# Engineering Drawing Techniques

Drawing in engineering is a vital method of communication. Clear diagrams and representations can allow for precise interpretation, reducing potential errors during the manufacturing process. The following are considered essential drawing techniques in engineering:

## Conventions

• Drawing scale: All engineering drawings should be made to scale. This ensures correct proportions, and information about the scale should be provided on the drawing sheet.
• Title block: The block located at the bottom right corner of the drawing sheet, containing essential information about the drawing, like the title, drafter, checker, scale, and issue date.
• Projection method: Two standard projection systems are used, which are First Angle Projection (most common worldwide) and Third Angle Projection (common in the USA).

## Types of Lines

• Construction lines: Light, thin lines used to lay out the preliminary design.
• Object lines: Solid lines that outline the object.
• Dimension lines: Thin, dark solid lines that show dimensions on the drawing.
• Extension lines: Thin lines used to define the extension of dimensions from the object.
• Leader lines: Thin lines leading from a dimension figure to the related extension line.
• Centre lines: Thin, broken lines indicating the center of an object or a hole.
• Hidden lines: Dotted lines showing hidden features of the object.

## Orthographic Projection

• The orthogonal projections are 2D drawings of 3D objects.
• It depicts the different views of the object (top, front, and side) in 2D planes.
• Each view should align correctly with the others.

## Isometric Drawing

• An isometric drawing displays the three sides of an object in one view.
• All measurements along the drawing’s axes are to scale, but diagonal and curved lines are not.
• Despite distortions, it visualises how an object looks from a specific angle, offering a more comprehensive view than orthographic projection.

## Dimensioning

• Dimensioning is the process of adding measurements to the drawing.
• It helps to communicate the size and scale of the object clearly.
• Dimensions are marked using dimension lines, with the actual measurement placed above the line.
• Do not dimension to hidden lines, and don’t duplicate dimensions.

## Sectional Views

• Sectional views are used to show “cut-open” or “see-through” images of the object.
• They are commonly used to show complex shapes, display interior features or to simplify a crowded exterior view.
• Sectional views must be correctly identified with labels or notes.

## Geometric Tolerance

• Geometric tolerances control the shape, position, and size of features.
• There are fourteen types of geometric tolerances: straightness, flatness, roundness (circularity), cylindricity, line profile, surface profile, angularity, perpendicularity, parallelism, position tolerance, concentricity, symmetry, runout, and total runout.
• Each tolerance has its specific symbols and specifications for application to a design.

This content provides a good basis for the topics relevant to engineering drawing techniques. Remember, practice is essential. Draw and label as much as possible, to understand the procedures and features of each drawing technique properly. It will also help to see objects from different aspects, boosting spatial awareness and comprehension.