Learning how to read engineering drawings is one of the most important skills for a mechanical design engineer. A good drawing communicates the shape, size, material, tolerances and manufacturing requirements of a component without needing a physical model.
What Is an Engineering Drawing?
An engineering drawing is a controlled technical document used to communicate product design information. It normally includes views of the component, dimensions, tolerances, notes, material information and drawing identification.
Understand the Main Orthographic Views
The most common orthographic projection views are the front, top and side views. Each view represents the object from a different direction. Start with the front view because it usually communicates the main shape and important features.
- Front view: shows the primary profile.
- Top view: shows features visible from above.
- Side view: communicates depth and side features.
How to Read Dimensions
Dimensions define the required size of a feature. Check linear dimensions, diameters, radii, angles and depth dimensions. Never assume a measurement from the drawing scale when a dimension is provided.
Look for Tolerances
A dimension may have a general tolerance or a specific tolerance. Tolerances define the acceptable variation during manufacturing. For precision parts, also look for GD&T symbols such as position, flatness, perpendicularity and profile.
Section Views and Hidden Features
Section views reveal internal geometry that cannot be understood easily from outside views. Hatching normally indicates the cut surface. Hidden lines can also show holes, pockets and internal steps.
A Practical Reading Sequence
- Read the title block.
- Identify the projection method.
- Study the main view.
- Match the related views.
- Read dimensions and tolerances.
- Check material, finish and manufacturing notes.
- Review revisions before manufacturing.
Final Tip for Mechanical Designers
Do not try to understand every line at once. Read the drawing from overall shape to individual features, then verify each feature against the dimensions and notes. Practicing with real mechanical drawings is the fastest way to improve.