Mechanical Workshop Practice 3

MECHANICAL WORKSHOP
PRACTICE 3

LATHE
MILLING

TIG
MIG

TIG AUTHOR:
MILLING
LATHE MOHD HELMY BIN ZAKARIA
GEGE NURFAIZEE BIN FADZIL
MIG ZAHIRAN BIN HAMZAH
ASRUL AFFENDI BIN AHMAD ROPAI
AZUWAN BIN SALEHUDDIN
FEROZ SHAH BIN ZAINORDIN
WAN MOHD NAGUIB BIN WAN ABD. RAHMAN
MOHD AMIRUDIN BIN MUSTAJAB

VERSI 1: 2021

TABLE OF CONTENTS

PREFACE i
COURSE OUTLINE ii
RECOMMENDED TIME iii
ALLOCATION (RTA)
ASSESSMENT v

GENERAL SAFETY 06
08
Safety in Workshop
General Requirements of
Safety in Workshop Policy

1.0 MACHINING - (LATHE & MILLING)

1.1 Lathe Machine 10
Basic Theory 11
Basic Operation 12

1.2 Milling Machine 13
Basic Theory 14
Basic Operation 15

2.0 WELDING - ( TIG & MIG) 17
18
2.1 TIG Welding 19
Basic Theory
PBasic Joint

2.2 MIG Welding 20
Basic Theory 21
Basic Joint 22

PREFACE

Mechanical Workshop Practice 3 has been developed and revised to meet the
requirement of the Mechanical Workshop Practice 3 Polytechnic Course Syllabus. This
module is written by the lecturers from the Department of Mechanical Engineering,
Polytechnic Sultan Azlan Shah, Perak.

There are notes, diagrams,
photographs/figures, lab sheets and
assessments throughout the text and
supported by well-designed background and
illustration to enhance the students learning
ability. We have put every effort to make this
module as effective, attractive and readable as
possible and it could be made as beneficial
references for students of the first semester
especially.

We would like to acknowledge our Head of Department, En. Shahrol Nizam Bin
Mokhktar and our Head of Programmed for the invaluable suggestions and comments
which in way, contributed to the completion of this module.
We hope this module would benefit the students in better knowledge and
understanding the mechanical engineering practice concepts. We welcome
constructive comments from the students, lecturers and other readers so that future
editions can be further improved.

Author:
Mohd Helmy Bin Zakaria, Gege Nurfaizee Bin Fadzil, Zahiran Bin Hamzah, Azuwan Bin

Salehuddin, Feroz Shah Bin Zainordin, Asrul Affendi Bin Ahmad Ropai, Wan Mohd
Naguib Bin Wan Abd. Rahman , Mohd Amirudin Bin Mustajab

MECHANICAL WORKSHOP

PRACTICE 3

SYNOPSIS

MECHANICAL WORKSHOP PRACTICE 3 expose the students to the use of tungsten inert gas (TIG)
and Metal Inert Gas (MIG) welding machines. Students also will perform a task by using lathe and
milling machine. In addition students will be exposed in safety procedures practice will be
emphasized in workshop.

COURSE LEARNING OUTCOMES

1. Follow welding tasks according to workshop Standard Operating Procedure. (P3)

2. Perform machining tasks according to workshop Standard Operating Procedure. (P4)

3. Demonstrate awareness of social responsibility and safety procedures in the workshop according
to the workshop safety regulations and create a secured environment in an organization while doing
practical work. (A3)

RECOMMENDED TIME ALLOCATION (RTA)

1.0 TIG and MIG Welding (00 : 28)
1.1 Perform TIG and MIG welding works
1.1.1 Follow safety procedures when operating TIG and MIG welding machines.
1.1.2 Select electrode size, electrode wire, current and voltage and adjust correct gas pressure.
1.1.3 Prepare welding process, determine speed, angle and wire feed rate and current polarity.
1.1.4 Prepare materials and welding process for basic joints.
1.1.5 Weld workpieces on flat position.
1.2 Keep the workshop clean and safe

2.0 Machining (00 : 28)
2.1 Operate lathe machine
2.1.1 Follow the safety procedures in the machining workshops.
2.1.2 Select spindle speed, feed and cutting tools for lathing works.
2.1.3 Perform the following lathe works.
a. Fillet / shoulder.
b. Stepped turning.
c. Chamfer cutting.
d. Groove cutting.
2.1.4 Practice cutting external metric thread on the lathe machine.
a. Follow safety procedures in the workshop.
b. Identify tools for cutting thread.
c. Set up machine and tools.
d. Cut metric thread.
2.2 Perform indexing on milling machine
2.2.1 Follow safety procedures while indexing works.
2.2.2 Install indexing head on the milling machine table.
2.2.3 Mill square / hexagon shape on a workpiece.
2.3 Keep the workshop clean and safe.

ASSESSMENT

CONTINUOUS ASSESSMENT (CA):

Continuous assessment is carried out throughout the semester and comprises the followings:

a. Practical Task (P) [4] 60%
b. Practical Task (A) [4] 10%
c. Report [4] 30%

[ Assessment Task above ( a-b ) to be executed during Lecture / Practical / Tutorial hour ]

Note :
1. Refer to Assessment Specification Table for the details.
2. The percentage of Continuous Assessment may vary depending in courses.

Remember: Safety first! In general, personnel in the
various mechanical workshops
WORKPLACE
1 of the polytechnic are trained
GENERAL on how to use the workshop
tools, machine tools and
SAFETY equipment.

No employee wants to get Only trained and competent
hurt on the job. By following a
few simple rules, you can 2 persons will be assigned to
greatly reduce your risk of these mechanical workshops
injury. and permitted to operate the
equipment.

Untrained personnel will be
denied from entering workshops

3 unless they have the level of
proficiency as determined by
the workshop supervisor.

The Safety in the workshops has
been written not only to provide
novices with appropriate safety
procedures but also to assist
trained workshop personnel with

4 the provision of a reference
document outlining the general
principles of safe working
practices relevant to the
mechanical engineering
aspects of the workshop
environment.

Remember: Safety first! It relates to the specific areas

WORKPLACE 5 where the definite safety
measures are required for the
GENERAL workshop operations.

SAFETY This policy is written as an
addition to and not as a
No employee wants to get substitute to the general safety
hurt on the job. By following a principles which is applicable
few simple rules, you can to all types of workplace such
greatly reduce your risk of
injury. 6 as fire precautions, proper use
of personal protective
equipment, hygiene standards,
workplace noise and proper
manual handling techniques.

GENERAL
REQUIREMENTS
OF SAFETY IN
WORKSHOPS
POLICY

1 Keep the workshop clean and tidy at all times
2 Always seek instruction before using an

unfamiliar piece of equipment

3 Only use tools and machines for their
intended purpose
Report all damaged equipment and do not

4 use it until it has been repaired by a qualified
person

5 Where machine guards are provide they must
be kept in place

Never distract the attention of another staff

6 member when that person is operating the
equipment and never indulge in horseplay
Always use the appropriate personal

7 protective devices and check if they are clean
and in good condition before and after use

8 Long hair needs to be restrained by either a
tie or hat (female students)

9 Never use compressed air for the cleaning
purpose such as on clothing and body

TOPIC 1

MACHINING

1.1 Lathe Machine
1.2 Milling Machine

1.1 LATHE
MACHINE

1.1 LATHE MACHINE

BASIC THEORY

Lathe machine is a machine which rotates the work piece on its axis to
perform various operations such as cutting, knurling, drilling, or

deformation. The tools are applied to the work piece to create an object
which has symmetry about an axis of rotation.



Headstock Assembly

The headstock assembly is the front section of the
machine that is attached to the bed. This assembly
contains the motor and drive system which powers
the spindle. The spindle supports and rotates the
workpiece, which is secured in a workpiece holder
or fixture, such as a chuck or collet.

Tailstock Assembly

The tailstock assembly is the rear section of the
machine that is attached to the bed. The purpose
of this assembly is to support the other end of the
workpiece and allow it to rotate, as it's driven by the
spindle. For some turning operations, the
workpiece is not supported by the tailstock so that
material can be removed from the end.

Compound

The compound is attached on top of the cross slide
and supports the cutting tool. The cutting tool is
secured in a tool post which is fixed to the
compound. The compound can rotate to alter the
angle of the cutting tool relative to the workpiece.

Carriage

The carriage is a platform that slides alongside the
workpiece, allowing the cutting tool to cut away
material as it moves. The carriage rests on tracks
that lay on the bed, called "ways", and is advanced
by a lead screw powered by a motor or hand wheel.

Bed

The bed of the turning machine is simply a large
base that sits on the ground or a table and supports
the other components of the machine.

BASIC OPERATION

1. FACING

A single-point turning tool moves radially,
along the end of the work piece, removing a
thin layer of material to provide a smooth flat
surface. The depth of the face, typically very
small, may be machined in a single pass or
may be reached by machining at a smaller
axial depth of cut and making multiple
passes.

2. STRAIGHT TURNING

A single-point turning tool moves axially,
along the side of the work piece, removing
material to form different features, including
steps, tapers, chamfers, and contours. These
features are typically machined at a small
radial depth of cut and multiple passes are
made until the end diameter is reached.

3. DRILLING

A single-point turning tool moves axially,
along the side of the work piece, removing
material to form different features, including
steps, tapers, chamfers, and contours. These
features are typically machined at a small
radial depth of cut and multiple passes are
made until the end diameter is reached.

4. KNURLING

Knurling is an operation used to produce a
texture on a turned machine part. Handles are
often knurled in order to provide a gripping
surface. The two wheels inserts as shown on
the tool below contact the work piece, and with
pressure, cold-form a pattern on the surface of
the part.

1.2 MILING
MACHINE

1.2 MILLING MACHINE
BASIC THEORY

Milling machines are very versatile. They are usually used to machine flat surfaces
on square or rectangular parts, but many other shapes. The type of milling
machine in the UCR Mechanical Engineering Machine Shop is a variable speed
vertical spindle, knee-mill with a swivelling head (also known as a “Bridgeport”).
Although there are several other types of milling machines, this document will
focus only on the vertical milling machine A milling machine removes metal by
rotating a multi-toothed cutter that is fed into the moving workpiece. The
spindle can be fed up and down with a quill handle on the head.

ON /OFF SWITCH BRAKE

For turning the spindle ON or OFF and for For manually stopping the rotation of the spindle
changing the direction of spindle rotation. after turning the spindle off.

SPEED KNOB

For adjusting the spindle rotation speed (RPM)

Z-AXIS HANDLE POWER DRAWBAR

For moving the machine table in the Z+ or Z- For inserting or removing of collets / cutters from
direction (up and down) the machine spindle.

QUILL HANDLE

For moving the quill up and down in the Z-axis
direction.

VICE

For clamping work pieces onto the milling machine
table.

X-AXIS HANDLE

For moving the machine table in the X+ or X-
direction (left or right)

Y-AXIS HANDLE

For moving the machine table in the Y+ or Y-
direction (front to back)

1.2 MILLING MACHINE: BASIC OPERATION

1.VERTICAL MILLING

The Milling Machine uses a rotating milling
cutter to produce machined surfaces by
progressively removing material from a work
piece. The vertical milling machine also can
function like a drill press because the spindle is
perpendicular to the table and can be lowered
into the work piece.

2. UP MILLING

In which the cutter and feed move in the
opposite direction i.e the rotary cutter
moves against the feed. With reference to
the adjacent figure, the cutter rotates in the
anti-clockwise direction, while the direction
of feed is from right to left.

3. INDEXING

The operation of rotating the job through a
required angle between two successive cuts
is termed as indexing. This is accomplished
with the help of a milling attachment known
as dividing head, which is an accessory to
the milling machine.

TOPIC 2

WELDING

2.1 TIG Welding
2.2 MIG Welding

2.1 TIG
WELDING

2.1 TIG WELDING

BASIC THEORY

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc
welding process that uses a non-consumable tungsten electrode to produce the weld. The weld
area and electrode is protected from oxidation or other atmospheric contamination by an
inertshielding gas (argon or helium), and a filler metal is normally used, though some welds, known
as autogenous welds, do not require it. A constant-currentwelding power supply produces
electrical energy, which is conducted across the arc through a column of highly ionized gas and
metal vapors known as a plasma.

GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such
as aluminium, magnesium, and copper alloys. The process grants the operator greater control over
the weld than competing processes such as shielded metal arc welding and gas metal arc welding,
allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and
difficult to master, and furthermore, it is significantly slower than most other welding techniques. A
related process, plasma arc welding, uses a slightly different welding torch to create a more
focused welding arc and as a result is often automated.

Power Source Torch

The power source for TIG welding can be either DC or AC, but in There is a wide range of torch designs for welding,
both the output is termed a drooping, or constant current depending on the application. Designs which have
characteristic; the arc voltage/welding current relationship the on/off switch and current control in the handle
delivers a constant current for a given power source setting. are often preferred to foot controls. Specialised
torches are available for mechanised applications,
e.g. orbital and bore welding of pipes.

Tungsten / Electrode

The electrode tip is usually ground to an angle of
60 to 90 degrees for manual welding, regardless of
the electrode diameter. For mechanised
applications as the tip angle determines the shape
of the arc and influences the penetration profile of
the weld pool, attention must be paid to
consistency in grinding the tip and checking its
condition between welds.

Sheilding Gas

A gas lens should be fitted within the torch nozzle,
to ensure laminar gas flow. This will improve gas
protection for sensitive welding operations like
welding vertical, corner and edge joints and on
curved surfaces. There is also a wide range of
nozzles available, ensuring different gas coverage.
The nozzle's selection depends mainly on the
electrode diameter and on the accessibility,
defined by the assembly to be welded.

2.1 TIG WELDING: BASIC JOINT

1.BUTT JOINT

i. Place two clean pieces of metal flat on the
table and tack weld both ends together.
ii. Point the torch so that the flame is
distributed equally on both sheets.
iii. When both sheet edges have melted, add
the filler rod in the same manner.
iv. Repeat this practise until you can keep the
width of the molten weld pool uniform and the
direction of travel in a straight line.

2. OPEN SQUARE BUTT JOINT

i. Using two clean piece of mild steel sheet.
ii. Arrange the two mild steel sheet
perpendicular orientations.
iii. Select the appropriate electrode with
type of work.
iv. Adjust the flow of electrical suitability of
the electrode size of 70 -90 ampere.
v. Assure that the angle for the mild steel is
90⁰.
vi. Make a tack weld at each end of the mild
steel sheet.
vii. Start at one end and hold the electrode
at a 30° angle in the direction of the weld.
viii. Move the electrode in a circular pattern
down the sheet toward the other end.
ix. If the size of the molten weld pool
changes, speed up or slow down to keep it
the same size all the way down the sheet.
x. Repeat this practice until you can keep
the width of the molten weld pool uniform
and the direction of travel in a straight line.
xi. After completion of welding, switch off
the welding machine. Clean the workpiece
from the mouldings.

2.2 MIG
WELDING

2.2 MIG WELDING

BASIC THEORY

Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG)
welding or metal active gas (MAG) welding, is a welding process in which an electric arc forms
between a consumable wireelectrode and the workpiece metal(s), which heats the workpiece
metal(s), causing them to melt and join.

Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the
process from contaminants in the air. The process can be semi-automatic or automatic. A
constant voltage, direct current power source is most commonly used with GMAW, but constant
current systems, as well as alternating current, can be used. There are four primary methods of
metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which
has distinct properties and corresponding advantages and limitations.

Power Source Wire Feed System

MIG is operated usually with a DC power source. The source is The conventional wire feeding system normally has
termed a flat, or constant voltage, characteristic power source, a set of rolls where one is grooved and the other
which refers to the voltage/welding current relationship. In MIG, has a flat surface. Roll pressure must not be too
welding current is determined by wire feed speed, and arc length is high otherwise the wire will deform and cause poor
determined by power source voltage level (open circuit voltage). current pick up in the contact tip. With copper
Wire burn-off rate is automatically adjusted for any slight variation coated wires, too high a roll pressure or use of
in the gun to workpiece distance, wire feed speed, or current pick- knurled rolls increases the risk of flaking of the
up in the contact tip. For example, if the arc momentarily shortens, coating (resulting in copper build up in the contact
arc voltage will decrease and welding current will be momentarily tip). For feeding soft wires such as aluminium dual-
increased to burn back the wire and maintain pre-set arc length. drive systems should be used to avoid deforming
The reverse will occur to counteract a momentary lengthening of the soft wire.
the arc.

Gun

There are two types of welding guns: 'air' cooled
and water cooled. The 'air' cooled guns rely on the
shielding gas passing through the body to cool the
nozzle and have a limited current-carrying capacity.
These are suited to light duty work. Although 'air'
cooled guns are available with current ratings up to
500A, water cooled guns are preferred for high
current levels, especially at high duty cycles.

Sheilding Gas

A gas lens should be fitted within the gun, to ensure
laminar gas flow. This will improve gas protection
for sensitive welding operations like welding
vertical, corner and edge joints and on curved
surfaces. There is also a wide range of nozzles
available, ensuring different gas coverage. The
nozzle's selection depends mainly on the electrode
diameter and on the accessibility, defined by the
assembly to be welded.

2.2 MIG WELDING: BASIC JOINT

1.BUTT JOINT

i. Place two clean pieces of metal flat on the
table and tack weld both ends together.
ii. Point the torch so that the flame is
distributed equally on both sheets.
iii. When both sheet edges have melted, add
the filler rod in the same manner.
iv. Repeat this practise until you can keep the
width of the molten weld pool uniform and the
direction of travel in a straight line.

2. OPEN SQUARE BUTT JOINT

i. Using two clean piece of mild steel sheet.
ii. Arrange the two mild steel sheet
perpendicular orientations.
iii. Select the appropriate electrode with
type of work.
iv. Adjust the flow of electrical suitability of
the electrode size of 70 -90 ampere.
v. Assure that the angle for the mild steel is
90⁰.
vi. Make a tack weld at each end of the mild
steel sheet.
vii. Start at one end and hold the electrode
at a 30° angle in the direction of the weld.
viii. Move the electrode in a circular pattern
down the sheet toward the other end.
ix. If the size of the molten weld pool
changes, speed up or slow down to keep it
the same size all the way down the sheet.
x. Repeat this practice until you can keep
the width of the molten weld pool uniform
and the direction of travel in a straight line.
xi. After completion of welding, switch off
the welding machine. Clean the workpiece
from the mouldings.

MECHANICAL ENGINEERING DEPARTMENT

LATHE
MILLING

TIG
MIG