Working With Plywood

by Blazing Saddles
(California)


Layers of real wood, called plies, are glued together to make the sheet material known as plywood. Softwood plywood is suitable for construction; hardwood-veneer plywood often substitutes for solid wood in frame-and-panel construction and in furniture.


The type of glue that joins the plies deter-mines whether the plywood is for interior or exterior use. Plywood's large (4- x 8-foot) sheets have advantages over solid wood. The sheers are strong and relatively stable you can get wide expanses, as for a door or a tabletop, without edge joints. However, its size makes it awkward to transport, handle, and store. Have someone help you with large sheets. When storing, avoid damp areas that will damage plywood fibers and cause warpage.


The secret of plywood's strength and stability lies in the crisscross layering of the plies. The center ply, or core, varies Face in thickness according to the type of plywood and may be sandwiched between crossband/ layers. The outer plies are the faces, or if not of equal quality the face and the back. If the outer layers are thin and you must hand sand the muse very fine grit paper.

When sawed, plywood splinters where the saw exits. To avoid splintering the good face, place it up when cutting with a table saw, down when using a circular saw. With handsaws, use a plywood or tenon saw and work with the good face up. When joining plywood, choose joints that cover the edge. Tongue-and-groove (facing page), multiple mortise-and-tenon, tourer dovetail, biscuit, and spline joints work well. Nails and screws fasten ply-wood to solid wood or to another piece of plywood. In some cases a combination of nails or screws and glue is necessary. Plywood resists splitting, so nails and screws can be placed close together and close 1/8 inch) to the edges of sheets on the face and back. Screws driven into plywood edges will split the layers apart.

However, knock-down fittings, such as cross dowels (facing page), create a strong interlocking joint and allow for easy disassemble (and reassembly) of a project. For hinges, choose a wrap-around style that allows screws in the edge and the face of the plywood piece. Cover exposed plywood edges with molding or with veneer tape that marches the plywood's face. Depending on the type of tape you buy, you will apply it with glue, iron it on, or peel and stick it on. For edges that will get hard use, such as a tabletop, choose solid wood molding.

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