1. Unit 8 Fastening Systems
Nails • Staples • Screws • Bolts • Hollow-wall Fasteners • Solid Concrete or Solid Masonry Wall Anchors • Drive Pins and Studs • Metal Connectors • Adhesives

2. Nails are available with a variety of heads and points
Nails are available with a variety of heads and points. Flat‑head, diamond‑point nails are most often used by carpenters.
Nails are available in many shapes and sizes, with a variety of heads, shanks, and points. See Figure 8‑1. Some nails, typically those with special finishes or de-formed shanks (barbs, spirals, rings), have greater holding power than other nails. Aluminum, stainless steel, and galvanized steel nails are used to fasten finish materials to a building exterior since they are corrosion-resistant and will not cause rust streaks on the surface of wood materials.

3. Nail sizes are designated by a number and the letter d.
A number and the letter d, which represents “penny,” are commonly used to designate nail sizes. Typical sizes are 6d, 8d, and 16d. A 6d nail is 2″ long, an 8d nail is 2 1/2″ long, and a 16d nail is 3 1/2″ long. See Figure 8‑2. The letter d stands for denarius, an ancient Roman word for coin (or penny). The penny system originated hundreds of years ago in England where nails were priced by the cost (in pennies) per hundred nails. Smaller nail sizes cost less per hundred than larger sizes. The gauge, or diameter, of a nail depends on the type and length of the nail. The gauge of a nail increases as the length increases.

4. Common nails are used most often for rough work.
Common nails are used most often in wood-frame construction. See Figure 8‑3. A common nail is cut from wire and given a head and a point. Common nails are available in sizes from 2d (1″ long) to 60d (6″ long).

5. Masonry nails can be driven into concrete or masonry.
Masonry nails are made with a special hardened steel. See Figure 8‑4. A masonry nail is used to fasten wood to masonry (solid concrete, concrete block, brick, or stone). Masonry nails must be driven in perfectly perpendicular or they may chip the masonry.

6. Nails used for finish work are thinner than nails used for rough work.
Nails used for finish work are thinner than common nails, making them easier to drive and less likely to split wood. See Figure 8‑5. Finish work nails are used for ap-plications, such as trim and moldings, where a nice final appearance is important. Finish nails have small, tulip-shaped heads, which are easily driven below the wood surface with a nail set. Finish nails are available in sizes from 2d (1″ long) to 20d (4″ long).

7. Wood fibers apply pressure against the shank of a nail to give a nail its holding power.
When a nail is driven into wood, the shank compresses and pushes aside the wood fibers. When the nail is in place, the wood fibers spring back toward their original position. The pressure of the wood fibers against the surface of the nail gives the nail its holding power. See Figure 8-6.

8. Nail shanks are smooth or deformed
Nail shanks are smooth or deformed. Deformed-shank nails provide greater holding power than smooth-shank nails.
Smooth-shank nails have sufficient holding power for most construction applications. Deformed-shank nails are recommended when greater holding power is required. See Figure 8-7.

9. Heavy-duty staples may be used to fasten plywood sheathing and subflooring. Light-duty and medium-duty staples are used for attaching molding and other interior trim.
Staples are available in a variety of shapes and sizes. See Figure 8-8. Staples may be used to fasten sub-flooring, sheathing, and paneling. Heavy-duty staples are driven in by electric or pneumatic tools. Smaller staples may be driven in by hand-operated tools.

10. The three basic screw heads are flat, round, and oval
The three basic screw heads are flat, round, and oval. Screw heads have a single slot or a recessed cross slot.
Wood screws have flat, round, or oval heads. Screw heads have a single slot, a recessed cross slot (Phillips), or a square (Robertson) recess. See Figure 8-9. Phillips and square screw heads provide better grip than single-slot screw heads when driven by an electric screwdriver. They are also more attractive when in place.

11. A higher gauge number for screws indicates a thicker screw shank.
Wood screws range in size from 1/4″ to 5″ long. The diameter of the screw shank is identified by a gauge number. A higher gauge number indicates a thicker screw. Figure 8‑10 shows screws with gauges ranging from #1 to #14.

12. Shank and pilot holes should be drilled when using wood screws to fasten wood pieces together.
When using wood screws to fasten wood pieces together, a shank hole should be drilled in the piece being fastened. An undersized pilot hole for the threads going into the receiving piece will make driving the screw easier and prevent splitting. See Figure Flat- head screws may be countersunk or counter-bored. Countersinking places the top of the screw head flush with the wood surface. Counterboring is used when the screw head is to be concealed with a wood plug.

13. Self-tapping screws are used to fasten metal framing members to each other by tapping their own threads in the metal members.
Self-tapping screws are used to fasten metal framing members to each other and to fasten other materials to metal framing members. Self-tapping screws tap their own threads as they are being driven into the metal members. Self-tapping screws are available as self-drilling and self-piercing screws. See Figure 8-12.

14. Concrete screws are used to fasten items to concrete, brick, or block without the use of additional anchors.
When installing concrete screws, first determine the proper length of screw to be installed. See Figure Add the thickness of the material to be fastened to the minimum depth of embedment and select a screw of that length or longer. Concrete screws must be embedded a minimum of 1″. Maximum strength is achieved when the screw is embedded approximately 1 3/4″. Drill a hole for the screw; 3/16″ screws require a 5/32″ diameter bit, 1/4″ screws require a 3/16″ diameter bit, and 5/16″ screws require a 1/4″ diameter bit. The hole should be drilled 1/4″ deeper than the length of the screw embedment. Hammer drills are commonly used to drill into masonry. Remove excess grit from the hole.

15. Machine screws have greater holding power than other types of screws that fasten to metal.
Machine screws are available with a variety of head shapes. See Figure 8‑14. Machine screws screw into threaded holes in metal and have greater holding power than other types of screws that fasten to metal. Machine screws are commonly used for fastening door hinges, push plates, locks, and door closers to metal jambs and doors.

16. Panel screws have coarse, steeply pitched threads in comparison to a standard wood screw.
Construction-grade screws differ from conventional screws in several ways. Construction-grade panel screws have coarser and more steeply pitched threads, allowing them to be driven through harder materials such as particleboard and other reconstituted wood panels. See Figure The high glue content of reconstituted panels makes them harder to penetrate with screws or nails.

17. Construction-grade panel screws are driven with coil or strip-type screwguns. An extension handle may be added to screwguns to allow carpenters to install screws from an upright position.
Construction-grade panel screws are typically manu-factured of corrosion-resistant materials, such as stain-less steel, or have a corrosion-resistant finish, such as gray phosphate or zinc. Panel screws are typically #8 gauge and are available with Phillips or square drive recesses. Panel screws are commonly driven with a coil or strip-type screwgun. See Figure 8-16.

18. Bolts are used to fasten together heavy wood and metal materials.
Bolts are used to fasten together heavy wood and metal materials. See Figure 8‑17. Most types of bolts require nuts. Whenever a nut bears against wood, a washer should be used to distribute pressure over a wider area and prevent the nut from digging into the wood. With the exception of carriage bolts and flat-head stove bolts, a washer should also be installed under the bolt head.

19. The shank below a carriage bolt head is embedded in the wood.
Carriage bolts are used in wood or metal. The square shank below the rounded head of a carriage bolt is embedded in the material as the nut is drawn up to prevent the bolt from turning as the nut is tightened. See Figure 8‑18.

20. Lag bolts are often used when it is inconvenient or impossible to use a nut‑and‑bolt arrangement. A washer should be used under the head.
Lag bolts are not true bolts; they are actually heavy screws with square or hexagonal heads. See Figure 8‑19. Lag bolts are used to fasten heavy material to wood when a regular bolt‑and‑nut arrangement is impractical or inconvenient. Shank and pilot holes are drilled for the lag bolt, which is then screwed in with a wrench.

21. A toggle bolt consists of a machine screw with a winged nut that folds back as the assembly is pushed through a predrilled hole in the wall.
A toggle bolt consists of a stove bolt with a winged nut that folds back as the assembly is pushed through a predrilled hole in the wall. The wings spring back to their original position inside the wall cavity. As the machine screw is tightened, the wings are drawn against the inner surface of the finish wall material. See Figure 8‑20. Toggle bolts are available with a variety of machine screw combinations and range in size from 1/8″ to 3/8″ in diameter and 2″ to 6″ in length.

22. When installing a screw anchor in a hollow wall, the shield spreads and flattens against the interior of the wall as the screw is tightened.
A screw anchor is used to fasten small cabinets, towel bars, drapery hangers, mirrors, electrical fixtures, and other lightweight items to hollow walls. A screw anchor is inserted into a predrilled hole in the wall so the prongs on the outside of the shield contact the wall surface. The prongs grip the wall surface to prevent the shield from turning. As the screw is tightened, the shield spreads and flattens against the inner surface of the wall. See Figure 8‑21. Screw anchors are sized for the thickness of hollow walls from 1/8″ to 1 3/4″ thick.

23. A wallboard anchor does not require predrilling prior to installation.
A wallboard anchor is installed by placing the point of the anchor against the wall and driving the anchor until it is firmly seated. See Figure The fixture is installed over the anchor and a screw is driven into the anchor to tighten the fixture into place. A 1″ minimum engagement is required between the anchor and screw.

24. A rotary hammer may be used to drill holes in concrete.
Most expansion anchors require that a hole equal to the outside diameter of the plug or shield be drilled in the concrete. The hole should be slightly deeper than the length of the plug or shield. Holes in concrete can be drilled with a standard electric drill or rotary hammer. See Figure 8-23.

25. A variety of masonry and core bits are used with electric drills or rotary hammers.
Electric drills use carbide-tipped masonry bits or core bits. Masonry bits are available in 1/8″ to 1 1/2″ diam-eters and 2 1/2″ to 18″ lengths. Core bits are available in 5/8″ to 6″ diameters and 6″ to 18″ lengths. See Figure Certain core bits cut through reinforcing bar and concrete. Smaller core bits have ports (holes) on the side to allow masonry debris to escape from the interior and be carried to the surface. Standard-, SDS-, or spline-drive masonry bits are used in rotary hammers.

26. Light‑duty plastic anchors are used with wood or sheet‑metal screws.
Light-duty anchors are typically used to secure light items such as electric fixtures, towel brackets, hooks, and other household accessories to solid masonry walls. Light- duty anchors are often made of plastic or lead. The plastic anchors in Figure 8‑25 are used with wood or sheet‑metal screws. A molded anchor has a tapered cavity, and can be used in masonry and gypsum board. The tubular anchor has longitudinal slots that aid expansion and prevent turning or twisting of the anchor in the predrilled hole in the wall.

27. Light‑duty lead‑alloy anchors are used with lag, wood, or sheet-metal screws.
The lead‑alloy anchor in Figure 8‑26 can be used with lag, wood, or sheet‑metal screws. The longitudinal ribs at the tip of the anchor grip the sides of the predrilled hole as a screw is driven into the anchor.

28. The anchor of a hammer-driven anchor expands as the expander pin is driven in.
A hammer‑driven anchor does not receive a screw or bolt; a special nail called an expander pin expands the anchor as it is hammered in. Figure 8‑27 shows a steel hammer-driven anchor. The anchor expands as the ex-pander pin is driven in.

29. The slotted head of a hammer‑driven nylon anchor allows the expander pin to be removed with a screwdriver.
Figure 8‑28 shows a plastic hammer‑driven anchor. In-stallation of a plastic hammer-driven anchor is similar to a steel hammer-driven anchor. The steel expander pin is threaded and has a screwdriver slot in the head to allow the pin to be removed with a screwdriver.

30. When installing a lag bolt expansion shield, the shield expands as the bolt is tightened.
A variety of expansion shields are available for medium to heavy loads. Expansion shields are used with lag or machine bolts. The shield expands as the bolt is tight-ened and grips the inside surface of a predrilled hole. See Figure 8‑29. This medium-duty anchor is made of zinc alloy and is available in sizes accommodating lag screws of 1/4″ to 3/4″ diameter.

31. A heavy-duty machine bolt expansion shield expands at both ends to distribute the anchor load.
Figure 8‑30 shows two machine bolt expansion shields. These shields require holes equal to their outside di-ameters and deep enough so that the shields will be flush or slightly below the concrete surface. The shields expand as the bolts are tightened. This type of fastener can be removed if desired, and the hole grouted to refinish the concrete surface.

32. The expansion plug expands the steel anchor as the anchor is driven onto the plug with a setting tool.
Figure 8‑31 shows a steel anchor with an expansion plug and a setting tool. The steel anchor and expansion plug are placed in a predrilled hole. The setting tool is used to drive the anchor onto the plug and expand the anchor. Steel anchors with expansion plugs are available in sizes accommodating bolts of 1/4″ to 3/4″ diameter.

33. A self-drilling anchor is placed in a special chuck head that is adapted for a rotary hammer.
Figure 8‑32 shows the procedure for installing a self-drilling anchor. The chuck end of the anchor is snapped off with a quick lateral movement of the rotary hammer or by using a snap‑off tool. Self‑drilling anchors are available in sizes accommodating bolts of 1/4″ to 3/4″ diameter.

34. Stud-bolt anchors are used to fasten large equipment and machinery in place.
Three types of stud-bolt anchors are available—expansion plug, sleeve, and wedge. See Figure 8‑33. Stud-bolt anchors are available in 1/4″ to 3/4″ diameters.

35. A tube-dispensed adhesive is mixed as it is forced down the nozzle.
Adhesive anchors include adhesives mixed and dis-pensed from tubes and adhesives stored in glass capsules. The adhesive is placed in a drilled hole and a stud-bolt is placed in the proper position. Tube-dispensed adhesives are typically a two-part epoxy mixed to the proper proportions as it is dispensed. When using tube-dispensed adhesives, the hole is drilled and properly prepared by removing particles with a brush and air from a blow-out bulb. See Figure When starting a new cartridge or tube, dispense and discard enough adhesive until a uniform dark gray color is achieved. Insert the nozzle tip into the bottom of the hole and fill to approximately one-half the hole depth. The stud-bolt is inserted into the hole and slowly rotated to provide a good bond between the concrete and the bolt. After the recommended cure time, the equipment can be positioned and secured.

36. A glass capsule adhesive anchor consists of a sealed glass capsule containing an adhesive mixture, a stud-bolt, and a nut and washer.
A glass capsule adhesive anchor consists of a sealed glass capsule containing an adhesive mixture, a stud-bolt, and a nut and washer. The capsules are available in a variety of sizes to accommodate various bolt di-ameters. Each capsule may contain synthetic resin and quartz aggregate filler. After a hole is drilled and properly prepared, the glass capsule is inserted into the hole. See Figure 8‑35. The stud-bolt, attached to a rotary hammer, is inserted into the hole, breaking the capsule and ag-itating the mixture. As the capsule is crushed, a chemical reaction occurs and the mixture fills the gap between the stud-bolt and sides of the hole and penetrates the pores of the concrete. When the adhesive hardens full holding power is achieved.

37. Many types of drive pins and studs can be driven into concrete or other masonry.
Drive pins and studs are also widely used devices for fastening materials to concrete and masonry walls. A drive pin is a hardened steel nail that is driven directly into the concrete to secure an object into place. A stud consists of a nail end that is embedded in concrete and a threaded end to receive a nut. See Figure 8‑36. Drive pins and studs are driven into the concrete with a powder‑actuated tool.

38. A powder‑actuated tool is used to drive pins and studs into concrete or other masonry.
A powder‑actuated tool quickly embeds drive pins or studs into concrete or other masonry. See Figure The tool can also be used to drive pins and studs into steel beams and columns. A powder‑actuated tool is a gun with a powder‑filled round (shell) that drives the pin or stud into the wall. Additional information on powder-actuated tools is found in Unit 18.

39. Metal fasteners are used to tie together members in wood‑framed construction.
Metal connectors are commonly used in wood- and metal-framed construction and are extremely important in areas subject to earthquakes, tornados, and hurricanes. Studies have shown that, when structural damage occurs, it is typically the result of framing members being pulled loose at their joints rather than being broken along their length. Metal connectors are available in many shapes and sizes for a variety of structural wood and metal connections. Some of the most commonly used metal connectors are joist and beam hangers, post bases, framing anchors, holddowns, and tiedowns. See Figure 8-38.

40. Metal connectors aligned vertically provide the most effective protection against wind damage.
The most effective installation of metal connectors is a vertical line of connectors from the foundation to the roof rafters. See Figure Information regarding metal connector installation is detailed in later units covering different stages of wood- and metal-framed construction.

41. Manufacturers may stamp the recommended nail size on metal connectors.
Holes are provided in metal connectors through which nails are driven to fasten the connectors to structural members. Common nail sizes used with metal con-nectors range from 4d (1 1/2″) to 16d (3 1/2″). The nail size and diameter used for metal connectors depends on the thickness of the structural member and manufacturer recommendations. Nails with a diameter thinner than recommended by the manufacturer do not provide enough shear strength and should not be used. Some manufacturers stamp the recommended nail size on the metal connector. See Figure Nail holes with domes or tabs guide nails into the structural members at a 45° angle. In most cases, all fastener holes in metal connectors must be filled with fasteners to ensure the rated load-carrying capacity. Nail heads should be seated flush with the surface of the metal connector to ensure maximum shear strength for the nail.

42. A pneumatic nailer must be fitted with a hole-locating mechanism or be designed to expose the nail tip when driving nails for metal connectors.
Nails for metal connectors can be driven using a ham-mer, palm nailer, or pneumatic nailer. When using a pneumatic nailer for fastening metal connectors, the nailer must be fitted with a hole-locating mechanism. Specialized pneumatic nailers, referred to as positive-placement nailers, are designed specifically for driving nails for metal connectors. See Figure 8-41.

43. Machine bolts may be used to fasten metal connectors to larger framing members.
Metal connectors for larger framing members may require machine bolts as fasteners. See Figure Holes for the bolts should not be more than 1/16″ larger than the bolt diameter, and the holes should be drilled from only one side of the member. When the nut for the machine bolt is to be placed against a wood member, a washer must be installed between the nut and member.

44. Glue is used to help fasten the joints of cabinets.
Glues, in conjunction with nails, staples, or screws, are commonly used to hold together joints in mill and cabinet work. See Figure 8‑43. Glues are sold in a liquid form or as a powder to which water must be added.

45. Tubes that fit into caulking guns are the most convenient way of applying mastics to the upper surfaces of floor joists.
Mastics have a thicker consistency than glues. Mastics are typically sold in cans, tubes, or canisters that fit into hand‑operated or pneumatic caulking guns. See Figure 8‑44.

46. When panels with tongue-and-groove edges are used for a subfloor, the mastic is placed in the grooves and on top of the joists.
In glued floor systems, a bead of mastic is applied with a caulking gun to the upper surface of the joists before each panel is placed. When tongue-and‑groove panels are installed, another bead of mastic is applied into the grooved edges of a row of floor panels before the tongues of the next row of panels are inserted in the grooves. The floor panels are then nailed or screwed down before the adhesive sets. See Figure 8‑45. The setting time of mastics varies, and manufacturer rec-ommendations should be followed. As a general rule, setting time accelerates during warm weather. Additional information regarding glued floor systems is provided in Unit 42.