ENGINEERING DRAWING : Mechanical Drawing

 1. Drawing Equipment and the Use of Instruments:

Definition: Drawing equipment refers to the tools used for creating technical drawings and precise geometrical representations. Instruments such as compasses, dividers, protractors, T-squares, and drafting machines are commonly used.

Example: A T-square is used to draw horizontal lines on a drafting board, while a compass is used to draw circles or arcs.

2. Basic Drafting Techniques and Standards:

Definition: Drafting techniques involve the methods used for creating clear and accurate technical drawings, adhering to specific standards such as line types, scaling, and symbols.

Example: Orthographic projection is a basic drafting technique where views of an object (front, top, and side) are drawn to represent the object in three dimensions on a two-dimensional surface.

3. Geometrical Curves:

Definition: Geometrical curves are mathematical curves that are used to represent different shapes and trajectories in mechanical drawing.

Example: Plan curves are flat curves lying on a plane. Examples include:

Cycloid: The path traced by a point on the circumference of a rolling circle.

Hypocycloid: The path traced by a point inside a smaller circle rolling inside a larger one.

Involute: A curve created by unwinding a taut string from a cylinder, often used in gear tooth design.

4. Intersection of Geometrical Bodies:

Definition: The intersection of geometrical bodies refers to the lines or curves that form where two shapes, such as cylinders or cones, meet at different positions.

Example: When a cone intersects with a cylinder, the curve formed at the intersection is called the intersection curve. These curves are essential in creating complex mechanical components.

5. Development of Surfaces:

Definition: Surface development involves unfolding a three-dimensional object into a flat surface, allowing the shape to be fabricated from flat materials.

Example: The development of a cylinder is a rectangle, representing the unwrapped surface of the cylinder, which can be cut from sheet metal and rolled into the desired shape.

6. Freehand Sketch of Machine and Engine Components:

Definition: Freehand sketches involve drawing components without the use of drafting tools, capturing essential details of parts like engine components and machine parts.

Example: A sketch of an engine connecting rod shows its shape, dimensions, and features without precision instruments but enough detail for conceptual understanding.

7. Locking Arrangements:

Definition: Locking arrangements are mechanisms that secure components in place to prevent movement or loosening under load or vibration.

Example: Lock nuts, cotter pins, and locking washers are examples of locking devices used in mechanical assemblies.

8. Foundation Bolts:

Definition: Foundation bolts are long bolts used to fix machinery or equipment to concrete or foundations.

Example: L-shaped foundation bolts are often embedded in concrete to provide secure fastening for heavy machinery.

9. Stuffing Box:

Definition: A stuffing box is a seal assembly used to prevent leakage of fluids or gases where a rotating or reciprocating shaft passes through a machine housing.

Example: A pump stuffing box ensures that fluid doesn't leak along the shaft of a pump.

10. Shaft Couplings:

Definition: Shaft couplings are devices used to connect two shafts together for the transmission of power.

Example: A flexible coupling allows for slight misalignment between connected shafts, ensuring smooth power transmission.

11. Footstep Bearing:

Definition: A footstep bearing supports the axial load of a vertical shaft.

Example: It is often used in vertical pumps or turbines to support the shaft at the bottom end.

12. Engine Connecting Rod:

Definition: A connecting rod connects the piston to the crankshaft in an internal combustion engine, converting the piston's linear motion into rotational motion.

Example: The connecting rod in a car engine transfers the motion of the pistons to the crankshaft, driving the vehicle's wheels.

13. Working Drawings of Components and Parts of Machine and Engines:

Definition: Working drawings are detailed drawings of machine or engine components, showing all necessary dimensions, specifications, and materials for manufacturing.

Example: A working drawing of a gearbox shows detailed views of the gears, shafts, and housing, with dimensions and materials specified.

14. Dimension and Specifications:

Definition: Dimensions specify the size and geometry of components in a technical drawing, while specifications provide additional details such as materials, finishes, or tolerances.

Example: The diameter of a shaft might be dimensioned as 50 mm, and the material specification could be stainless steel.