Here we are with Mechanical Engineering Interview Questions

Do you know Design,Research and Development are core department of Mechanical Engineering? . The language of communication used in these department is through drawings Its a global language. The alphabet for this language are symbols of GD&T. We think being mechanical engineers you should know some of the basics about it.

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1) What is GD&T and Who introduced the concept of GD&T?
GD&T is Geometric Dimensioning and Tolerancing .Its a language through which Design Engineers
communicate.Stanley Parker introduced the concept of Geometric Dimensioning and Tolerancing (GD&T) in 1930’s and he was from Scotland.

2) What is the need of GD&T?
As we all know that its impossible to get a machine which gives you exact physical parts according to the required dimension. There is always some sort of deviation in the part manufactured. The deviations are caused due to following reasons:

1)Vibration in the machine
2)Tool Wear and Tear
4)Mounting Error
5)Human Error
6)Environment conditions.

 So to meet the actual condition of machining tolerances and allowances are provided to the dimensions. So we require GD&T.

3) What is a micron?
A micron is 1000th part of 1mm. That is divide 1mm into 1000 equal parts the value that you would get is 1micron. For example the diameter of human hair is approximately 70 to 80 microns.

4) Which Angle of Projection of system is used currently in industry and why?

Currently in industries 1st angle and 3rd angle projection system is used. As of rule we rotate the horizontal plane clockwise. Now after taking the projection and rotating the horizontal planes we get perfect individual views in 1st and 3rd angle projection system but in the second and fourth angle projection system the planes overlap and the views are merged

 The second question to this query would be what if we go against the rule and rotate the vertical plane clockwise? 

The viewer is on 2nd angle projection and vertical plane is rotated clockwise then top view will be on bottom of front view and in 4th angle projection the  top view will be on top of front view that is it will make the same view point as 1st and 3rd angle projection system Depicted in the figure below so we use only 1st and 3rd angle projection system.

5) What are the benefits of GD & T?
Precision & Accuracy
Reduced rework cost
Reduced Defects
Increased understanding

6) What does 8.8 mark on the bolt signify?
It gives you value of tensile strength and yield strength.
For eg. The tensile strength over here in 8.8 marking bolt would be 800 N/mm^2 and its yield strength is 640 which is 80% of the tensile strength.

7) Name different types of fits
Clearance fit
Interference fit
Transition fit

8) What are jigs and fixture?
this question is often asked and it always confuses. So here is a clear answer for difference between jigs and fixture.

-Jigs gives direction to cutting tool
-We can perform various operations like drilling, reaming ,tapping and polishing.

-Fixtures are used to hold the workpiece
-Fixture are not used to perform any of the operations

9) If you are provided a bottle then how will you increase its strength?
The strength depends on design, material and thickness of the part. So in order to increase strength of the bottle one can provide the ribs and make the bottom of the bottle concave shaped. You can also increase its strength by using a stronger material and increasing its thickness.

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