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Carpentry for Vocational Schools - A Teacher's handbook (GTZ, 252 p.)
	7. FASTENERS
		(introduction...)
		7.1. Nails
		7.2. Screws
		7.3. Bolts and nuts
		7.4. Building accessories

Carpentry for Vocational Schools - A Teacher's handbook (GTZ, 252 p.)

7. FASTENERS

TOPIC: 7. FASTENERS

INTRODUCTION: Certain fasteners have certain uses.

This topic teaches students where and how to use which fasteners, their names and characteristics.

OBJECTIVES:

7.1. Students should be able to identify the different nails and their characteristics as well as being able to use them correctly.
7.2. Students should be able to recognise the different types of screws and use them in a correct way.
7.3. Students have to be able to identify the different types of bolts and nuts, state their uses and how to use them correctly.
7.4. Students should know the most important building accessories and how to apply them correctly.

METHOD: We prepare samples of all fasteners and display them in the classroom. Also samples using fasteners, can be prepared and displayed for better understanding.

Photocopies of the most important fasteners can be prepared and handed out to students after the theory lesson which have to be glued into their trade theory books.

For practical exercise, wood samples can be prepared which students join by nailing screwing or bolting. Students will see which fastener is the strongest.

NOTE: At the end of this section prepare a worksheet for students to fill in in their own time for reinforcement of this topic.

Fasteners are metal pieces for fixing members together. There are four main kinds of fasteners. They are named Nails, Screws, Bolts and Nuts and Building Accessories.

7.1. Nails

Nails are made of drawn iron wire. One end is upset and forms the nail head. The other end is pointed. Nails are used for joining wood, assembling ironwork to wood, fastening flooring boards, wooden partitions, etc... When ordering nails you must state the Quality, the Length, the Finish, the Type eg. 25 kg 100x4,5 galvanised Flat head nails.

a) Jolt or Bullet head nail: - A strong nail giving a neat appearance when driven and punched into the wood. Widely used in buildings.

Figure

b) Flat head nail: - Wire nails are available in sizes from 13 mm to 250 mm in length and are obtainable in bright mild steel and galvanised. The shank is roughened near the head to increase the friction grip. The head is round and flat and knurled to prevent the hammer from slipping off. These nails are also known as French nails.

Figure

c) Panel pin: - Panel pins are round in cross section. They are available in sizes from 13 mm to 50 mm in length and are used for light construction. The head is easily punched beneath the surface with no damage to the wood surface surrounding the head. Available in bright steel and various coatings. Veneer pins are similar to panel pins but finer in section and are used for small mouldings and fixing veneers in position.

Figure

d) Fibro nails: - Wire nail coated with zinc to prevent it from getting rusty. A thin nail of about 15 mm to 30 mm length with flat head and blunt end.

Figure

e) Spring head or roofing nail: - An umbrella shaped type of nail which is commonly used to nail roofing iron (corrugated iron) on to the roof frames. The nail is galvanised to protect it from getting rusty.

Figure

f) Clout nail: - Made in steel or copper and may be galvanized. It is round in cross section and has a large head which makes it ideal for fixing roofing felt and webbing.

Figure

7.2. Screws

Woodscrews are used for joining wood, fastening ironwork to wood, fastening hardware (hinges, locks, catches) to wood. A screw is a metal fastener with a spiral thread cut in. Wood-screws are made of iron, brass or other material. Screws provide much greater holding power than nails. The spiral thread of the screw turns its way into the wood to become firmly embedded in the fibres. A thread is formed in the wood and enables screws to be removed and replaced if required.

a) Parts of a screw: - A screw consists of a Slot, the Head, the Gauge, the Shank, the Thread and the Point.

Figure

b) Different types of screws:

Figure

c) Fitting screws: - Softwood: It is necessary to bore a clearance hole for the shank of the screw through the top piece of wood. Countersinking will also be required for a countersunk head screw.

Hardwood: A clearance hole must be bored in the top piece and a pilot hole for the thread of the screw in the bottom piece.

Figure

7.3. Bolts and nuts

Bolts and nuts are used for joining wood in heavy wood construction (roof trusses and rafters), fastening heavy wood structures to iron constructions, connection of parts on iron construction.

The bolt consists of a cylindrical shank with a head. The shank is threaded for a nut.

Fastening two (or more) pieces of wood by means of a bolt gives a very strong connection.

A washer is put between wood and nut to prevent damaging the wood, when the nut is tightened up.

When ordering any Bolts and Nuts you must specify the quantity, the diameter of shank, the length, the finish, the type eg. Fifteen M10 x 100 galvanised cup head bolts.

a) Coach screw: - Extra large wood screw with bolt type head that is tightened with a spanner.

Figure

b) Self-tapping screw: - Used for sheet metal work. It cuts its own thread as it is screwed. Has either slotted or Philips cross slot head.

Figure

c) Machine bolts: - All bolts with square or hexagonal heads referred to as machine bolts.

Figure

d) Coach or Carriage bolts: - All bolts with round heads are referred to as coach or carriage bolts. They have square or ribbed collars that prevent them from turning once the nut has tightened.

Figure

e) Stove bolts: - Functions as a bolt but have screw heads flat or round.

Figure

f) Rag bolt: - For bolting wood to concrete, jagged head is set in wet concrete and holds firmly when concrete dries.

Figure

g) Hexagonal nuts: - Commonest type of nut available in a wider range of sizes.

Figure

h) Square nuts: - Mainly in large sizes only for coach bolts.

Figure

i) Flat square nuts: - In smaller sizes only for lighter jobs.

Figure

j) Handrail nut: - Used on handrail screw and in places where there is a space problem and where it is necessary for nuts to be tightened from the sides.

Figure

k) Winged nuts: - Used where nuts have to be easily undone and tightened by hand.

Figure

1) Dome nuts: - Decorative nut, usually chromium plated.

Figure

m) locking nut: - Is used where vibrations might make normal nuts undone. Has fibre ring inside to make it hard to turn.

Figure

n) Flat washer: - For round head screws, spreads the load to give good grip. Also used in conjunction with bolts to prevent bolt from falling into wood and give a smooth surface to tighten the nut on.

Figure