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INTRODUCTION ABOUT MACHINE DRAWING

❖ Definition Of machine drawing

• Machine drawing may be defined as the representation of a machine
component or machine by lines according to certain set rules. A
machine drawing generally gives all the external and internal details of
the machine component from which it can be manufactured. The
machining symbols, tolerances, bill of material, etc. are specified on the
drawing. The-relative position of the different components and to
make assembly drawing are also specified

❖ What is machine drawing

• Drawing representing components of machine parts with intricate
details and dimensions, depicting side view, front view and top view
for better understanding and development of original parts is machine
drawing.
• Before making any parts in real, its necessary to draw them on charts
or computers for imagination purposes. Also, it’s very useful as one
can do any amendments before making it in real.
• Machine drawings are graphic representations of any part or any
assembly of parts which we see all around us. Some of the examples
are electric fan, switch, gear box, grinder, boiler, valves, electric motor,
water pump, printer, car, air planes, ship etc. Machine drawings give
complete information about a part or a component or a group of
components working as one unit.
• This information is in the form of material, measurements,
manufacturing process, machining or finishing process, precision
required etc. The machine drawings are PRIMARILY used in
manufacturing activities.
• All or part of this information is used for designing a part, its
manufacturing, its machining and finishing and also in positioning
 correctly in the final assembly to obtain the desirable or predetermined
performance.
• The information given by the machine drawings is needed for setting
tools, inspection and quality control, sales and service. In advance
methods, the machine drawings are translated into / interpreted by
digital signals and electronic circuits, leading to higher levels of
automation.

❖ Example of machine drawing

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Introduction about sheet layout and sketching

❖ Layout of a sheet
• Every drawing sheet is to follow a particular layout. As a standard practice
sufficient margins are to be provided on all sides of the drawing sheet. The
drawing sheet should have drawing space and title page. A typical layout of
a drawing sheet is shown in the photo

• Borders – A minimum of 10 mm space left all around in between the trimmed

edges of the sheet.
• Filing margin – Minimum 20 mm space left on the left-hand side with border
included. This provided for taking perforations.
• Grid reference system – This is provided on all sizes of industrial drawing
sheets for easy location of drawing within the frame. The length and the
width of the frames are divided into even number of divisions and labeled
using numerals or capital letters. Number of divisions for a particular sheet
depends on complexity of the drawing. The grids along the horizontal edges
are labeled in numerals where as grids along vertical edges are labeled using
capital letters. The length of each grids can be between 25 mm and 75
 mm. Numbering and lettering start from the corner of the sheet opposite to
the title box and are repeated on the opposite sides. they are written upright.
Repetition of letters or numbers like AA, BB, etc., if they exceed that of the
alphabets. For first year engineering students grid references need not be
followed.
• Title box – An important feature on every drawing sheet. This is located at
the bottom right-hand corner of every sheet and provides the technical and
administrative details of the drawing. The title box is divided into two zones
• A. Identification zone: In this zone the details like the identification number
or part number, Title of the drawing, legal owner of the drawing, etc. are to be
mentioned.
• b. Additional information zone: Here indicative items lime symbols indicting
the system of projection, scale used, etc., the technical items lime method of
surface texture, tolerances, etc., and other administrative items are to be
mentioned.

• Layout of the title box recommended for Engineering Drawing Course

The title box shown in figure 2 can be used for the engineering Drawing

Course.

❖SKETCHING
 • Lettering is used for writing of titles, sub-titles, dimensions, scales and other
details on a drawing. Typical lettering features used for engineering drawing
is shown in figure.
• The following rules are to be followed in lettering. The letter sizes generally
recommended for various items are shown in Table 1.
• Essential features of lettering – legibility, uniformity, ease, rapidity, and
suitability for microfilming/photocopying/any other photographic processes.
• No ornamental and embellishing style of letter.
• Plain letters and numerals which are clearly distinguishable from each other
in order to avoid any confusion even in case of slight mutilations.
• The Indian standard followed for lettering is BIS: 9609.
• Single stroke lettering for use in engineering drawing – width of the stem of
the letters and numerals will be uniformly thick equal to thickness of lines
produced by the tip of the pencil.
• Single stroke does not mean – entire letter written without lifting the
pencil/pen.

❖ Lettering types generally used for creating a drawing are

• Lettering A – Height of the capital letter is divided into 14 equal part

• Lettering B – Height of the capital letter is divided into 10 equal parts

❖ Table 2 and Table 3 indicates the specifications for Type A and Type B letters.

❖ Heights of Letters and Numerals

1. Height of the capital letters is equal to the height of the numerals used in
dimensioning
 2. Height of letters and numerals – different for different purposes

❖ Table 1 The letter sizes recommended for various items

❖ To start with the preparation of a drawing the procedure
mentioned below followed.
• Clean the drawing board and all the drawing instruments using duster.
• Fix the drawing sheet on the drawing board.
• Fix the mini-drafter in a convenient position.
• Draw border lines using HB pencil.
• Complete the title box using HB pencil
• Plan spacing of drawings b/n two problems/views beforehand.
• Never sharpen pencils over drawing.
• Clean pencil point with a soft cloth after sharpening.
• Keep drawing instruments clean.
• Rest hands on drawing instruments as much as possible – to avoid smearing
the graphite on the drawing.
• When darkening lines – try to work from the top of the drawing to the bottom,
and from left to the right across the drawing.
• Use brush to remove eraser particles. Never use hands.
• Always use appropriate drawing pencils.
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Assembly and detailed drawing of cotter joint

❖ Introduction:
• A cotter is a flat wedge-shaped piece of rectangular cross-section and its
width is tapered (either on one side or both sides) from one end to another
for an easy adjustment.
• The taper varies from 1 in 48 to 1 in 24 and it may be increased up to 1 in 8,
if a locking device is provided. The locking device may be a taper pin or a
set screw used on the lower end of the cotter.
• The cotter is usually made of mild steel or wrought iron. A cotter joint is a
temporary fastening and is used to connect rigidly two co-axial rods or
bars which are subjected to axial tensile or compressive forces.
• It is usually used in connecting a piston rod to the cross head of a
reciprocating steam engine, a piston rod and its extension as a tail or pump
rod, strap end of connecting rod etc.
 • A cotter joint, also known as a socket and spigot joint, is a method of
temporarily joining two coaxial rods. One rod is fitted with a spigot, which
fits inside a socket on one end of the other rod. Slots in the socket and the
spigot align so that a cotter can be inserted to lock the two rods together.
• The cotter used within a cotter joint is typically an elongated wedge, which
can be driven into the slots.
• Cotter joints are used to support axial loads between the two rods, tensile
or compressive. Although a cotter joint will resist rotation of one rod
relative to the other, it should not be used to join rotating shafts. This is
because the cotter will not be balanced and may work loose under the
combination of vibration and centrifugal force.

• These components were historically used to join connecting rods in steam

engines and pumps used to drain mines. Cotter joints were favoured because
they are relatively easy to design and manufacture, they produce a rigid
connection and they are not prone to working loose in reciprocating
machinery.
• Today they still find applications in a number of areas such as anchor bolts.
Knuckle joints are often used instead A cotter joint is formed by first inserting
the spigot end into the socket end. The slots are then aligned before the cotter
is driven through the slots in both components.
• The slots are positions so that as the cotter is driven into position, the spigot is
drawn into the socket until a shoulder on the spigot rests securely against the
 end of the socket. The angle of the cotter is determined by the coefficient of
friction and the ease of disassembly required.
• Typically, the taper angle is less than the angle of friction so that no axial force
would cause the cotter to push out of the slots. Additional positive locking
devices may be used for cotter joints subjected to vibration.

❖ Advantages:
• Quick assembly and disassembly is possible
• It can take tensile as well as compressive force.

❖Application:
• Joint between piston rod and cross head of a steam engine
• Joint between valve rod and its steam
• A steam engine connecting rod strap end
• Foundation bolt

❖Detailed drawing
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Assembly and detailed drawing of knuckle joint

❖ Introduction: -
• In mechanical & automobile domain the joints play very crucial role,
depending upon the application the joints are used may be temporary or
permanent. For power transmission or motion transfer application we
generally use temporary joints like screwed joint, cotter joint, sleeve cotter
joint, universal joint or knuckle joint.
• The Knuckle joint is a type of joint which is used in steering system in
between the steering rod and pinion of the steering gear, as the line of the
action axis of both the mechanical parts are intersecting and lies in
different planes, so it is the only joint that we can employ here In order to
gain the maximum productivity for the plant, the manufacturing
technology must not be stiff.
• A Knuckle joint is used to connect two rods under tensile load. This joint
permit angular misalignment of the rods and may take compressive load if
it is guided. These joints are used for different types of connections i.e. tie
 rods, tension links in bridge structure. In this, one of the rods as an eye at
the rod end and other end is forked with eyes at the both the legs.
• A pin (knuckle pin) is inserted through the rod-end and fork end eyes and
is secured by collar and a split pin. Failure of knuckle joint may cause
accident so it necessary to design knuckle joint to withstand under tension
without failure. The effective design of mechanical device or assembly
demand the predictive knowledge of its behaviour in working condition.
It became necessary for the designer to know the forces and stress
developed during its operation.
• We know that during working condition pin is subjected to high stress. As
pin is flexible element which can be easily replaced. So, we can take pin for
analysing purpose. Then we are using ANSYS software for analysing
knuckle pin.
• Knuckle joint is joint between two parts allowing movement in one plane
only. It is kind of hinged joint between two rods.
• Knuckle joint is used for connecting two rods whose axes either coincide
or intersect and lies in one plane only.
• They are widely used in tractor trailer, tie rod in roof truss, joint between
the links of suspension bridge and also used in steering system in between
the steering rod and pinion of the steering gear.
• If failure of knuckle joint occurs then possibilities of accident. So it is
necessary that design and analysis of knuckle joint should be proper
enough to withstand in working condition without failure. So, modelling
and analysis of knuckle joint under a certain condition is carried out.
Modelling and analysis of a knuckle joint was performed by using 3D
software CATIA & Finite Element Analysis (FEA) respectively.
• the commercial finite element package ANSYS version 15 was used for
the solution of problem. Result shows that 30C8 material having
maximum permissible stress are 400MPa and Maximum stresses
developed in knuckle joint are 201MPa. So, design is safe. The analysis
shows that pin of 25 mm diameter can sustain load of 50 KN without a
failure.
❖Advantage:
• Knuckle joint can withstand large tensile loads.
• It has good mechanical rigidity.
• It is easy to manufacture and setup.
• Long tool life.
• Design is simple and easy.
❖ APPLICATIONS OF A KNUCKLE JOINT
 • Knuckle joints are mainly used to connect two coaches of a train.
• Knuckle joints are used in windshield wipers in automobiles. In
automotive engine sml end of commenting rod is connected to piston
by means of a knuckle joint.
• Knuckle joints are used in the robotic arms.
• Knuckle joints are used in the links of the cyck chains. Knuckle joints
are used in the cranes.
• Knuckle joints are used in the earth movers.
• Knuckle joints are used in the chain straps.
❖Drawing of knuckle joint
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Design of lever
❖ Introduction

 A lever is a rigid rod or bar capable of turning about a fixed point called
fulcrum. It is used as a machine to lift a load by the application of a small
effort.

 The ratio of load lifted to the effort applied is called mechanical advantage.

 The perpendicular distance between the load point and fulcrum (l1) is known
as load arm and the perpendicular distance between the effort point and
fulcrum (l2) is called effort arm. According to the principle of moments,
 In the first type of levers, the fulcrum is in between the load and effort. In this
case, the effort arm is greater than load arm, therefore mechanical advantage
obtained is more than one. Such type of levers are commonly found in bell
cranked levers used in railway signaling arrangement, rocker arm in internal
combustion engines, handle of a hand pump, hand wheel of a punching
press, beam of a balance, foot lever etc.

 In the second type of levers, the load is in between the fulcrum and effort. In
this case, the effort arm is more than load arm, therefore the mechanical
advantage is more than one. The application of such type of levers is found in
levers of loaded safety valves.

 In the third type of levers, the effort is in between the fulcrum and load. Since
the effort arm, in this case, is less than the load arm, therefore the mechanical
advantage is less that one. The use of such type of levers is not recommended in
engineering practice. However, a pair of tongs, the treadle of a sewing machine etc.
are examples of this type of lever.
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Design of power screw
❖ Introduction
• The power screw is used for lifting and lowering the mass slowly which is
required in Any assembly shop of heavy industry.
• It mainly contains a set of worm and worm gears, a pinion and bevel gear,
a screw and bronze nut and a motor to drive. These frames are fabricated
out of steel channel of 100x50x6 size. A worm is fixed to a motor shaft
through a coupling. The worm drives a worm gear when the motor is
switched on.
• The worm gear and the bevel pinion are mounted on a shaft on either
end. This shaft is supported by two ball bearings on the vertical frame.
Hence when the worm gear rotated, the bevel gear pinion drives the bevel
gear.
• This bevel gear is fitted with a bronze bush with internal square thread.
This bevel gear with bronze bush is mounted on a flat support frame with
a thrust bearing over the plate. The extended portion of the bush is locked
at the bottom side of the support frame to arrest and make bevel gear to
rotate at its position.
• A motor is provided with a bidirectional switch so that the motor can be
operated on both directions for raising or lowering the load. Here in this
arrangement, main base frame, vertical channel with bevel support, top
support guide plate, screw, load base, guide pipe support etc are
detachable since they are bolted together

❖ FUNCTION OF A POWER SCREW

• Provide a means for obtaining a large mechanical advantage
• Transmit power by converting angular, into linear motion
• Common applications include
• Lifting jacks, presses, vices, and lead screws for lathe machines
• Figure 1shows the application in a lifting jack, while Figure 2 shows the
same concept when used for a press.
• POWER SCREWS USE EITHER SQUARE, OR TRAPEZOIDAL THREAD FORMS
• Two types of trapezoidal thread forms are
• ACME thread standard, used widely in the English speaking countries, and based on the
inches units,
• Metric trapezoidal standard, originating in Europe, and now adopted by the
International Standards Organisation (ISO).
❖THREAD FORMS FOR POWER SCREWS
• (ISO) METRIC TRAPEZOIDAL THREAD FORM STANDARD
SPECIFICATIONS RELATE
• Screw shaft DIAMETER to PITCH, as shown in next slide
• For the SQUARE and ACME thread form standards, only the geometric
profile of the thread form is specified
• The designer is left to choose the size of thread for each screw shaft diameter
• This does not pose any serious problem because each power screw
application is often a special case.

❖ DIAMETER, PITCH SPECIFICATIONS

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Introduction about production drawing
❖ Introduction
• A component or part drawing is termed as a production drawing, if it
facilities its manufacture. It is an authorized document to produce the
component in the shop floor. It furnishes all dimensions, limits and special
finishing processes such as heat treatment, grinding, etc., in addition to the
material used. It should also mention the number of parts that are
required for making of the assembled unit, of which the part is a member.
Production drawing of a component should also indicate the sub or main
assembly where it will be assembled. It is necessary to prepare the
production drawing of each component on a separate sheet, since a
craftsman will ordinarily make one component at a time. However, in
some cases, the drawings of related components may also appear on the
same sheet. Figure 1.2 shows the production drawing of a jig bush.

❖Need for a production drawing

 ❖ The graphic representation of a product, starts at the transformation stage
of ideas into a drawing by a design engineer. A production drawing is a
complete working drawing, representing all the details of the product,
regarding size, shape, material, process, tools and equipment. The
craftsman is completely guided by the production drawing, during the
manufacture of the product. Hence, any mistake in a production drawing
will result in loss of time, money and decreased productivity. Further, it is
a legal document while going for subcontracting of works. Hence, a
production drawing should be prepared without any scope for more than
one interpretation. The design engineer uses orthographic or pictorial
views to record his ideas, free hand. These are called working sketches.
These sketches are used for both the component and assembly drawings.
The working drawings are sent to the shop, in the form of blue prints,
ammonia prints or other similar forms of reproduction. Therefore, the
drawings must be made as tracings.
❖ Elements of production drawing
Following are the basic elements of a production drawing.
1. Format of drawing sheet,
2. Size and shape of the component.
3. Projection method,
4. Material specification and shape such as castings, forgings, plates, rounds,
etc.,
5. Indication of surface roughness and other heat treatments, if any,
6. Limits, fits and tolerances of size, form, and position,
7. Production method,
8. Process sheet,
9. Specification of standard components,
10. Conventions used to represent certain machine components, and
11. Inspection and testing methods.