WOOD AND ITS USES 325 



five, or seven layers, or plies, of veneer glued together with the 

 grain of individual sheets laid at right angles to one another. 

 In this way a product far stronger than a single board of like 

 thickness is obtained. Plywoods are manufactured in thicknesses 

 of from one thirty second of an inch up to one and one-fourth 

 inches, the most commonly used form being a one-fourth inch, 

 three ply sheet. Plywoods are widely used in the manufacture of 

 car and trailer bodies, containers, and for interior finish, in place 

 of plaster and wall paper. Ornamental, as well as common woods, 

 are used in the plywood industry. 



There are three general methods of making veneers. The 

 largest volume of wood is converted into veneers by the rotary- 

 cut method, in which a continuous slice of wood is cut from a 

 log of given length by rotating it against a stationary knife which 

 "peels" the log down to a five inch core. Practically all tree 

 species that grow to be over a foot in diameter are used for rotary 

 cut veneers. 



Sliced veneers are produced by moving a log rapidly down- 

 ward past a stationary knife, a slice being removed each time the 

 log passes. This method is slightly more wasteful than the rotary 

 cut method, but the sheets may be cut to desired sizes and grains 

 matched. Oak, mahogany, Spanish cedar, rosewood, and other 

 beautifully grained woods are cut by this method. Most wasteful 

 process of producing veneers is the sawing method, in which 

 successive thin sheets of wood are sawed from a log by a special, 

 thin-edged, circular saw. Only the finest ornamental woods, 

 with grains that are to be matched, are produced in this manner. 

 Uneven-grained woods, burls, stumps, and knotted woods which 

 would split or tear if knife cut, are used. 



Boxes and Crates. — ^The manufacture of these containers 

 is closely associated with the lumber industry, since the raw 

 materials are often supplied in the form of lumber. The impor- 

 tance of this seemingly minor industry can only be appreciated 

 when it is realized that about 15% of the annual timber cut is 

 used in producing such wooden containers. There are about seven 

 hundred box factories, constituting a SI 00,000,000 industry, in 

 the United States. Even though substitute materials are replacing 

 wooden boxes in some uses, great quantities are still in demand 



