10 Engineering Drawing Interview Questions and Answers

Engineering drawing is a critical skill in the field of engineering, serving as the universal language for engineers to communicate complex designs and ideas. It involves the creation of detailed and precise diagrams that convey the specifications, dimensions, and construction of various components and systems. Mastery of engineering drawing ensures that designs are accurately interpreted and executed, minimizing errors and enhancing the efficiency of the engineering process.

This article provides a curated selection of interview questions focused on engineering drawing. Reviewing these questions will help you solidify your understanding of key concepts and techniques, ensuring you are well-prepared to demonstrate your proficiency in this essential area during your interview.

Engineering Drawing Interview Questions and Answers

1. Explain the difference between first-angle and third-angle projection.

In engineering drawing, first-angle and third-angle projections are methods to create 2D representations of 3D objects. The main difference lies in the positioning of the object relative to the projection planes.

In first-angle projection, the object is between the observer and the projection plane, resulting in views projected onto planes behind the object. The top view is below the front view, and the right-side view is on the left side of the front view.

In third-angle projection, the projection plane is between the observer and the object, with views projected onto planes in front of the object. The top view is above the front view, and the right-side view is on the right side of the front view.

These differences are important for interpreting engineering drawings, as the placement of views affects the understanding of the object’s geometry.

2. What are the key differences between ISO and ANSI drawing standards?

The differences between ISO (International Organization for Standardization) and ANSI (American National Standards Institute) drawing standards are in dimensioning, tolerancing, and symbols.

Dimensioning:

• ISO: Uses the metric system (millimeters) as the standard unit. Dimensions are typically placed outside the object with extension lines.
• ANSI: Uses both metric and imperial systems (inches). Dimensions can be placed inside or outside the object, with more flexible placement compared to ISO.

Tolerancing:

• ISO: Uses the ISO 2768 standard for general tolerances, with specific classes (fine, medium, coarse, very coarse).
• ANSI: Uses the ASME Y14.5 standard for geometric dimensioning and tolerancing (GD&T), which is more detailed with various symbols for different tolerances.

Symbols:

• ISO: Uses internationally recognized standardized symbols, often more simplified.
• ANSI: Uses a different set of more detailed symbols, especially in GD&T, widely used in North America.

3. Describe the purpose of geometric dimensioning and tolerancing (GD&T).

Geometric Dimensioning and Tolerancing (GD&T) is a system in engineering drawings to define allowable variations in a part’s geometry. Its purpose is to ensure parts fit and function correctly in their assembly, even with slight manufacturing variations. GD&T specifies the size, form, orientation, and location of features, aiding consistency and quality in manufacturing.

Benefits of GD&T include:

• Improved Communication: Provides a universal language for engineers, machinists, and inspectors, reducing misinterpretation.
• Enhanced Quality Control: Specifies allowable variations, maintaining quality and functionality of parts.
• Increased Tolerance Flexibility: Allows for more flexible tolerances, leading to cost savings without compromising functionality.
• Better Fit and Function: Ensures parts fit and function as intended, even with slight dimensional variations.

4. What is the purpose of a section view, and how is it created?

A section view in engineering drawing reveals internal features of a part or assembly not visible from the outside. This is useful for complex parts where internal details need clear communication. The section view aids in understanding internal geometry, important for manufacturing, inspection, and assembly.

To create a section view, a cutting plane passes through the object, removing the part in front of the plane. The resulting view shows internal features as if the object is cut along the plane. The cutting plane is represented by a line with arrows indicating the direction of sight. The sectioned area is often hatched with lines to differentiate it from the rest of the drawing.

Types of section views include:

• Full Section: The cutting plane passes entirely through the object.
• Half Section: Only half of the object is sectioned, often used for symmetrical objects.
• Offset Section: The cutting plane is offset to pass through important features not in a straight line.
• Broken-Out Section: Only a small portion of the object is sectioned to show a specific feature.

5. What information is typically included in a Bill of Materials (BOM)?

A Bill of Materials (BOM) is a list of materials, components, and assemblies required to construct, manufacture, or repair a product. It is essential in engineering, manufacturing, and production processes, ensuring all necessary parts are available for efficient production and assembly.

Typically, a BOM includes:

• Part Number: A unique identifier for each component or material.
• Part Name: The name or description of the component or material.
• Quantity: The number of units required for each component or material.
• Unit of Measure: The unit in which the quantity is measured (e.g., pieces, meters, kilograms).
• Material Specifications: Details about the material, such as grade, type, and properties.
• Supplier Information: Details about the supplier or manufacturer of the component or material.
• Reference Designators: Identifiers indicating where the component is used in the assembly (commonly used in electronic BOMs).
• Assembly Instructions: Specific instructions or notes related to the assembly or use of the component.
• Cost: The cost of each component or material, used for budgeting and cost analysis.
• Lead Time: The time required to procure or manufacture the component or material.

6. Explain the concept of true position in GD&T.

True position in GD&T refers to the exact, theoretical location of a feature as defined by design specifications. It is a three-dimensional tolerance zone within which the center, axis, or surface of a feature must lie. True position is often represented by a tolerance zone, typically cylindrical or spherical, within which the feature must be located.

True position ensures parts fit together correctly in an assembly, allowing for precise and flexible control of feature location compared to traditional linear tolerancing. It is often used with datums, which are reference points, lines, or surfaces on a part serving as a starting point for measurements.

In GD&T, true position is indicated by a feature control frame, specifying the tolerance zone and any applicable datums. The feature control frame includes the geometric characteristic symbol for position, the tolerance value, and any datum references.

7. How do you manage revision control in engineering drawings?

Revision control in engineering drawings maintains the integrity and accuracy of design documents, ensuring all changes are documented and the most current version is available. This process involves several practices:

• Versioning: Each revision of a drawing is assigned a unique version number or letter, identifying the sequence of changes and ensuring the latest version is recognizable.
• Change Logs: A change log or revision history documents changes made, by whom, and when, providing a record of the drawing’s evolution.
• Approval Workflow: Changes to drawings often require approval from multiple stakeholders, ensuring necessary reviews and sign-offs before finalizing a revision.
• Document Management Systems (DMS): Tools like Autodesk Vault, SolidWorks PDM, or other DMS store and manage drawings, providing features like version control, access control, and audit trails.
• Annotations and Markups: Changes are often annotated directly on the drawing using standardized symbols and notes, clarifying modifications made.
• Backup and Archiving: Older versions of drawings are archived and backed up for retrieval if needed, important for traceability and compliance with industry standards.

8. Explain the difference between unilateral and bilateral tolerances.

In engineering drawing, tolerances specify permissible limits of variation in a physical dimension, ensuring parts fit together properly in an assembly, even with slight variations. There are two main types of tolerances: unilateral and bilateral.

Unilateral tolerances allow variation in only one direction from the nominal dimension. For example, if a dimension is specified as 50 mm with a unilateral tolerance of +0.1 mm, the acceptable range is from 50 mm to 50.1 mm, meaning the dimension can only increase from the nominal value but cannot decrease.

Bilateral tolerances allow variation in both directions from the nominal dimension. For example, if a dimension is specified as 50 mm with a bilateral tolerance of ±0.1 mm, the acceptable range is from 49.9 mm to 50.1 mm, meaning the dimension can either increase or decrease from the nominal value within the specified limits.

9. How do you interpret surface finish symbols on a drawing?

Surface finish symbols on engineering drawings specify the desired surface texture of a part, providing information about surface roughness, waviness, and lay, which are important for ensuring parts fit and function correctly.

The most common surface finish symbol is a check mark-like symbol, modified with additional information to convey specific requirements. Key elements include:

• Basic Symbol: A check mark (or a check mark with a horizontal line) indicating a surface finish requirement.
• Roughness Value: A number above the basic symbol indicating the maximum allowable roughness, typically measured in micrometers (µm) or microinches (µin).
• Machining Allowance: A number below the basic symbol indicating the amount of material to be removed by machining.
• Lay Direction: Additional symbols or letters indicating the direction of the lay, the predominant direction of the surface texture.
• Production Method: Additional notes or symbols specifying the production method, such as grinding, milling, or turning.

10. How are material specifications indicated on engineering drawings?

Material specifications on engineering drawings are indicated using standardized notations and symbols, providing information about the materials to be used in manufacturing, ensuring the final product meets required standards and performance criteria.

Typically, material specifications are included in the title block or a dedicated materials list on the drawing. The title block, usually at the bottom right corner, contains essential information such as the drawing number, revision number, and material specifications. The materials list, if used, is a separate table detailing all materials required for the project.

Material specifications can also be indicated directly on the drawing using leader lines and notes, often accompanied by standardized abbreviations and symbols for clarity and consistency. For example, steel might be indicated as STL, aluminum as AL, and so on. The specific grade or type of material is also included, such as STL 304 for stainless steel 304.

Engineering drawings often reference industry standards and specifications, such as ASTM (American Society for Testing and Materials) or ISO (International Organization for Standardization) standards, providing additional details about material properties like tensile strength, hardness, and chemical composition.