Engineering Graphics
First Year • Semester 2 • NEP Syllabus
Engineering Graphics (1ME107EL)
**Course Aim:** To provide understanding of engineering drawing standards, scales, projections of points, lines, planes, solids, and orthographic/isometric views.
[b] Introduction to Planes of projections, Projections of points in all possible positions.
[c] Projections of lines: Perpendicular to reference planes, inclined to one and parallel to other, inclined to both reference planes.
[b] Projection of Solids (Prisms, Pyramids, Cylinder, Cone) when axis is perpendicular/inclined to reference planes.
[b] Development of surfaces of simple regular solids.
2. Jolhe D. A. - Engineering Drawing with Auto CAD, Tata McGraw-Hill.
3. Shah P. J. - Engineering Drawing, S. Chand Publication.
Introduction to Scales
Drawings of small objects are usually made full-size. However, for large objects like buildings, we use scales to reduce dimensions proportionately. Representative Fraction (R.F.) = (Length on drawing) / (Actual length).
Types of Scales
Plain Scales: Represents two units or a unit and its fraction.
Diagonal Scales: Measures up to three consecutive units (e.g., meters, decimeters, centimeters) based on similar triangles.
Projections of Planes
A plane is a 2D surface with length and breadth but no thickness. When a plane is perpendicular to a reference plane, its projection is a straight line (Trace). We analyze planes parallel to HP, perpendicular to VP, or inclined to both.
Tip for Solving
Always start drawing the view where the true shape of the plane is visible.
Sections of Solids
When a solid is cut by a plane (Section Plane), the surface obtained is called a Section. If the section plane is parallel to a reference plane, the section reveals the True Shape of the cut surface.
Development of Surfaces
Imagine unfolding a hollow 3D object onto a flat plane. This 2D shape is its development.
Methods: Parallel Line (Prisms, Cylinders) & Radial Line (Pyramids, Cones).
Principles of Projection
Orthographic projection transforms a 3D object into multiple 2D views (Front, Top, Side). Projectors are parallel to each other and perpendicular to the plane of projection.
First Angle Projection
We use First Angle Projection:
• Object is placed in the 1st Quadrant.
• Top View is drawn below the Front View.
Isometric Projection
A method to represent 3D objects in 2D where all three axes (Length, Width, Height) are equally inclined at 120° to each other.
Isometric Scale vs View
Isometric Projection: Drawn using Isometric Scale (0.816 x True Length).
Isometric View: Drawn using True Scale (Actual dimensions). This is more commonly used in exams for simplicity.
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