T-Box is simplv a building block. Like a frame and panel, or a chair leg, it isn't much without the addition of other T-Boxes, or other parts.

How a T-Box Works

Individually, the parts of a T-Box can be easily bent or broken. Yet when assembled into a single, unified structure, they create a box or panel with great strength and stability. The strength comes from the glue.

We tend lo think of slue as that

yellow or white liquid in Ihe bottle. But when glue has cured in our project, it is a very ihin. very hard layer of material, with incredibly strong sheer strength properties. No mailer how you try to bend, iw isl. or destroy a T-Box, you arc trying to sheer a glue line somewhere.

Glues that bond by mechanical adhesion. such as contact adhesive, do not have this properly. You must use a specific adhesion glue such as polyvinyl acetate (white giue). or alaphatic resin, (yellow glue).

The Core

The core consists of several core strips attached to form a grid that the skins will be attached to. There we're using in.

Pico if circle No. JO on the Reader Service Card. 7