Mechanical Design Interview Questions and Answers

If you have a degree or diploma in mechanical engineering. And looking for a job in the mechanical field. Then this article can help you with your interview preparation. In this article, we will discuss commonly asked interview questions and answers on mechanical Design. Interview questions discussed here are from the engineering curriculum. If you are aware of mechanical engineering basics, You can answer these questions.

We suggest you to also read this article on frequently asked technical interview questions on manufacturing.

Here are the commonly asked interview questions and answers on mechanical design.

What are engineering tolerance?

Engineering Tolerances are allowable variation from given dimensions. In other words, it is the total amount by which a given dimension may vary without affecting product function.

Tolerance (for hole) = Hole (MMC) – Hole (LMC)

Why are Tolerance Required? 

The production of closely mating parts, without tolerances is economically unfeasible. This will increase the rejection rate and manufacturing cost. Therefore, tolerances are used with part dimensions to facilitate manufacturer and reduce cost.

Refer this article for more details on engineering tolerance.

What is tolerance Stackup Analysis?

Tolerance Stackup analysis is a design tool used to analyse and optimize product assembly. It calculates the cumulative effects of part tolerances in an assembly.

Read this article for more details on tolerance stackup analysis.

What are the types of tolerance?
  1. Unilateral Tolerance
  2. Bilateral Tolerance
What do you understand by fit?

The term fit refers to the permissible clearances between mating parts. The clearance between mating parts determines the type of Fit. 

What are the different types of fits?
  1. Clearance Fit
  2. Interference Fit
  3. Transition Fit
What do you understand by Engineering Drawing?

Engineering drawing is a technical document used to transfer technical information and define requirements. In other words, it’s a graphical language that communicates ideas and information from one mind to another.

What is Section, Projection, Isometric & Detailed View?

  • Projection View : Projection view represents a 3 dimensional objects in 2 dimensions while looking from one side.
  • Section View: It is used to show the interior construction of a part in engineering drawing.
  • Isometric View: Isometric projection represents a 3D objects into 2D in an engineering drawings. In this three coordinate axes appear equally foreshortened and the angle between any two axes is 120 degrees.
  • Detailed View: It represents the larger view of any section of engineering drawing.
What is the symbol of 1st and 3rd angle projection?
First Angle Projection Symbol
First Angle Projection Symbol
Third Angle Projection Symbol
Third Angle Projection Symbol
Which projections are preferred for engineering drawings?

Following two types of projections are used :

What is the difference Between First and third angle Projection?

In 1st angle projection part lies in first quardent. Therefore object lies in between plane and observer.

in First angle projection object lies in between observer and projection plane

Whereas in third angle projection projection plane lies in between observer and object.

In third angle projection projection plane lies in between observer and object.

Why 2nd and 4th angle projections are not used?

Because of overlapping of front and top views 2nd and 4th angle projections are not used.

Refer this article to know in detail why 2nd and 4th angle projections are not used for making engineering drawings?

What is the least count and how it is calculated?

It is the smallest value measured with the measuring instrument. For example, the least count for a normal scale is 1 mm whereas for vernier scale it is 0.01 mm. Read this article for more details on Least Count. 

Least Count= Value of one main scale Division – Total Number of Vernier scale division

What is the least count for Vernier Scale, Micrometer and normal scale?
  • Vernier Caliper Least Count = 0.01 mm (Digital) , 0.02 mm (manual)
  • Micrometer Least Count = 0.01 mm
  • Normal scale Least Count = 1 mm 
What is the factor of safety and how it is calculated?

FOS describes the load carrying capacity of a system beyond the expected or actual loads. In other words, FOS represents : how much stronger the system is compared to intended load.

FOS is calculated considering design load maximum value. Value of FOS is always greater than one.

What are types of screws?

Here are the various types of screw available in the market:

According to the type of  Screw Head

  1. Countersunk Screw
  2. Raised or oval head screw
  3. Pan Head Screw
  4. Flat Head Screw
  5. Flange Head Screw

According to Screw Drive Type

  1. Sloted
  2. Phillip 
  3. Pozi Drive
  4. Torx Head
  5. Hex Socket
  6. Trangular head
  7. Security Head Socket

According to Screw Thread Type

  1. Machine Screw
  2. Thread Forming
  3. Thread Cutting Screw
What is Stress-Strain Curve?

Stress Strain curve represents the behavior of material when an external force is applied to it. This diagram is used by product design engineers during material selection and structure design calculations.

This curve represents the relation between stress and strain produced in a material when load is applied.

Refer this article for more details on stress-strain curve.

Draw Stress and Strain Curve for Ductile and Brittle Material?

Ductile, Brittle and plastic material stress strain diagram comparison.

What is a datum plane?

A datum is a theoretical exact plane, axis or point location that GD&T or dimensional tolerances are referenced to.

What is GD&T (Geometric Dimension & Tolerance) ?

GD&T is a system for defining engineering tolerances. It helps in conveying product assembly requirements to manufacturers. Read this article to know the basics of GD&T.

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