INTRODUCTION

SAFETY TALK

Technician Mr A . Ogolla

Introduction

Safety – it is ensuring you yourself, people around you and the environment are out of danger.

Always ensure the working environment is safe.

PPEs used in the workshop

 Head – helmet
 Hands- leather gloves
 Eyes – welding shields and clear goggles
 Nose – dust mask
 Ear – ear muffs
 Legs- safety boots

Conduct of people in a working environment

 Never work and the influence of drugs in the workshop

 Ask anything that you are not sure of before working
 Avoid loose clothing around machines
 Use first aid kits when an injury occurs
 Avoid stress when working
 Don’t work while having fatigue-take a rest when tired
 Rings, jewelry must be removed in the workshop
 Long hair must be tied

 Safety switching
 Use electrical emergency stop button during emergency- they are placed in the
workshop red in color

General workshop safety

 Always be in a dust coat and safety boots
 Meals and drinks are not alloyed
 Always work in a clean environment
 Clean the machines before and after use
 Never work without the help of the technician
 Dress properly while working
 Never work under distractions
 Always read the instructions given before working
 Never pocket sharp tools while working
 Safety gears must be used for the right purpose
 TOOLS
A tool is a device, usually a simple one, for making , measuring or assembling components or
parts.
They are classified into;

type examples
Hand tools Open ended spanner, ring spanner, filer, ball
peen mallet, hack saw, G-clamp, claw
hammer, hex key, caliper, pliers, wrench,
screw driver, torque wrench, ratchet
Marking out tools Dot punch, scriber, divider, enter punch
Measuring tools Height gauge, try square, steel rule,
protractor, tape measure, calipers,
micrometer, marking gauge, depth gauge,

Tuesday

MACHINES

Technician Mr kiptoo Amon

Sheet metal shop

 Hydraulic press brakes

 Plate rolls
 Profile rolls
 Folders and benders

Machine shop

 lathe machine
 drillers
 power hacksaw
 CNC machine
 UTM machine
 Bench grinder
 Milling machine
 Riverting machine

Welding and fitting shop

Grinder
Welder

Machine shop safety

 Do not work alone
 Do not wear loose clothing, neckwear, jewelry, while operating the machine.
  Be in safety shoes always.
 Pull back long hair.
 Clean the machines after use.
 Ensure the machines are in good conditions before use.

Wednesday

Hand Tools showcase

Technician

Mr Hanniel kipchirchir

micrimeter

steel rule
ratchet
scriber

G-clamp

reverting machine
tape measure

letter punch

spirit lever

mallet
grinder key

hand drill

tin slip
 combined spanner

locking pliers

linesman’s pliers
 mallet

chisel

try square
 star screw driver

flat file

hack saw

Afternoon
Lathe machine parts
Technician Mr Henry Koech
steady rest

4jaw chucker
 knurling tool

die and tips

dialogue gauge

Thursday

Introduction to welding

Technician Mr Henry Omondi

Welding- is the process of joining two or more pieces of metal by means of heat.

Types of welding

Solid state

Fusion

 Gas welding
 Arc welding

Types of joints

I. T – joint
II. Lap joint
III. But joint

 Arc welding

In arc welding , electricity is the source of heat.

Welding defects

Cracks
Overfill
Porosity
Undercast
Underfill
Spatter

Test and evaluation

Destructive test

Non-destructive test

 Gas welding

Oxy-acetylene is the main source of heat

Gases used in welding

 Acetylene – it is the main source of fuel

 Oxygen – supports combustion
WEEK 2
SHEET METAL
Technician Mr Kiptoo Amon
Introduction
Sheet metal refers to nay metal that can be formed into flat pieces of varying thickness.
It plays a key role in engineering field.
Sheet metal safety.
a. Wear heavy duty gloves when handling sheet metal
b. Wear a mask to prevent inhalation of sheet metal dust
c. Never carry an oversized piece of sheet metal by yourself
d. Clean your hands after working on sheet metal.

Machines used in sheet metal shop

Light keel rolling machine

Task one
Development of 90 degrees elbow
 By the aid of solidworks sheet metal commands we the development of the
elbow below
 We extracted the development of each segment fully dimensioned
 And transferred the dimensions into a manila paper and cut them
 We used the developments obtain to cut the pieces on a metal sheet
 Cutting the sheet metal was by a grinder
 Filed the edges to make them smoth.
 Join of the metal sheet pieces was by brazing to produce 90 degrees elbow
reducer.
 90 degrees wlbow

Task two
Hopper development
 By the aid of solid works we developed the flat pattern of the hopper and extracted it
 Transfer the dimension into a manila paper
 Cut the flat pattern on a meta sheet
 By the use of a tin slip cut the metal sheet according to the dimensions
 Fold the flat pattern and join by the use of a reverting machine

solid works development

 after joining
Task three
Development of 90 degrees reducer elbow
Requirements
 Drawing instruments
 Manila paper
 Tape
 scissors
Develop the flat pattern by solid works

The elbow reducer was drawn manually

Cut of the pieces by scissor and join by a tape
References
Mechanics of sheet metal forming by Z . Marciniak, 1992
Professional sheet metal fabrication by Ed Barr , 2019
WEEK THREE

MACHINING

Technician, Mr Koech Raymond

Introduction

Lathe is a machine that is used to create a piece which has a symmetry about an axis of rotation.

Lathe machine accessories

 Face plate
 Chuck (4-jaw chuck)
 Self centered chucker (3-jaw chucker)
 Steady rest center
 Follower steady rest
 Life center
 Dead center

Main parts of a lathe machine

1. Bed
2. Head stock
3. Tail stock
4. Carriage assembly

Bed
The bed of the lathe forms the base of the machine. It is supported on two legs at a convenient
height. It carries the head stock and the tail stock for supporting the work and provides a base for
the movement of the carriage assembly which carries the tool

Head stock
The head stock houses the spindle and the means for supporting and rotating the spindle

Tail stock

The tail stock is for the purpose of primarily giving an outer bearing, support for work being
turned on centers. It can be adjusted for alignment or non-alignment with respect to the spindle
center and carries a center called dead center for supporting one end of the work. Both live and
dead centers have 60 conical points to fit center holes in the work, the other end tapering to allow
for good fitting into the spindles.

Carriage Assembly

The carriage assembly of the lathe comprises of a number of components which support,
move and control the tool. The carriage assembly consists of a saddle, cross slide,
compound rest, top slide, tool post and apron.
Lathe machine operations
 Turning
 Straight turning
 Step turning
 Facing
Facing is an operation used to produce a flat surface at right angles to the
rotational axis of the work piece.
 Taper turning
Process of turning at an angle and a given distance
 Drilling
Process of making a hole by the aid of a drill bit
 Boring
Boring is the process of enlarging a hole produced by drilling, casting, punching
or forging with the help of a single point tool
 Parting
Is the process of cutting of a work piece into two
 Chamfering
Is the process of removing sharp edges from a work piece to prevent cuts
 Center drilling
Making a small hole at the end of a work piece for holding by the life or dead centers
 Knurling
Knurling is the process of embossing a diamond shaped pattern on the cylindrical
surface of a work pie is done on the work piece so that it does not slip when held
and operated by hand.
 Threading
 External threading
 Internal threading

Minor operations
 Contour turning
Form turning
Discussion
 Vernier calipers is used for measurements done
 One should know how to use it properly
 Always withdrawal the tool before turning off the lathe machine
 One person should operate lathe machine at a time

Task one
Sharpening of tools
Bench grinder is used in sharpening of tools
 Thread cutting tool
 Turning, taper turning tool, turning tool

Task two
Internal and externa thread making
Procedure

I. Part off a work piece of diameter 38mm by 125 long

II. Mount the work piece in the lathe machine and tighten using chuck key
III. Set the machine at moderate speed
Operations done the work piece
The operations are done from larger diameter to a small diameter
 Facing
 Straight turning , diameter 36 mm by 125 mm long
 Step turning , 55 mm
 Taper turning, 45 degrees for 4 mm
 Straight turning , diameter 25 mm, by 25 mm long
 Taper tuning, 45 degrees by 4 mm long
 Straight turning , diameter 16 mm by 30 mm long
 External thread cutting, M16*2
 Drilling , diameter 16 mm by 40 mm long
 Internal thread cutting, M16*2
 Chamfering both ends
Task three
Hinge making
Procedure 1
I. Part of a work piece of diameter 38 mm by 85 mm long
II. Mount the work piece on lathe machine and tighten by chuck
key
III. Set the machine at moderate speed
operations done on the work piece
 Facing
 external step turning
Step turning (1), diameter 30 mm by 40 mm long
Facing
Step turning (2), diameter 20 mm by 20 mm long
 Facing to obtain a work piece of 80 mm long
 Chamfering both ends
Procedure 2

I. Cut off a work piece of diameter 38 mm by 45 mm

long
II. Mount it and tighten
Operations done
  Facing
 Center drilling
 Drilling, diameter 20 mm by 45 mm long
 Boring
 Diameter 30 mm by 20 mm long to
obtain internal step turning
 Facing to obtain 40 mm long
 Chamfering done on one end

Task four

Setting of a long work piece

Done when a 4-jaw chucker is used for holding

Dial gauge , block gauge, steady rest and unsteady rest are used for setting

Done to prevent vibrations which may be caused by a long work piece

Procedure

I. Mount a long work piece on a 4-jaw chucker

II. Set the machine at moderate speed
III. Set the block gauge pointer near the work piece, note the distane
IV. The distance between the work piece and the pointer should be uniform when the machine
rotates
V. For a dial gauge, the pointer should be at a steady position when the machine rotates
VI. Steady and unsteady rests are for holing the work piece
using steady rest

using block gauge

using dial gauge

Nut and bolt

Procedure

I. Part off a work piece of diameter 25 mm by 255 long

II. Mount the work piece in the lathe machine and tighten using chuck key
III. Set the machine at moderate speed

Operations done the work piece

 Bolt
a. Facing one end
b. Knurling diameter 22 mm by 200 mm long
c. External thread cutting of M22 by 2.5, 200 mm long
d. Grooving , diameter 18 mm by 10 mm long at the edge
e. Another grooving of 18 mm by 10 mm after the threads
f. Facing to make the bolt 250 mm long
g. Drilling, diameter 8 mm for the handle
h. Welding the handle

 Nut
a. Part a work piece of diameter 38 mm by 43 mm long
b. Face the ends to make it 40 mm long
c. Drilling, diameter 19.5mm
d. Internal thread cutting ,M22 by 2.5
e. Chamfering the ends of the nut

f.
Recommendations.

1. The school should make an effort of increasing the lathe machines in the
workshop to ensure that all students are able to assess and interact with the
machine for a longer period to ensure they learn more.

2. Students need to make sure they cooperate and all participate in the practice to
learn more.

References

 machining fundamentals by John R Walker , 1969

 Machining and CNC technology by Michael Fitzpatrick , 2018
 Basic lathework for home mechanist by Stan Bray , 2013
Week 5

BENCH WORK

Technician , Mr Hanniel

Tools used

 Hack saw
 Flat file
 Round file
 Scriber
 Try square
 Steel rule
 Bench vice
 Center punch
 Drill bit
 Ball peen hammer

Task one
Procedure
a. Cut a work piece of length 110 mm and width 30 mm
b. File the ends to make them 90 degrees , use a try square to measure 90 degrees
c. Cut of each corner 6 mm by 6 mm deep
d. Chamfer the corners
e. Mark 8 mm frim the 6 mm mark and punch using a center punch in each corner
f. Drill holes of diameter 6
g. Mark the center of the work and punch
h. Drill a hole of diameter 8 mm at the center
Task two

Grinder key

Procedure

a) Using a hacksaw cut a work piece of length 230 mm by 50 mm wide from a plate
b) Mark out the profile of the grinder key
c) Using a hacksaw cut along the out line leaving 1 mm allowance for filling
d) Chamfer the sharp corners
e) Mark out a radius of 8 mm at the handle and cut it
f) Drill a hole of 6 mm at end of the handle
g) Make fillets of radius 5 mm
h) Do finishing by use of a sand paper

i) the profile
Task three
Open ended spanner
Procedure
 Using a hacksaw cut a work piece of length 130 mm by 30 mm width
 Using a flat file, file the ends to make them 90 degrees
 Mark out the profile of the spanner using a scriber on the work piece
 Using a hack saw, flat file and round file make the open end
 Using a hacksaw cut a handle of 12 mm leaving 1 mm allowance for filling
 Mark 10 mm frim the end and dot punch
 Drill 6 mm hole
 Step down the grip section from 6 mm to a final thickness of 3 mm
 Do finishing by use of a sand paper

the profile
Task four

Procedure

 Using a hacksaw, cut a work piece of length 130 mm and 50 mm width

 Mark out the profile of the double ended spanner
 Make the open ends proceeding to the handle
 Locate the centers of the holes and curves and draw the arcs and the circles
 Using a hacksaw cut along the handle of 11 mm leaving an allowance I I mm for filling
 File at the sharp corners to radius of 0.5 mm on faces of the circles
 Fillet the grip section to a radius of 2 mm
 Do finishing use of a sand paper
Conclusion
Geometrical Misalignments were the main challenge faced and minor injuries
Recommedations
Students should be accurate on their measurements
Use hand gloves to avoid minor injuries
References
The workbench book by Scott Landis
Engineering Practice Module 13
AUTOMOTIVE SHOP

Technician Mr Aggrey Ogolla

Vehicle systems

 c‌ ombustion system
 ‌cooling system
 ‌transmission system
 ‌braking system
 ‌lubrication system
 ‌electrical system

Combustion (engine)

It's the prime mover

Types of engines

 ‌S.I engine ( spark egination)

Uses petrol as fuel

Used for light duty operations

 ‌compression ignition engineer C.I

Uses diesel as fuel

Used for heavy duty operations

Strokes- two strokes... Motor cycle

Four strokes ... vehicle

 i‌nduction ( intakes) stroke

 ‌compression stroke
 ‌power stroke
 ‌exhaust stroke

Engine components

‌crank shaft

End cap

‌intake and exhaust valve

Pistons are attached here by connecting rod

Operates on reciprocating rotary motion

Major components of the engine

 Engine block
 Cylinder head
 Oil sump casing
 1. ‌induction stroke

Piston positions

 Top dead center (TDC)

 Bottom dead center (BDC)

Piston moves from TDC to BDC

Inlet valve opens to allow air fuel mixture into the cylinder

2. ‌compression stroke

Piston moves from BDC to TDC

Both valves are closed

3. ‌power stroke

Spark plug introduces a spark in the compressed air-fuel mixture. Piston moves from TDC to BDC. Both
valves are closed

4. ‌exhaust stroke

Piston moves from BDC to TDC. Exhaust valve opens

S.I engine
Camshaft

Opera the opening and closing of the valves

Starter motor

Fuel pumb

 Has a pinion

CI engine

Strokes remain same like for SI

Only air is drawn into the engine cylinder

Induction stroke

Piston moves from TDC to BDC

Inlet valve opens to allow air into the cylinder

‌compression stroke

Piston moves from BDC to TDC

Both valves are closed

‌power stroke

Spark plug introduces a spark in the compressed air. Piston moves from TDC to BDC. Both valves are
closed

‌exhaust stroke

Piston moves from BDC to TDC. Exhaust valve opens

Injector pump

Pumps diesel into injector which releases fuel inform of atomised fuel for it to easily burn

Power stroke... Atomised fuel introduced into compressed air

Air fuel ratio

 Cooling system

Due to friction of the piston rings and cylinder Walls heat is generated.

The engine should never be cold or hot.

Types of cooling system

 Air cooling
 Water cooling

1 cooling system
Heat from from hot engine moves to fins
Fins create surface for heat to flow

side fins

2. Water cooling system

Radiator is the reservoir of the coolant

Water pump , pumps water from radiator to engine

 Fans
Electrically driven
Rotates
 Hose pipe
Connects radiator and engine
 Thermostat
 It’s a sensor

radiator

Lubrication system
Done to minimise friction
Lubricants used
 Sump
Stores oil
 Strainer
Filters bigger sold particles
 Oil filter
Filters smallest particles
 Oil pump
Pumps oil to engine

oil filter oil sump

Electrical system
 It is the ignition system
 Current from battery must pass through the fuse box .
 The fuses are rated 10 A and 30 A

The charging system

 Alternator charges the battery
 Charge controller disconnects charging at 12 V
 The starting system
 Starter motor connects battery and ignition key

The lighting system

Head lamps, brake lights , parking light, ,Indicators uses the battery to operate
 The wipers, power windows and doors also use the battery
 Music system also uses the battery
 The horn uses the electrical system

battery head lights

indicators fuse box

Braking system
 Starts from the brake pedals. It’s connected electrically to brake lights.
 Connected mechanical by the master cylinder containing a brake fluid with a booster.
 Pipes connect master cylinder with the pistons
 Pressure from brake pedals pushes the brake fluid to the piston to press the brake disc
 Front wheels uses brake pads and rear wheels uses brake shoes and brake drums

brake disk brake pads

 master cylinder and brake

fluid

Advantages of a Good Braking System

 (i) To stop the vehicle in the shortest possible distance and time.
 (ii) To control the vehicle speed while moving on plain roads and hills.
 (iii) To work equally well on fair and bad roads.

Requirements of A Good Braking System

 (i) To stop the vehicle in the shortest possible distance and time.
 (ii) To control the vehicle speed while moving on plain roads and hills.
 (iii) To work equally well on fair and bad roads.

Transmission system
 Power from engine is regulated at the gear box
 When starting a vehicle start with low gears
 Power is transmitted from gear box by a propeller shaft to the differential unit
  From the differential unit power is transmitted to the wheels
 Clutch plate connects the engine and gearbox

gear box

Functions of a gear box

(i) To provide a means to vary the leverage or torque ratio between the engine and the road
wheels as required.
(ii) The transmission also provides a neutral position so that the engine and the road wheels are
disconnected even with the clutch in the engaged position.
(iii) It provides a means to reverse the car by selecting the reverse gear
(iv) Functions of clutch
(v) (a) To disconnect the engine power from the gear box as required, under the following
circumstances:
(vi) (i) to start the engine and warm it up;
(vii) (ii) to engage first and second gear to start the vehicle from rest;
(viii) (iii) to facilitate changing the gear as required; and
(ix) (v) disconnect from the engine to stop the vehicle after application of brakes.
(x)
(xi) (b) To allow the engine to take up load gradually without

References
 Automotive engineering fundamentals by DR Jeffrey K Ball, 2004
 Introduction to automotive engineering by M .U Kaisan , 2019
ELECTRICAL

Technician Mr Rop

Electrical safety

Electrical safety is a practice of handling and maintaining electrically powered equipment to prevent
accidents.

 Prevent electrical equipment from contacting wet areas

 Ensure safe use when unplugging
 Install properly and tidy electrical cords
 Understand your switchboard
 Install warning signs
 Call for help when in danger
 Don’t short circuit circuits.

Electrical generation
Electricity is produced from different sources
They include
 Wind
 Thermal
 Solar energy
 Hydro power

Electrical transmission

It is the transmission of electricity from the source to the consumers

Types of transmission systems

Single phase AC systems

Two phase AC system

Three phase AC system

DC systems

Transmission line voltage

 It varies in the range of 33 KV, 66 KV, 132KV, 275 KV , 500 KV

Electrical materials
  Circuit breakers
 Electrical box
 Lugs
 Electrical wire and cable
 Electrical connectors
 Motor control
 Explosion proof enclosures
 Junction boxes
 Light boxes switches and plates
 Fan boxes
 AC conduits
 Sockets

Cables
 Cables are used to connect two or more devices enabling the transfer of electrical
signals or power from one device to another
 Cables are of different sizes depending on the work they do.

They are classified into two

Type of insulation

 Cotton covered
 Silk covered
 Rubber coated
 PVC coated

Type of conducting materials

 Copper
 Aluminum

Cable sizes
Measured by the cross section area
 1.5 mm
 2.5 mm
 4.0mm
 6.0 mm

Electrical symbols

Are graphical representation of basic electrical and electronic devices or components

They are used to recognize a component in a circuit

 Electrical tools
 Pliers
 Hammer
 Screw drivers
 Electrician knife
 Phase tester
 Measuring tools

Electrical meters

They measure the total power consumed over a period of time.

Types

 Single phase energy meter

 Three phase energy meter
 BTU meter
 Smart electricity meter
 Prepaid electricity meter

Practical work

final circuit theory

Code of conduct

 Installation
 Use of tools
 Use of meters

Termination procedures

 Main switch
 Junction
 Socket
 Switch point
 Lamp point

Junction Terminator
Final circuit
References
Practical electronics for inventors, Fourth edition by Simon Monks
Practical electrical engineering by Reinhold Ludwing, 2016
CARPENTRY
Technician Mr Richard

Safety

 Wipe spilt oil/grease from the floor

 Do not use tools with loose handles/heads
 Do not use machines when in doubt
 Put on overalls, googles and boots when in the shop
 Put off power incase of an accident

Tress that produce timber

 Cypress
 Eucalyptus
 Pine
 Teak
 Jacaranda
 Meru Oaks
 Walnuts

Timer sizes

There’s different sizes of timber used in carpentry

They include

 2 by 1  6 by 6
 3 by 1  8 by 8
 4 by 1
 5 by 1
 6 by 1
 10 by 1
 8 by 1
 12 by 1
 2 by 2
 3 by 2
 4 by 2
 4 by 2
 6 by 2
 8 by 2
 10 by 2
 12 by 2
 4 by 4
 6 by 4
 8 by 4
 8 by 1 3 by 2

6 by 1

How to determine the type of timbers

They are determined by

 Density – different timbers have different densities

 Smell – each type of timber has a different smell
 Grains – the produce different grains

Others classes of timber

 Block boards
 G – boards
 MDF
 Tools used on carpentry
 Tape measure
 Pencil
 Fold rule
 Sliding square
 Wood chisel
 Wood mallets
 Handsaws ( cross cut saw, rip saw, tenon saw )
 Planes ( block plane, claw plane )
 Driving tools ( claw hammer, ratchet screw driver)
 Sash clamp
 Nail punch

Machines used in carpentry

Wood lathe machine

Is a machine used to shape wood into cylindrical profiles

Objects made on wood lathe machine

 Furniture legs
 Lamp posts
 Baseball bats
 Bowls
 Mortiser

Is a machine used to cut square or rectangular holes in a piece of timber

Jointer surface planner

Wood machine used to produce a flat surface along a board’s length

Circular table saw

Performs the following functions

 Chamfering
 Grooving
 Metering
 Cross cutting

Band saw

Band saw safety rules

 Safety googles are required

 Never clear small pieces while saw blade is running
 Never cross arms

Practical work
Constructing CNC machine rack
 Procedure
Cutting the required timber sizes by circular table saw
Planning the timber by jointer planner
Setting up the set up
 Tools used
 Claw hammer
 Try square
 Pencil
 Tape measure

References

Carpentry and joinery by David R. Bates

Woodworking book
PLUMBING
Technician Mr Terence Abere

Plumbing is the work of installing and maintaining plumbing systems

Types of pipes

 PVC pipes
 PEX pipes
 ABS pipes
 Copper pipes
 Galvanized steel pipes

Basic pipe works

 Cutting
 Joining
 Fitting
 Installation

Types of plumbing

 Sanitary drainage
 Storm water drainage
 Portable drainage

Classes of pipes

 Light class (class A)

 Medium class ( Class B)
 Heavy gauge class ( Class C)

Color coding of pipes

class color
A Yellow/brown
B blue
C red

Types of PVC pipes

class Max pressure Color code

B 6 bars red
 C 9 bars blue
D 12 bars green
E 15 bars brown
Classes of PPR

 Light class
 Medium class
 Heavy gauge
 HDP (high density pipes)

Pipe sizes
 0.25 inch
 0.75 inch
 1 inch
 1.25 inch
 1.5 inch
 2 inch
 2.5 inch
 3 inch
 4 inch
 6 inch

Fittings

Are factory made items that enable one join threaded pipes

They enable to ;

 Make a pipe straight

 Change direction
 To join pipes

Fittings used
I. Valve – regulate water flow
II. Union – connects joints
III. Reducing socket – connects pipes of different diameter
IV. Plain socket – connects pipes of same diameter
V. Reducing bush- has male and female threads
VI. Nipple – connects male and female threads
VII. Elbow – connects pipes along corners
VIII. Adapter socket
IX. Gauge valve – regulate the rate of flow
X. End cap – prevents flow

Practical
Fittings used

 0.75 ‘’ elbow (4)

 0.75’’ T-joint (5)
 0.75’’ union
 0.75’’ pipes
 0.75’’ end cap

Tools used
a) Hack saw
b) Pipe wrench (2)

References

plumbing by Roy Treloar , 2011

plumbing and central heating by Albert Jackson, 1988

WELDING

Mr Henry Omondi

Application of welding

 Pressure pipes
 Vehicle bodies
 Water tanks

Arc welding
Uses electricity

Welding machines
 MIG welder
 Rectifier welder
 SMAW welder
 Spot welder
 Thyristor welder
 TIG welder

Types of electrodes

 6011 welding rods

 7018 welding rods
 7024 welding rods
 6010 welding rods
 6013 welding rods
 6012 welding rods

Welding procedure
1. Use an electrode code MS6013 or E6013 with diameter 2.6mm or 3.2mm.
2. Adjust the ampere scale around 60-100 for electrode diameter 3.2mm.
3. Put an electrode on the electrode holder and ensure that there are no movements of
electrode at the holder.
4. Hold the electrode at 45’ degrees work angle and 2mm-3mm above the base metal.
5. Hold that position over a spot just inside the left edge of the base metal until a molten
pool is established.
6. Welding then proceeds from left to right (for the right hand).
7. Stop the process at the end of the work piece.
8. The correct technique is hold an electrode at the start position for 1s or 2s and continue
until the end of the process. At the end, hold the electrode at the last position for 1s or 2s
before finishing the process.
9. The frequency of this action will be determined by the size of the weld being deposited,
and the correct action improves with practice.

Practical activity
1. cut 6 pieces of mild steel flat bars 30mm by 112mm
2. file the bars to obtain 110 mm long
3. Then we welded the pieces together .
Joints welded on the workpiece
 T – joint
 Lap joint
 Butt joint
 Edge joint
Advantages of arc welding
 Affordable cost of equipment and doesn’t need much due to lack of gas
 Versatile and works well on metal that is dirty
 Shielding gas not necessary , can be done in all types weather

Disadvantages
 Low efficiency as more waste is produced compared to other types
 Require trained personnel
 Tough to use on thin materials

Gas welding

Ignition procedure
 Open the acetylene tank open valve a quarter to half
 Open the regulator valve to the left
 Open the oxygen tank open valve quarter to half
 Open the regulator valve to the right
 Open the acetylene nozzle valve
 Ignite
 Open the oxygen nozzle valve and regulate
 Welding flux is used

Practical activity

 Cut 2 bars of mild steel , 30 mm width by 55 mm long

 File the ends
 Remove the coating
 Join the bars by gas welding
 Lap joint was used
 gas cylinders

Gas cutting

The same ignition procedure is used but the welding nozzle is change with cutting nozzle

The flame heats the area to be cut weaking the forces of the metal

Oxygen is blown to break the steel and ejects the oxide as dross
 cutting flame

Advantages of gas welding

 Ability to weld ferrous and nonferrous metals together

 Does not require electricity
 It is portable
 Equipment and tooling are not expensive

Disadvantages
 Not suitable for thick sections
 Cannot be used for high strength steel
 Cannot reach the temperatures of arc welding
References
How to weld by Todd Bridigum , 2008