UNIT 4: METALS AND METAL WORK

OBJECTIVES

4.1 Define terminology4.2 Discuss safety practices in cold metal work4.3 Discuss the kinds of metals used and how

to distinguish between them4.4 Select and use tools in cold metal work4.5 Discuss the uses of taps and dies in

agricultural metals work

4.1 DEFINE TERMS

1. Alloy – a mixture of two or more substances of which at least one is a metal

2. Angle – a common shape for mild steel comprised of two flat edges formed at a right angle

3. Anneal – cooling steel slowly to make it soft4. Channel – a common shape for mild steel

comprised of three flat edges formed in the shape of a C

5. Die – a tool used to make or cut threads on a rod

4.1 DEFINE TERMS

6. Ferrous metal – a metal containing iron7. Flat – a common shape for mild steel

comprised of one flat piece8. I-beam – a common shape for mild steel

formed as an I9. Malleable – a metal or other material that

can be shaped by pounding with a mallet (hammer) or pressure of rollers

10. Nonferrous metal – a metal that does not contain iron

11. Rod – a round cylindrical piece of metal

4.1 DEFINE TERMS

12. Sheet metal – metal in the form of a sheet; usually thin

13. Tap – a tool used to cut threads inside a piece of metal

14. Tee – a common shape for mild steel formed as a T

15. Tempering – controlled cooling after heating metal to attain a degree of hardness

16. Tube – a hollow cylindrical material such as a pipe

4.2 DISCUSS SAFETY PRACTICES IN COLD METAL WORK

SAFETY PRACTICES

Keep the work area clean. Wipe up oil and grease spills immediately to

prevent injuries caused by slipping and falling. Keep paths to exits clear.

When doing cold metalwork, wear approved safety glasses or a face shield.

SAFETY PRACTICES

Store oily and greasy rags in a fireproof metal container to prevent the spreading of spontaneous fires.

SAFETY PRACTICES

Serious injury may result from straining due to incorrect lifting. Lift heavy objects with the leg muscles, not the

back muscles. When lifting heavy objects, obtain assistance.

SAFETY PRACTICES

Always use the proper-sized tools and equipment for the job.

Use equipment only with the instructor’s permission. Notify the instructor immediately if you are

injured.

SAFETY PRACTICES

Wear clothing that is not loose or bulky and wear hard-toed shoes with non-skid soles.

SAFETY PRACTICES

Each electrical tool should be equipped with a three-prong plug and plugged into a grounded three-hole receptacle. When used outside, portable tools should be

connected to ground fault circuit interrupter outlets.

SAFETY PRACTICES

Restrain excessively long hair with a band or cap to keep hair from getting entangled in machines. When using a drill or drill press, be extremely

careful with long hair. Be certain that stock to be cut, filed or

chiseled is securely fastened in a vise or by clamps to prevent tools from slipping. Mount vises, anvils, and clamps securely for cold

metalwork.

4.3 DISCUSS THE KINDS OF METALS USED AND HOW TO DISTINGUISH BETWEEN THEM

4.3.2 DISTINGUISH BETWEEN FERROUS AND NONFERROUS METALS

A. FERROUS METALS

Metals whose chief ingredient is iron.

Pig iron, cast iron, wrought iron, and steel are examples.

PIG IRON OR CURED IRON

is iron ore changed to pig iron by a blast furnace.

CAST IRON

is a product of pig iron and contains a considerable amount of carbon and some impurities.

It is brittle and granular in structure. It is

formed by pouring into special castings.

CAST IRON

Gray cast iron has been cooled slowly, allowing carbon to separate from the iron into pockets of carbon in the form of graphite.

Gray cast iron is used in sprockets, stoves, and manifolds.

CAST IRON

White cast iron has been cooled quickly to prevent separation of carbon.

White cast iron is used for agitators in grain drills.

CAST IRON

Malleable cast iron has been made soft, strong, and malleable through a long re-heating and cooling process called annealing.

Malleable cast iron will bend slightly, such as for a conventional mower guard.

WROUGHT IRON

a product of pig iron that has had most of the carbon removed, is a two-component metal consisting of high purity iron and iron silicate.

Wrought iron is the only ferrous metal that contains siliceous slag.

WROUGHT IRON

The slag is responsible for the desirable properties of wrought iron, particularly its resistance to corrosion and fatigue.

It is used for rivets, porch furniture, and decorative roof supports.

STEEL

is iron characterized chiefly by its carbon content.

B. NON-FERROUS METALS

are those which have no iron and are made up of a single element.

These are aluminum, copper, lead,

magnesium, nickel, tin, tungsten, zinc, silver, and gold.

ALUMINUM

is a silver-white, malleable, ductile metal.

It is known for it’s electrical conductivity, heat conductivity, rust resistance, and light weight.

COPPER

reddish-brown in color is used for tubes, wire, sheets, and plates. It has excellent workability, either hot or

cold, and the highest electrical and heat conductivity of all commercial metals.

LEAD

has a bluish-white color and a bright luster. It is soft, highly malleable, and ductile; has

slight tenacity; and is a poor conductor of electricity.

It is used for making pipe and containers for corrosive liquids.

MAGNESIUM is a very lightweight, silver-white metal, which is

malleable and ductile and burns in air. It is usually found in the alloy known as dowmetal.

It is useful for airplane bodies, truck and auto wheels, ladders, lawn mower frames, and any place where weight reduction is important.

NICKEL

is a hard, malleable, ductile, tenacious white metal that is somewhat magnetic.

It is valuable for the alloys it forms with other metals.

TIN

does not corrode in humid conditions, adheres tenaciously to iron, has a low melting point

used extensively in solder, brass, bronze, and pewter.

TUNGSTEN

one of the heaviest metals used for making filaments for incandescent

lamps. Tungsten carbide is almost as hard as

diamond and is used extensively for cutting tools.

ZINC

bluish-white metal at ordinary temperatures is brittle but malleable at high temperatures used as a galvanizing metal coating to

prevent corrosion.

SILVER

shiny, white metal used mostly for ornamental work, jewelry,

and table-ware. Silver is the best conductor of electricity.

GOLD

is most often used for ornamental jewelry.

4.4 SELECT AND USE TOOLS IN COLD METAL WORK

HOW MANY OF THE FOLLOWING TOOLS DO YOU KNOW??

LAYOUT TOOLS

1. Framing Square

2. Combination Square

3. T-Square4. Center Punch5. Scratch Awl

6. Scriber7. Spring Dividers

8. Ball Peen Hammer

9. Straight Edge

SQUARES

1. The framing square is used for squaring large pieces.

2. The combination square has a blade to which three different heads may be attached. These heads consist of one square and miter

head, one centering head, and one bevel protractor head.

SQUARES

The heads may be purchased as a set or separately and can be attached quickly and locked in any position along the blade.

3. The T-square is used for squaring small objects.

THE CENTER PUNCH

4. The center punch is ground to about a 60 degree angle to the center lines and is used to mark the location of holes and to make a starting hole for a drill .

SCRATCH AWL

5. The scratch awl is made of high carbon steel and a hardwood handle, and is used to scribe lines on metal. Since the metal of the awl protrudes through the handle, it can be tapped with a hammer to make a light center punch.

SCRIBER

6. A scriber is a hand tool used in metalworking to mark lines on work pieces, prior to machining.

The scriber is made of high carbon steel in different patterns and shapes, and is sharpened to a needle point.

SPRING DIVIDERS

7. Dividers are used for marking circles, dividing circles, and stepping off equal lengths for spacing of holes.

DIVIDERS

The two legs of the dividers are sharpened to needle points; they can be adjusted to varying widths.

The size of dividers is determined by the length from the pivot to the point of the leg.

BALL PEEN HAMMER

8. The original function of the hammer was to peen riveted or welded material, which makes it as flexible as the surrounding metal. Today, the ball end of the hammer is used to cut gaskets, expand and shape the free end of copper roves, light rivets, and "set" rivets (which completes the joint).

STRAIGHT EDGE

9. A straight edge is used for marking straight lines between two points or a chalk line can be used for marking long lines.

MEASURING COLD STEEL

Select a rule or tape that is long enough to measure the entire distance at one time.

The most suitable rules and tapes are those in which the inches are divided into one or more of the following: 1/2, 1/4, 1/8 , 1/16 , 1/32 , and 1/64 . A 1/10 and 1/12 rule is used for special jobs.

4.5 DISCUSS THE USES OF TAPS AND DIES IN AGRICULTURAL METALS WORK

TAPPING COLD METAL

A common metalworking job in agricultural mechanics is the cutting of threads on bolts and nuts. Taps and dies are used for thread cutting.

A TAP

A screw-like tool used to cut inside threads. There are three types of taps.

Taper Tap Plug Tap Bottoming Tap

TAPER TAP

The taper tap, with the first 0 to 10 threads that do not cut full-depth threads, is used alone for tapping a hole that is drilled completely through the metal.

When tapping a blind hole all three taps must be used.

PLUG TAP

The plug tap, with five or six partial threads, is used after the taper tap.

It is screwed down to the bottom of the hole.

BOTTOMING TAP

The bottoming tap is used after the plug tap to cut full-size threads to the bottom of the hole.

HOLE TAPPING PROCEDURE

1. Drill the proper sized hole for tapping.

2. Select the proper taper tap and insert the square end in a tap wrench.

3. Place the item to be tapped in a vise and clamp securely.

4. Grasp the tap wrench with the hand directly over the tap and place the end of the tap in the hole.

HOLE TAPPING PROCEDURE

5. Apply downward pressure on the wrench, and turn it clockwise to start the tap. Continue turning the wrench in this manner until

the tap starts to feed itself.

HOLE TAPPING PROCEDURE

6. When the tap begins to feed itself, grasp the tap wrench handles with both hands, and continue turning slowly. Apply the same turning power on each handle to

prevent breaking the tap. Apply the proper lubricant to keep the tap cool so that it will cut properly.

HOLE TAPPING PROCEDURE

7. After the tap has been properly started, turn it one full turn forward.

Then, back it up one-quarter turn to break and clear away the chips.

This will help to make a smoother thread.

Continue in this manner until the tap reaches the bottom or turns freely in the hole.

HOLE TAPPING PROCEDURE

8. Back the tap out slowly.

9. Thoroughly clean the tap before placing it in the rack.

A DIE Used for cutting outside threads, like those found on

the threads of bolts. There are three common types of dies:

round-split die two-piece die solid die.

A DIE

The round-split and two-piece dies can be adjusted to vary the depth of cut, but the solid die is not adjustable.

BOLT THREADING PROCEDURE

1. Place the rod in a perpendicular position in a vise and clamp securely.

2. File off any projections on the end of the rod or bolt, slightly tapering it.

3. Select the proper size of die. The tool used for holding and

turning the die is called the die stock.

BOLT THREADING PROCEDURE

4. Place the die squarely on the rod or bolt and apply pressure evenly as the die is turned.

5. Apply oil so that the die will run through it while cutting.

BOLT THREADING PROCEDURE

6. Move the die back and forth so the chips of metal will fall out.

7. Remove the die by turning it counterclockwise after the required number of threads are made.

TAPS AND DIES HAVE THEIR SIZES AND CLASSIFICATIONS STAMPED ON THEM.

THERE ARE THREE CLASSIFICATIONS OF THREADS:

National Coarse (NC) Are commonly used on parts of

machinery where there is very little vibration.

National Fine (NF) Fine threads will stand more

vibration than coarse threads before the nut loosens.

National Pipe Thread (NPT).

REVIEW

4.1 Define terminology4.2 Discuss safety practices in cold metal work4.3 Discuss the kinds of metals used and how

to distinguish between them4.4 Select and use tools in cold metal work4.5 Discuss the uses of taps and dies in

agricultural metals work