Lecture Notes

Wood Basics

In the US and Canada more wood, measured either by weight or by volume, is used in construction than all other construction materials combined.^(p.vii) It is multicomponent, hygroscopic, anisotropic, inhomogeneous, discontinuous, inelastic, fibrous, porous, biodegradable, and renewable. Its already complex nature is further modified when used in products ranging from large glued-laminated members spanning hundreds of feet to small items such as a sheet of paper or a toy. (Mechanics of Wood and Wood Composites, J. Bodig & B.A. Jayne, Krieger Publishing, 1993, pp. vii, 5, 291, 297, 299, 305.)

In the USA, there are over 1,000 species of trees. Of these, only about 100 are used for constructing and manufacturing wood products. There are basically two kinds of wood to choose from — hardwoods and softwoods. In addition, there are certain characteristics that are common in all wood types. Here are some common terms and definitions. (Lowe's)

Wood Descriptions and Uses

Hardwoods

Oak Oak is hard, tough, heavy, and durable, and it is available as red and white groupings. This close-grained material splits with difficulty and cracks if not very carefully seasoned. It takes a high polish and resists marring and denting, making it desirable for interior finishing, cabinet work, and commercial furniture. The pores of white oak are tighter than red oak, and it is therefore more suited for tight cooperage and finer furniture.

Hickory The toughest of all North American hardwoods, hickory is shock-resistant, heavy, very hard, and commonly employed for tool handles, furniture, dowels, gymnasium apparatus, and agricultural implements.

Maple A beautifully patterned, heavy, strong, tough, close-grained material, maple takes a good polish and is light in color. It is used as flooring material, interior finishing, veneers, cabinetwork, toys, and furniture.

Ash Ash is heavy, hard, and resilient, and employed for interior finishing and cabinetwork, baseball bats, handles, and oars. It also finds limited use in furniture.

Birch Strong, hard, heavy, shock-resistant, and close grained, birch warps badly and is rather difficult to work. Products include veneered plywood, woodenware, cabinets, and occasional furniture.

Black Walnut This is one of the most popular materials for architectural woodwork and furniture construction because it is hard, durable, rich, and takes a fine finish. Especially desirable are furniture panels made from patterned walnut, in which a beautiful gradation of color is present because of sapwood running through the solid grain. This material is available, as are most hardwoods, as either solid stock or veneers and plywoods.

Mahogany Grown in several parts of the world, the African and Honduran varieties of mahogany are somewhat lighter in color than the Philippine variety, which is characterized by a reddish appearance. These woods are widely used in cabinetwork and furniture, and as veneered panels. It is also a very important wood in boat construction.

Teak Teak, which comes from Thailand, has emerged as a material almost symbolic of contemporary furniture and attractive woodcraft items. It is used all over the world and is characterized by a golden grain appearance, with occasional dark sap streaks present, as evident in the lovely turned bowl in Figure 3.17. Because of its oily nature, it is most generally finished with oils, or oil and wax in combination, in order to enhance the appearance of the final product. It is strong and easy to work, but it wears edge tools rapidly because of the solidified grains of oil in its structure.

Rosewood A brittle, very hard material, rosewood is difficult to work. Its use results in some of the most expensive pieces of furniture and assumes a beautiful finish either as a satin luster or a high gloss. Veneers and panels are common forms for this material.

Ebony This wood is extremely difficult to work, hard, brittle, and checks badly if not dried properly. It is seldom used for anything other than furniture appointments such as drawer pulls and knobs, and some veneers utilized as accent paneling or overlays.

Softwoods

White Pine This is a light, very soft, straight-grained, easy-to-work material with a clear beige color. It is not a very strong wood; consequently, it is used primarily for interior finish work, toys, and pattern making. The knotty variety is popular for occasional paneling and cabinetwork.

Douglas Fir Hard, strong, and durable, fir splits easily and is rather difficult to work. It is used in all kinds of heavy construction, occasional finish work, and some modern furniture.

Cedar A very fine grain characterizes this wood, which is extremely durable and light in weight. Red cedar is an aromatic variety and has some applications in clothing chests and closets. White cedar is used extensively for interior finish work, and because of its durability, exterior fencing, posts, shingles, and boat construction.

from Product Design and Manufacture, by J.R. Lindbeck, Prentice Hall, 1995, pages 120-123

Natural Fibers

Fiber Description Characteristics Uses

Linen Bast or inner bark fibers of flax stems; seed pods crushed to extract linseed oil; fibers up to one meter in length. Most expensive cellulose fiber; has great strength and high rate of water absorption; crushes easily; inelastic. Household textiles and clothing.

Cotton Seed fiber of cotton plant; fibers separated from seed by ginning; average length, 50 mm; most widely used fiber. Moderate strength and elasticity; easy to dye; good wet strength. Clothing, household textiles, industrial fibers.

Jute Stem fiber of jute plant; second only to cotton in amount used; fibers 2 to 3 meters in length. Jute fibers (or gunny) are inexpensive, or medium strength, and deteriorate quickly in presence of moisture. Burlap bags and sacks, rope and twine.

Sisal Leaf fiber of sisal (heneguen) plant; fibers about one meter long. Deteriorates in salt water; inexpensive; stronger than jute. Floor mats, light cord, and binder twine.

Hemp Bast or stem fibers of hemp plant, up to 2 meters in length; similar to flax in processing. Has great strength and water resistance; coarser fibers than linen. Rope, cordage, sailcloth; waste fibers (oakum) are used for caulking.

Wool Hair fiber of sheep, staple length from 25 to 250 mm; most important of the hair fibers; lanolin oil is a byproduct of fleece. Moderately strong, highly elastic, resilient, crease-resistant, easy to dye, extremely absorbent, pliant because of high oil content. Clothing, blankets, carpets.

Silk Filament fiber extruded from the spinning gland of the silkworm and hardened by exposure to air; filaments 3000 to 5000 meters long. Stronger but less elastic than wool; lustrous filament which readily accepts dyes. Fine clothing, textiles, fabrics and scarves; largely replaced by synthetic filaments such as nylon.

from Product Design and Manufacture, by J.R. Lindbeck, Prentice Hall, 1995, pages 138

Oak	Oak is hard, tough, heavy, and durable, and it is available as red and white groupings. This close-grained material splits with difficulty and cracks if not very carefully seasoned. It takes a high polish and resists marring and denting, making it desirable for interior finishing, cabinet work, and commercial furniture. The pores of white oak are tighter than red oak, and it is therefore more suited for tight cooperage and finer furniture.
Hickory	The toughest of all North American hardwoods, hickory is shock-resistant, heavy, very hard, and commonly employed for tool handles, furniture, dowels, gymnasium apparatus, and agricultural implements.
Maple	A beautifully patterned, heavy, strong, tough, close-grained material, maple takes a good polish and is light in color. It is used as flooring material, interior finishing, veneers, cabinetwork, toys, and furniture.
Ash	Ash is heavy, hard, and resilient, and employed for interior finishing and cabinetwork, baseball bats, handles, and oars. It also finds limited use in furniture.
Birch	Strong, hard, heavy, shock-resistant, and close grained, birch warps badly and is rather difficult to work. Products include veneered plywood, woodenware, cabinets, and occasional furniture.
Black Walnut	This is one of the most popular materials for architectural woodwork and furniture construction because it is hard, durable, rich, and takes a fine finish. Especially desirable are furniture panels made from patterned walnut, in which a beautiful gradation of color is present because of sapwood running through the solid grain. This material is available, as are most hardwoods, as either solid stock or veneers and plywoods.
Mahogany	Grown in several parts of the world, the African and Honduran varieties of mahogany are somewhat lighter in color than the Philippine variety, which is characterized by a reddish appearance. These woods are widely used in cabinetwork and furniture, and as veneered panels. It is also a very important wood in boat construction.
Teak	Teak, which comes from Thailand, has emerged as a material almost symbolic of contemporary furniture and attractive woodcraft items. It is used all over the world and is characterized by a golden grain appearance, with occasional dark sap streaks present, as evident in the lovely turned bowl in Figure 3.17. Because of its oily nature, it is most generally finished with oils, or oil and wax in combination, in order to enhance the appearance of the final product. It is strong and easy to work, but it wears edge tools rapidly because of the solidified grains of oil in its structure.
Rosewood	A brittle, very hard material, rosewood is difficult to work. Its use results in some of the most expensive pieces of furniture and assumes a beautiful finish either as a satin luster or a high gloss. Veneers and panels are common forms for this material.
Ebony	This wood is extremely difficult to work, hard, brittle, and checks badly if not dried properly. It is seldom used for anything other than furniture appointments such as drawer pulls and knobs, and some veneers utilized as accent paneling or overlays.

White Pine	This is a light, very soft, straight-grained, easy-to-work material with a clear beige color. It is not a very strong wood; consequently, it is used primarily for interior finish work, toys, and pattern making. The knotty variety is popular for occasional paneling and cabinetwork.
Douglas Fir	Hard, strong, and durable, fir splits easily and is rather difficult to work. It is used in all kinds of heavy construction, occasional finish work, and some modern furniture.
Cedar	A very fine grain characterizes this wood, which is extremely durable and light in weight. Red cedar is an aromatic variety and has some applications in clothing chests and closets. White cedar is used extensively for interior finish work, and because of its durability, exterior fencing, posts, shingles, and boat construction.

Fiber	Description	Characteristics	Uses
Linen	Bast or inner bark fibers of flax stems; seed pods crushed to extract linseed oil; fibers up to one meter in length.	Most expensive cellulose fiber; has great strength and high rate of water absorption; crushes easily; inelastic.	Household textiles and clothing.
Cotton	Seed fiber of cotton plant; fibers separated from seed by ginning; average length, 50 mm; most widely used fiber.	Moderate strength and elasticity; easy to dye; good wet strength.	Clothing, household textiles, industrial fibers.
Jute	Stem fiber of jute plant; second only to cotton in amount used; fibers 2 to 3 meters in length.	Jute fibers (or gunny) are inexpensive, or medium strength, and deteriorate quickly in presence of moisture.	Burlap bags and sacks, rope and twine.
Sisal	Leaf fiber of sisal (heneguen) plant; fibers about one meter long.	Deteriorates in salt water; inexpensive; stronger than jute.	Floor mats, light cord, and binder twine.
Hemp	Bast or stem fibers of hemp plant, up to 2 meters in length; similar to flax in processing.	Has great strength and water resistance; coarser fibers than linen.	Rope, cordage, sailcloth; waste fibers (oakum) are used for caulking.
Wool	Hair fiber of sheep, staple length from 25 to 250 mm; most important of the hair fibers; lanolin oil is a byproduct of fleece.	Moderately strong, highly elastic, resilient, crease-resistant, easy to dye, extremely absorbent, pliant because of high oil content.	Clothing, blankets, carpets.
Silk	Filament fiber extruded from the spinning gland of the silkworm and hardened by exposure to air; filaments 3000 to 5000 meters long.	Stronger but less elastic than wool; lustrous filament which readily accepts dyes.	Fine clothing, textiles, fabrics and scarves; largely replaced by synthetic filaments such as nylon.