Basics of engineering drawing by Rishabh Natholia

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ENGINEERING DRAWING

CHAPTERS
1. INTRODUCTION TO ENGINEERING DRAWING
2. DRAWING STANDARDS
3. DRAWING SHEET
4. TRADITIONAL DRAWING TOOL
5. SCALES
6. LINES
7. LETTERING
8. PROJECTION
9. SECTIONING
10. DIMENSIONING
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INTRODUCTION
An Engineering Drawing is a type of technical drawing,
used to fully and clearly define requirements for
engineered items, and is usually created in accordance
with standardized conventions for layout, nomenclature
interpretation, appearance size etc.
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DRAWING STANDARD
 Standard are the set of rules that govern how technical drawing are
represented.
 Drawing Standard are used so that drawing convey the same meaning to
everyone who reads them.
 Different countries use different standards according to there ease.
 In India we follow IS (Indian Standard) which is some what like JIS system
IS: 1071 I-1983 Sizes of Drawing Sheet
IS: 9609 (Part 2)1985 Lettering on Technical Drawing
IS: 10713-1983 Scales on Drawing
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JIS STANDARD PRACTICES
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DRAWING
SHEET

DRAWING SHEET
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• Sheet Size
• Margin
• Edge Line
• Border and Frame
• Orientation Mark
• Grid References
• Title Block
• Folding Sheet

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Example of Drawing Sheet
Margin
Untrimmed Size
Trimmed Size
Margin Line
Orientation Mark
Title Block
Grid Reference
Frame
Border

SHEET SIZE
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This section specifies sizes of blank and pre-printed drawing sheets for use
with all technical drawings in any field of engineering. There are various
standards for paper size such as A series, B series, C series.
• Series A (ISO 216) is taken as standard all over the world
• A0 size defined to have area of 1 square meter.
• The length divided by the width is 1.4142.
• Each subsequent size A(n) is defined as A(n-1) cut in half parallel to its
shorter sides.
The area of B series sheets is the geometric mean of successive A series
sheets. The international standard for envelopes is the C series of ISO 269.

Series A Paper Size (ISO 216)
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 In printing, bleed is printing that goes beyond the edge of the sheet before trimming.
 Gives the printer a small amount of space to account for movement of the paper.
 RA stands for "raw format A" and is conceptually defined as being 105% of the A series size.
 SRA stands for "supplementary raw format A" and is conceptually defined as being 115% of
the A series size
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Untrimmed Paper

MARGIN AND ORIENTATION OF PAPER
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 This section covers methods of folding of drawing prints.
 All large prints of sizes higher than A4 are folded to A4 sizes.
 The title blocks of all the folded prints appear in topmost position.
 The bottom right corner shall be outermost visible section and shall have a
width not less than 190 mm.
FOLDING OF DRAWING PRINTS
TYPES OF FOLD
• Folding of prinits for Filing or Binding
• Folding of prints for storing in Filing Cabinet

Folding of prinits for Filing or Binding
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Folding of prints for storing in Filing Cabinet
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TRADITIONAL DRAWING TOOLS
 Drawing Table
 Drawing Sheet
 Drafting Tape
 Pencil
 Eraser
 Sharpener
 Drafter
 Scale
 Set-Square
 T-Square
 Compass
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Drawing Instruments or tools are used to prepare neat and accurate drawings.
To a greater extent, the ac-curacy of the Drawings depends on curacy of the
Drawings depends on the quality of instruments used to prepare them.
The following is the list of Drawing Instruments and other materials required
Drawing Board Drafter (Drafting machine)
• Set Squares
• Protractor
• Drawing Instrument Box
• Drawing Sheet
• Drawing Pencils
• Drawing Pins/Clips
DRAWING TOOLS

Drawing Board
 Drawing board is made from strips of well seasoned soft wood generally 25
mm thick. It is cleated at the back by two battens to prevent warping.
 One of the shorter edges of the rectangular board is pro One of the shorter
edges of the rectangular board is pro-vided with perfectly straight ebony
edge which is used as working edge on which the T edge on which the T-
square is moved while making Drawings square is moved while making
Drawing
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PENCIL
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• The difference is seen in the type of lead is in the pencil.
• The hardness written as H, Black the mark the lead makes written as B.
• The pencil No. 2(HB) pencil stands in middle.
• The hardest lead in a pencil is a 9H pencil, the blackest lead is a 9B pencil.

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TRY TO NAME THESE

SCALES
Ratio of the linear dimension of an element of an object as represented in the
original drawing to the real linear dimension of the same element of the
object itself.
• Full Size - A scale with the ratio 1: 1.
• Enlargement Scale - A scale where the ratio is larger than 1 :1. It is said to
be larger as its ratio increases.
• Reduction Scale - A scale where ratio is smaller than 1: 1. It is said to be
smaller as its ratio decreases.
SCALE 1 : 1 for full size
SCALE X : 1 for En-largement scale
SCALE 1 : X for Reduction scales
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 In all cases, the selected scale shall be large enough to permit easy and
clear interpretation of the information depicted.
 Details that are too small for complete dimensioning in the main
representation shall be shown adjacent to the main representation in a
separate detail view (or section) which is drawn to a large scale.
 The scale to be chosen for a drawing will depend upon the complexity of
the object to be depicted and the purpose of the representation.
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Scales for Use on Technical Drawings

LINES
 This section specifies the types of lines, their thickness and application for
use in technical drawings.
 Lines on an engineering drawing signify more than just the geometry of the
object and it is important that the appropriate line type is used.
o Line Thickness
o Line Style
o Precedence of line
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PROPERTIES OF LINE

Line Thickness
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Line Style

Precedence of line
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TYPES OF LINE
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LETTERING
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• Lettering used in engineering drawing is referred to as a Single Stroke,
Commercial Gothic.
• The height h of the capital letter is taken as the base of dimensioning
• The lettering may be inclined 15’ to the right, or may be vertical
Lettering in Engineering Drawing
To communicate non graphic information
Thus must be written with-
1. Legibility
• Shape
• Space between words and letters
2. Uniformity
• Size
• Line Thickness

Use of Lettering
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WORD SPACING
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WORD SPACING
General conclusion are:
• Space between the letters depends on the countour of the letter at
an adjacent side
• Good Spacing creates approximately equal background are between
letters.

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SENTENCE SPACING
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• Leave space between the words equal to space required
for writing a letter ‘O’

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DIMENSIONING
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Dimension as a numerical value expressed in appropriate units of
measurement and indicated graphically on technical drawings with lines,
symbols and notes.
Units of Measurement: The most commonly used unit for length is the
millimeter. In civil engineering and architectural drawing, inch or foot is often
used as a unit of length. Angles are shown in degrees.
Symbols are incorporated to indicate specific geometry wherever necessary.
Providing information on a drawing about
o Distances (size or functional dimensions)
o Sizes and positions (location or datum dimensions) of holes, grooves and
other features.
o Details relating to manufacture etc.

FUNCTIONAL DIMENSIONS (FDS)
These are dimensions, which directly dictate the functioning of the component.
That is a FD is a dimension defined on the basis of the function of the product
and the method of locating it in any assembly of which it may form part of, e.g.
the diameter of a shaft, the length of a bolt, etc.
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NON FUNCTIONAL DIMENSIONS (NFDS)
AUXILLARY DIMENSIONS (FDS)
These are dimensions, which do not directly affect the functioning of the
component but have to be specified to enable production of that component, e.g.
the size of a bolt head.
These are dimensions which should not necessarily appear on the drawing but
are sometimes included to avoid calculations or when they would provide
additional/useful information. ADs are usually written in brackets.
CATOGRIES OF DIMENSIONING

DIMENSION TERMINOLOGY
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LEADER LINES AND NOTES
• Leader (or pointer) line – Thin continuous line connecting a note or
dimension figure with the feature to which it applies. One end of the
leader terminates in an arrowhead or dot.
• The arrowhead touches the outline while the dot is placed within the
object or on the outline
• The other end of a leader is terminated in a horizontal line underlining the
note
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RULES FOR LEADER LINE
• A leader line is never drawn horizontal, vertical or curved
• It is drawn at an angle not less than 30o to the line that it touches
• When pointing to a circle or arc, it is drawn radially
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ARROWHEADS AND DIMENSION LINE POSITIONING
 A dimension line is placed at least 6-8 mm away from an outline and from
each other
 An extension line extends ~3mm beyond a dimension line
 Arrowhead – Placed at each end of a dimension line, its pointed end
touches an outline, extension line or a centerline. It is also placed at the
end of a leader line
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SYMBOLS AND ABBREVIATIONS USED IN ENGG.
DRAWING
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TYPES OF DIMENSIONING
 Aligned
• Dimension are aligned with the entity
being measured.
• They are placed perpendicular to the
dimension line such that they may be
read from the bottom or right-hand side
of the drawing sheet.
• Dimensions are placed at the middle
and on top of the dimension lines.
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 Unidirectional
• Dimensions are placed in such a way
that they can be read from the bottom
edge of the drawing sheet.
• Dimensions are inserted by breaking
the dimension lines at the middle.

PLACING DIMENSION
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METHOD FOR DIMENSIONING
• Parallel Dimensioning
• Continues Dimensioning

PARALLEL (PROGRESSIVE) DIMENSIONING
All the dimensions are shown from a common reference line. Obviously,
all these dimensions share a common extension line. This method is
adopted when dimensions have to be established from a particular datum
surface
Smaller dimensions should always be placed nearer the view. The next
smaller dimension should be placed next and so on.
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CHAIN (CONTINUOUS) DIMENSIONING
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All the dimensions are aligned in such a way that an arrowhead of one
dimension touches tip-to-tip the arrowhead of the adjacent dimension. The
overall dimension is placed outside the other smaller dimensions

COMBINED DIMENSIONING
When both the methods, i.e., chain dimensioning and parallel dimensioning
are used on the same drawing, the method of dimensioning is called
combined dimensioning
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CYLINDRICAL DIMENSIONS
Cylindrical features should be dimensioned by giving their diameters.
They should be dimensioned in the views in which they appear as rectangles
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CYLINDER – OUTER DIMENSION IS ALSO
CIRCULAR. CAN BE HOLLOW OR SOLID

DIMENSIONING ARCS
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DIMENSIONING CONICAL FEATURES
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DIMENSIONING WRONG VS. CORRECT

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 NOTE that all “rules” on dimensioning are just guidelines. Use common
sense depending on circumstances (i.e. there are no strict rules/regulations
on dimensioning)
 In metric system, all linear dimensions are considered to be in millimeters
 Show full size dimensions regardless of the scale used in the drawing
 Dimension any feature only once (i.e. no repetitions are allowed)
 Dimension obviously identical features only once
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General Hints on Dimensioning

For any query or error feel free to mail me :
natholiarishabh@gmail.com
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Basics of engineering drawing by Rishabh Natholia

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Basics of engineering drawing by Rishabh Natholia