Fasteners

Ms. Parker Home Maintenance

What is a fastener?

• A fastener is anything that is used to hold two or more pieces of material together.

• Common fasteners are:– Nails – Screws– Bolts– Glue

Nails• Nails are classified according to their usage and

are selected based on the desired holding ability, and the desired head shape.

• Sized– In the United States, some types of nails are sized in

pennies (symbol, d), a system that originated in England centuries ago.

• The penny size was originally the price in pennies of 100 nails of that size

• Diameter– Several types of small nails are sized by length and

wire gauge.• The bigger the number, the thinner the nail.

Nails cont.• Materials

– Stainless steel less strong than ordinary steel nails and are about three times as expensive.

– Galvanized nails are rust resistant.

– Aluminum nails are not strong enough for most structural framing and are primarily used to fasten aluminum siding or screening.

– Copper nails are used in roofing and in marine applications.

As rules of thumb

• In fastening sheathing, shingles, clapboard, etc., the nail should be at least three times longer than the thickness of the sheet or board being fastened with it. 

• A nail driven perpendicular to the grain should penetrate

the lumber a minimum of 12 times its diameter

• Building codes often call for at least half the length of the nail. 

• Longer is not necessarily better

– the longer the nail, the greater the danger of splitting the wood.

Packaging

• Most nails are sold by weight– usually in 1-pound boxes.

• Some stores still offer them in bulk, to be bagged by the purchaser.

• Five-pound, 10-pound, and 25-pound boxes are also available.

Finnish• Bright nails have no finish.

– They can cause rust streaks if they are used in siding or decking, for example.

• A common way of making nails corrosion-resistant is to coat them with zinc. – Hot-dipped (H.D.) nails have been galvanized by dipping them in

molten zinc.

– Electrogalvanized nails are plated with zinc, and are not as corrosion-resistant as hot-dipped nails.

• Blued nails have very little resistance to corrosion and are meant to be used indoors.

Examples:

Common nail: • general construction,

sheeting, board fencing

Finishing nail: • interior finish, furniture

Box nail: • light construction, siding,

crates

Screws

• Screws are classified in the following ways: – By the material they hold– By the metal they are made from– By the shape of their head– By the tool used to turn them.

• The length and diameter of the screw body are important in providing the size of the screw.

Materials• Screws are chrome or brass plated, and can be made

from several materials, including brass or stainless steel.

• Bluing is a finishing (actually black in color) that prevents rust.

• Some screws are galvanized (plated with zinc for rust-resistance). Galvanized screws are recommended where wood will be attached to metal.

• Exterior screws such as deck screws can react to certain types of wood. Specially treated screws are available for specific applications such as pine, cedar, birch or oak.

• Stainless steel can also react to the tannins in certain woods (oak for example). Find an alternate material such as brass or use a treated screw in these cases.

Direction of Screws• Almost all threaded fasteners tighten

when the head or nut is rotated clockwise. – Such a fastener is said to have a right-hand thread; all

screw fasteners are assumed to be right-hand unless otherwise specified.

• Left-hand threads are usually found only on rotating machinery. – For example, the axles of bicycle pedals screw into

threaded holes in the cranks. In a pair of pedals one will have a right-hand thread and the other a left-hand thread.

• That way the rotation of the pedals doesn't tend to unscrew their axles.

• To designate a left-hand thread, the letters “LH” are placed after the class of fit, like this:– 3/8-16 UNC 2B LH (21)

Examples:Wood screws: • Securing wood to wood • Wood screws are threaded 3/4 of the length of the

screw • May be made from stainless steel, zinc chrome, or

brass • Phillips or slotted head • Head types can be flat oval or round • Work best with a pre-drilled pilot hole Sheet metal: • Attaching metal components • Short, thick screw. Usually zinc-plated, but can be

stainless steel or aluminum • Heads can be Phillips or regular slotted • Head types can be oval, flat, round, or hex • Threaded all the way down the shank

Lag screws: • used for fastening wood to brick and concrete, or

metal to wood.

Examples:

Drywall• Attaching drywall to wood or metal studs,

performing general construction • Long, thin screw with a sharp, self-drilling

point. Black in finish • Available in fine thread (for metal studs) and

coarse (for wood) • The threads go all the way to the head

Deck• Fastening in outdoor applications where

strength and resistance to elements is essential

• Similar is design to drywall screws but larger • Galvanized or specially treated for outdoor

use

Bolts

• Bolts differ from nails and screws by having a threaded nut.

• Bolts are more commonly used when strength is desired, or when frequent re-tightening and dismantlement is required.

• The type of bolt selected depends on the usage.

Bolts• Usually fastener standards specify two types of

marks to be on the head of a bolt.

• The manufacturer's mark is a symbol identifying the manufacturer (or importer).

– This is the organization that accepts the responsibility that the fastener meets specified requirements.

• The grade mark is a standardized mark that identifies the material properties that the fastener meets.

– For example 307A on a bolt head indicates that the fastener properties conform to the ASTM A307 Grade A standard.

• The bolt head shown at the side indicates that it is of property class 8.8 and ML is the manufacturer's mark.

• Both marks are usually located on the top of the bolt head, most standards indicating that the marks can be raised or depressed.

• Raised marks are usually preferred by manufacturers because these can only be added during the forging process whereas depressed marks can subsequently added (possibly with illegitimate marks).

Examples:Machine Bolt: • used for machinery, works best

where periodic retightening is necessary

Carriage Bolt: • bottom part of bolt head is pulled

into wood to prevent turning, used in construction of doors, wagon bodies

Stove bolt: • used for lightweight structures,

threaded entire length, has a screwdriver slot on head

How do bolts differ from wood screws?

• Bolts are usually threaded about 1 inch at the end and use a tap or nut to hold material together.

• Wood screws are self-tapping; the threads are used to hold to material.

Glue

• Glue can be used with other types of fasteners previously discussed, or it can be used in place of the other fasteners.– There are several types of glues to choose from.– Selection depends on use.

• If glue is used in addition to other fasteners, the bond formed is much stronger than the wood itself.

• Glue works better for furniture assembly, and glued pieced are more suitable for planning than nailed pieces.

Examples:White glue:• Wood, paper, cloth

Plastic-resin: • Wood and leather

Resorcinol:• Outdoor furniture and wood

Contact cement: • Wood, plastics

Helpful information:

• Alison Hanham.The Celys and their World. An English Merchant Family of the fifteenth century.Cambridge (UK): Cambridge University Press, 2008.Page 331.

• American Electrician's Handbook, 12th ed.Page 4-185.

• http://www.sizes.com/tools/nails.htm#common_wire_spikes