MECH 1802
ENGINEERING WORKSHOP
PROJECT REPORT
1: G-CLAMP
Student
:
SEBASTIAN LEE
Matric ID No.
:
183020372
Semester
:
November 2019 – February 2020
Program
:
AME 302
Lecturer
:
Mr. Ir. Malek Faizal Idrus
Submission Date :
4th of February, 2019 (Week 13)
Table of Contents
Index
Subject
Page No.
A
Table of Contents
i
1
Introduction
1
2
Aim and Objectives
2
2.1
Aim of Project
2.2
Project Objectives
3
Project Specifications
3
4
Project Planning and Implementation
4
4.1
Materials and Instruments/Equipment Selection
4.2
Parameters Identification
4.3
Safety and Quality Attributes
4.4
Work Procedure
5
Findings and Discussion
5.1
Discussion
5.2
Challenges Encountered and Countermeasures
6
Conclusion
6.1
Inferences
6.2
Recommendations
7
25
References
7.1
Reference List
7.2
Bibliography
B
21
27
Appendices
ii
1B
Complete Set of Technical Drawings
2B
Sheets of Process Plan
i
1 | INTRODUCTION
Through my trajectory in the Bachelor’s Degree in Mechanical Engineering (Hons.) program in
the halls of ivy called Infrastructure University Kuala Lumpur (IUKL) in pursuit of my future prospective
career as a mechanical engineer, the module Engineering Workshop (Code: MECH 1802) is a requisite
academic provision to completing mechanical engineering students’ comprehension other than in
theories that fall in the scope or perimeter of mechanical engineering alone. Besides getting the lay of
the land about several key terminologies, concepts, and principles germane to this course through weekly
class lessons, we received first-hand hands-on training in machining and other related operations and
processes. In a group of five and each equipped with adequate pre-existing nuts-and-bolts of know-hows,
we cooperated in milling, lathing, drilling, and grinding, among a few machining operations in the
workshop over the course of implementation and fabrication of the first project until the final product is
yielded as anticipated within the stipulated timeline.
Before executing the first project, which is a G-clamp made of low-carbon steel, it is imperative that we
establish a well-coordinated teamwork to ensure efficiency and effectiveness of the work performance.
As the first phase of the project, we planned and discussed among ourselves as we perused the given
project’s technical drawings with two workshop trainers, alongside Mr. Ir. Malek there to facilitate all
the students time and again. Much more to that, through this project I genned myself up with a plethora
of tools and machines which are integral to the fabrication of the G-clamp as I learned which to choose
and how to utilize them. My teammates and I unanimously decided who to mostly handle the milling
machine, lathe machine, drilling machine, grinding machine, tap and die, and everything in between
according to each member’s competency. Conforming to the process plan we had outlined as a bedrock
of the project, our group constituents had to work separately but simultaneously such that some milled a
block from a raw cuboid stock and some performed turning on a cylindrical workpiece to produce a shaft
because we were working against the clock, while each and every one of us also took turns to operate
the power-hungry machines. Machining is a term used to describe a variety of material removal processes
in which a cutting tool removes unwanted parts from a workpiece to produce the desired shape.
If there’s one thing to also keep in mind, it’s focus. Attention can make or break the project and
there is no turning back for most of the machining processes. As a practice, we invested a great deal of
meticulousness in computing necessary calculations to determine certain parameters on the workpiece
as well as the machines’ settings, when selecting the right tools such as the cutting tools, and not to forget
prioritizing our safety with personal protective equipment (PPE). With all of these aspects taken into
account, the quality of the G-clamp can be guaranteed, which correspondingly translates to satisfactory
grades, and many problems can be sidestepped during the machining course of action.
1
2 | AIM AND OBJECTIVES
2.1 | AIM OF PROJECT
With respect to the project as a whole, this undertaking is focused toward discovering and enriching
students’ understanding in the Engineering Workshop lesson which deals with mechanical machining
and all of its processes encompassing the wellspring of machinery, tools and equipment, and materials
and consumables, including all the techniques and requirements when deploying them.
2.2 | PROJECT OBJECTIVES
Within the completion of this project, I should be able:i.
To learn the ways and rules of utilizing the various types of machinery, tools, equipment, and
raw materials correctly by getting up close and personal with the milling machine, lathe
machine, surface grinder, distinctive machining cutters and drills, tap and die, accommodative
peripherals, and many more in the mechanical engineering workshop whereby students are
obligated to conduct a practical hands-on task in fabricating an assembly of G-clamp from two
separate workpieces given with the brick-by-brick assistance and supervision of workshop
trainers as mere class lessons could not relay adequate knowledge.
ii.
To work proficiently with full meticulousness in any technical and engineering projects within
tight time constraint especially those of metalworking and manufacturing-based through
practice of fabricating a low-carbon-steel G-clamp according to the process plan whilst
rectifying any arising complications through orthodox means in order to deliver the optimal
final product quality and also ensure the safety of the handlers as well as end users as solutions
and possible causes are identified during the implementation of the project heuristically.
iii.
To meet the requirements of the Bachelor’s Degree in Mechanical Engineering (Hons.) program
of Infrastructure University Kuala Lumpur whereby prospective graduates shall satisfy specific
Programme Learning Outcomes (PLO) as well as Course Learning Outcomes of the
Engineering Workshop module which are vital to establishing the career trajectory and
professional accomplishments as prospective practicing engineers post-graduation, in
accordance with the two Programme Educational Objectives (PEO) as formulated by the
academic program through a practical project of fabrication of a G-clamp using traditional
machining methodology.
2
3 | PROJECT SPECIFICATIONS
The G-clamp project is fabricated guided by a set of pre-made technical drawings on hand
illustrating multiple views of two components or parts, i.e. the main body (cuboid block) and the
cylindrical shaft, which compose the G-clamp as one unit after machining, finishing, and assembly works
are done. This section enumerates the superficial characteristics of the final product such as the
dimensions and the material it is made of. The material properties and machining parameters are
accentuated in-depth in the next section, i.e. Project Planning and Implementation. The following table
presents the data which describe the project specifications.
Table 3.1: Specifications datasheet of Project 1, G-Clamp.
Property/Variable/Parameter
Quantity/Type
Material of construction
Low-carbon steel
Net weight
~ 0.4 – 0.5 kg
Color
Mostly silver
Resembles a ‘G’ with the cylindrical movable jaw or
Overall shape
shaft inserted
Static part
Frame
Dynamic (non-static) part
Shaft of the clamp
Dimensions
Frame / Main body (W x H x L)
(14 x 35 x 55) mm
Major diameter
15 mm
(collar)
Sliding jaw / Shaft
Minor diameter
10 mm
(shaft)
Length
65 mm
Shaft
Collar
Image 3.1: Orthographic projection of the frame.
Frame
Image 3.2: An assembly of simple G-clamp.
3
4 | PROJECT PLANNING AND IMPLEMENTATION
It holds true that a project well implemented and catered of its output which serves the objectives
of the project initially determined and is constructive in its reliability dedicated to all relevant
stakeholders is a successful project. However, there is no smooth sail in the project implementation
process without proper planning beforehand. It goes without saying that in order to accomplish this
project, there are as a matter of fact a few prerequisites I need to know such as materials science,
including the Engineering Workshop lessons which furnish me with the various essential tools,
instruments and machines used in mechanical machining, of which are elaborated in Materials and
Instruments/Equipment Selection. What’s more, precision and accuracy are two crucial elements to take
into consideration when it comes to designing and building products, even as small as the simple Gclamp. These elements can be achieved through Parameters Identification. Additionally, a product that
is efficacious can sometimes do more harm than good. For every invention on Earth, there are undeniably
hidden downsides, whether you notice them or not, and they cannot be eliminated altogether but it is
possible to minimize the risks through incorporating Safety and Quality Attributes so as to steer clear
from physical afflictions. In this report, readers will also get to the heart of the modus operandi or Work
Procedure that will definitely help prospective students of this lesson in the same project in the future.
4.1 | MATERIALS AND INSTRUMENTS/EQUIPMENT SELECTION
Table 4.1: List of materials and instruments used in implementing Project 1 and their characteristics.
Materials / Substances
Item
Function(s)
Qty.
Remark
Material: Ferrous alloy
low-carbon steel
Properties
Rectangular/Cuboid
stock (workpiece)
of
low-
carbon steel:
Frame of the G-clamp.
1
i. Contains less that
~0.25 wt % carbon
and
an
iota
of
manganese.
ii. Machinable
weldable.
4
and
iii. Nonresponsive
to
heat treatments.
iv. Soft and weak but
have
outstanding
ductility
and
toughness.
Cylindrical bar
Shaft of the G-clamp.
1
Material: Ferrous alloy
low-carbon steel
i. To lubricate the workpiece when
cutting, flushing away swarf
easily from the cutting zone.
Coolant (cutting
fluid)
ii. To reduce the amount of heat
generated
by
friction
when
-
Soluble oil-type
cutting so as to decrease wear and
extend cutting tool’s shelf life.
iii. To dial down the occurrence of
built-up edges.
Applied onto parts at work during
Lubricant
tapping and threading to bring about
longer tap life, more efficient chip
-
Used the lubricant made
for alloy steel materials.
removal, and more accurate threads.
Instruments / Equipment
Item
Function(s)
Qty.
Remark
Used to measure the
initial dimensions and
To measure the internal and external
Vernier caliper
dimensions
including
of
the
thickness,
workpiece,
depth,
and
diameters
1
cuboid
of
both
stock
and
cylindrical workpiece so
diameter with accuracy.
as to determine the
amount to cut.
To cut surfaces that are perpendicular
Face shell mill
(right angle) to the cutter’s axis and
create flat surfaces on the workpiece,
or also known as squaring.
5
It is also practically
1
interchangeable with a
fly cutter.
i. Material:
(heavy,
Carbide
dull
in
color, less tool wear,
stiffer, and suitable
for hard workpiece
materials like steels)
ii. Diameter: 60 mm
iii. Flute: 4 (finer finish,
greater feed rate,
and stronger cutter)
iv. Pitch: 90º
v. Rake angle:
+15º (Neutral rake)
vi. Relief angle: 3º– 15º
vii. Helix angle: ~40º
(suitable
for
roughing)
Flat end mill
To produce 90º-angle slot or plunge
Material: Solid carbide
cut.
A tapered spindle installed in the
Morse taper
milling machine to mount cutting tools
1
of different sizes.
As a collar to exert strong gripping
Collet and collet
force onto the face mill when
holder
installing into the milling machine’s
They are used together
1 each
with a suitably handcurated arbor with tang.
spindle through a mill chuck.
To hold a workpiece during hand
Table vise
operations, such as filing, hammering,
1
and sawing.
Has a rectangular cross
Designed for general-purpose filing
Flat file
and finishing of external and internal
flat surfaces and edges to remove burrs
and enhance the appearance of a part.
section and the edges
1
along the width are
parallel up to two-thirds
of the length, and it
tapers toward the point.
6
Brush
Machinist square
To clear away swarf off workpieces.
To check for squareness and also to
mark out the body of the workpiece.
1
1
To raise the workpiece above the
milling machine’s vise, or give
Parallels
clearance, so that the cutters are able
to come into contact with the
Used
3
parallels
of
various thicknesses or
sizes.
workpiece and to keep workpiece
parallel with the machine bed.
Used to nondestructively knock on the
Rubber mallet
clamped workpiece into place on the
1
vise of which parallels are used.
Basic handsaw
To part or hack off workpieces into
two or more pieces.
Used to truncate excess
1
part of the cylindrical
shaft.
When threading, dies
are used, whereas for
tapping, taps are used.
Diameter: 10 mm
1 type of
die, 3
Taps and die with tap
handle and die holder
To create screw threads and internal
threads, called threading and tapping
respectively.
types of
taps,
1 die
holder, 1
tap
handle
Pitch: 1.5 mm
i. Taper tap – Used to
start the thread in a
blind
hole
for
another tap to finish
so as to reduce the
amount of torque
required
to
cut
threads
from
the
surface.
ii. Plug tap – Used to
thread and get close
to the bottom of the
7
hole after a taper tap
is used.
iii. Bottoming
Used
tap
to
–
finish
threading
through
the bottom of a hole.
Material:
Titanium
nitride-coated
To produce a hole of 10 mm in
Twist drill bit
diameter through a part of the
high-
speed steel
1
workpiece.
Diameter:
8.5
mm
(metric), as per drill and
tap sizes chart.
To hold the drill bit and to be mounted
Drill chuck
into the spindle of the milling
1
machine.
Drill chuck key
To tighten or loosen the drill bit.
1
To allow the collar of the shaft to flush
Countersunk a hole for
with the surface of the workpiece
Countersunk drill bit
when fastened into the hole, and also
1
to remove any burrs that are left
To measure angles and used when
marking on workpieces.
smaller than the tap’s
major diameter.
behind after drilling the hole.
Machinist protractor
the shaft to a diameter
1
To mark the center of a point, which is
Center punch
usually done by striking it with a
1
hammer.
Vernier height gauge
Scriber
Radius gauge
To measure height on workpieces and
mark on them.
To mark lines on workpieces.
To measure specific radius which is to
be marked on or cut off a workpiece.
1
surface for checking, gaging, and
marking of workpieces.
8
with a surface table.
1
1
To provide a precision reference
Surface table/plate
It is used in conjunction
1
Used
convex
radius
gauge of radius 10 mm.
i. Diameter: 10 mm
Corner rounding end
mill
To round off the corners of the
workpiece (frame).
1
ii. Material:
Solid
carbide
iii. Flute: 4
T-wrench
Lathe chuck wrench
Lathe tool post
wrench
To tighten or loosen the nut or bolt
head on the milling machine’s head.
To tighten/close or loosen/open the
jaws of chuck on the lathe machine.
To tighten or loosen the nuts on the
lathe machine’s tool post.
Loosening of the nut in
1
turn loosens the drawbar
within the head.
1
1
To raise the lathe cutter by filling
spaces between the cutter and the base
Shims
of the tool post so as to level the
4
cutting edge with the workpiece
clamped onto the chuck.
Used
a
right-hand
single-point
turning
high-speed
(shinier,
lighter)
Lathe tool bit
Acts as a blade to remove parts from
rotating workpieces.
steel
softer,
and
cutting
tool,
which cuts the material
1
while moving leftward.
The thumb of a right
hand
represents
the
tool’s feed direction.
The cutting edge is
situated at the left side
of the tool.
Lathe tool bit holder
with key
Center drill
To hold the tool bit, at an angle of
about 15˚.
Right-hand type;
1
Is held by the lathe’s
tool post.
To produce an accurate center hole in
the face of a rotating workpiece.
9
Before the live center
1
can be used to support
the load of a longer
workpiece,
a
small
center hole must be
made.
To ensure concentricity on workpieces
Both center drills and
accurately and to support longer
Live center
workpieces where the feed would
1
deflect them out of place or chatter
tool
To produce better gripping surface on
a metal part especially knobs where
into the tailstock of the
lathe machine.
might occur.
Single-wheel knurling
live centers are installed
1
turning them by hand is required.
Used
diamond-pattern
knurling tool.
To make complex, compound cuts
from metal workpieces and drill holes
Vertical milling
machine
with
the
revolving
machine’s
accommodation
cutter
of
a
in
which
the
spindle
axis
is
For drilling operation,
1
the quill feed handle is
used to feed the drill bit
into the workpiece.
perpendicular to the worktable.
To cut, face, drill, and knurl spinning
Engine lathe machine
workpieces with the cutting tool being
Has a four-jaw chuck
1
stationary.
attached
to
the
abrasive
grains
faceplate.
Has
bonded into a wheel that
Surface grinder
To improve the surface finish of a
workpiece.
rotates
1
against
the
workpiece and most of
the dynamic parts are
driven
by
mechanism.
10
hydraulic
4.2 | PARAMETERS IDENTIFICATION
i.
Speed (face milling / squaring)
• Material of cuboid stock: Low-carbon steel (also known as mild steel)
• Material of face mill cutter: Carbide
• Diameter of cutting tool = 60 mm
• Cutting speed, CS [m/min] = 100 (constant, recommended for the type of work material)
𝐶𝑆 × 1000
• Spindle speed, RPM [rev/min] = 𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑜𝑓 𝑐𝑢𝑡𝑡𝑒𝑟 =
100 ×1000
𝜋 × 60
= 530 (HIGH SPEED)
Image 4.1: Table of cutting parameters of milling operations from the machinist handbook.
ii.
Feed (face milling / squaring)
• Spindle speed, RPM = 530 rev/min
• Number of flutes, Z = 4
• Feed, 𝑓𝑍 = 0.25 mm/tooth (based on table of cutting parameters of milling operations)
0.25 𝑚𝑚/𝑡𝑜𝑜𝑡ℎ
• Chip load [IPT] = (
25.4
) in/tooth = 0.00984 in/tooth
• Feed rate, FR [IPM] = RPM × 𝑓𝑍 × Z = 530 × 0.25 × 4 = 530 mm/min = 20.87 in/min
𝐼𝑃𝑀
• Feed rate, FR [IPR] = 𝑅𝑃𝑀 =
20.87
530
= 0.039 in/rev;
= IPT × Z = 0.00984 × 4 = 0.039 in/rev ≡ 0.99 mm/rev
11
iii.
Tap drill size
• Hole size on G-clamp frame = M10 x 1.5
• Tap’s major diameter, MD = 10 mm
• Pitch of the thread = 1.5 mm
• Tap drill diameter, TD = MD – Pitch = 10 mm – 1.5 mm = 8.5 mm
iv.
Speed (drilling)
• Material of cuboid stock: Low-carbon steel (also known as mild steel)
• Material of drill bit: HSS
• Diameter of drill = 8.5 mm
• Cutting speed, CS = 100 surface ft/min ≡ 30 m/min (according to table of cutting parameters
for drilling process)
• Spindle speed, RPM [rev/min] =
30 × 1000
𝜋 × 8.5
= 1123 (HIGH SPEED)
Image 4.2: Table of cutting parameters of drilling operation from the machinist handbook.
v.
Feed (drilling)
• Drill/Hole diameter = 8.5 mm
• Feed rate, FR [mm/rev] = 0.18 (according to table of cutting parameters for drilling operation)
12
vi.
Speed (turning)
• Material of cylindrical workpiece: Low-carbon steel (also known as mild steel)
• Material of tool bit: High-speed steel (HSS)
• Initial diameters of cylindrical workpiece, 𝑑0 = 18.96 mm (minor - shaft), 20.40 mm (major collar)
• Diameters of machined part, 𝑑1 = 10 mm (minor), 15 mm (major)
• Depth of cut =
(20.4 − 15) 𝑚𝑚
2
= 2.7 mm
• Cutting speed, CS [m/min] (speed of workpiece surface relative to the edge of the cutter during
a cut) = 30 (according to table of cutting parameters for turning process)
• Spindle speed, RPM [rev/min] (rotational speed of spindle and workpiece) =
𝐶𝑆𝑡𝑜𝑜𝑙 × 1000
𝜋 × 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑤𝑜𝑟𝑘𝑝𝑖𝑒𝑐𝑒
=
30 × 1000
𝜋 × 20.4
= 468
Image 4.3: Table of cutting parameters of turning operation from the machinist handbook.
vii.
Feed (turning)
• Feed rate, FR [mm/rev] = 0.3 (as per table of cutting parameters for turning operation)
13
viii.
Machine time (turning)
• Length, 𝑙 of cylindrical workpiece to cut (for shaft part) = 50 mm
• Feed rate, FR = 0.3 mm/rev
• Spindle speed, RPM = 468 rev/min
50
• Time required for complete cut = 0.3 × 468 = 0.36 minutes ≡ 21.6 seconds
ix.
Speed (center drilling)
• Material of cylindrical workpiece: Low-carbon steel (also known as mild steel)
• Drill diameter, D = ~6 mm
• Cutting speed, CS [m/min] = 23 (according to table of cutting parameters for drilling process)
• Spindle speed, RPM [rev/min] =
23 ×1000
𝜋×6
= 1220
Image 4.4: Table of metric center drill sizes.
x.
Feed (center drilling)
• Feed rate, FR [mm/rev] = 0.14 (average, according to table of cutting parameters for drilling
operation)
xi.
Speed (knurling)
• Diameter of part to knurl = 15 mm
• Cutting speed, CS [m/min] = 50 (recommended, to prevent seizing of the rolls)
• Spindle speed, RPM [rev/min] =
50 × 1000
𝜋 × 15
= 1061
14
4.3 | SAFETY AND QUALITY ATTRIBUTES
If there is one thing to keep in mind when it comes to personal physical safety at the machining
workspace, it’s certainly preparing myself with personal protective equipment (PPE) such as wearing of
safety googles, lab jacket, safety boots, and gloves when machining to avoid unforeseen and uncalledfor incidents to happen to me that could inflict serious injuries or even worse due to misoperation or
misconduct during work, unmaintained hazardous machinery, or simply negligence.
Not only that but the safe-to-use condition of the product per se is not an option either, which is
part and parcel of quality control, failing which the product may engender unwarranted by-product more
than what the end-user has bargained for. One notable safety provision I did unto the two component
workpieces is the removal of burrs, or called deburring. Burrs are raised edges or small pieces of material
that remain attached to a workpiece after a cutting process. They are usually unwanted pieces of material
and are removed with deburring tools using various types of method. As for this activity, I used a flat
file with the aid of a table vise to get rid of the burrs on the cuboid stock and cylindrical workpiece before
and after any machining processes are done. We need to debur workpieces so that the edges do not
interfere with the fitting or movement of parts and also to ensure proper finishing when doing surface
grinding. More importantly, burrs are sometimes so minute that they are not noticeable through naked
eyes by anyone who handles the workpiece and may cause injury due to the sharp edges. In terms of
quality, if burrs are remained, the workpiece cannot be accurately set onto the chuck of a lathe or the
vise of a milling machine. To this end, the piece will be mounted at askew or off-center. Apart from that,
if the burrs are left undeburred, the size of the part cannot be accurately measured.
On the other hand, to account for longer workpieces’ shelf lives and quality, with my safety
safeguarded into the bargain, the workpieces are handled with care at all times so that they are not
dropped on the floor accidentally. This is because at a high position, the object embodies considerable
potential energy, wherein the high impact received by the falling object upon hitting the hard solid ground
and abruptly stopped may cause it to deform, and consequently diminishing its strength due to fracture.
Which is why it is born in mind never to change the speed, especially of a running lathe machine, or
withdraw the tailstock spindle when the workpiece is rotating or it can be thrown out not only to damage
it but also poses danger to me as the operator.
As far as product quality is concerned, another factor to consider is chatter. Chatter is the
harmonic machining vibration due to low rigidity of the cutting tool, toolholder, or spindle running at
high speed. Chatter can be detected when the milling machine or lathe machine generates a loud,
dissonant noise. The vibration leaves visible waves on the surface of the workpiece, known as chatter
15
marks. Chatter can interfere with the accuracy of the operation, cause poor surface finishes, and shorten
tool or machine life. One of the many ways to attenuate chatter while milling or lathing is making the
cutting tool and the machine as rigid as possible. For instance, on the lathe machine, when center drilling,
I have set down the brake of the tailstock so that the spindle is seized up from spinning when the drill is
plunged into the center of the opposing end of the rotating cylindrical workpiece by means of applying
pressure with the aid of the tailstock handwheel. Otherwise, not only does the feed rate becomes
inaccurate, but chatter can also occur on the cross sectional surface of the workpiece due to vibrating
center drill. Secondly, the correct spindle speed and feed rate are calculated prior to cutting. Usually, too
high spindle speed or too low feed rate is responsible for the flaw. Therefore, to be safe, the spindle speed
and feed rate of a machine and cutting tool are determined by applying the aforementioned formulas
correctly by first understanding the types of material for both workpiece and cutting tool, cutting speed,
and other significant parameters. Another method I employed was using a face mill cutter with an
appropriate length-to-diameter ratio (L/D) for the purpose of squaring or face milling the cuboid stock
by referring to a given rule of thumb.
Another imperative quality aspect to reckon with when developing the G-clamp is the threads of
the cylindrical shaft and frame hole. When making threads on both of the components, it is imperative
to apply proper lubricant because it can ensure longer tap life, better shaft shape control, smoother and
more accurate threads, less resharpening, and more efficient chip removal while tapping or threading
manually with tap and die. Without lubrication, it will be hard to intermittently reverse the turn direction
of the tapping or threading process to wash away the chips that are accumulating on the cutting edges of
the tool as lubricants work wonders in paring down friction. Any purposeful force exerted to cut threads
on the parts without applying this liquid adequately will cause permanent deformation on the body of
the work material as low-carbon steel is very malleable and ductile. It is also important to take heed of
the right method of applying the lubricant. For tapping, the nozzle of the lubricant receptacle should be
pointing as close to the surface of the part as possible, be positioned at an angle close to the axis of the
tool, and pointing directly into the hole to flush chips from the teeth of the tool.
Last but not least, for the sake of quality as well as safety of the G-clamp, I used a corner rounding
end mill to round off two corners of the frame of the G-clamp. They do not solely offer aesthetic feature
but also to reduce edge chipping. In mechanical engineering jargon, edge chipping is simply the breakage
as the result of an overload of mechanical tensile stresses at parts with high stress concentration, such as
the sharp corners of the cuboid stock. I have learned and applied the knowledge I have attained through
Engineering Materials lesson ergo. The rounded corners will also come in handy when the G-clamp is
being held on the hand as the user can comfortably clench onto the frame on the longer rectangular side.
This feature can also be attributed to ergonomics in the design of the project.
16
4.4 | WORK PROCEDURE
Part: Low-carbon steel cuboid stock
1.
All the views of the given technical drawings of the end product are studied and examined.
2.
The material the rectangular workpiece/stock is made of is identified – low-carbon steel.
3.
The initial dimensions are measured using a vernier caliper and how much to rough cut are
computed.
4.
The stock is deburred by using a flat file, facilitated by a table vise.
5.
A suitable cutting tool assembly which includes befitting collet and arbor is selected for the first
machining process – squaring or face milling, namely a face shell mill. An operator can also opt
for a fly cutter.
6.
By referring to the machinist handbook, particularly on the table of cutting parameters for milling,
the cutting speed, CS of the material is known.
7.
The spindle speed, RPM is computed by using a formula that associates the cutting speed, CS and
diameter of the cutting tool.
8.
The feed rate, FR is calculated by using a formula that applies the feed, 𝑓𝑍 as per the machinist
handbook; spindle speed, RPM; and number of flutes of the face mill.
9.
The milling machine is set up and initialized with the cutting tool assembly mounted into the mill
chuck by leveraging a T-wrench, while the workpiece is clamped on the milling table with the vise
properly. Parallels are also used to give clearance to the workpiece as well as to set it at right angle
to the cutter’s axis.
10.
The spindle speed, RPM is set on the milling machine.
11.
With the spindle spinning, the Z-position of the workpiece on the table is zeroed out on the digital
readout and vertical knee traverse crank dial when slight screech is heard when the teeth or cutting
edge of the cutting tool has bitten the surface of the workpiece.
12.
The workpiece is moved away from the cutting tool laterally using the longitudinal table traverse
hand crank.
13.
A small amount of depth of cut is set on the vertical knee traverse crank dial, e.g. 1 mm.
14.
The table is moved side to side by using the longitudinal table traverse hand crank for manual
movement or table power feed for automatic movement when squaring the stock. Coolant is also
applied throughout the milling process.
15.
The steps 13 – 14 are repeated with the depth of cut gradually increased by 1 mm and the cutting
tool fed into the stock until the affected surface of the stock looks dressed.
17
16.
This process is done for all four sides of the stock until they are equally square and the correct
dimensions are achieved in the order of adjacent larger sides and then followed up by the adjacent
smaller sides. A machinist square is used to check for the squareness of the workpiece.
17.
The squared stock is deburred again.
18.
By using a vernier height gauge, the tangent points of the corner radii on the larger surface near
one of the longer edges of the stock are marked on top of a surface table.
19.
By placing a 10-mm convex radius gauge on the surface in consideration, a scriber is used to
inscribe arcs connecting the tangent points for both corners.
20.
Steps 5 – 12 are repeated with the cutting tool changed to a 10-mm corner rounding end mill.
21.
At the part where the corner is to be cut, one corner radius flute of the cutting tool is translated to
align with the marked radius on the stock.
22.
The corner rounding cut is made as the length of cut (LOC) is advanced or fed through one corner
of the stock.
23.
The stock is turned over the other way around and steps 21 – 22 are repeated until the desired shape
is achieved.
24.
The workpiece is deburred again.
25.
Steps 5 – 15 are repeated by using a suitable flat end mill to rough cut a slot profile of 35-mm long
and 20-mm wide while moving the table with the longitudinal table traverse hand crank and cross
feed handwheel in both climb and conventional milling fashions.
26.
The center of the hole for the shaft is measured and marked using the vernier height gauge.
27.
A pilot hole is made on the marked center so that it is more apparent and will ease the drilling work
by using a center punch and one gentle strike of a mallet with the workpiece being clamped in the
table vise.
28.
Steps 5 – 10 are repeated by using an 8.5-mm drill bit with the correct drill chuck.
29.
The marked hole center of the workpiece which is clamped in the vise is set to be collinear with
the drill bit.
30.
The hole is drilled through by using the quill feed lever on the milling machine.
31.
The cutting tool is changed to a countersunk drill bit and a countersunk is made at the top of the
hole.
32.
The workpiece is deburred and clamped in the table vise with the hole to be tapped facing outward.
33.
The tapping process for making threads in the hole is started by plugging the taper tap of 10 mm
in diameter into the tap handle.
34.
The handle is held at 90 ̊ to the surface of the hole where the tap’s head is placed directly onto.
35.
The handle is turned in one direction of the rotation while periodic reversal is done to break the
chips and prevent them from crowding, with the sufficient application of lubricant into the work
region.
18
36.
After the tapping is made about a quarter of the depth of the hole, the cutting tool is changed to a
plug tap and the tapping process is resumed in the through-hole.
37.
As the tap gets close to the bottom of the hole, the cutting tool is changed to a bottoming tap and
the tapping work is exercised through the end of the hole.
38.
For the finishing work, the workpiece is held firmly on the magnetic chuck of the surface grinding
machine, positioned at the grinding area of the abrasive wheel.
39.
The abrasive wheel is checked for quality and ensured that it is installed sturdily, and the speed of
the automatic movement of the reciprocating table is set by using the lever located at the base.
40.
The first count of depth of cut is set using the hydraulic switches and buttons mechanism for great
precision while monitoring the digital readout.
41.
The larger surface of the stock is allowed to surface finish with the abrasive wheel and coolant
running, making passes back and forth along the x-axis.
42.
Once the nominal surface has been sufficiently finished, the opposite larger surface is ground by
turning over the stock.
Part: Low-carbon steel cylindrical shaft
1.
All the views of the given technical drawings of the end product are studied and examined.
2.
The material the cylindrical stock is made of is identified – low-carbon steel.
3.
The initial dimensions such as the length and diameter are measured using a vernier caliper and
how much to rough cut are computed.
4.
The workpiece is deburred by using a flat file, facilitated by a table vise.
5.
An HSS right-hand tool bit is acquired and it is affixed onto a tool bit holder which is mounted
onto the tool post at the compound rest of the lathe machine. If the nose of the cutting tool is not
sharp enough, it is sharpened with a bench grinder.
6.
By referring to the machinist handbook, particularly on the table of cutting parameters for turning
and facing, the cutting speed, CS, according to the cutting tool’s material and depth of cut of the
workpiece is known.
7.
The spindle speed, RPM is computed by using a formula that associates the cutting speed, CS and
the initial diameter of the workpiece.
8.
The feed rate, FR is determined by referring to the tabled data on hand.
9.
The cylindrical workpiece is clamped onto the four-jaw chuck at the headstock horizontally.
10.
For the first operation – facing, the tool bit is set at 45º by swiveling the compound rest so that the
nose is pointing and touching the center of the circular cross section of the workpiece which is
determined by making the tool bit’s nose and the tip of the lathe center mounted into the tailstock
perpendicular to each other.
19
11.
After the spindle speed, RPM is set on the machine, the exposed end of the workpiece is faced
radially by making multiple passes from its center by moving the cross slide with its handwheel
for a very thin depth of 1 mm each time until the surface looks smooth and finished.
12.
A center drill with its chuck is installed into the tailstock assembly’s barrel and then it is locked
using the lever.
13.
The tailstock is moved closer until the end of the clamped workpiece is touched by the tip of the
drill by using the handwheel and pushing the tailstock assembly along the ways of the machine.
14.
The spindle speed, RPM for drilling is set after it is computed and the machine is turned on.
15.
The drill is fed into the center of the end of the workpiece by advancing the barrel of the tailstock
for a depth equal to the length of the drill tip.
16.
The center drill is changed to a live center in which it is used to support the workpiece through the
center hole made previously as more area of the cylindrical workpiece must be taken out of the
chuck in order for the body to be cut.
17.
The tool bit on the tool post is set perpendicular to the workpiece.
18.
With the workpiece rotating at the spindle speed, RPM for turning, the nose of the tool bit is slowly
advanced forward in the y-axis by using the cross slide handwheel so that the curved surface of the
workpiece is touched until a soft screeching sound is heard.
19.
The y-position is zeroed out on the dial of the cross slide handwheel, and then the carriage is moved
away along the ways.
20.
The end of the workpiece where the collar is to be made is rough turned by setting a depth of cut
of 1 mm by using the cross slide handwheel.
21.
The tool bit is fed axially along the body of the workpiece by moving the carriage toward the left,
parallel to the axis of rotation with gradual depth of cut increment of 1 mm until the desired
diameter of the collar is produced. Coolant is applied throughout the process.
22.
Next, the end of the workpiece is flipped and clamped onto the chuck and the similar turning
process is performed for the shaft of the desired diameter. The step, where the collar and the shaft
are separated are determined by prior measurement using the vernier caliper’s depth rod.
23.
Excess part of the shaft is parted by using a hand saw with the aid of a table vise.
24.
Steps 9 – 11 are repeated to finish the end’s surface where the excess part is severed off.
25.
The workpiece is clamped onto the spindle with the collar end situated outside of the spindle, and
the diamond-pattern knurling tool is mounted on the tool post, perpendicular to the workpiece
shaft.
26.
With the computed spindle speed, RPM set, the knurling tool is pressed against the rotating shaft
until the serrated pattern is produced on the shaft.
27.
The carriage is moved toward the left automatically along the shaft’s length by using the power
feed mechanism until the shaft is fully knurled.
20
28.
Finally, the shaft is inserted perpendicularly into an M10 x 1.5 die which is mounted in a die holder.
29.
The shaft is lubricated sufficiently while it is threaded, with intermittent reversals of the sense of
the holder to break the chips and prevent them from crowding.
30.
The finished frame and shaft are cleaned and polished, and the component parts are ultimately
assembled to make the G-clamp.
5 | FINDINGS AND DISCUSSION
After all things considered and all is said and done, it is safe to say that there are a couple of
significant facts and figures to interpret and articulate with respect to this subject matter in light of new
understanding or insights that emerged throughout the implementation of the project which could be
correlated with what are known about the processes involved in mechanical machining. These
descriptions can generally account for useful contribution to knowledge, whether theoretically or
empirically so that future projects of the same kind could be ameliorated to prevent any adverse effects
from precluding the work processes, thereby transpiring an organized and effective workflow. Therefore,
this section presents the necessary explanations in Discussion. In addition, in making this project a
success, numerous technical stumbling blocks are inevitable. Nevertheless, by proactively finding and
developing solutions in a task force based upon a synthesis of progressive findings and profound
knowledge of machining, the issues can be overcome. This information is fleshed out in Challenges
Encountered and Countermeasures.
5.1 | DISCUSSION
i.
Effects of depth of cut (DOC)
• Larger DOC gives higher material removal rate (MRR), as MRR is proportional to the speed,
feed, and DOC.
• Productivity of machining can be enhanced by employing larger DOC, thereby minimizing
machining cost (in real-life applications).
• Cutting force depends on chip load, which is proportional to DOC. Thus, larger value of DOC
can increase cutting force, which may hamper machining performance and induce chatter.
• Higher DOC may also break the tool bit.
• DOC influences chip thickness, type of chips produced, shear deformation, etc., which are
indication of machinability.
21
ii.
Selection of depth of cut (DOC)
• Productivity – Cuts down machine time, thus improving productivity and efficiency.
• Quality and quantity of cut – For finish cut such as the final facing of the end of the shaft on
the lathe machine, lower DOC is imparted, whereas for rough cut such as cutting a slot profile
and rounding the corners of the frame on the milling machine, larger DOC is made instead.
• Machining operation type – Various machining operations possess the capability to handle
various ranges of DOC. For example, milling operation using the face mill cutter can handle
a larger DOC, whereas operation like knurling is limited in its magnitude.
• Strength of cutting tool – For machining hard and brittle materials, a lower value of DOC is
of ideal choice, otherwise the force exerted may be very high and chances are, the cutting tool
will break.
iii.
Selection of cutting tools’ angles
• Helix angle – The angle formed by a line tangent to the angle of the flute grind, and parallel
to the centreline of the tool. The helix angle of end mills and drill bits is a variable that
determines chip formation. A medium helix angle of about 40º is ideal for operations like
squaring or face milling as it is tailored for both roughing and finishing. Larger helix angle of
about 45º is suitable for soft materials and aggressive finishing works, and it contributes to
easy chip flow, whereas smaller helix angle of about 35º is optimized for tough materials and
rough cuts, and it contributes to hard, short chips.
• Relief angle / Clearance angle – The angled relief behind the cutting edge that is designed to
avoid the rubbing of the cutting tool and the workpiece, and provide clearance to the cutting
action, hence reducing tool wear. For the face milling or squaring, the face mill cutter selected
has an angle of between 3º to 15º.
• Rake angle – The inclined angle of the top surface of the tooth that makes contact with the
chip. The rake controls the degree of cutting forces and cutting edge strength. For the face
milling or squaring, the face mill cutter selected has an angle of between +15º. Positive rake
angle reduces the chip thickness and shearing occurs smoothly.
iv.
Milling technique
• Climb or down milling technique is primarily employed in this project because it decreases
chip thickness from the start of cut, gradually reaching zero at the end of the cut. It prevents
the edge from rubbing and burnishing against the surface before engaging in the cut, thus
increasing tool life.
22
5.2 | CHALLENGES ENCOUNTERED AND COUNTERMEASURES
i.
Problem: Excessive chatter marks are formed on the workpieces when milling and lathing.
Solutions:
• In an ideal world, chatter is technically proven inevitable. It is the direct result of vibrations
and sounds when the cutting tool engages with the workpiece. However I toned down chatter
by checking the rigidity of the tool’s fixturing to make sure that it does not wobble.
• Ensuring that the fixturing of the workpieces being clamped in the vise (for milling), chuck
(for lathing), and magnetic chuck (for surface grinder) is substantial.
• Slightly increasing the feed.
• Reducing the spindle speed, RPM of the machine.
• Taking shallower cut.
• Filing the workpieces.
ii.
Problem: Work surface of the cuboid stock looks uneven and feels rough.
Solutions:
• Increasing the system rigidity.
• Increasing the spindle speed, RPM of the machine.
• Reducing the feed.
• Changing to cutting tool with greater helix geometry.
• Changing to cutting tool with more flutes.
iii.
Problem: Crooked cylindrical workpiece when threading.
Solutions:
• Making sure to use a low-carbon steel workpiece that was kept in climate-controlled room
with proper surrounding condition factors, namely temperature and humidity.
• The low-carbon steel workpiece is strengthened and improved of its mechanical properties
through strain hardening or work hardening (low-carbon steels are non-responsive to heat
treatment).
• Holding the die holder’s handles and turn with both hands so that stress is not exerted on the
workpiece asymmetrically, causing the cut to go off-center. This action ensures even
distribution of stress and maintains symmetry.
• Slowly taking the time to thread the workpiece and do not hurry.
23
iv.
Problem: Cutting tool wearing at cutting edges or teeth causes poor performance.
Solutions:
• Adjusting (increasing or decreasing) the speed and feed wisely. A feed rate that is too light
will cause excess rubbing.
• Changing the cutting tool with a different geometry.
• Changing the cutting tool’s material grade.
• For the lathe tool bit, the bench grinder is used to sharpen its nose and the side cutting edge.
v.
Problem: Unintentional feed or edge breaking happens during milling operations.
Solution:
• In down/climb milling, the cutter tends to be pulled into the workpiece due to backlash (the
play between the lead screw and the nut in the saddle) or hysteresis as the cutting tool is fed
with the direction of rotation. Therefore, in the event of edge breaking, up/conventional
milling shall be opted for.
vi.
Problem: Backlashes in milling and lathe machines give rise to imprecise setting of the position
of workpiece and cutting tool, hence cutting operations.
Solutions:
• Regular maintenance of the machines, on the moving mechanical parts in particular.
• As a possible solution, making use of anti-backlash nut on the lead screw.
• Monitoring the digital readout for precise zeroing of the table and saddle assembly’s position
and its changes in real-time.
• Controlling and compensating for thermal influences in the work environment to avoid
expansion or contraction of the moving parts.
24
6 | CONCLUSION
For some final words, this section of the report wraps up the project of a simple G-clamp with
some useful key takeaways to share based on the works that were done and the results that were produced.
The gists presented in Inferences basically are the synthesis and summary of the machining undertaking
and conclusions derived from the justified works. Equally important, taking advantage of the things
learned, there are also a few suggestions to consider should this work be reproduced, as enunciated in
Recommendations.
6.1 | INFERENCES
To sum it all up, from this project, I have learned through pragmatic approach on how to prepare
for workshop machining operations and operate chiefly the milling machine, lathe machine, surface
grinding machine, and several other tools. From what I understand, the milling machine is used for
cutting certain metal blocks of workpiece that typically have flat surfaces into multifaceted shapes and
sizes, and they are fixed in a stationary state with the cutting tool being set in motion, while the lathe
machine is used for cutting round, circular, and cylindrical metal workpieces, and they are in rotary
motion. Furthermore, I have learned that the diverse end mills and drill bits are in fact made for some
reasons, and that wise decision in selecting the cutting tools is of the essence. As a case in point, when
milling, we should not merely pick the type of end mill meant for the type of milling operation we are
going for, but should also select one by looking at its number of flutes, tooling material, etc. based on
the material of the workpiece, because these factors determine the cutting speed, CS; machine speed,
RPM; and chip formation. It is learned that the cutting speed is proportional to the softness of the
workpiece material, and also the strength of the tooling material. Low-carbon steel is regarded as a hard
material relative to lead. On the other hand, carbide tooling material is stronger than high-speed steel
(HSS). Likewise, for the number of flutes, it is proportional to the strength of the tooling material and
hardness of the workpiece material, but inversely proportional to the chips clearance. One major setback
that I faced during the implementation of this project was the cylindrical shaft became crooked and
eventually fractured when threading (it was replaced with a new part after that). For this reason, I checked
for its material quality in an attempt to investigate the reason behind the deformation through spark
testing. The cross-sectional area of the failed material was ground onto the grinding wheel of a bench
grinder to observe the sparks emitted. The sparks were compared with that of emitted by a good mildsteel part. From this test, it was found that the failed mild steel did not produce bright, tiny and long
spark stream just like the good one did but instead emitted dark and short spark stream. Thus, an inference
can be made that the mild-steel shaft failed due to either sudden temperature change such as ductile-tobrittle transition temperature or low yield strength.
25
6.2 | RECOMMENDATIONS
It is recommended that:i.
Edge-finder is to be used on the milling machine to accurately align the cutting tool with the
workpiece center, workpiece edges, layout markings, or previously machined feature or profile
when zeroing the coordinates. It will come in handy especially when making holes when their
centers must be correct.
ii.
Dial indicator is to be used on the lathe machine to accurately measure and adjust the centering
of a workpiece in a four-jaw chuck. It can indicate the run out (the misalignment between the
workpiece’s axis of rotational symmetry and the axis of rotation of the spindle) of the workpiece
while the dial indicator’s probe is touching the outer surface of the workpiece, with the aim of
minimizing it to a suitably small range by making small chuck jaw locking adjustments while
the other end of the workpiece is supported by the lathe center.
iii.
The drilled hole should be subsequently bored and reamed using their respective tools to finish
the surface of the hole and improve dimensional accuracy.
iv.
Computer numerical control (CNC) is also to be employed for the purpose of practical learning
in the workshop, besides attaining greater precision and accuracy; saving time, energy and cost
for machining and maintenance as it works by computerized automation and electronic means;
and providing more complex functionality in multifaceted machining in real-life applications.
v.
A micrometer screw gauge should be used to measure the outer diameters of the cylindrical
workpiece because it accounts for greater precision of 0.01 mm’s least count.
26
7 | REFERENCES
7.1 | REFERENCE LIST
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iv.
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28
APPENDICES
ii