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Prepared by : Mechanical Teacher Module 1: Introduction to Machining 1
Institute of Applied Technology
Year 12
Machining
Semester 1
September 2013
Module 1: Introduction to Machining Prepared by : Mechanical Teacher 2
Machining
Module 1: Introduction to Machining
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Video 1 – The Lathe
Lets Warm Up – Think, Pair, Share
Minds On Activity
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 4
Objectives
After the completion of this unit, you will be able to:
1. Recognize the function and importance of machine tools.
2. Differentiate between the basic categories of machine tools.
3. Read and understand the main technical drawings’ symbols.
4. Take precise measurement using Vernier Caliper and Micrometer.
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 5
1.0 Introduction
How much a nation produces determines how well its people live.
Today, every known Product from a paper clip to a space vehicle
is a product of machine tools.
If machine tools are not used directly in the manufacture of the
product itself, machine tools are required to produce the
machinery and the equipment necessary for its processing.
Without machine tools, modern civilization could not exist.
Think of what would the world be without the automobile,
electric power generators, aircrafts… etc. Fig. 1.1.
Fig. 1.1
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 6
1.1 What is Machine Tool?
A machine tool is a power-driven machine not
portable by hand, used to shape or form metals or materials by cutting, impacting, forming, eroding, or a combination of these processes.
Example of machine tools is shown in Fig. 1.2
Fig. 1.2: CNC milling is one of
the machine tools
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 7
2.0 Basic Machine Tools
There are three main categories of machine tools:
1. Non-chip producing machine tools.
2. Conventional chip producing machine tools.
3. New Generation of machine tools.
Non-chip producing machine tool
2.1 Non-chip producing machine tools This type of machines shapes metals by shearing, pressing, and drawing to a desired shape. Fig. 1.3
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 8
2.0 Basic Machine Tools
2.2 Conventional chip producing machine tools
Machines of this type shape metal to a size and contour by cutting away the unwanted portions in form of metal chips. Fig. 1.4
The collection of material-working processes in which conventional machine tools are used is called conventional machining.
This is the type of machine tools that we are going to cover in this course.
Process of Chip removal
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 9
2.0 Basic Machine Tools
Machine tools products
Fig. 1.5 shows many parts of different shape that made by this type of machine tools.
These parts could be used in the production of engines, machines or any industrial product.
With conventional machine tools, the operator uses machine hand-wheels to manually control the table or spindle movements to produce the part. Fig. 1.6
The accuracy of the part produced depends upon the skills of the operator or machinist.
Hand wheels of conventional machine tool
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 10
2.0 Basic Machine Tools
Lathe and Milling machines are examples of this type of machine tools.
Fig 1.7 (a) shows lathe machine.
Fig. 1.7 (b) shows milling machine.
Conventional lathe machine
Conventional milling machine
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 11
2.0 Basic Machine Tools
2.3 New Generation of machine tools
To increase the rate of production as well as
preciseness of machined parts, automatic programming has also been added to conventional
machines and called NC or CNC (Computer Numerical Control) machines.
With Computerized Numerical Control machine tools (example, CNC lathe and CNC milling), the programmer
programs the machine control unit (MCU), through
the use of symbols, letters, and numbers
(coded instructions) which automatically control the machine tool movements to produce the desired part.
Fig 1.8
Computerized Numerical Control machine tool
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 12
2.0 Basic Machine Tools
The cutting action of CNC machine tools is similar to conventional machining.
Fig 1.9 (a) and 1.9 (b) show a CNC milling
machine and CNC lathe machine respectively.
Electric discharge machines (EDM) and
electrochemical machines are also examples
of new generation machine tools but are
completely different in construction and in the
way they shape metals so they will not be part
of this course. (b) CNC lathe machine
Fig. 1.9 (a) : CNC milling machine
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Video 2 – Thread Cutting
Lets increase our knowledge!
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 14
3.0 Skills required to use Conventional Machine Tools
In order to machine any part using the chip removal machine tools, you need to:
1. Acquire certain skills, ex: for the part shown in Fig. 1:10.
2. Have the skills of drafting, read drawings and taking precise measurements.
Machined Part
Drilling bit
Module 1: Introduction to Machining Prepared by : Mechanical Teacher
Show and Tell
WHOEVER PARTICIPATES & WINS,
PLENTY OF BONUS MARKS!
Think Fast…
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 16
3.1 Engineering Drawing
Engineering drawing is a common language by which drafts persons, tool designers, and engineers indicate to the machinist and toolmaker the physical requirements of a part.
Drawings are made up of a variety of lines, which represent surfaces, edges, and contours of a workpiece.
By adding symbols, dimension lines and sizes, and word notes, the draftsperson can indicate the exact specifications of each individual part. Fig. 1.11
Technical Drawing
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Recap from AutoCAD
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 18
3.1 Engineering Drawing
3.1.1 Orthographic Projection:
Orthographic Projection is a way of drawing a 3D object from different directions.
Usually a front, side and top view (Three standard views) are drawn so that a person looking at the drawing can see all the important sides.
Orthographic drawings are useful especially when a design has been developed to a stage whereby it is almost ready to manufacture. Fig. 1.12.
Three standard views in orthographic drawings
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Recap from AutoCAD
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 20
3.1 Engineering Drawing
3.1.2 Sectional Views:
Sectional views are used to clarify interior or hidden details on a multi-view drawing of an object. Fig. 1.13
Sectional views are located by creating a Cutting Plane Line in one view.
"Section Lining" or "Hatching" is added to the Section view mainly to distinguish the solid portions from the hollow areas of an object.
Sectional View
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Recap from AutoCAD
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.1 Engineering Drawing
3.1.3 Isometric drawing:
Isometric drawings consist of two-dimensional drawings that are tilted at some angle to expose other views and give the viewer the feeling that what he or she is viewing is a three-dimensional drawing. Fig. 1.14
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Isometric Drawing
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.1.4 Tolerance:
It is the permissible variation of specified size of a part.
The basic dimensions plus or minus the variation allowed is given on a drawing.
Example:
From Fig.1.15 the following can be calculated:
The largest permissible dimension = 70.1 mm (70 + 0.1 = 70.1 mm)
The smallest permissible dimension = 69.7 mm (70 – 0.3 = 69.7 mm)
The tolerance = 70.1 – 69.7 = 0.4 mm
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3.1 Engineering Drawing
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.1 Engineering Drawing
3.1.5 Allowance:
Allowance (Fig. 1.16) is the intentional difference in the sizes of mating parts, such as the diameter of a shaft and the size of the hole.
On a shop drawing, both the shaft and the hole would be indicated with maximum and minimum sizes to produce the best fit.
Fit is the range of tightness between two mating parts.
24
There are two general classes of fits: 1. Clearance fits, whereby a part
may revolve or move in relation to a mating part.
2. Interference fits, whereby two parts are forced together to act
as a single piece.
Fig. 1.16: Largest and smallest dimensions of two mating parts
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.1 Engineering Drawing
3.1.6 Common Symbols and abbreviations:
R: Radius of a circle. Fig. 1.17
Ø: Dia. = Diameter. Fig. 1.18
TYP: Typical dimensions. Fig. 2.18
P: Pitch of the thread Fig. 1.19
mm: the unit of measurement is millimeter
M: Metric Thread
Example: M10 X 1.5
M = metric thread (Screw)
10 = diameter, 1.5 = Thread pitch
25
R: means radius
The diameter of the two similar holes is 5.5 mm
Pitch of a thread
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Students Presentation
Each group of students teach/present the next few topics of module 1 followed by teacher’s lesson/clarification.
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Prepared by : Mechanical Teacher Module 1: Introduction to Machining 27
3.2 Measurement There are two measuring systems:
1. International system of measurements
(Abbreviated SI from Systeme Internationale the
French version of the name).
Meter (m) is the basic unit of length measurement.
1m=100 cm=1000 mm
1cm=10 mm
Note:
In machine shop, most dimensions are in millimeters (mm).
Large dimensions are in meters (m) and millimeters (mm).
Fig 1.20 shows a steel ruler with mm scale at the top and inch scale on
the
bottom.
Steel ruler with two measuring systems
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 28
3.2 Measurement
2. Imperial system (Old system using Yard as basic unit of length)
1 yard = 36 inch
I inch = 25.4 mm
Note:
Care must be taken when using measuring tools. Most of tools have very sharp edges that may result in severe injuries. (Fig. 1.21),
Tools could be damaged easily if bended, twisted or screwed with extra force.
When using the graduated measuring tools, you must look at 90 degrees for accurate measurement.
Fig. 1.21 Sharp edges of tools may result in severe injuries
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 29
3.2 Measurement
3.2.1 Steel Ruler:
Metric steel rulers, are usually graduated in millimeters and half-millimeters, and used for making linear metric measurements that do not require great accuracy. Fig. 1.22
Metric steel ruler A: 12 mm B:31.5 mm
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 30
3.2 Measurement
3.2.2 Metric Vernier:
There are three basic types of Vernier caliper:
1. Standard, Fig. 1.23 – a
2. Dial, Fig. 1.23 - b
3. Digital, Fig. 1.23 - c.
GRP car frame
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.2 Measurement
The Vernier caliper is used to measure outside, inside and depth measurement as shown in Fig. 1.24 below:
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Outside measurement Inside measurement Depth measurement
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.2 Measurement Reading – Vernier Caliper
The accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual (true) value.
1. The Vernier caliper with 10 divisions in Vernier scale (Vernier scale is
the bottom scale on the Vernier) is accurate to (1/10) ±0.1 mm.
Fig.1.25 (a)
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reading = 15.8 mm
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Examples of measurements
2. The Vernier caliper with 20 divisions in Vernier scale is
accurate to (1/20) ±0.05 mm.
Fig. 1.25 (b).
33
reading = 31.85 mm
3. The Vernier caliper with 50 divisions in
Vernier scale is accurate to (1/50) ±0.02 mm. Fig. 1.25 (c).
reading = 19.26 mm
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Main scale = 28.0mm
Vernier scale = 37 divisions (0.02) = 0.74mm
Total reading = 28.0mm + 0.74mm = 28.74mm
34
Extra examples of vernier caliper reading
Prepared by : Mechanical Teacher Module 1: Introduction to Machining 35
The reading is 7.5mm Main scale = 7.0mm Vernier scale = 5 divisions (0.1) = 0.5mm Total reading = 7.0mm + 0.5mm = 7.5mm
Extra examples of vernier caliper reading
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.2 Measurement 3.2.3 Metric Micrometer:
A Micrometer is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades.
There are three basic types of micrometers:
1. Outside micrometer, used for external
measurement. Fig. 1.26 (a)
2. Inside micrometer, used to measure the diameter of holes. Fig. 1.26 (b)
3. Depth micrometer, measures depths of slots and steps. Fig. 1.26 (c)
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Outside Micrometer
Inside Micrometer
Depth Micrometer
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Zero Error > Not acceptable > False reading!
37
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Lets check our knowledge!!
38
Video – Micrometer Reading
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.2 Measurement 3.2.4 Reading the micrometer:
Each division on the upper scale on the sleeve
equal 1 mm. (Fig. 1.27)
Each line appears after the upper scale reading is equal to 0.5 mm.
The micrometer screw gauge also uses an auxiliary
scale (measuring hundredths of a millimeter) which is marked on a rotary thimble. (Fig.1.27).
The micrometers in our laboratory have a pitch of
0.50 mm i.e. the thimble must be rotated through two revolutions to open the jaws by 1 mm.
The rotating thimble is subdivided into 50 equal
divisions. This means each division on the thimble
= 0.01 mm
39
Fig. 1.27 sleeve and thimble of the micrometer
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Ex 1:
Fig. 1.28 (a) shows example 1 of a micrometer reading.
Steps of solution:
5.00 +0.50 +0.28 = 5.78 mm
40
3.2 Measurement
Ex 2:
Fig. 1.28 (b), shows example 2 of a micrometer reading.
Steps of solution:
5.00 + 0.28 = 5.28 mm
Fig. 1.28 (a)
Fig. 1.28 (b)
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Sleeve reading up= 7 mm down=0.5 mm Thimble reading=22 x0.1=.22 mm Total reading= 7.72mm
Extra examples of micrometer reading
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Sleeve reading =7mm
=0mm
Thimble reading= 38x0.1=38mm
Total reading=7+.38=7.38 mm
Extra examples of micrometer reading
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
3.2.5 Digital micrometers:
Digital micrometers are also available to give direct reading. Fig 1.29
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3.2 Measurement
Digital micrometers
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
In class activity – Scavenger Hunts!
In groups of 4, follow your path and do the following:
a. Measure (in mm) the physical parts listed below with a (i) micrometer and (ii) vernier caliper.
b. Provide your accurate reading and show all step calculations.
1. Brass round tip specimen (outer diameter) – micrometer / vernier
2. Hand wheel on tail stock (inner diameter) – vernier
3. Gear (thickness) – micrometer
4. White Teflon specimen (height) – micrometer / vernier
5. 3-jaw chuck (inner diameter across flat) – vernier
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Prepared by : Mechanical Teacher Module 1: Introduction to Machining
4.0 Prepare the blank part
Power hacksaw (Fig. 1.30) is used to cut the
blank part from a long bar (stock bar).
Cutting fluids must be used when cutting hard materials (steel).
(For practical tasks, the teacher will provide
each group of students with a ready blank
part).
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Power hacksaw
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
For further reading, you can use the following links:
1. http://www.stefanelli.eng.br/webpage/en-vernier-caliper-
pachymetercalliper-simulator-millimeter-05-mm.html
2. http://www.stefanelli.eng.br/webpage/en-vernier-caliper-pachymetercalliper-simulator-millimeter-02-mm.html
3. http://www.stefanelli.eng.br/webpage/en-aka-micrometer-caliperoutside-millimetre-hundredth.html
4. http://mdmetric.com/tech/surfruff.htm
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Prepared by : Mechanical Teacher Module 1: Introduction to Machining
References
1. Technology of Machine Tools. Seventh Edition, McGraw-Hill Companies,
2. Machine shop operations and setups, 4th edition, Lascoe nelson Porter.
3 . Machine tool and Manufacturing technology, Steve F. Krar, Mario Rapisarda, Albert F. Check., Delmar Publishers.
4. en.wikipedia.org/wiki/Machining
* Teacher’s weebly site
http://misshannahsclassroom.weebly.com/
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Prepared by : Mechanical Teacher Module 1: Introduction to Machining
IN CLASS WORKSHEET - 1
48
Finish in class worksheet
- Share your answers
and thoughts with your
partner
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
IN CLASS WORKSHEET2 – posted on weebly
49
Work on questions -
Share your answers and
thoughts with your
partner.
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
HOMEWORK M1 (worksheet back of module 1)
50
Given to students on
Wednesday Sept 11th, 2013.
Homework Due date – 2nd
week - Sunday Sept 13th,
2013
Prepared by : Mechanical Teacher Module 1: Introduction to Machining
Quiz Module 1
51
TBD