25. mechanical engineering interview questions and answers


Mechanical Engineering interview questions and answers

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1.What are the different types of fits? Explain?
2. What are the factors that can affect the Factor of safety selection?
3. What is heat treatment and why is it done?
4. What are the rules that must be kept in mind while designing castings?
5. What are the points that should be kept in mind during forging design?
6. Describe briefly the different cold drawing processes.
7. What are the different theories of failure under static load, explain briefly?

What are the different types of fits? Explain?

On the basis of Indian standards fits can mainly be categorized into three groups:
> Clearance Fit: These types of fits are characterized by the occurrence of a clearance between the two mating parts. The difference between the minimum size of the hole and the maximum size of the shaft is called the minimum clearance, the difference between the maximum size of the hole and the minimum size of the shaft is known as maximum clearance.
> Interference Fit: In these types of fits the size of the mating parts are predefined so that interference between them always occurs. The tolerance zone of the hole is completely below the tolerance zone of the shaft.
> Transition Fit: As the name suggests these type of fit has its mating parts sized limited to allow either clearance or interference. The tolerance zone of the hole and the shaft overlaps in case of such fits.

For a shaft designated as 40 H8/f7, calculate the tolerances.

Given: Shaft designation = 40 H8/f7
The shaft designation 40 H8/f 7 means that the basic size is 40 mm and the tolerance grade for
the hole is 8 ( i. e. I T 8) and for the shaft is 7 ( i. e. I T 7).
Since 40 mm lies in the diameter steps of 30 to 50 mm, therefore the geometric mean diameter,
D = Square root of (30 x 50) = 38.73 mm
We know that standard tolerance unit,
i = 0.45 x Cube root of (D) + 0.001 D
i = 0.45 × 3.38 + 0.03873 = 1.559 73 or 1.56 microns
i = 1.56 × 0.001 = 0.001 56 mm ...(1 micron = 0.001 mm)
The standard tolerance for the hole of grade 8 (IT8)
= 25 i = 25 × 0.001 56 = 0.039 mm
The standard tolerance for the shaft of grade 7 (IT7)
= 16 i = 16 × 0.001 56 = 0.025 mm

What are the factors that can affect the Factor of safety selection?

The factor of safety is used in designing a machine component. Prior to selecting the correct factor of safety certain points must be taken into consideration such as:
> The properties of the material used for the machine and the changes in its intrinsic properties over the time period of service.
> The accuracy and authenticity of test results to the actual machine parts.
> The applied load reliability.
> The limit of stresses (localized).
> The loss of property and life in case of failures.
> The limit of initial stresses at the time period of manufacture.
> The extent to which the assumptions can be simplified.

The factor of safety also depends on numerous other considerations such as the material, the method of manufacturing , the various types of stress, the part shapes etc.

What is heat treatment and why is it done?

Heat treatment can be defined as a combination of processes or operations in which the heating and cooling of a metal or alloy is done in order to obtain desirable characteristics without changing the compositions. Some of the motives or purpose of heat treatment are as follows:
> In order to improve the hardness of metals.
> For the softening of the metal.
> In order to improve the machinability of the metal.
> To change the grain size.
> To provide better resistance to heat, corrosion, wear etc.

Heat treatment is generally performed in the following ways:
> Normalizing
> Annealing
> Spheroidising
> Hardening
> Tempering
> Surface or case hardening

What are the rules that must be kept in mind while designing castings?

Some of the points that must be kept in mind during the process of cast designing are as follows:
> To avoid the concentration of stresses sharp corners and frequent use of fillets should be avoided.
> Section thicknesses should be uniform as much as possible. For variations it must be done gradually.
> Abrupt changes in the thickness should be avoided at all costs.
> Simplicity is the key, the casting should be designed as simple as possible.
> It is difficult to create true large spaces and henceforth large flat surfaces must be avoided.
> Webs and ribs used for stiffening in castings should as minimal as possible.
> Curved shapes can be used in order to improve the stress handling of the cast.

What are the points that should be kept in mind during forging design?

Some of the points that should be followed while forging design are:
> A radial flow of grains or fibers must be achieved in the forged components.
> The forged items such as drop and press forgings should have a parting line that should divide the forging into two equal halves.
> The ribs in a forging should not be high or thin.
> In order to avoid increased die wear the pockets and recesses in forgings should be minimum.
> In forgings the parting line of it should lie as far as possible in a single plane.
> For ease of forging and easy removal of forgings the surfaces of the metal should contain sufficient drafts.

Describe briefly the different cold drawing processes.

Some of the important cold drawing processes are as follows:
> Bar and Rod Drawing: In the case of bar drawing the hot drawn bars are at first pickled, washed and coated to prevent oxidation. Once this is done a draw bench is used for the process of cold drawing. In order to make an end possible to enter a drawing die the diameter of the rod is reduced by the swaging operation. This end is fastened by chains to the draw bench and the end is gripped by the jaws of the carriage. In this method a high surface finish and accuracy dimensionally is obtained. The products of this process can be used directly without any further machining.
> Wire Drawing: Similar to the above process the bars are first pickled, washed and coated to prevent any oxidation. After this the rods are passed through several dies of decreasing diameter to provide a desired reduction in the size ( diameter ). The dies used for the reduction process is generally made up of carbide materials.
>Tube Drawing: This type of drawing is very similar to the bar drawing process and in majority of cases it is accomplished by the use of a draw bench.

What are the different theories of failure under static load, explain briefly?

The main theories of failure of a member subjected to bi-axial stress are as follows:
> Maximum principal stress theory ( Rankine’s theory): This theory states that failure occurs at a point in member where the maximum principal or normal stress in a bi-axial system reaches the maximum strength in a simple tension test.
> Maximum shear stress theory ( Guest’s or Tresca’s theory): This theory states that failure occurs when the biaxial stress reaches a value equal to the shear stress at yield point in a simple tension test.
> Maximum principal strain theory ( Saint Venant theory): This theory states that failure occurs when bi-axial stress reaches the limiting value of strain.
> Maximum strain energy theory ( Haigh’s theory): This theory states that failure occurs when strain energy per unit volume of the stress system reaches the limiting strain energy point.
> Maximum distortion energy theory ( Hencky and Von Mises theory): This theory states that failure occurs when strain energy per unit volume reaches the limiting distortion energy.

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shuffleos.com 09-10-2020 03:48 PM

Mechanical Eng

For an experience guys job change make some time critical due to prolong non contact of engineering basic, such thing is easily shown here and well explained this help to brush up me for an Interview.
I would like to take this Opportunity to Thanks you for acquiring such material and helping the needy Engineer over here.

vijendra shrivastav 10-1-2019 04:33 AM

Heat Treatment

Thank you for Remembering the basic terms for my interview.It helped me a lot.

Ramanandh.H 07-24-2019 01:35 AM

interview questions

Excellent efforts have been put to prepare the questions and answers which will be helpful to college freshouts and also candidates already in jobs to brushup their subjects.
New areas like statutory environment requirement can be added

SRINIVASAIAH 01-7-2019 07:03 AM

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ABDUL CHYYAAAMFER 10-15-2018 12:40 AM

questions during an interview

Very useful questions.Thanks a lot.

ABHIRAM CHANDRA 10-15-2018 12:32 AM

Content related

Some questions related to Equipments like measuring gage, pressure gauge, and others will definitely help to us.

Kishan Rajbhar 07-17-2017 05:11 AM

Mechanical interview

This question is well define. More questions about mechanical aptitude is also ask in interview. So my humble request is that provide that type of questions and its answer.

Hardik prajapati 06-7-2017 02:32 AM

interview question

all que nd ans are helpful but when i had gone to take interview for production .interviewer ask me question another types relete to our sub for ex what is mechanical engg,nd what is engg etc.

HASMAT ALI 02-7-2017 12:37 PM


Kindly provide some questions regarding Pistons in petrol and Deisel engine

Dayashankar A S 12-20-2016 12:19 AM


Fits are very difficult to understand theoretically and if there will be practical examples also ,then it is very easy to understand

Rohit 12-14-2016 02:17 AM

Mechanical Engineering

this answer is very nice. but write some engine related question.

kumaresan.k 10-16-2016 05:38 AM

mechanical engineering questions and answers for interview

these question are very important
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Chandra prakash 09-20-2016 12:56 PM


These questions are very helpful for revisen of topics when we have a distance with our subjects so I wanna suggest please mention some interview questions related to quality and producton .

Navneet Upadhyay 09-4-2016 06:41 PM

Heat treatment Types

please add Quenching to heat treatment types.
thanks for al information.

Abdulelah 08-23-2016 06:09 AM

Mechanical engineering

I remember correctly what I learn Tq

Jeevarathinam S 08-17-2016 07:09 AM


thank you for the basic information about this

ritesh mahapatra 08-10-2016 04:19 AM



vengi 07-20-2016 02:22 AM

mechaical engg.

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BESTON.J 06-23-2016 07:49 AM

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subramani 06-10-2016 12:14 AM

Interview quest(mech)

Very useful

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Sai 02-23-2016 07:06 AM


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mech 01-19-2016 08:55 AM


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vishwanath v 01-7-2016 08:42 AM

mech. engg

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santhosh g 12-2-2015 11:49 AM

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D.satya praveen 11-8-2015 10:39 AM

mechanical engg.

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Naveen 10-27-2015 05:13 PM

Mechanical Engg.

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Dhiraj 10-12-2015 11:42 PM

Heat treatment

While defining Heat treatment, we cannot say for obtaining desired characteristics without changing composition.
Because in case of case hardening, we are increasing the carbon potential at the surface to get hard case and soft core. Hence the Carbon composition is getting more upto total case depth.

Y.D. LENKA 09-17-2015 06:10 AM


Good Explanation....

Omshree Bagnawar 08-13-2015 03:30 AM


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JALAKAM SHIVAJI 07-22-2015 09:04 AM


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about notes

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mechanical engg

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jay prakash 05-30-2015 03:34 PM


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anil patil mach,,engg 05-21-2015 04:47 AM

Important for Mechanical engineering Students

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Yogesh Ove 04-29-2015 01:47 PM


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Melaku Gedefaw 04-2-2015 04:19 AM

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Mohanraj 04-1-2015 12:57 PM

mechanical engineering

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mech. Engineer

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mech engineerining

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interview question

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Mech. Engg.

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Ashish M. Harinkhede 01-31-2015 04:23 PM

mechanical engg

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mechanical engg

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gaurav singh 01-16-2015 12:08 PM

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kisan vishnu kale 01-10-2015 07:06 AM



NIBAS BEURA 12-20-2014 02:40 AM


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vikash 10-30-2014 05:24 AM

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soumya parida 06-20-2014 12:33 AM


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