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Machine drawing and Industrial drafting
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MACHINE DRAWING
&
INDUSTRIAL DRAFTING
(MH402)
1
MACHINE DRAWING & INDUSTRIAL DRAFTING
Teaching Scheme (Hours/Week) Examination Scheme (Marks)
Lectures Tutorial Practical Theory Sessional Practical T.W. Total
--- --- 2+3 --- --- 50 50 100
PART A (MACHINE DRAWING) 1 PRINCIPLES OF DRAWING:
Drawing sheet (sizes and designations, title block, borders and frames, grid reference system), Scales (Designation, recommended scales, specifications), lines, lettering, sectioning, conventional representations, dimensioning, standard abbreviations
2 DETACHABLE FASTNERS:
Screw threads, approximate and conventional representations, specifications, Threaded fasteners (Types, forms, standard and specifications), Foundation bolts, locking devices (Classification, principles of operation, standard types and their proportions
3 PERMANENT FASTNERS:
Rivets (Standard forms and proportions), Riveted joints (Common types of joints, terminology, proportions and representations), Types of welds and welded joints, edge preparation, specifications and representation of welds on drawings, IS designation of weld symbols
4 ASSEMBLY DRAWING:
Review of sheet preparation, boundary lines, zones, title block, revision panel, parts list, numbering of components and associated detail drawing, bill of materials, assembly drawings of various machine sub-assemblies and assemblies from detail drawings, sketches and actual machine components
5 PRODUCTION DRAWING:
Limits, fits and tolerances of size and form, types and grade, use of tolerance tables and specification of tolerances, form and cumulative tolerances, tolerance dimensioning, general tolerances, surface quality symbols, terminology and representation on drawings, correlation of tolerances and surface quality with manufacturing techniques.
2
MACHINE DRAWING & INDUSTRIAL DRAFTING
PART B (COMPUTER AIDED DRAFTING)
1 INTRODUCTION TO AutoCAD:
Starting with AutoCAD, AutoCAD dialog boxes, Co-ordinate Systems, drawing lines, circle, arcs, rectangle, ellipse, polygons, etc
2 EDITING SKETCHED OBJECTS:
Editing sketches, moving, copying, pasting, offsetting, scaling, chamfering, trimming, mirroring. Filleting, sketched objects
3 BASIC DIMENSIONING:
Geometric dimensioning and Tolerance: Dimensioning AutoCAD, Creating linear, rotated, angular aligned base line Dimensions, Modifying dimensions
4 PLOTTING:
Plotting the drawings in AutoCAD, plotting drawing using the plot dialog box, adding plotters and using plot styles, plotting sheets
5 BASIC 3D MODELLING
3
MACHINE DRAWING & INDUSTRIAL DRAFTING
Text Books: Machine Drawing K. L. Narayana, P. Kannaiah, K. Venkata Reddy, 3rd edition, New age international (P) Ltd.
Machine Drawing N. Sidheswar, P. Kannaiah, V.V.S. Sastry, Tata McGraw Hill
Machine Drawing N. D. Junnarkar, Pearson Education Pvt. Ltd
Reference Books: P.S. Gill, Machine Drawing by S.K. Kataria, New Delhi
Sham Tickoo, AutoCAD 2012 CENGAGE learning Technical Drawing byGiesecke, F.E., Mitchel, A., Spencer, H.C., Hill, I.L.,, 13th Ed., Prentice-Hall SP 46: 1988 Engineering Drawing Practice for Schools and Colleges, Bureau of Indian standards 1988
PSG Design data book 4
5
Drawing sheet
Scales
Title block
Borders and Frames
Grid reference system (zoning)
Lines
Lettering
Sections
Conventional representation
Dimensioning
Standard Abbreviations
PRINCIPLES OF DRAWING
6
Use of standard size sheet saves paper and facilitates convenient storage of drawing
For sheet sizes the basic principles are; (a) (b) XY=1 For A0 size, surface area is 1m
2, X=841mm and Y=1189mm
Preferred drawing sheet sizes as per ISO-A series is given in Table 1.1
DRAWING SHEET
2:1Y:X
Table 1.1 7
The special elongated sizes are obtained by multiplying the shorter sides of the chosen basic format as shown in Table 1.2
DRAWING SHEET
Table 1.2
8
DRAWING SHEET
Figure 1.1 Drawing sheet formats
Different drawing sheet formats are shown in Figure 1.1
9
DRAWING SCALE
The proportion by which we either reduce
or increase the actual size of an object on
a drawing is known as drawing to scale or
simply Scale.
Scale is the ratio of linear dimension of an
element of an object as represented in the
drawing to the real linear dimension of the
same element of the object
Where ever possible, full scale is desirable
Enlarged scales are used for drawing very
small objects
Reduced scales are used for drawing very
large objects 10
DRAWING SCALE
SIZES OF THE SCALE
Full scale : 1:1
Reduced scales
The standard reducing proportions are;
1:2, 1:5, 1:10, 1:20, 1:50 and 1:100
Enlarged scales
The standard enlarging proportions are;
2:1, 5:1, 10:1, 20:1 and 50:1
11
DRAWING SCALE Complete designation of scale consists of
the word scale followed by the indication
of its ratio as:
SCALE 1:1 for full size
SCALE X:1 for enlarged size
SCALE 1:X for reduced size
Standard scales are shown in Table 1.2
Table 1.2 12
TITLE BLOCK
Important feature of the drawing
It gives all the information of the
prepared drawing
It is drawn at the bottom right corner
The recommended size of the title block
by Bureau of Indian Standards (B.I.S.)
SP-46:1998 is 185mm x 65mm for all
designations of drawing sheets
13
TITLE BLOCK
The title block should contain
- Title of the drawing
- Drawing/sheet number
- Scale
- Symbol, denoting the method of projection
- Name of the company/firm
14
TITLE BLOCK
15
DHARMSINH DESAI UNIVERSITY, NADIAD
FACULTY OF TECHNOLOGY
MECHANICAL ENGINEERING DEPARTMENT
NAME : CLASS : ROLL NO : START: COMP.: YEAR: 2011-12
DRAWING NO.: CHECKED BY:
TITLE OF THE DRAWING
50 50 150
15
15
50
BORDERS AND FRAMES
Border should be provided with all sheet
sizes
Borders have a minimum width of 20mm for
the sizes A0 and A1
Borders have a minimum width of 10mm for
the sizes A2, A3 and A4
A filling margin may be provided on far left
edge
16
BORDERS AND FRAMES
The drawing sheet layout is shown in Figure 1.3
Figure 1.3 17
CENTRING MARKS
Provided to facilitate positioning of the drawing when reproduced
Four centring marks may be provided
18
ORIENTATION MARKS
Provided to indicate the orientation of the drawing sheet on the board
19
METRIC REFERENCE GRADUATION
Provide figure-less metric reference Provided with minimum length 100mm and
divided into 10 intervals Drawn symmetrically about the centring mark
with width 5mm
20
TRIMMING MARKS
Provided at four corners of the sheet in order to facilitate trimming
These marks are in the form of right angled isosceles triangles
21
GRID REFERENCE SYSTEM
Recommended in order to permit easy location
on the drawing of details, additions or
modifications
Number of divisions should be divisible by two
Chosen in relation to the complexity of the
drawing
Length of any side of grid should not be less than
25mm and should not be more than 75mm
The rectangles of the grid should be referenced
by means of capital letters along one edge and
numerals along the other edge
The numbering may start at the sheet corner
opposite to the title block as shown in Figure 1.5
22
LINES
23
LINES
24
THICK LINE / OBJECT OUTLINES
LINES
Represented by thick line (0.7mm thickness) and is used to show the outer visible feature of the object in the drawing
HIDDEN LINES
LINES
Represented by short dashes closely and evenly spaced
Used to show the invisible or hidden parts on the drawing
CHAIN THIN DOUBLE DASHED
(PHANTOM LINES)
LINES
These Lines are used to represent the outline of an adjacent part, show alternate position of a moving part or replace repetitive details such as gear teeth and threads
LONG BREAK LINES
LINES
Represented by thin ruled line provided with free hand zig-zags at suitable intervals and is used to show the break for a considerable length of the object
SHORT BREAK LINES
LINES
Represented by thin free-hand and is used to show the break of an object for a short length
CUTTING PLANE LINE
LINES
Represented by thick long line at the ends with thin long and short lines at the centre
Used to show the edge of the cutting plane
CONTINUOUS THIN LINE
LINES
Used for showing dimension lines, extension lines, construction lines, hatching lines or section lines
CENTRE LINE
LINES
Represented by long and short dashed in proportion ranging from 6:1 to 4:1, closely and evenly spaced in any drawing
Used to show the centre line location of cylindrical, conical and spherical objects
LETTERING
Lettering on a drawing enables engineer,
architect or designer to communicate a complete
description of an object
Standard lettering for technical drawing are
called Gothic lettering
All letters in words are capitalized and squared
LETTERING
The height (h) of capital letters is taken as the base of dimensioning
Two standard ratios for d/h, 1/14 and 1/10 are used
The lettering may be vertical or inclined at 150 to the right
The proportions of different dimensions are shown below
LETTERING
For standard ratios for d/h, 1/14 different dimensions are shown below
LETTERING
For standard ratios for d/h, 1/10 different dimensions are shown below
LETTERING
Use the single-stroke, vertical, gothic style of
lettering
Use upper case (capital) letters only!
Always skip a space between rows of letters
Always use very light guide
Fraction bars are always drawn horizontal
Use a medium (B, HB, H) lead for normal
lettering
Use a hard (4H to 9H) lead for drawing guide
lines
RULES FOR LETTERING
LETTERING
Draw 2 lines parallel and write letters in it
The lines can be drawn using 2H pencil
The line must be very soft enough for our own
eyes to be seen
Line can be drawn horizontally using T Square
Firstly, determine the height (h) of the letter to
be drawn
The length between 2 line must be h mm
STEPS FOR LETTERING
h
LETTERING
VERTICAL LETTERING
LETTERING
VERTICAL LETTERING
LETTERING
INCLINED LETTERING
LETTERING
Don't mix capital letters with small letters (a)
Write in a form of same type of letter (b)
LETTERING
Dont mix letters which written straight with
leaning letters
LETTERING
Letter must have uniform thickness and
blackness
INCORRECT
CORRECT
45
SECTIONS
A section drawing shows the inside details of an object by cutting away part of the object
Normal multiview drawing
Normal section view
Section view drawing with
convention
SECTIONS
SECTIONS
Cutting plane lines mark the point at which the
object is to be cut apart (with dashed line)
Sight lines point to the part of the object that is
to be kept
CUTTING
PLANE LINE
SIGHT LINE
CUTTING PLANE LINES
SECTIONS
Used to show where the object has been cut
If the part was cut with a saw, the hatching
would represent where the saw actually touched
the object as it was being cut
Hatch lines should match the color of the cutting
plane line
The pattern of the hatching used represents
different types of materials
HATCHING
Hatch lines
SECTIONS
FULL SECTION
The cutting plane line cuts through the entire length, height, or width
SECTIONS
HALF SECTION
The cutting plane line cuts through only Half the length, height, or width of the object
This line divides the object so the sectioned
portion and the non-sectioned portion can
be defined.
SECTIONS
OFFSET SECTION
Offset sections allow one cutting plane line to transect multiple areas of a part
This reduces the amount of work needed to complete a drawing
SECTIONS
PARTIAL OR LOCAL SECTION
Local section is drawn if half or full section is not convenient
Local break may be shown by continuous thin free hand line
SECTIONS
REVOLVED SECTION
Cross sections may be revolved in relevant view The outline of the section should be shown with
thin continuous line inside the object as shown
SECTIONS
REVOLVED AND REMOVED SECTION
The removed section may be placed near to and connected with the view by a chain thin line (a) or in a different position and identified in the conventional manner (b)
SECTIONS
SECTIONS NOT TO BE HATCHED
INVISIBLE LINE TECHNIQUE
INVISIBLE LINE TECHNIQUE
AXIS REPRESENTATION
59
CONVENTIONAL REPRESENTATION OF MATERIALS
60
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
61
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
62
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
63
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
64
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
65
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
Title
66
CONVENTIONAL REPRESENTATION OF M/C COMPONENTS
DIMENSIONING
Dimension is a numerical value expressed in
appropriate units of measurement and indicated
on drawing using lines, symbols, notes etc
As far as possible, dimensions should be placed
outside the view
Dimensions should be taken from visible outlines
rather than from hidden lines
Each feature should be dimensioned once on a
drawing
Dimensions should be placed on the view or
section that relates most clearly to the
corresponding features
Each drawing should use the same unit for all
dimensions but without unit symbol
DIMENSIONING
Dimensions should be indicated on a drawing
according to any one of the following methods;
(a) Aligned system
(b) Uni-directional system
METHODS
(b) (a)
Angular dimensions are placed so that they show the angle
of an inclined feature on a drawing
DIMENSIONING
BASIC TYPES
DIMENSIONING
BASIC TYPES
Arrowless dimensions are used in confined areas where other dimensioning methods would confuse the reader
Also arrowless dimensioning is very accurate since all features are dimensioned from an origin point or datum point
Chain dimensions are placed end to end
This practice is not as accurate as datum dimensioning because
the location of the each feature is dependent upon neighboring
features
DIMENSIONING
BASIC TYPES
Datum dimensions are placed so that all dimensions originate at the same
coordinate
This practice is accurate than chain dimensioning because the location of each
feature is independent of the other feature
DIMENSIONING
BASIC TYPES
Chart dimensioning is used when part sizes change to fit an application. In the
above example part #ADD120 may be needed: therefore a note is placed on
the drawing to indicate that the part is to be fabricated according to these
specifications.
This type of method eliminates the need to create a separate drawing for each
suitable change in design.
If new part is needed with a larger hole, that instance is added to the table with
its own part number
DIMENSIONING
BASIC TYPES
Tabular dimensioning is used to locate features on a (X,Y)
coordinate system.
In the above example a hole is identifying by a letter, and its
location is identified by a coordinate
This method saves space and avoids confusing and error
If a new hole is needed or the location is changed another hole
number may be added or the coordinate may be quickly changed
DIMENSIONING
BASIC TYPES
Radius/Diameter dimensioning is used to dimension fillets,
rounds and circles
Fillets are small inside arcs and rounds are small outside arcs
DIMENSIONING
BASIC TYPES
To avoid repetitious dimensions on a drawing the abbreviation
TYP (meaning typical) is used. When TYP appears after a size
dimension, such as a diameter, un-dimensioned circles are
intended to be the same dimension.
DIMENSIONING
BASIC TYPES
77
MEANING OF NOTES
78
DRAFTING ABBREVIATIONS
79
MATERIAL ABBREVIATIONS
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