Answer / m asim

A typical bearing is the 6203ZZ bearing. This part number
can be divided into it's components:

6203ZZ

which means:

Type Code
Series
Bore
Suffix
The type code indicates the type of bearing. While each
manufacturer uses their own numbers, there are a few
numbers that could be considered standard in the industry.

1 Self-Aligning Ball Bearing

This kind of ball bearing has a spherical outer race,
allowing the axis of the bearing to "wander around". This
is important because misalignment is one of the big causes
of bearing failure.

2 Spherical Roller Bearing
3 Double-Row Angular Contact Ball Bearing

Designed to take axial as well as radial loads.

4 Double-Row Ball Bearing

Designed for heavy radial loads.

5 Thrust Ball Bearing

Intended for exclusively axial loads.

6 Single-Row Deep Groove Ball Bearing

Typical ball bearing. Handles light axial loads as well as
radial loads.

7 Single-Row Angular Contact Bearing

For axial (one direction only!) as well as radial loads.

8 Felt Seal

To assure that the entire inside edge of the seal touches
the inner ring, the inner ring is enlarged. If a bearing of
more normal proportions is required, the outer ring is also
enlarged, and the bearing is referred to as a "wide cup"
bearing.

32 Tapered Roller Bearing

This is the kind of wheel bearings used in cars. The
rollers are not cylindrical, but conical. They handle large
raidal and axial loads.

R Inch (Non-Metric) Bearing
Varies
N Cylindrical Roller Bearing

Instead of balls, cylindrical rollers are used. These
bearings can handle much more radial load, but can handle
much less axial load, than ball bearings.

NN Double-Row Roller Bearing

Handles greater radial loads than standard cylindrical
roller bearings.

NA Needle Roller Bearing

Needle bearings are basically roller bearings, but the
rollers are much smaller, making the bearing more compact.
Varies


Type 6, "single-row deep groove", is perhaps the most
common type of bearing.

If the bearing is an inch bearing (the first digit in the
number is an R), then the size is the digit or digits
immediately following the R, in 16ths of an inch. An R8-2RS
bearing, for example, has an 8/16th or 1/2 inch bore.

If the first digit is a number, however, it is a metric
bearing, and the second digit is the series, which reflects
the robustness of the bearing. The series are, from
lightest to heaviest: 8 Extra thin section
9 Very thin section
0 Extra light
1 Extra light thrust
2 Light
3 Medium
4 Heavy


Yes, they go in that order. Gotta keep things simple, you
know.

Each of these series also establishes a relationship
between the bore size, outer diameter, and thickness of the
bearing, in accordance with ISO standards. I have no idea
what they are.

The third and fourth digits indicate the bore size in
millimeters. Except for 0 through 3, the bore size is
simply five times the third and fourth digits together. 0
through 3, however, are different: 00 10mm
01 12mm
02 15mm
03 17mm


If there is no fourth digit - for example, a 608 bearing, a
common roller skate bearing - then the size is the last
digit in millimeters.

The last letters indicate something special about the
bearing. For example: Z Single shielded
ZZ Double shielded
RS Single sealed
2RS Double sealed
V Single non-contact seal
VV Double non-contact seal
DDU Double contact seals
NR Snap ring and groove
M Brass cage


And then there are the completely off-the-wall bearing
numbers, like 499502H. I have no idea what that number is
supposed to mean, but it applies to what is basically an
R10-2RS bearing, only a bit thicker and with a groove and
snap ring.

Examples
Common Skate Bearings
Number Bore
(mm) O.D.
(mm) Width
(mm)
608 8 22 7
627 7 22 7
688 8 16 4
698 8 19 6

All these bearing numbers start with 6, which tells us
they're Single-row deep groove ball bearings. The second
digits tell us the robustness of the bearings. The last
two, in series 8 and 9, are very thin and lightweight
bearings, while the first, in series 0, is an "extra light"
bearing without being abnormally thin. The third bearing,
in series 2, is the most robust of all, being
merely "light".

Light vs Heavy Comparison

Consider the following three bearings: Number Bore
mm O.D.
mm Thickness
mm
6010-2RS 50 80 16
6210-2RS 50 90 20
6310-2RS 50 110 27


We can see from the part numbers that they're all 50mm
single-row deep groove ball bearings. However, we can also
see that they're each a different series; specifically,
Extra Light, Light, and Medium. Compare the O.D. and
thickness of each bearing, and you can see how the Extra
Light bearing (series 0) is the smallest, and the Medium
Bearing (series 3) is the largest. The larger bearing can
take much more load than the smaller bearing, though how
much depends on the manufacturer and the RPM the bearing is
run at.

Number Bore
mm O.D.
mm Thickness
mm
6904-2RS 20 37 9
6004-2RS 20 42 12
6204-2RS 20 47 14
6304-2RS 20 52 15


These are all 20mm single-row deep groove ball bearings of
different series. The first, of series 9, is a "very thin
section" bearing, meaning it is much thinner than usual -
it is only 25% as thick as its O.D., while the others are
approximately 30% as thick as their O.D.

Answer / carl gomes

A bearing is essentially 'a part of a machine that bears friction'. It is always used to reduce the friction between 2 revolving parts or between a fixed part and a moveable part.

• Why do you think you would do well at this job?

2 Answers   Petro Star Mount,

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. Where can you find the feed check valve and feed stop valve and give the purpose of it?

1 Answers   ABC Inc, RRB, Siemens,

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I qualified the written exam conducted by BARC and attended the interview. First let me tell you that this is the most genuine and toughest interview among all the PSUs. This is the best interview methodology that they adopt. They just ask for very basic questions of Intermediate (12th) level and want to check the basic understanding. Almost all the questions are practical questions no direct relation with the knowledge of core technical. In this way they look for the way you approach to solve a problem. Because the post they offer you is scientific officers’ post. This is a research oriented job that requires the great skills and knowledge to solve a real practical problem. So, this was a basic idea about the interview. Now let's talk about the methodology, actually they ask you 4-5 subjects in which you are more comfortable and ask the basic questions. But keep in mind that you are really comfortable with those subjects and you should be thoroughly prepared. Because they will try to divert you from your answer and will drill on topic till you surrender. But anyway you don't worry even if you are not able to solve a problem for whole but the way you approach and the basic concepts should be correct. They are generally the minimum time for interview is more than 45 minutes. Even the person they know will not be qualified; they drill him at least for 45 minutes. As the interview timing cross more than 45-60 minutes, your chance goes on increasing to get selected. Finally If they are satisfied with your performance then they give you a medical slip that insures your eligibility fir the interview. Final Result depends on the no. of posts and the merit list prepared on the basis of marks you achieved in written and interview. I wish you all the best for your interview. It is well known that hard work and the luck both are that major factor that plays important roles in every exam. Your Luck also plays an important role that by which panel you are going to be interviewed. During my interview I was a victim of bad luck so I could not qualified the interview. I had heard that the panel members being very helpful they bring you out of the pressure if you feel during the interview but this was not true in my case. Anyways, I entered in the room, there were 5 members. The committee chairman asked me about my hometown. The whole conversation was in Hindi, so the people who are from Hindi background they don't need to be afraid of this problem in PSU interviews. Then he asked me "Is it your first interview or you have gone through any other interview?", Me: "Sir this is my first interview". This normal conversation is just to make you feel good and to make you comfortable. Chairman: So you have done your B.Tech from IIIT? Me: Yes Sir. Suddenly another person interrupted as he was looking at my cv, he told to the chairman that I got first Prize in solid modeling Contest. This was a curse for me for that interview. Chairman: So you got first prize in Modeling? Me: Yes sir. Chairman: What is Computer Aided Design? Me: I told. Chairman: You have been taught the Finite Element Methods course? Me: Yes sir. Chairman: Can you do the analysis of a cylindrical pressure vessel? Me: No sir, actually we just learnt the analysis of one dimensional objects. Chairman: But you know the basics of analysis steps? Me: Yes sir. Chairman: What will be the first step? Me: We will take the symmetry and will not require going through the analysis of whole section. Chairman: Draw the element of symmetry? Me: I drawn. Chairman: Next step? Me: Boundary conditions and Forces. Chairman: What will be the boundary conditions, forces etc.....? I could not give the answers, and the trials were wrong and I was totally confused. but he rammed me a lot and wasted almost 10 minutes. It was a bad impression that lead me through the darkness. Then he asked me to put the name of subjects I studied in B.Tech as our curriculum is different from other colleges curriculum, It has major emphasize on Design. So under pressure I was not able to recall the subjects. I started to recall them and listed on the paper but didn't minded to put them in the order I prepared. Actually I prepared Material science, Thermodynamics, Heat Transfer and Micro Metal Forming (for the fabrication of MEMS devices, a recent topic). So they just started asking the questions randomly from the subjects they got in that list. After a sometime chairman asked me about the subjects I am comfortable. I told and given the preference to Micro-Metal Forming that was a new topic for him and he decided to get out of the topic and asked about the issues when we go through the micro forming. I told that as we go from macro size to micro, the strength, isotropic behavior and surface roughness changes and affect a lot. Then he asked how surface roughness comes into picture? Me: As material thickness approaches towards micro size, the no. of grain boundaries becomes fewer and grain boundaries sizes are in the order of microns so the very early surface has a lot of deviations that comes in picture. Then he asked: What is inside the space between two grain boundaries; Gas or Vacuum? Me: Sir Vacuum. He Said: You are wrong, go and refer the books. and in this way he came out of the topic that he was trying for. So, I will suggest you not to give any new topic as the persons taking interview may or may not be comfortable with that and it may be a curse to you. In Thermo….. he asked He: there is a cylinder-piston system that contains a gas, a weight W is kept on piston what will be the pressure? Me: Sir W/(g*A)---A: area, g: gravity (It was wrong actually I was in such a pressure that to calculate the pressure I was using the formula M/A) Then another person asked me about "g", why I am using it ? I confidently said: sir to get the mass from weight He knew that I am confused so he asked me to derive it's dimension I derived then he asked me to derive the dimension of force by area and he asked me to compare, and I found my mistake. I said sorry and then He: I am giving it "Q" all the boundaries are insulated so that no heat goes outside, calculate it's final volume? Me: I was confused and was asking about a lot of irrelevant information needed to solve. He: This is all I told you now calculate the volume...no other information. I could not derive it. Then......Fluid: He: I am having an wedge shaped vessel (triangular shaped) I want to know the water level at different places, what will be the levels of water at different tubes? Me: Same level in every tube. He: why? Me: because of fluids property...pressure at a level is same at every point So the height raised will compensate for it. He: ok so, pressure is constant at all the points in same level but different at different levels? Me: Yes sir. He: So if I make two holes at different levels and fit a tube at outside from the vessel then water will flow? Me: yes sir. He: If I place a turbine in between the pipe then will the electricity produced? Me: No. He: why? Me: because water will flow once only. He: but pressure difference is continuously acting at two different levels? Me: as once water flows and the section gets filled pressure at the same level in vessel and pipe will be same, So no way it will flow again. This was a section where I was somewhat comfortable and answered correctly. SOM: Shear stresses, how shear stress comes ....Is bending stress and shear stress same and a lot....they make me totally confused. Mohr's Circle related questions. That I replied correctly. As you know that I am from Department of Mechanical Engineering. I qualified the written exam conducted by BARC and attended the interview. First let me tell you that this is the most genuine and toughest interview among all the PSUs. This is the best interview methodology that they adopt. They just ask for very basic questions of Intermediate (12th) level and want to check the basic understanding. Almost all the questions are practical questions no direct relation with the knowledge of core technical. In this way they look for the way you approach to solve a problem. Because the post they offer you is scientific officers’ post. This is a research oriented job that requires the great skills and knowledge to solve a real practical problem. So, this was a basic idea about the interview. Now let's talk about the methodology, actually they ask you 4-5 subjects in which you are more comfortable and ask the basic questions. But keep in mind that you are really comfortable with those subjects and you should be thoroughly prepared. Because they will try to divert you from your answer and will drill on topic till you surrender. But anyway you don't worry even if you are not able to solve a problem for whole but the way you approach and the basic concepts should be correct. They are generally the minimum time for interview is more than 45 minutes. Even the person they know will not be qualified; they drill him at least for 45 minutes. As the interview timing cross more than 45-60 minutes, your chance goes on increasing to get selected. Finally If they are satisfied with your performance then they give you a medical slip that insures your eligibility fir the interview. Final Result depends on the no. of posts and the merit list prepared on the basis of marks you achieved in written and interview. I wish you all the best for your interview. It is well known that hard work and the luck both are that major factor that plays important roles in every exam. Your Luck also plays an important role that by which panel you are going to be interviewed. During my interview I was a victim of bad luck so I could not qualified the interview. I had heard that the panel members being very helpful they bring you out of the pressure if you feel during the interview but this was not true in my case. Anyways, I entered in the room, there were 5 members. The committee chairman asked me about my hometown. The whole conversation was in Hindi, so the people who are from Hindi background they don't need to be afraid of this problem in PSU interviews. Then he asked me "Is it your first interview or you have gone through any other interview?", Me: "Sir this is my first interview". This normal conversation is just to make you feel good and to make you comfortable. Chairman: So you have done your B.Tech from IIIT? Me: Yes Sir. Suddenly another person interrupted as he was looking at my cv, he told to the chairman that I got first Prize in solid modeling Contest. This was a curse for me for that interview. Chairman: So you got first prize in Modeling? Me: Yes sir. Chairman: What is Computer Aided Design? Me: I told. Chairman: You have been taught the Finite Element Methods course? Me: Yes sir. Chairman: Can you do the analysis of a cylindrical pressure vessel? Me: No sir, actually we just learnt the analysis of one dimensional objects. Chairman: But you know the basics of analysis steps? Me: Yes sir. Chairman: What will be the first step? Me: We will take the symmetry and will not require going through the analysis of whole section. Chairman: Draw the element of symmetry? Me: I drawn. Chairman: Next step? Me: Boundary conditions and Forces. Chairman: What will be the boundary conditions, forces etc.....? I could not give the answers, and the trials were wrong and I was totally confused. but he rammed me a lot and wasted almost 10 minutes. It was a bad impression that lead me through the darkness. Then he asked me to put the name of subjects I studied in B.Tech as our curriculum is different from other colleges curriculum, It has major emphasize on Design. So under pressure I was not able to recall the subjects. I started to recall them and listed on the paper but didn't minded to put them in the order I prepared. Actually I prepared Material science, Thermodynamics, Heat Transfer and Micro Metal Forming (for the fabrication of MEMS devices, a recent topic). So they just started asking the questions randomly from the subjects they got in that list. After a sometime chairman asked me about the subjects I am comfortable. I told and given the preference to Micro-Metal Forming that was a new topic for him and he decided to get out of the topic and asked about the issues when we go through the micro forming. I told that as we go from macro size to micro, the strength, isotropic behavior and surface roughness changes and affect a lot. Then he asked how surface roughness comes into picture? Me: As material thickness approaches towards micro size, the no. of grain boundaries becomes fewer and grain boundaries sizes are in the order of microns so the very early surface has a lot of deviations that comes in picture. Then he asked: What is inside the space between two grain boundaries; Gas or Vacuum? Me: Sir Vacuum. He Said: You are wrong, go and refer the books. and in this way he came out of the topic that he was trying for. So, I will suggest you not to give any new topic as the persons taking interview may or may not be comfortable with that and it may be a curse to you. In Thermo….. he asked He: there is a cylinder-piston system that contains a gas, a weight W is kept on piston what will be the pressure? Me: Sir W/(g*A)---A: area, g: gravity (It was wrong actually I was in such a pressure that to calculate the pressure I was using the formula M/A) Then another person asked me about "g", why I am using it ? I confidently said: sir to get the mass from weight He knew that I am confused so he asked me to derive it's dimension I derived then he asked me to derive the dimension of force by area and he asked me to compare, and I found my mistake. I said sorry and then He: I am giving it "Q" all the boundaries are insulated so that no heat goes outside, calculate it's final volume? Me: I was confused and was asking about a lot of irrelevant information needed to solve. He: This is all I told you now calculate the volume...no other information. I could not derive it. Then......Fluid: He: I am having an wedge shaped vessel (triangular shaped) I want to know the water level at different places, what will be the levels of water at different tubes? Me: Same level in every tube. He: why? Me: because of fluids property...pressure at a level is same at every point So the height raised will compensate for it. He: ok so, pressure is constant at all the points in same level but different at different levels? Me: Yes sir. He: So if I make two holes at different levels and fit a tube at outside from the vessel then water will flow? Me: yes sir. He: If I place a turbine in between the pipe then will the electricity produced? Me: No. He: why? Me: because water will flow once only. He: but pressure difference is continuously acting at two different levels? Me: as once water flows and the section gets filled pressure at the same level in vessel and pipe will be same, So no way it will flow again. This was a section where I was somewhat comfortable and answered correctly. SOM: Shear stresses, how shear stress comes ....Is bending stress and shear stress same and a lot....they make me totally confused. Mohr's Circle related questions. That I replied correctly.

0 Answers   BARC,

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