Lumber and Millwork

CHAPTER 14 Lumber and Millwork Objectives pitch pockets shop grade plain sawing soft rot After studying this chapter, you should beableto: • Explain the sequence of steps used to convert plain sawn spindles trees to usable lumber. quarter sawing splits • Describe the three methods of sawing. raised grain surfacing • Explain hardwood and softwood grading random widths and systematic felling practices. lengths (RWL) torn grain • Order lumber and millwork. remanufacture grade trim • Identify various lumber defects. rift sawing twist seasoning wane Technical Terms sectional felling warp Selects air drying (AD) finish lumber wavy dressing Selects and Better bark pockets Firsts and Seconds (FAS) wormholes shakes blue stain flat sawn board foot grub holes Wood is a natural material available worldwide bow heart rot for use in cabinetmaking and construction. Trees are brown rot honeycomb a renewable resource for lumber, millwork, and man- checks kilns ufactured wood products. Wood used for softwood construction is purchased in nominal size boards construction grade kiln drying (KD) (1 × 3, 2 × 4, etc.). Nominal size boards are rough- crook kink sawn dimensional lumber, before planing. Wood cup knots used in hardwood construction is purchased in decay knot hole random widths and lengths (RWL). RWL is wood dimension grade machine burn sawn to various widths and lengths, maximiz- ing the yield of usable wood from a log. Millwork dimension lumber millwork includes manufactured dowels, mouldings, and dec- dog hole moulding orative wood products. Manufactured wood materi- dowel No. 1 Common als include plywood, particleboard, and fiberboard. dry rot No. 2 Common All wood species are brought to market as lumber through a sequence of steps. These include har- factory grade No. 3 Common vesting, sawing, drying, and grading. Individuals or FAS 1-Face nominal size boards industries then order lumber and millwork to meet FAS 1-Face and Better pattern lumber their needs. Copyright Goodheart-Willcox Co., Inc. 183 / 184 Section 3 Materials 14.1 Harvesting Lumber begins its journey to you as a mature tree that is harvested. Logging industries select and fell (cut) trees for market by sectional felling and systematic felling. 14.1.1 Sectional Felling Sectional felling is the harvesting of large sections of forest at one time using heavy machinery, Figure 14-1.Clearing large portions of a forest is less expensive than cutting individual trees. Sectional felling occurs most often in softwood harvesting. Christopher Kolaczan/Shutterstock.com These trees grow faster and mature quicker than Figure 14-2. New seedlings are replanted after hardwoods. The cleared sections are replanted and sectional felling of softwood forests. reach maturity within a person’s lifetime. Seed- lings are grown at tree farms and later transported Trees marked for systematic felling are notched to planned forests. See Figure 14-2. Replenish- and cut with a saw. The trees are cut near the ground. ing wood resources is under the guidance of the Systematic felling is done using hydraulic American Tree Farm System. It is the largest and machines that both cut and transfer the tree. Single oldest woodland management organization in trees are difficult and more costly to harvest. Nearby North America. They help ensure that wood will trees may be destroyed in the process. Large scale be harvested in a sustainable and environmentally replanting is impossible. responsible manner. Once the trees are felled, small branches are trimmed from the main trunk. The trunk is cut into logs suitable for transporting. This process is called 14.1.2 Systematic Felling bucking. Logs are then transported to the sawmill Systematic felling is the harvesting of single by truck or railroad cars. trees. They may be selected because wood of a cer- Most lumber mills are located near harvest- tain species is needed. They may also be cut because able forests and at least one body of water. See they are diseased or infested with insects. Removal Figure 14-3. Logs can be stored in the water until of these trees allows those nearby to grow quicker sawing. Water prevents insect damage and end and healthier. checking (short separations in ends and surfaces of Western Wood Products Assoc. Western Wood Products Assoc. Figure 14-1. After felling, a log loader stacks the lumber. Figure 14-3. Water may be used for transporting and storing logs. Copyright Goodheart-Willcox Co., Inc. / Chapter 14 Lumber and Millwork 185 seasoned boards) due to premature drying. Some Lumber is sawn one of three ways: plain sawn, denser species may not float, so they are often quarter sawn, or rift sawn. Quarter-sawn and rift- stacked and sprayed with water. sawn lumber are more costly than plain-sawn lumber because they require additional handling time. Once a log is quartered for quarter-sawn and rift- 14.1.3 Sawing sawn lumber, each piece must be loaded onto the At the lumber mill, logs are loaded onto a jack lad- carriage and positioned for sawing. In plain sawing, der and transported to a preparation area. There they the log only needs to be rotated. are washed and sometimes debarked in preparation for sawing, Figure 14-4. Each log is placed on a car- Plain Sawing riage that moves it through a large band saw or circu- Plain sawing cuts are made tangent to the lar saw. SeeFigure 14-5.The saw creates rough-edged annual rings. This is the most common sawing planks. The angle at which the saw cuts through the method, Figure 14-6A. Softwood cut by this method log determines the grain pattern, amount of shrink- is often called flat sawn and hardwood is called age during seasoning, and value of the lumber. plain sawn. Plain sawing is less costly and wasteful than any other method. The average plank width is larger. More lumber can be produced per log. The wood is also easier to kiln dry. However, plain-sawn lumber is more likely to be lower quality and has a greater tendency to warp. Annual rings attempt to straighten during drying. Plain-sawn lumber also tends to check and split more than lumber sawn by quarter and rift methods. Knots often appear round, caused by saw cuts across branches. Plain-sawn grain is more figured, and is often referred to as cathedral grain because of its charac- teristic V shape. These V shapes are formed by the earlywood and latewood of a single growing season. M. Bohlke Veneer Corp. Quarter Sawing Figure 14-4. Bark is removed before sawing. It will be Quarter sawing involves cutting logs into four used to make other products. sections, called quarters. Each quarter is then sawn at an angle between 60° and 90° to the annual rings. See Figure 14-6B. The grain pattern, for the most part, will be straight lines. Cuts farthest from the center of the log will produce the most figured grain. Cuts near the center are perpendicular to the annual rings and will produce straight grain. Quarter-sawn lumber twists and cups (curves across its face from edge to edge) less than plain- sawn lumber. There are fewer checks and splits because cuts are parallel with the wood rays. The rays appear as flakes running along the length of the board. Rift Sawing Rift sawing begins by cutting logs into quarters, but the quarters are sawn at between a 30° and M. Bohlke Veneer Corp. 60° angle to the annual rings. See Figure 14-6C. The Figure 14-5. Logs are mounted on a carriage to be advantages of rift sawing over plain sawing are the sawn. The carriage moves the log into a circular saw same as those gained by quarter sawing. However, or band saw blade. Copyright Goodheart-Willcox Co., Inc. / 186 Section 3 Materials Wood rays A. Plain (Flat) Sawn Wood ray Wood ray James L.Taylor Mfg. Figure 14-7. Boards are ripped manually to maximize Saw cuts Saw cuts width. Use of scanners to automate this process is B. Quarter Sawn C. Rift Sawn increasing. Georgia-Pacific Corp. Figure 14-6. Each method of sawing produces different appearance and structural qualities. the straight grain pattern runs lengthwise and is very thin and uniform. Wood rays are apparent, but are less pronounced than as in quarter sawn. Ripping Once the logs are sawn, the boards are ripped to width and crosscut to length. See Figure 14-7. Each cut must be determined by the saw operator, or sawyer, to achieve the longest and widest possible board. Hardwood lumber is sold in random widths and lengths. Timetable for Air-Seasoning (in days) 14.2 Drying Hardwoods After sawing, lumber must be dried to reduce Ash 70–110 Gum 70–160 the moisture content. The drying process is called Basswood 30–60 Hickory 150–200 Beech 150–200 Mahogany 70–110 seasoning. Wood can be seasoned either by air dry- Birch 150–200 Maple 150–200 ing or by kiln drying. Cherry 150–200 Oak 180–300 Chestnut 85–125 Walnut 120–170 14.2.1 Air Drying Elm 80–130 Softwoods Air drying (AD) requires that boards be stacked using stickers (narrow strips) to separate the layers, Red cedar 50–140 White pine 45–150 allowing for air movement. Drying is done either Cypress 200–275 Redwood 60–180 outdoors or in a shelter, Figure 14-8. When dried Hoge Lumber Co. Hoadley Western Wood Products Assoc. outdoors, the top of the stack is covered to prevent Figure 14-8. Reducing moisture content by air drying water from wetting the wood. takes time. Copyright Goodheart-Willcox Co., Inc. / Chapter 14 Lumber and Millwork 187 Beware of air-dried lumber. Even after years 14.2.2 Kiln Drying of sheltered protection, the moisture content may remain at 15% to 19%.Remember, wood used for cab- Kiln drying (KD) uses large ovens, called kilns, inetmaking should be between 6% and 8% moisture to reduce the moisture content of the lumber.

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