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General Principles of Design, Drawing & Safety – Study Notes

ESE / IES Paper I

Complete notes for General Principles of Design, Drawing & Safety — ESE Paper I General Studies. Covers engineering design process, BIS/ISO drawing conventions, orthographic and sectional views, tolerances and fits, and occupational health and safety regulations.

Ch 1 · Principles of Design Ch 2 · Engineering Drawing Conventions Ch 3 · Views and Sections Ch 4 · Tolerances, Fits & Limits Ch 5 · Workplace Safety ★ Quick Revision

1Principles of Design►

1.1 Engineering Design Process

Engineering design is a systematic, iterative process of converting needs/requirements into a product or system. Key stages: (1) Define problem; (2) Research and gather data; (3) Generate concepts; (4) Select best concept; (5) Detail design; (6) Prototype and test; (7) Iterate; (8) Manufacture and deliver.

1.2 Design Principles

Principle	Description
Functionality	Design must fulfil its intended purpose reliably
Safety	Must not pose hazard to users, operators or environment; factor of safety applied
Ergonomics	Designed for human use — comfortable, efficient, minimises fatigue and errors
Aesthetics	Visually appealing and contextually appropriate
Economy	Minimum cost consistent with required performance and durability
Manufacturability	Design for ease of manufacture (DFM); minimise machining, use standard parts
Maintainability	Easy to inspect, service, repair; accessible components
Sustainability	Minimise environmental impact; use recyclable materials; energy-efficient operation

1.3 Factor of Safety

FOS = Ultimate / Working stress (or Failure load / Design load)
Higher FOS → safer but heavier/costlier
Typical values: steel structures 1.5–2.5; concrete 3–4; brittle materials 4–6
FOS selected based on: material variability, load uncertainty, consequences of failure, inspection frequency

📝 ESE Tip: Factor of safety definition and its governing factors are directly asked. Ergonomics and DFM principles are tested conceptually in Paper I.

2Engineering Drawing Conventions►

2.1 BIS / ISO Standards for Engineering Drawing

Standard	Content
IS 696	Conventions for surface texture (roughness)
IS 9609	Lettering on technical drawings (inclined and upright)
IS 11065	General tolerances for linear dimensions
ISO 128	General principles of presentation of drawings
ISO 2768	General tolerances — untoleranced linear and angular dimensions

2.2 Drawing Sheet Sizes (ISO A series)

Sheet	Size (mm)
A0	841 × 1189
A1	594 × 841
A2	420 × 594
A3	297 × 420
A4	210 × 297

2.3 Line Types

Line Type	Appearance	Use
Continuous thick	Solid wide line	Visible edges and outlines
Continuous thin	Solid narrow line	Dimension lines, hatching, leader lines
Dashed thin	Short dashes	Hidden edges
Chain thin	Long dash–dot	Centre lines, axes of symmetry
Chain thin (thick at ends)	Long dash–dot–dot	Cutting planes for sections
Continuous thin zigzag	Freehand wavy	Break lines (short breaks)

📝 ESE Tip: Line types (especially hidden = dashed; centre = chain) and their correct applications are tested. Sheet sizes A0–A4 and the ratio √2:1 between successive sizes are standard knowledge.

3Views and Sections►

3.1 Orthographic Projection

First Angle Projection (European / BIS standard in India):
Object placed in first quadrant; view projected onto planes behind the object
Front view (FV) → front plane; Top view → below FV; Side view → to the left of FV

Third Angle Projection (American standard):
Object placed in third quadrant; views appear in their natural position
Top view → above FV; Right side view → to the right of FV

Symbol on drawing: First angle = circle with cone pointing left; Third angle = circle with cone pointing right

3.2 Sectional Views

Type	Description
Full section	Cutting plane passes entirely through the object
Half section	Only half the object is cut; other half shows external features (for symmetric objects)
Offset section	Stepped cutting plane passes through multiple features
Revolved section	Cross-section of rib/spoke revolved 90° into the view
Removed section	Cross-section drawn outside the main view with reference

3.3 Auxiliary Views and Isometric Drawing

Auxiliary view: used to show true shape of inclined surfaces; projected perpendicular to the inclined face

Isometric drawing: 3D representation; all three axes at 120° to each other; measurements along axes are true length
Isometric scale = cos 45° / cos 30° = 0.816 (isometric lengths are ~82% of true length)
Perspective drawing: shows depth effect; not used for engineering dimensioning

📝 ESE Tip: Distinction between first-angle and third-angle projection is directly tested. Hatching direction (45° to main outline, thin continuous lines) and the rule that hidden lines become solid in sections must be known.

4Tolerances, Fits & Limits►

4.1 Definitions

Term	Definition
Nominal size	Basic theoretical size specified on drawing
Basic size	Size from which deviations are applied (same as nominal for standard fits)
Tolerance	Permissible variation = Upper limit − Lower limit
Allowance	Intentional (designed) difference between mating parts; minimum clearance or maximum interference
Upper Deviation (ES/es)	Upper limit − Basic size (ES for hole; es for shaft)
Lower Deviation (EI/ei)	Lower limit − Basic size (EI for hole; ei for shaft)

4.2 Types of Fit

Fit Type	Condition	Application
Clearance fit	Shaft always smaller than hole; positive clearance	Rotating/sliding parts — bearings, pistons
Interference fit	Shaft always larger than hole; assembly requires force/heating	Press-fitted hubs, gears, couplings
Transition fit	May be clearance or interference depending on actual sizes	Keys, locating fits

4.3 BIS Hole-Basis and Shaft-Basis Systems

Hole-basis system (preferred in India): hole tolerance fixed (H); shaft varies
H7/f6 = clearance fit; H7/k6 = transition fit; H7/p6 = interference fit

Shaft-basis system: shaft tolerance fixed (h); hole varies
Used when shaft from stock (e.g. standard bar stock) is the common element

IT grades (International Tolerance): IT01, IT0, IT1 … IT18 in increasing order of tolerance
IT6: precision fits (machine tools); IT7: general engineering; IT8–IT11: agricultural machinery; IT12–IT16: sheet metal

📝 ESE Tip: Clearance = max clearance / min clearance calculations from given limits are common numericals. Hole-basis (H designation for hole) is the standard system in India per BIS.

5Workplace Safety►

5.1 Key Safety Legislation in India

Act / Rule	Scope
Factories Act, 1948	Health, safety, welfare of workers in factories; working hours; occupational hazards
Mines Act, 1952	Safety in mines and quarries
Building & Other Construction Workers Act, 1996	Safety of construction workers; health and welfare provisions
Occupational Safety, Health and Working Conditions Code, 2020	Consolidated code replacing multiple older acts
IS 4082	BIS standard for stacking and storage of materials on construction sites

5.2 Hazard Identification and Risk Assessment

Risk = Probability × Severity (consequence)
Risk matrix: Low / Medium / High / Critical — drives control priority

Hierarchy of controls (preferred order):
1. Elimination — remove the hazard completely
2. Substitution — replace with a less hazardous process
3. Engineering controls — isolation, guarding, ventilation
4. Administrative controls — procedures, training, work permits
5. PPE — last resort; personal protective equipment

5.3 Common Hazards on Construction Sites

Hazard	Controls
Working at height (falls)	Scaffolding with guard rails; harnesses; safety nets; edge protection
Falling objects	Toe boards; debris nets; helmets; exclusion zones
Electrical hazards	Lockout-tagout (LOTO); insulation; residual current devices (RCD)
Excavation collapse	Shoring; battering; inspection before each shift
Crane and lifting operations	SWL markings; banksman; pre-lift checks; exclusion zones
Noise	Engineering controls; hearing protection (85 dB exposure limit per IS)

📝 ESE Tip: The hierarchy of controls (elimination → substitution → engineering → administrative → PPE) is a core conceptual question. Factories Act, 1948 provisions and the 85 dB noise limit are directly tested facts.

★Quick Revision►

Topic	Key Fact
FOS	Ultimate stress / Working stress
A4 sheet size	210 × 297 mm
First angle projection	BIS / Indian standard; top view below front view
Hidden lines	Dashed (short dash) lines
Clearance fit	Shaft always smaller than hole
Interference fit	Shaft always larger than hole
Hole-basis system	H designation for hole; shaft designation varies
IT grades	IT01 finest → IT18 coarsest
Hierarchy of controls	Elimination → Substitution → Engineering → Admin → PPE
Noise limit (India)	85 dB(A) for 8-hour exposure
Risk formula	Risk = Probability × Severity

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General Principles of Design, Drawing & Safety – Study Notes

1.1 Engineering Design Process

1.2 Design Principles

1.3 Factor of Safety

2.1 BIS / ISO Standards for Engineering Drawing

2.2 Drawing Sheet Sizes (ISO A series)

2.3 Line Types

3.1 Orthographic Projection

3.2 Sectional Views

3.3 Auxiliary Views and Isometric Drawing

4.1 Definitions

4.2 Types of Fit

4.3 BIS Hole-Basis and Shaft-Basis Systems

5.1 Key Safety Legislation in India

5.2 Hazard Identification and Risk Assessment

5.3 Common Hazards on Construction Sites