Woodworking is one of the most visible of the builder trades. Quality woodworking begins with selection of the appropriate materials for the job; its important for builders to understand which wood is best for the job. You as the builder select the methods to join the pieces of the job so the joints are sturdy and present a good appearance. You also choose the best fasteners to hold the job together.
When you have completed this course, you will be able to:
Of all construction materials, wood is probably the most often used and perhaps the most important. The variety of uses of wood is practically unlimited. Builders accomplish few construction projects without using some type of wood. It is used for permanent structures as well as concrete forms, scaffolding, shoring, and bracing. The wood from these temporary structures is reusable again and again. The types, sources, uses, and characteristics of common woods are given in Table 1. The types of classifications of wood for a large project are usually designated in the project specifications and included in the project drawings.
Table 1 Common Woods
|ASH||East of Rockies||Oars, boat thwarts, benches, gratings, hammer handles, cabinets, ball bats, wagon construction, farm implements||Strong, heavy, hard, tough, elastic, close straight grain, shrinks very little, takes excellent finish, lasts well|
|BEECH||East of Mississippi and Southeastern Canada||Cabinetwork, imitation mahogany furniture, wood dowels, capping, boat trim, interior finish, tool handles, turnery, shoe lasts, carving, flooring||Similar to birch but not so durable when exposed to weather, shrinks and checks considerably, close grain, light or dark red color|
|BIRCH||East of Mississippi River and North of Gulf Coast states, Southeast Canada, and Newfoundland||Cabinetwork, imitation mahogany furniture , wood dowels, capping, boat trim, interior finish, tool handles, turnery, carving||Hard, durable, fine grain, even texture, heavy, stiff, strong, tough, takes high polish, works easily, forms excellent base for white enamel finish, but not durable when exposed. Heartwood is light to dark reddish brown in color|
|BUTTERNUT||Southern Canada, Minnesota, Eastern U.S. as far South as Alabama and Florida||Toys, altars, woodenware, millwork, interior trim, furniture, boats, scientific instruments||Very much like walnut in color but softer, not as soft as white pine and basswood, easy to work, coarse grained, fairly strong|
|DOUGLAS FIR||Pacific Coast and British Columbia||Deck planking on large ships, shores, strongbacks, plugs, filling pieces and bulkheads of small boats, building construction, dimension timber, plywood||Excellent lumber, strong, easy to work. Clear straight grained, soft but brittle. Heartwood is durable in contact with ground, best structural timber of northwest.|
|ELM||States East of Colorado||Agricultural implements, wheel-stock, boats, furniture, crossties, posts, poles||Slippery, heavy, hard, tough, durable, difficult to split, not resistant to decay|
|HICKORY||Arkansas, Tennessee, Ohio, and Kentucky||Tools, handles, wagon stock, hoops, baskets, vehicles, wagon spokes||Very heavy, hard, stronger and tougher than other native woods, but checks, shrinks, difficult to work, subject to decay and insect attack|
|LIVE OAK||Southern Atlantic and Gulf Coasts of U.S., Oregon, and California||Implements, wagons, shipbuilding||Very heavy, hard, tough, strong, durable, difficult to work. Heartwood is light brown or yellow, sap wood is nearly white|
|MAHOGANY||Honduras, Mexico, Central America, Florida, West Indies, Central Africa, and other tropical sections||Furniture, boats, decks, fixtures, interior trim in expensive homes, musical instruments||Brown to red color, one of most useful of cabinet woods, hard, durable, does not split badly, open grained, takes beautiful finish when grain is filled but checks, swells, shrinks, warps slightly|
|MAPLE||All states East of Colorado and Southern Canada||Excellent furniture, highgrade floors, tool handles, ship construction, crossties, counter tops, bowling pins||Fine grained, grain often curly or Birds Eyes, heavy, tough, hard, strong, rather easy to work, but not durable. Heartwood is light brown, sap wood is nearly white|
|NORWAY PINE||States bordering Great Lakes||Dimension timber, masts, spars, piling, interior trim||Light, fairly hard, strong, not durable in contact with ground|
|PHILIPPINE MAHOGANY||Philippine Islands||Pleasure boats, medium-grade furniture, interior trim||Not a true mahogany, shrinks, expands, splits, warps, but available in long, wide, clear boards|
|POPLAR||Virginias, Tennessee, Kentucky, and Mississippi Valley||Low-grade furniture, cheaply constructed buildings, interior finish, shelving, drawers, boxes||Soft, cheap, obtainable in wide boards, warps, shrinks, rots easily, light, brittle, weak, but works easily and holds nails well, fine-textured|
|RED CEDAR||East of Colorado and North of Florida||Mothproof closets, lining for linen closets, sills, and other uses similar to white cedar||Very light, soft, weak, brittle, low shrinkage, great durability, fragrant scent, generally knotty, beautiful when finished in natural color, easily worked|
|RED OAK||Virginias, Tennessee, Arkansas, Kentucky, Ohio, Missouri, Maryland||Interior finish, furniture, cabinets, millwork, crossties when preserved||Tends to warp, coarse grain, does not last well when exposed to weather, porous, easily impregnated with preservative, heavy, tough, strong|
|REDWOOD||California||General construction, tanks, paneling||Inferior to yellow pine and fir in strength, shrinks and splits little, extremely soft, light, straight grained, very durable, exceptionally resistant to decay|
|SPRUCE||New York, New England, West Virginia, Central Canada, Great Lakes states, Idaho, Washington, Oregon||Railway ties, resonance wood, piles, airplanes, oars, masts, spars, baskets||Light, soft, low strength, fair durability, close grain, yellowish, sap wood indistinct|
|SUGAR PINE||California and Oregon||Same as white pine||Very light, soft, resembles white pine|
|TEAK||India, Burma, Thailand, and Java||Deck planking, shaft legs for small boats||Light brown color, strong, easily worked, durable, resistant to moisture damage|
|WALNUT||Eastern half of U.S. except Southern Atlantic and Gulf Coasts, some in New Mexico, Arizona, California||Expensive furniture, cabinets, interior woodwork, gun stocks, tool handles, airplane propellers, fine boats, musical instruments||Fine cabinet wood, coarse grained but takes beautiful finish when pores closed with wood filler, medium weight, hard, strong, easily worked, dark chocolate color, does not warp or check, brittle|
|WHITE CEDAR||Eastern coast of U.S., around Great Lakes||Boat planking, railroad ties, shingles, siding, posts, poles||Soft, lightweight, close grained, exceptionally durable when exposed to water, not strong enough for building construction, brittle, low shrinkage, fragment, generally knotty|
|WHITE OAK||Virginias, Tennessee, Arkansas, Kentucky, Ohio, Missouri, Maryland, and Indiana||Boat and ship stems, sternposts, knees, sheer strakes, fenders, capping, transoms, shaft logs, framing for buildings, strong furniture, tool handles, crossties, agricultural implements, fence posts||Heavy, hard, strong, medium coarse grain, tough, dense, most durable of hardwoods, elastic, rather easy to work, but shrinks and likely to check. Light brownish grey in color with reddish tinge, medullary rays are large and outstanding and present beautiful figures when quarter sawed, receives high polish|
|WHITE PINE||Minnesota, Wisconsin, Main, Michigan, Idaho, Montana, Washington, Oregon, California||Patterns, any interior job or exterior job that doesnt require maximum strength, window sash, interior trim, millwork, cabinets, cornices||Easy to work, fine grain, free of knots, takes excellent finish, durable when exposed to water, expands when wet, shrinks when dry, soft, white, nails without splitting, not very strong, straight grained|
|YELLOW PINE||Virginia to Texas||Most important lumber for heavy construction and exterior work, keelsons, risings, filling pieces, clamps, floors, bulkheads of small boats, shores, wedges, plugs, strongbacks, staging, joists, posts, piling, ties, paving blocks||Hard, strong, heartwood is durable in the ground, grain varies, heavy, tough, reddish brown in color, resinous, medullary rays well marked|
The terms wood, lumber, and timber are often spoken or written as if their meanings are alike or nearly so. In the builders language, the terms have distinct, separate meanings. Wood is the hard, fibrous substance that forms the major part of the trunk and branches of a tree. Lumber is wood that has been cut and surfaced for use in construction work. Timber is lumber that is 5 inches or more in both thickness and width.
Seasoning lumber is removing moisture from the small and large cells of wood, or drying. The advantages of seasoning lumber are reducing its weight, increasing its strength and resistance to decay, and decreasing shrinkage, which helps to avoid checking and warping after placing the lumber. A seldom used and rather slow method of seasoning lumber is air drying in a shed or stacking in the open until dry. A faster method, known as kiln drying, has lumber placed in a large oven or kiln and dried with heat supplied by gas or oil fired burners. Lumber is dry enough for most uses when its moisture content has been reduced to about 12 to 15 percent. As a builder, you will learn to judge the dryness of lumber by its color, weight, smell, and feel. After the lumber is cut, you will be able to judge the moisture content by looking at the shavings and chips.
A defect in lumber is any flaw that tends to affect the strength, durability, or utility value of the lumber. A blemish is a flaw that mars only the appearance of lumber. A blemish that affects the utility value of lumber, such as a tight knot that mars the appearance of lumber intended for fine cabinet work, is also considered a defect. Various flaws apparent in lumber are listed in Table 2.
Table 2 Wood Defects & Blemishes
|Bark Pocket||Patch of bark over which the tree has grown, and which it has entirely or almost entirely enclosed|
|Check||Separation along the lengthwise grain, caused by too rapid or nonuniform drying|
|Cross Grain||Grain does not run parallel to or spiral around the lengthwise|
|Decay||Deterioration caused by various fungi|
|Knot||Root section of a branch that may appear on a surface in cross section or lengthwise. A cross-sectional knot may become may be loose or tight. A lengthwise knot is called a spike knot.|
|Pitch Pocket||Deposit of solid or liquid pitch enclosed in the wood|
|Shake||Separation along the lengthwise grain that exists before the tree is cut. A heart shake moves outward from the center of the tree and is caused by decay at the center of the trunk. A wind shake follows the circular lines of the annual rings; its cause is not definitely known.|
|Wane||Flaw in an edge or corner of a board or timber. It is caused by the presence of bark or lack of wood in that part.|
|Warp||Twist or curve caused by shrinkage that develops in a once flat or straight board.|
|Blue Stain||A blemish caused by a mold fungus; it does not weaken the wood.|
Trees are classified as either softwood or hardwood, as shown in Table 3. All lumber is therefore classified in the same way. The terms softwood and hardwood can be confusing since some softwood lumber is harder than some hardwood lumber. Generally, hardwoods are more dense and harder than softwoods. Lumber can be further classified by the name of the tree from which it comes. For example, Douglas fir lumber comes from a Douglas fir tree; walnut lumber comes from a walnut tree, and so forth.
Table 3 Different Types of Softwoods and Hardwoods
The quality of softwood lumber is classified, according to its intended use, as being yard, structural, factory, or shop lumber. Yard lumber consists of those grades, sizes, and patterns generally intended for ordinary building purposes. Structural lumber is 2 or more inches in nominal thickness and width and is used where strength is required. Factory and shop lumber are used primarily for building cabinets and interior finish work.
Lumber manufacturing classifications consist of rough dressed (surfaced) and worked lumber. Rough lumber has not been dressed but has been sawed, edged, and trimmed. Dressed lumber is rough lumber that has been planed on one or more sides to attain smoothness and uniformity. Worked lumber, in addition to being dressed, has also been matched, shiplapped, or patterned. Matched lumber is tongue and groove, either sides or ends or both. Shiplapped lumber has been rabbeted on both edges to provide a close lapped joint. Patterned lumber is designed to a pattern or molded form.
The grade of a piece of lumber is based on its strength, stiffness, and appearance. A high grade of lumber has very few knots or other blemishes. A low grade of lumber may have knotholes and many loose knots. The lowest grades are apt to have splits, checks, honeycombs, and some warpage. The grade of lumber to be used on any construction job is usually stated in the specifications for a set of blueprints. Basic classifications of softwood grading include boards, dimension, and timbers. The grades within these classifications are shown in Table 4.
Table 4 Softwood Lumber Grades
Lumber is graded for quality in accordance with American Lumber Standards set by the National Bureau of Standards for the U.S. Department of Commerce. The major quality grades, in descending order of quality, are select lumber and common lumber. Table 5 lists the subdivisions for each grade in descending order of quality.
Table 5 Grades and Subdivisions of Lumber
|Grade A||This lumber is practically free of defects and blemishes.|
|Grade B||This lumber contains a few minor blemishes.|
|Grade C||This lumber contains more numerous and more significant blemishes than grade B. Those blemishes must be capable of being easily and thoroughly concealed with paint.|
|Grade D||This lumber contains more numerous and more significant blemishes than grade C, but it is still capable of presenting a satisfactory appearance when painted.|
|No. 1||Sound, tight-knotted stock containing only a few minor defects. Must be suitable for use as watertight lumber.|
|No. 2||Contains a limited number of significant defects but no knotholes or other serious defects. Must be suitable for use as grain-tight lumber.|
|No. 3||Contains a few defects that are larger and coarser than those in No. 2 common; for example, occasional knotholes.|
|No. 4||Low-quality material containing serious defects like knotholes, checks, shakes, and decay|
|No. 5||Capable only of holding together under ordinary handling.|
Grades of hardwood lumber are established by the National Hardwood Lumber Association. Firsts and Seconds (FAS) is the best grade. It specifies that pieces be no less than 6 inches wide by 8 feet long and yield at least 83 1/3 percent clear cuttings. The next lower grade is selects, which permits pieces 4 inches wide by 6 feet long. A still lower grade is No. 1 common. Lumber in this group is expected to yield 66 2/3 percent clear cuttings.
Standard lumber sizes have been established in the United States for uniformity in planning structures and in ordering materials. Lumber is identified by nominal sizes. The nominal size of a piece of lumber is larger than the actual dressed dimensions.
Referring to Table 6, you can determine the common widths and thicknesses of lumber in their nominal and dressed dimensions.
Table 6 Nominal and Dressed Sizes of Lumber
|Nominal Size (Inches)||Dressed Size (Inches)|
|1 x 3||3/4 x 2 1/2|
|1 x 4||3/4 x 3 1/2|
|1 x 6||3/4 x 5 1/2|
|1 x 8||3/4 x 7 1/4|
|1 x 10||3/4 x 9 1/4|
|1 x 12||3/4 x 11 1/4|
|2 x 4||1 1/2 x 3 1/2|
|2 x 6||1 1/2 x 5 1/2|
|2 x 8||1 1/2 x 7 1/4|
|2 x 10||1 1/2 x 9 1/4|
|2 x 12||1 1/2 x 11 1/4|
|3 x 8||2 1/2 x 7 1/4|
|3 x 12||2 1/2 x 11 1/4|
|4 x 12||3 1/2 x 11 1/4|
|4 x 16||3 1/2 x 15 1/4|
|6 x 12||5 1/2 x 11 1/2|
|6 x 16||5 1/2 x 15 1/2|
|6 x 18||5 1/2 x 17 1/2|
|8 x 16||7 1/2 x 15 1/2|
|8 x 20||7 1/2 x 19 1/2|
|8 x 24||7 1/2 x 23 1/2|
You can see in Table 6 that nominal lumber sizes are a little larger than dressed lumber sizes. For softwood boards, there is a general rule to figure the dressed size of a piece of lumber, based on the nominal size. For boards with a nominal width up to and including one inch, the dressed size will be 1/4 inch smaller. For boards with a nominal width of two to six inches, the dressed size will be 1/2 inch smaller. For boards with a width larger than six inches, the dressed size will be 3/4 inch smaller. This rule may not be accurate in every case, so if there is any doubt about the size of a dressed piece of lumber, measure the piece.
Years ago, there were more abundant old-growth forests, which provided structural beams, timbers, joists, and other weight-bearing lumber. These old-growth forests have been reduced, driving up the cost of construction material and increasing conflict with forest conservation groups.
Lumber producers have developed laminating techniques that allow the use of younger trees to create a variety of building products. These products, called engineered wood products, have a number of benefits over products from old-growth forests.
There are five main categories of engineered wood products. These include laminated veneer lumber, parallel strand lumber, laminated strand lumber, wood I-beams, and glue-laminated lumber, also known as glue-lam.
LVL is similar to plywood because it is made from multiple layers of laminated thin wood veneer. Unlike plywood, the layers in LVL run in the same direction, parallel to the long direction, and do not have crossbands. The layers are glued with exterior grade adhesive, then pressed together and heated under pressure. You can use LVL for permanent application in floor and roof beams, as well as door and window headers, or for temporary applications like scaffolding and concrete forms.
PSL is made from long veneer strands. These strands are laid parallel to each other and bonded together with an adhesive in a specialized heating process.
You can use PSL as beams, posts, and columns. It is good for use in load-bearing applications.
LSL is made from small logs that cant be used for standard lumber. The bark is removed from the logs, and then the logs are cut into short strands. The strands are dried, coated with resin, and pressed into long blocks called billets by a process that includes steam injection.
You can use LSL for millwork such as doors and windows, or other applications that require high-grade lumber. LSL does not have the load bearing capacity of PSL.
The wood I-beam shown in Figure 1 is a composite structural member made up of a web with flanges bonded to it with exterior type adhesives. The web is made of oriented strand board or plywood; the flanges are made of dimension lumber or laminated veneer lumber with grooves that fit over the web. Like the steel I-beam that it resembles, the wood I-beam is exceptionally strong. You can use it for floor joists, rafters, and headers.
Figure 1 Wood I-beam.
The laminated lumber shown in Figure 2 is made of several pieces of kiln-dried lumber held together as a single unit, a process called lamination. The pieces are nailed, bolted, or glued together with the grain of all pieces running parallel.
Glulam is very versatile; it can be shaped into forms from straight beams to complex curved members. You can use it for headers, floor girders, ridge beams, stair treads and stringers, purlins, cantilever beam systems, and arches.
Figure 2 Laminated lumber.
Laminating greatly increases the load carrying capacity and rigidity of the wood. When extra length is needed, the pieces are spliced with the splices staggered so that no two adjacent laminations are spliced at the same point. Built up beams and girders are examples. They are built as shown in Figure 3, usually nailed or bolted together and spliced.
Figure 3 Built up beam.
Lamination can be used independently or with other materials in the construction of a structural unit. Trusses can be made with lamination for the chords and sawed lumber for the web members as shown in Figure 4.
Figure 4 Truss using laminated and sawed lumber.
Units such as plywood box beams and stressed skin panels can contain both plywood and lamination, as shown in Figure 5.
Probably the most common use of lamination is in the fabrication of large beams and arches. Beams with spans in excess of 100 feet and depths of 8 1/2 feet have been constructed using 2-inch boards. Laminations this large are factory produced. They are glued together under pressure. Most laminations are spliced using scarf joints as shown in Figure 6, and the entire piece is dressed to ensure uniform thickness and width.
Figure 5 Stressed skin panel.
Figure 6 Scarf joints.
The depth of the lamination is placed in a horizontal position and is usually the full width of the beam, as shown in Figure 7.
Figure 7 Laminated beam.
Plywood is constructed by gluing together a number of layers (plies) of wood with the grain direction turned at right angles in each successive layer. This design feature makes plywood highly resistant to splitting. It is one of the strongest building materials available to builders. An odd number (3, 5, or 7) of plies is used so that they will be balanced on either side of a center core and so that the grain of the outside layers runs in the same direction.
The outer plies are called faces or face and back. The next layers under these are called crossbands, and the other inside layer or layers are called the core, as shown in Figure 8. A plywood panel made of three layers would consist of two faces and a core.
Figure 8 Grain directions in a sheet of plywood.
There are two basic types of plywood, exterior and interior. Exterior plywood is bonded with waterproof glues. It can be used for siding, concrete forms, and other constructions where it will be exposed to the weather or excessive moisture. Interior plywood is bonded with glues that are not waterproof. It is used for cabinets and other inside construction where the moisture content of the panels will not exceed 20 percent.
Plywood is made in thicknesses of 1/8 inch to more than 1 inch, with the common sizes being 1/4, 3/8, 1/2, 5/8, and 3/4 inch. A standard panel size is 4 feet wide by 8 feet long. Smaller size panels are available in the hardwoods.
Plywood can be worked quickly and easily with common carpentry tools. It holds nails well and normally does not split when nails are driven close to the edges. Finishing plywood presents no unusual problems; it can be sanded, texture coated with a permanent finish, or left to weather naturally.
There is probably no other building material as versatile as plywood. It is used for concrete forms, wall and roof sheathing, flooring, box beams, soffits, stressed skin panels, paneling, shelving, doors, furniture, cabinets, crates, signs, and many other items.
All plywood panels are quality graded based on products standards (currently PS 1/74). The grade of each type of plywood is determined by the kind of veneer (N, A, B, C, or D) used for the face and back of the panel and by the type of glue used in construction. The plywood veneer grades are shown in Table 7.
Table 7 Plywood Veneer Grades
|N||Special order natural-finish veneer. Select all heartwood or all sapwood. Free of open defects. Allows some repairs.|
|A||Smooth and paintable. Neatly made repairs permissible. Also used for natural finish in less demanding applications.|
|B||Solid surface veneer. Circular repair plugs and tight knots permitted.|
|C||Knotholes to 1 inch. Occasional knotholes 1/2 inch larger permitted providing total width of all knots and knotholes within a specified section does not exceed certain limits. Limited splits permitted. Minimum veneer permitted in exterior-type plywood|
|C Plgd||Improved C veneer with splits limited to 1/8 inch in width and knotholes and borer holes limited to 1/4 inch by 1/2 inch.|
|D||Permits knots and knotholes to 2 1/2 inches in width and 1/2 inch larger under certain specified limits. Limited splits permitted.|
Many species of softwood are used in making plywood. There are five separate plywood groups based on stiffness and strength. Group 1 includes the stiffest and strongest and group 5 the weakest woods. A list of groupings and associated woods is shown in Table 8.
Table 8 Classification of Softwood Plywood Rates Species for Strength and Stiffness
Construction and industrial plywood panels are marked with different stamps.
Construction Panels - Grading identification stamps, as shown in Figure 9, indicate the kind and type of plywood. The stamps are placed on the back and sometimes on the edges of each sheet of plywood.
For example, a sheet of plywood having the designation A-C would have A grade veneer on the face and C grade veneer on the back. Grading is also based on the number of defects, such as knotholes, pitch pockets, splits, discolorations, and patches in the face of each panel. Each panel or sheet of plywood has a stamp on the back that gives all the information you need. Table 9 lists some uses for construction grade plywood.
Figure 9 Standard plywood identification symbols.
Table 9 Plywood Uses
SOFTWOOD PLYWOOD GRADES FOR EXTERIOR USES
|Grade (Exterior)||Face||Back||Inner Plies||Uses|
|A-A||A||A||C||Outdoor where appearance of both sides is important.|
|A-B||A||B||C||Alternate for A-A where appearance of one side is less important.|
|A-C||A||C||C||Siding, soffits, fences. Face is finish grade.|
|B-C||B||C||C||For utility uses, such as farm buildings, some kinds of fences, etc.|
|C-C (Plugged)||C (Plugged)||C||C||Excellent base fir tile and linoleum, backing for wall coverings.|
|C-C||C||C||C||Unsanded, for backing and rough construction exposed to weather.|
|B-B Concrete Forms||B||B||C||Concrete forms. Reuse until wood literally wears out.|
|MDO||B||B or C||C or C-Plugged||Medium density overlay. Ideal base for paint; for siding, built-ins, signs, displays.|
|HDO||A or B||A or B||C- Plugged||High density overlay. Hard surface, no paint needed. For concrete forms, cabinets, counter tops, tanks.|
|A-A||A||A||D||Cabinet doors, built-ins, furniture where both sides will show.|
|A-B||A||B||D||Alternate of A-A. Face is finish grade, back is solid and smooth.|
|A-D||A||D||D||Finish grade face for paneling, built-ins, backing.|
|B-D||B||D||D||Utility grade. One paintable side. For backing, cabinet sides, etc.|
|Standard||C||D||D||Sheathing and structural uses such as temporary enclosures, subfloor. Unsanded.|
Industrial Panels - Structural and sheeting panels have a stamp found on the back. A typical example for an industrial panel grade of plywood is shown in Figure 10.
Figure 10 Structural stamp.
The span rating shows a pair of numbers separated by a slash mark (/). The number on the left indicates the maximum recommended span in inches when the plywood is used as roof decking (sheeting). The right hand number applies to span when the plywood is used as subflooring. The rating applies only when the sheet is placed the long dimension across three or more supports. Generally, the larger the span rating, the greater the stiffness of the panel.
Figure 11 lists some typical engineered grades of plywood.
Figure 11 List of engineered grade of softwood plywood.
Exposure Ratings - The grade/trademark stamp lists the exposure durability classification for plywood. There are two basic types or ratings, exterior and interior. The exterior type has a 100 percent waterproof glue line, and the interior type has a highly moisture resistant glue line. Panels can be manufactured in three exposure durability classifications; Exterior, Exposure 1, and Exposure 2.
Panels marked Exterior can be used where there is continual exposure to weather and moisture. Panels marked Exposure 1 can withstand moisture during extended periods, but they should be used only indoors. Panels marked Exposure 2 can be used in protected locations. They may be subjected to some water leakage or high humidity but generally should be protected from weather.
Most plywood is made with waterproof exterior glue. Interior panels may be made with intermediate or interior glue.
Hardwood plywood panels are primarily used for door skins, cabinets, and wall paneling. The Hardwood Plywood Manufacturers Association has established a grading system with the following grades: premium (A), good grade (1), sound grade (2), utility grade (3), and backing grade (4). For example, A-3 grade hardwood plywood has a premium face and a utility back. 1-1 grade has a good face and a good back.
Test Your Knowledge
1. A blemish in a piece of lumber is classified as a defect when it affects what quality?
- A. Utility value
- B. Strength
- C. Durability
- D. Size
2. By weight, plywood is one of the strongest building materials available. Which of the following factors is primarily responsible for this strength?
- A. Grade of wood
- B. Number of plies
- C. High-strength glue
- D. Cross lamination
- To Table of Contents -
This section covers some of the methods builders use to join wood.
Planing and squaring a small piece of board to dimensions is what you might call the first lesson in woodworking. Like many other things you may have tried to do, it looks easy until you try it. The six major steps in this process are illustrated and described in Figures 9-12 through 9-17. You should practice these steps until you can get a smooth, square board with a minimum of planing.
Figure 15 Working the second end.
One basic skill of woodworking is the art of joining pieces of wood to form tight, strong, well made joints. The two pieces that are to be joined together are called members. The two major steps in making joints are (1) laying out the joint on the ends, edges, or faces and (2) cutting the members to the required shapes for joining.
The instruments normally used for laying out joints are as follows:
For cutting the more complex joints by hand, the hacksaw, dovetail saw, and various chisels are essential. The rabbet and fillister plane for rabbet joints and the router plane for smoothing the bottoms of dadoes and gains are also helpful.
Simple joints are used mostly in rough or finish carpentry. They may be used occasionally in millwork and furniture making. They include:
More complex joints are used mostly in making furniture and cabinets and in millwork. They include:
Edge joints are used mainly in furniture and cabinet work. They include:
Plain butt joints and tongue and groove joints are used in practically all types of woodworking.
The joints used in rough and finished carpentry are, for the most part, simply nailed together. Nails in a 90° plain butt joint can be driven through the member abutted against and into the end of the abutting member. The joints can also be toenailed at an angle through the faces of the abutting member into the face of the member abutted against, as shown in Figure 18. Studs and joists are usually toenailed to soleplates and sills.
Figure 18 Toenailing.
The more complex furniture and cabinet making joints are usually fastened with glue. Dowels, splines, corrugated fasteners, keys, and other types of joint fasteners can provide additional strength. In the dado joint, the gain joint, the mortise and tenon joint, the box corner joint, and the dovetail joint, the interlocking character of the joint is an additional factor in fastening.
All the joints we have mentioned can be cut either by hand or by machine, and are shown in Figure 19.
Figure 19 Edge joints.
Whatever the method used and whatever the type of joint, remember, to ensure a tight joint, always cut on the waste side of the line, never on the line itself. Preliminary grooving on the waste side of the line with a knife or chisel will help a backsaw start smoothly.
A 90° plain butt joint is two boards glued edge to edge or face to edge without overlapping as shown in Figure 20. It is mostly used for thin wood, under 1 inch thick. A butt joint can have a wood or plywood piece called a fishplate used to fasten the ends of two members together with nails or bolts, shown in Figure 21. These are sometimes used at the junction of opposite rafters near the ridge line.
Figure 20 - 90° plain butt joints.
Figure 21 End butt joints with fishplates.
For half lap joints, the members to be jointed are usually of the same thickness, as shown in Figure 22.
Figure 22 Lap joints.
The method of laying out and cutting an end butt half lap as shown in Figure 22 is as follows:
Other half lap joints are laid out in a similar manner; the main difference is in the cutting method. A cross half lap joint is best cut with a dado head or wood chisel rather than a handsaw. Others may easily be cut on a bandsaw. When you cut a half lap joint this way, be certain to cut on the waste side of the lines and make all lines from the face of the material.
A miter joint is made by mitering the ends or edges of the members to be joined together as shown in Figure 23. The angle of the miter cut is one half of the angle formed by the joined members. In rectangular mirror frames, windows, and door casing boxes, adjacent members form a 90° angle, so the correct angle for mitering is one half of 90°, or 45°. For members forming an equal sided figure with other than four sides, such as an octagon or a pentagon, find the correct mitering angle by dividing the number of sides the figure will have into 180° and subtracting the result from 90°.
Figure 23 Miter joint.
For an octagon, a figure with eight sides, determine the mitering angle by subtracting 180° divided by 8 from 90°. This is shown by the following formula:
90° - (180° χ8)
90° - 22.5° = 67.5°
For a pentagon, a figure with five sides, the angle is:
90° - (180° χ 5)
90° - 36° = 54°
End miter members to 45° in the wooden miter box and to any angle in the steel miter box by setting the saw to the desired angle, or on the circular saw by setting the miter gauge to the desired angle. Edge miter members to any angle on the circular saw by tilting the saw to the required angle. Sawed edges are sometimes unsuitable for gluing. If the joint is to be glued, the edges can be mitered on a jointer, as shown in Figure 24. Please note that the saw guard does not appear in this figure to better show the relationship of the blade to the stock.
Figure 24 Beveling on a jointer for a mitered edge joint.
This is a dangerous operation and caution should be taken.
Since abutting surfaces of end mitered members do not hold well when they are merely glued, they should be reinforced. One type of reinforcement is the corrugated fastener. This is a corrugated strip of metal with one edge sharpened for driving into the joint. Place the fastener at a right angle to the line between the members, half on one member and half on the other, and drive it down flush with the member. The corrugated fastener mars the appearance of the surface into which it is driven, so use it only on the backs of picture frames and the like.
A more satisfactory type of fastener for a joint between end mitered members is the biscuit. This is a thin piece of wood or veneer that is glued into a kerf cut in the thickest dimension of the joint. Use the biscuit in the following manner:
A joint between edge mitered members can also be reinforced with a spline. This is a thick piece of wood that extends across the joint into grooves cut in the abutting surfaces. A spline for a plain miter joint is shown in Figure 25. Cut the groove for a spline either by hand or with a circular saw.
Figure 25 Plain miter joint.
A three-sided recess running with the grain is called a groove, and a recess running across the grain is called a dado. A groove or dado that does not extend all the way across the wood is called a stopped groove or stopped dado. A stopped dado, also known as a gain, is shown in Figure 26.
Figure 26 Dado and gain joints.
A two-sided recess running along an edge, as shown in Figure 27, is called a rabbet T. Dadoes, gains, and rabbets are not, strictly speaking, grooves; but joints that include them are generally called grooved joints.
Figure 27 Rabbet joints.
Cut a groove or dado with a circular saw as follows:
The procedure for grooving or dadoing with the dado head is about the same, except that in many cases you can build up the dado head to take out all the waste in a single cut. The two outside cutters alone will cut a groove 1/4 inch wide. Inside cutters vary in thickness from 1/16 to 1/4 inch.
Cut a stopped groove or stopped dado on the circular saw, using either a saw blade or a dado head, as follows:
A rabbet joint requires two cuts; the cut into the face of the wood is called the shoulder cut, and the cut into the edge or end is called the cheek cut. A rabbet can be cut on the circular saw. Make the shoulder cut first, as follows:
By using the dado head, you can cut most ordinary rabbets in a single cut.
On some jointers, a rabbeting ledge attached to the outer edge of the infeed table can be depressed for rabbeting, as shown in Figure 28. Please note that the saw guard does not appear in this figure to better show the relationship of the blade to the stock.
Figure 28 Rabbeting on a jointer with a rabbeting ledge.
The ledge is located on the outer end of the cutterhead. To rabbet on a jointer of this type, depress the infeed table and the rabbeting ledge the depth of the rabbet below the outfeed table, and set the fence the width of the rabbet away from the outer end of the cutterhead. When the piece is fed through, the unrabbeted part feeds onto the rabbeting ledge. The rabbeted portion feeds onto the outfeed table.
Various combinations of the grooved joints are used in woodworking. The tongue and groove joint is a combination of the groove and the rabbet, with the tongued member rabbeted on both faces. In some types of paneling, the tongue is made by rabbeting only one face. A tongue of this kind is called a barefaced tongue. A joint often used in making boxes, drawers, and cabinets is the dado and rabbet joint, shown in Figure 29. As you can see, one of the members is rabbeted on one face to form a barefaced tongue.
Figure 29 Dado and rabbet joint.
The mortise and tenon joint is most frequently used in furniture and cabinet work. In the blind mortise and tenon joint, the tenon does not penetrate all the way through the mortised member. This type of joint is shown in Figure 30.
Figure 30 Tenon joints.
A joint in which the tenon does penetrate all the way through is a through mortise and tenon joint, shown in Figure 31. Besides the ordinary stub joint seen in Figure 31 view A, there are haunched joints, as seen in view B, and table haunched joints, as seen in view C. Haunching and table haunching increase the strength and rigidity of the joint.
Figure 31 Stub (view A), haunched (view B), and table haunched (view C) mortise and tenon joints.
The layout procedure for an ordinary stub mortise and tenon joint is shown in Figure 32.
Figure 32 Layout of stub mortise and tenon joint.
The shoulder and cheek cuts of the tenon are shown in Figures 9-33 and 9-34. Please note that the saw guard does not appear in these figures to better show the relationship of the blade to the stock.
To maintain the stock upright while making the cheek cuts, use a push board similar to the one shown in Figure 34. Tenons can also be cut with a dado head by the same method previously described for cutting end half lap joints.
Mortises are cut mechanically on a hollow chisel mortising machine like the one shown in Figure 35. The cutting mechanism on this machine consists of a boring bit encased in a square, hollow, steel chisel. As the mechanism is pressed into the wood, the bit takes out most of the waste while the chisel pares the sides of the mortise square. Chisels come in various sizes, with corresponding sizes of bits to match.
Figure 35 Hollow chisel mortising machine.
If a mortising machine is not available, the same results can be attained by using a simple drill press to take out most of the waste and a hand chisel, for paring the sides square.
In some mortise and tenon joints, such as those between rails and legs in tables, the tenon member is much thinner than the mortise member. Sometimes a member of this kind is too thin to shape with shoulder cuts on both faces in the customary reamer. When this is the case, use a barefaced mortise and tenon joint. For a barefaced joint, cut the tenon member on one side only. The cheek on the opposite side is simply a continuation of the face of the member.
Mortise and tenon joints are fastened with glue and with additional fasteners, as required.
The dovetail joint, shown in Figure 36, is the strongest of all the woodworking joints. It is used principally for joining the sides and ends of drawers in fine grades of furniture and cabinets. You might seldom use dovetail joints since they are laborious and time consuming to make.
Figure 36 Dovetail joints.
A through dovetail joint is a joint in which the pins pass all the way through the tail member. Where the pins pass only part way through, the member is known as a blind dovetail joint.
The simplest of the dovetail joints is the dovetail half lap joint, shown in Figure 37.
Figure 37 Dovetail half lap joint.
Figure 38 shows how this type of joint is laid out, and Figure 39 shows the completed joint.
A multiple dovetail joint is shown in Figure 40; Figure 41 shows how the waste is chiseled from the multiple joint.
With the exception of the obvious difference in the layout, the box corner joint shown in Figure 42 is made in a manner similar to that of the through multiple dovetail joint.
Figure 42 Box corner joint.
Inside corner joints between molding trim members are usually made by butting the end of one member against the face of the other. Figure 43 shows the method of shaping the end of the abutting member to fit the face of the other member:
Figure 43 Making a coping joint.
Figure 44 shows the simplest and most common moldings and trims used in woodworking.
Figure 44 Simple molding and trim shapes.
Test Your Knowledge
3. To ensure a tight joint on cut lumber, which of the following procedures should you follow?
- A. Cut directly in the middle of the line
- B. Cut on the waste side of the line
- C. Cut out the entire line
- D. Cut out the line plus a little extra
4. What type of woodworking joint is considered the strongest?
- A. Mortise and tenon
- B. Rabbet
- C. Dovetail
- D. Tongue and groove
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A variety of metal fastening devices are used by workers in construction. Although nails are the most commonly used fastener, the use of staples to attach wood structural members is growing. For certain operations, screws and bolts are required. In addition, various metal devices exist for anchoring materials into concrete, masonry, and steel.
The increasing use of adhesives such as glues and mastics is an important development in the building industry. Adhesives are used in combination with, or in place of, nails and screws.
Nails, the most common type of metal fasteners, are available in a wide range of types and sizes.
Some basic nail types are shown in Figure 45. The common nail is designed for rough framing. The box nail is used for toenailing and light work in frame construction. The casing nail is used in finished carpentry work to fasten doors and window casings and other wood trim. The finishing nail and brad are used for light wood trim material and are easy to drive below the surface of lumber with a nail set.
Figure 45 Basic types of nails.
The size of a nail is measured in a unit known as a penny. Penny is abbreviated with the lowercase letter d. It indicates the length of the nail. A 6d (6 penny) nail is 2 inches long. A 10d (10 penny) nail is 3 inches long as shown in Figure 46. These measurements apply to common, box, casing, and finish nails only. Brads and small box nails are identified by their actual length and gauge number.
Figure 46 Nail sizes given in penny (d) units.
A nail, whatever the type, should be at least three times as long as the thickness of the wood it is intended to hold. Two thirds of the length of the nail is driven into the other piece of wood for proper anchorage. The other one third of the length provides the necessary anchorage of the piece being fastened. Bend over protruding nails to prevent damage to materials and injury to workers.
There are a few general rules to follow using nails in building. Drive nails at an angle slightly toward each other to improve their holding power. Be careful in placing nails to provide the greatest holding power. Nails driven with the grain do not hold as well as nails driven across the grain. A few nails of proper type and size, properly placed and properly driven, will hold better than a great many driven close together. Nails are generally the cheapest and easiest fasteners.
Figure 47 shows a few of the many specialized nails. Some nails are specially coated with zinc, cement, or resin materials. Some have threading for increased holding power. Nails are made from many materials, including iron, steel, copper, bronze, aluminum, and stainless steel.
Figure 47 Specialized nails.
Annular and spiral nails are threaded for greater holding power. They are good for fastening paneling or plywood flooring. The drywall nail is used for hanging drywall and has a special coating to prevent rust. Roofing nails are not specified by the penny system; they are referred to by length. They are available in lengths from 3/4 inch to 2 inches and have large heads. The double headed nail, or duplex head nail, is used for temporary construction, such as form work or scaffolding. The double head on this nail makes it easy to pull out when forms or scaffolding are torn down.
Nails for power nailing come in rolls or clips for easy loading into a nailer. They are coated for easier driving and greater holding power. Table 10 gives the general size and type of nails prefered for specific applications.
Table 10 Size, Type, and Use of Nails
Staples are available in a wide variety of shapes and sizes, some of which are shown in Figure 48. Heavy duty staples are used to fasten plywood sheeting and subflooring. Heavy duty staples are driven by electrically or pneumatically operated tools. Light duty and medium duty staples are used for attaching molding and other interior trim. Staples are sometimes driven in by hand operated tools.
Figure 48 Types of staples.
The use of screws, rather than nails, as fasteners may be dictated by a number of factors. These may include the type of material to be fastened, the requirement for greater holding power than can be obtained with nails, the finished appearance desired, and the fact that the number of fasteners that can be used is limited. Using screws, rather than nails, is more expensive in terms of time and money, but it is often necessary to meet requirements for superior results.
The main advantages of screws are that they provide more holding power, can be easily tightened to draw the items being fastened securely together, are neater in appearance if properly driven, and can be withdrawn without damaging the material. All screws can have slotted or Phillips heads, as shown in Figure 49.
Figure 49 Types of screws.
For the assembly of metal parts, use sheet metal screws. These screws are made regularly in steel and brass with four types of heads: flat, round, oval, and fillister, shown in that order in Figure 49.
The proper name for a lag screw shown in Figure 49 is lag bolt. These screws are often required in constructing large projects, such as a building. They are longer and much heavier than the common wood screw and have coarser threads that extend from a cone, or gimlet point, slightly more than half the length of the screw. Square head and hexagonal head lag screws are always externally driven, usually by means of a wrench. They are used when ordinary wood screws would be too short or too light and spikes would not be strong enough. Table 11 gives lengths and diameters of lag screws. Combined with expansion anchors, they are used to frame timbers to existing masonry.
Table 11 Lag Screw Sizes
Expansion shields, or expansion anchors as they are sometimes called, are inserted in a predrilled hole, usually in masonry, to provide a gripping base or anchor for a screw, bolt, or nail intended to fasten an item to the surface in which the hole was bored. The shield can be obtained separately, or it may include the screw, bolt, or nail. After the expansion shield is inserted in the predrilled hole, the fastener is driven into the hole in the shield, expanding the shield and wedging it firmly against the surface of the hole.
The common wood screw is usually made of unhardened steel, stainless steel, aluminum, or brass. The steel may be bright finished or blued; or zinc, cadmium, or chrome plated. Wood screws are threaded from a gimlet point for approximately two-thirds of the length of the screw and provided with a slotted head designed to be driven by an inserted driver. Wood screws, as shown in Figure 50, are designated according to head style. The most common types are flathead, oval head, and roundhead, shown in that order. Proper nomenclature of a screw, shown in Figure 50, includes the type, material, finish, length, screw size number indicating the wire gauge of the body, drill or bit size for the body hole, and drill or bit size for the starter hole.
Figure 50 Types and nomenclature of wood screws.
To prepare wood for receiving the screws, bore a body hole the diameter of the screw to be used in the piece of wood to be fastened as shown in Figure 51.
Figure 51 Proper way to sink a screw.
Then bore a starter hole in the base wood with a diameter less than that of the screw threads and a depth of one-half or twothirds the length of the threads to be anchored. The purpose of this careful preparation is to assure accuracy in the placement of the screws, to reduce the possibility of splitting the wood, and reduce the time and effort required to drive the screw. Properly set slotted and Phillips flathead and oval head screws are countersunk sufficiently to permit a covering material to cover the head. Slotted roundhead and Phillips roundhead screws are not countersunk, but they are driven so that the head is firmly flush with the surface of the wood. The slot of the roundhead screw is left parallel with the grain of the wood.
Wood screws come in sizes that vary from 1/4 inch to 6 inches. Screws up to 1 inch in length increase by eighths, screws from 1 to 3 inches increase by quarters, and screws from 3 to 6 inches increase by half inches. Screws vary in length and size of shaft. Each length is made in a number of shaft sizes specified by an arbitrary number that represents no particular measurement but indicates relative differences in the diameter of the screws. Tables 9-12 and 9-13 provide size, length, gauge, and applicable drill and auger bit sizes for screws.
Table 12 Screw Sizes and Dimensions
Table 13 Drill and Auger Bit Sizes for Wood
Bolts are used in construction requiring great strength or when the work under construction must be frequently disassembled. Their use usually implies the use of nuts for fastening and sometimes the use of washers to protect the surface of the materials they fasten. Bolts are selected for application to specific requirements in terms of length, diameter, threads, style of head, and type. Proper selection of head style and type of bolt results in good appearance as well as good construction. The use of washers between the nut and a wood surface or between both the nut and the head and their opposing surfaces helps you avoid marring the surfaces and permits additional torque in tightening.
Carriage bolts fall into three categories: square neck, finned neck, and ribbed neck. All three are shown in Figure 52.
Figure 52 Carriage bolts.
These bolts have round heads that are not designed to be driven. They are threaded only part of the way up the shaft. Usually, the threads are two to four times the diameter of the bolt in length. In each type of carriage bolt, the upper part of the shank, immediately below the head, is designed to grip the material in which the bolt is inserted and keep the bolt from turning when a nut is tightened down on it or removed. The finned type is designed with two or more fins extending from the head to the shank. The ribbed type is designed with longitudinal ribs, splines, or serrations on all or part of a shoulder located immediately beneath the head. Holes bored to receive carriage bolts are bored to be a **44 tight fit for the body of the bolt and counterbored to permit the head of the bolt to fit flush with, or below the surface of, the material being fastened. The bolt is then driven through the hole with a hammer. Carriage bolts are chiefly for wood to wood application, but they can also be used for wood to metal applications. If used for wood to metal application, the head should be fitted to the wood item. Metal surfaces are sometimes predrilled and countersunk to permit the use of carriage bolts metal to metal. Carriage bolts can be obtained from 1/4 inch to 1 inch in diameter and from 3/4 inch to 20 inches long (Table 14). Use a common flat washer with carriage bolts between the nut and the surface.
Table 14 Carriage Bolt Sizes
The machine bolts shown in Figure 53 are made with cut national fine and national coarse threads extending in length from twice the diameter of the bolt plus 1/4 inch for bolts less than 6 inches in length to twice the diameter of the bolt plus 1/2 inch for bolts over 6 inches in length.
Figure 53 Machine bolts.
They are precision made and generally applied metal to metal where close tolerance is desirable. The head may be square, hexagonal, rounded, or flat countersunk. The nut usually corresponds in shape to the head of the bolt with which it is used. Machine bolts are externally driven only. Selection of the proper machine bolt is made on the basis of head style, length, diameter, number of threads per inch, and coarseness of thread. The hole through which the bolt is to pass is bored to the same diameter as the bolt. Machine bolts are made in diameters from 1/4 inch to 3 inches and may be obtained in any length desired, as shown in Table 15.
Table 15 Machine
The stove bolts shown in Figure 54 are less precisely made than machine bolts. They are made with either flat or round slotted heads and may have threads extending over the full length of the body, over part of the body, or over most of the body. They are generally used with square nuts and applied metal to metal, wood to wood, or wood to metal. If flat-headed, they are countersunk. If round-headed, they are drawn flush to the surface.
Figure 54 Stove bolts.
The expansion bolt, shown in Figure 55 is a bolt used in conjunction with an expansion shield to provide anchorage in substances in which a threaded fastener alone is useless. The shield, or expansion anchor, is inserted in a predrilled hole and expands when the bolt is driven into it. It becomes wedged firmly in the hole, providing a secure base for the grip of the fastener.
Figure 55 Expansion bolt.
The toggle bolt, shown in Figure 56, is a machine screw with a spring action, wing head nut that folds back as the entire assembly is pushed through a prepared hole in a hollow wall. The wing head then springs open inside the wall cavity. As the screw is tightened, the wing head is drawn against the inside surface of the finished wall material. Spring action, wing head toggle bolts are available in a variety of machine screw combinations. Common sizes range from 1/8 inch to 3/8 inch in diameter and 2 inches to 6 inches in length. They are particularly useful with sheetrock wall surfaces.
Figure 56 Toggle bolt.
The molly bolt or molly expansion anchor, shown in Figure 57, is used to fasten small cabinets, towel bars, drapery hangers, mirrors, electrical fixtures, and other lightweight items to hollow walls. It is inserted in a prepared hole. Prongs on the outside of the shield grip the wall surfaces to prevent the shield from turning as the anchor screw is being driven. As the screw is tightened, the shield spreads and flattens against the interior of the wall. Various sizes of screw anchors can be used in hollow walls 1/8 inch to 1 3/4 inches thick.
Figure 57 Molly bolt.
The driftpin, shown in Figure 58, is a long, heavy, threadless bolt used to hold heavy pieces of timber together. It has a head that varies in diameter from 1/2 to 1 inch and in length from 18 to 26 inches. The term driftpin is almost universally used in practice. For supply purposes, the correct designation is driftbolt.
Figure 58 Driftpin.
To use the driftpin, make a hole slightly smaller than the diameter of the pin in the timber. Drive the pin into the hole. The compression action of the wood fibers holds the pin in place.
The corrugated fastener is one of many means by which joints and splices are fastened in small timber and boards. It is used particularly in the miter joint. Corrugated fasteners are made of 18 to 22 gauge sheet metal with alternate ridges and grooves; the ridges vary from 3/16 to 5/ 16 inch, center to center. One end is cut square; the other end is sharpened with beveled edges. There are two types of corrugated fasteners: one with the ridges running parallel, as shown in Figure 59, view A, the other with ridges running at a slight angle to one another, as shown in Figure 59, view B.
Figure 59 Corrugated fasteners and their uses.
The latter type has a tendency to compress the material since the ridges and grooves are closer at the top than at the bottom. These fasteners are made in several different lengths and widths. The width varies from 5/8 to 1 1/8 inches; the length varies from 1/4 to 3/4 inch. The fasteners also are made with different numbers of ridges, ranging from three to six ridges per fastener. Corrugated fasteners are used in a number of ways: to fasten parallel boards together, as in fastening tabletops; to make any type of joint, and as a substitute for nails where nails may split the timber. In small timber, corrugated fasteners have greater holding power than nails. The proper method of using the fasteners is shown in Figure 59.
Builders use many different types of adhesives in various phases of their construction projects. Glues (which have a plastic base) and mastics (which have an asphalt, rubber, or resin base) are the two major categories of adhesives. The method of applying adhesives, their drying time, and their bonding characteristics vary. Some adhesives are more resistant to moisture and hot and cold temperatures than others.
Some adhesives are highly flammable; they should be used only in a well-ventilated work area. Others are highly irritating to the skin and eyes.
The primary function of glue is to hold together joints in mill and cabinet work. Most modern glues have a plastic base. Glues are sold as a powder to which water must be added or in liquid form. Many types of glue are available under brand names. A brief description of some of the more popular types of glue is listed below.
Polyvinyl resin, also known as white glue, is a liquid that comes in ready to use plastic squeeze bottles. It does a good job of bonding wood together and it sets up (dries) quickly after being applied. Because white glue is not waterproof, do not use it on work that will be subjected to constant moisture or high humidity.
Urea resin is plastic based glue sold in a powder form. The required amount is mixed with water when the glue is needed. Urea resin makes an excellent bond for wood and has fair water resistance.
Phenolic resin glue is highly resistant to temperature extremes and water. It is often used for bonding the veneer layers of exterior grade plywood.
Resorcinol glue has excellent water resistance and temperature resistance, and it makes a very strong bond. Resorcinol resin is often used for bonding the wood layers of laminated timbers.
Contact cement is used to bond plastic laminates to wood surfaces. This glue has a neoprene rubber base. Because contact cement bonds very rapidly, it is useful for joining parts that cannot be clamped together.
Mastics are widely used throughout the construction industry. They are generally used to apply floor coverings, roofing materials, ceramic tiles, and wall paneling. The asphalt, rubber, or resin base of mastics gives them a thick consistency. Mastics are sold in cans, tubes, or canisters that fit into hand-operated or air-operated caulking guns. These adhesives can be used to bond materials directly to masonry or concrete walls. If furring strips are required on a wavy concrete wall, the strips can be applied with mastic rather than by the more difficult procedure of driving in concrete nails. You can also fasten insulation materials to masonry and concrete walls, bond drywall (gypsum board) directly to wall studs, and bond gypsum board to furring strips or directly to concrete or masonry walls with a mastic adhesive. Because you dont use nails, there are no nail indentations to fill. By using mastic adhesives, you can apply paneling with very few or no nails at all. Wall panels can be bonded to studs, furring strips, or directly against concrete or masonry walls. Mastic adhesives can be used with nails or staples to fasten plywood panels to floor joists. The mastic adhesive helps eliminate squeaks, bounce, and nail popping. It also increases the stiffness and strength of the floor unit.
Test Your Knowledge
5. Which of the following nailing techniques gives maximum holding power?
- A. Drive the nails with the grain
- B. Drive the nails at an angle toward each other
- C. Drive the nails vertically
- D. Drive the nails through an edge
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Wood is arguably the most often used and perhaps the most important of all construction materials. It is used for permanent and temporary structures, different types used according to the project being built. The project specifications and project drawings show what types of wood products are needed for the project.
Builders use many methods for joining wood. The types of joints vary depending on the type of project being built.
Builders use a variety of metal fastening devices in construction. Nails are the most commonly used fastener, but the use of staples to attach wood structural members is growing. Screws and bolts are required in some building projects. There are also various metal devices for anchoring materials into concrete, masonry, and steel. Glues and mastics are adhesives used in combination with or in place of nails and screws.
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1. Timber is wood cut to which of the following dimensions?
2. Which of the following factors is NOT an advantage of seasoned lumber?
3. Lumber is considered dry enough for most uses when its moisture content is in what range?
4. As a builder, you should be able to judge the moisture content of lumber by which of the following characteristics?
5. A root section of a branch appearing on the surface of a board is what kind of defect?
6. A twist or curve that develops in a flat board is what kind of defect?
7. Which of the following types of wood should be used where strength is the primary requirement?
8. Using manufacturing classifications, wood that has not been dressed but has been sawed, edged, and trimmed is considered what type?
9. Which of the following qualities is NOT considered when grading lumber?
10. Where will you find the grade of lumber to be used on a construction project?
11. Of the following grade listings, which is nearly free of defects and blemishes?
12. FAS grade of hardwood lumber should have what portion of clear cutting?
13. The nominal size of lumber is larger than actual dressed dimensions.
14. What is the primary advantage of laminated lumber?
15. The most common use of lamination is in the fabrication of large beams and arches.
16. Most lamination splices are made with what type of joint?
17. In a sheet of plywood, the outer plies are called
18. What is the essential difference between exterior and interior plywood?
19. Plywood is only manufactured in thicknesses ranging from 1/4 to 3/4 inch.
20. Using stiffness and strength as criteria, plywood can be classified into what maximum number of groups?
21. What veneer grade of plywood permits knots and knotholes to 2 1/2 inch in width (1/2 inch larger under specified conditions)?
22. Plywood with a solid surface veneer and circular repair plugs is what grade?
23. On plywood, which of the following trademark stamps gives you the span rating?
24. What class of plywood is best suited for exposure to extended periods of moisture?
25. In laying off a piece of lumber for an end-butt half-lap joint, the shoulder line should be drawn around the board at what distance from the end of the board?
26. When laying off a piece of lumber for a half-lap joint, you gauge the cheek line from what point?
27. In cutting an end-butt half-lap joint on a piece of lumber, what cut should you make first?
28. When mitering a board for a hexagonal (six-sided) frame, what miter angle should you use?
29. When reinforcing miter joints, biscuits are often preferred over corrugated fasteners because bicsuits
30. A three-sided recess running across the grain from one side of a board to the other is known by what term?
31. A two-sided recess running along an edge of a board is known by what term?
32. A circular saw can be used to cut a stopped groove using which of the following attachments?
33. To adjust the fence to the depth of the cheek when cutting a rabbet joint with a circular saw, you should measure from what point?
34. With proper attachments, jointers can be used for rabbeting.
35. Which of the following mortise and tenon joints penetrates through the mortised member?
36. Table haunching a mortise and tenon joint has what effect on the joint?
37. When cutting inside corner molding, you should normally use which of the following handsaws?
38. What type of nail should you use for wood trim?
9. You are nailing a 1 inch thick board. The nail used should be what length?
40. Of the following nail types, which has the greatest holding power?
41. Of the following nail types, which is most suitable for temporary work such as forms and scaffolding?
42. To what depth should you drill a wood screw starter hole?
43. What type of bolt can be square necked, fin necked, or rib necked?
44. Which of the following types of bolts has a machine thread with spring action and winghead nuts and is particularly useful with sheetrock wall surfaces?
45. Of the following types of adhesive, which has an asphalt, rubber, or resin base?
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