 I just imagine that I am a train that you are so desperate to catch after your mid same exams, to reach your respective destinations where you come from. Somebody comes from Delhi, somebody comes from Bihar, somebody comes from the south, who comes from the south, I am lost. So, let me rephrase, how many of you guys are able to catch your respective trains to your destinations on time, who has missed a train to his or her house. So far, nobody was that was that, you have missed a train once, twice, once from where to where, Chennai too. Anyhow, forget about that. So, this Friday and this Friday and Saturday, you are going to be having your AutoCAD labs. So, the plan is the same as last time last week. So, two badges per session, both on Friday and Saturday, four noon sessions on Friday, afternoon sessions on Saturday. So, if you go through my webpage, I have chosen six problems, 1, 2, 3, 4, 5, 6. So, go through my webpage, you know which session you belong to, click on the respective problem, prepare the sketch, this time you are going to be getting only one hour to work on the AutoCAD lab. So, prepare your sketch as well, make sure you understand the object very nicely, very well. Go to your respective AutoCAD labs, work on the object, submit the problem and get graded. So, Friday and Saturday, we have AutoCAD labs. I would not be there, but two of my students, Mohit and Ramesh, they will be there to help you out and of course, collect your assignment sheets. So, was a little announcement, let us get started. So, a little recap, so I started with this example last time, last week and start with the top view and then drew the front view and we both agreed, we both agreed that the front view was quite congested, it had too many hidden lines, solid lines, center lines and that was something that we wanted to avoid. And one of the options was to of course, section an object into two parts and look at the section and draw the front view. So, there were different options that we had explored last time. The first one was the full section view, you take a section, you essentially divide the object into two halves, just throw one half off and look at the object, where the section plane incident towards you and then you draw the sectional front view, which is a lot much clearer option. So, the first choice, full section view, the second choice was the half section view, you can use the symmetry of the object, just take one quarter of the object out. On the left hand side in this example, you can choose to show the features as if you are drawing the orthographic view of the object, full details, hidden lines, solid lines, center lines. The right hand side, you can choose to show the section view. So, you have clarity over here, you have information over here, half and half, option two, full section view, half section view, then you have got offset section, where you choose the section plane to pass through different features of the object in the top view and correspondingly section the object in the front view, full section, half section, offset section, revolve section. So, this is an option that you choose to show the cross section of an object, cross section, not the section of an object, but the cross section of an object at some chosen section plane. . .Chosen section plane, cross section of an object, revolve the cross section to show show that on the front plane fourth option. Fifth option removed section very similar to revolve section you choose a section and show the cross section of the object in the front view not with the front view, but may be a little below or on the side that is the only difference and of course, aligned section here you tend to align different features with the section plane and then show the section front view with two things in mind number 1 clarity number 2 two dimensions. For example, Kevin last time said that you know if we did not align this thing along with this section plane because of taking the projection of this web over here that would not have shown the two dimensions of this web in the front view and that is the reason why we tend to go for aligned section in cases where our objects are not symmetric. Just a little recap we had seen this last time for clarity standard parts of course, they are not sectioned even when the cutting plane passes to them. So, some of those parts are shafts nuts bolts ribs spokes webs are sectioned lugs are not sectioned. Some examples that you had seen last time bottom line sectioning pertains to trade off between information and clarity. You have to choose what kind of information you want to give and alongside you have also to choose how clear you want your section view to be and these two terms information clarity pertains to both features and dimensions. So, since we are working with source peak orthographic projections I mean section view is in a way orthographic projection you need to show two dimensions. Of course, rules of orthographic projections are relaxed when we are working with sections we do not have to diligently follow those rules. Supporting and passing elements that do not participate directly in the main machine part are not sectioned essentially I refer to these ribs lugs bolts nuts spokes shafts these guys they are not sectioned. But then this is big question when do you decide what is section which part I will share little secret with you. So, this is a problem that was rejected as a medicine problem for you guys question number 4, but that is ok I mean do not get any ideas that I am going to be asking you this problem that is not going to happen. So, I chose this problem I start working on the solution to this problem. So, you have a big cylindrical feature over here a small cylindrical feature over here and this feature on the right and these three features are connected by this guy here and this guy here one look and the impression that you are going to be getting is that these two guys are what what are these two guys somebody said ribs what are they no clue. So, let me rephrase this question do these two parts participate in the main machine part are these important both of these. So, if I want to take a section of this object from here till here bottom through will I be sectioning these parts yes or no absolutely sure positively sure definitely sure these are not ribs these are not ribs fine I chose to represent them or I chose to depict them as ribs when I was working on the solution for this. So, I did not section I sectioned only the three main features the center cylindrical feature the top left cylindrical feature and this one I did not section the two parts in question and we sat we discussed this and one of my colleagues said well you know this does not seem right because they happen to be a part of the main machine part. So, they need to be sectioned. So, the entire thing gets sectioned. So, there is no point asking you guys to work on this question because you are going to be drawing the auto profile in the front view and you are going to be you are going to be sectioning everything. So, the entire thing is going to be hashed I agreed with them. So, these guys they need to be sectioned, but you know you guys are smart very soon you will figure a loophole in these rules I can foresee that and this is one of the things this is one of the counter arguments that you guys you guys are going to be giving me how about pulleys or wheels with spokes are spokes not the main part of the pulley because if you remove the spokes then the central part is hanging in the air what do we do in that case should be sectioned the spokes as well yes no see you guys are divided who says yes long hands both hands who guys I mean who if you say no of course the rest are you expecting me to give you the right answer I want I will not. So, there are certain questions for which you need to find the answers for yourself and I have given you two options either refer to your Bible or as God bottom line is yeah see the moment you say there can be various perceptions you are introducing subjectivity absolutely. So, in this case yeah. Is there a correct answer for these type of questions or there can be various answers various possible solutions find the answer for yourself you know I told you something about what is right and what is wrong quite some time ago no. So, find the answer for yourself. So, in this case you make the judgment that these guys are not to be treated as ribs and therefore, they need to be sectioned why because they happen to be the main part they happen to be part sparing in the main machine part on the other hand these guys happen to be quite important to some not to all but you choose not to section the spokes judgment is to be made yeah no. So, ribs think about the ribs what do they do you remove them you still have the object intact fasteners they are essentially different components they are different from the main machine part right no. So, I am not talking about the assembly I am talking about a single part in the assembly a single part in the assembly I am not talking about the entire assembly of course, I mean if I remove the bolts and that is from there the assembly is going to dismantle fine, but I am talking about a single part. So, go back ask yourself this what is important what is not ribs question ribs fasteners question fasteners spokes hubs question everything do a little bit of reading everybody little bit of reading follow the conventions and make a judgment try to develop some sense of judgment as to where you are going to be sectioning what. So, the certain conventions that you need to follow and you need to be finding the answers to these yourself of course, I have actually given you some help. So, if you have looked at that pdf document more in sectioning you will get something from there yeah you are thinking no think think a little more find the answer for yourself I am not going to be giving the answer. So, do not casual me do not coax me I am not going to be giving the answer I came here with my mind made I am not going to be giving an answer to this thing anyhow. So, keep working so something that I want to talk to you guys about you know you guys are in your second semester you still have 6 more semesters to go after this. So, it is a long marathon for you guys head of you 3 years the way I see and it was not long time ago that I was sitting along with you guys the way I see from both ends of the table that instructors help you guys prepare for pressure hunt you know at the end of your 8th semester or 7th semester you get something called a pay package pay package treasure exposure versus expertise. So, we do not expect you to become experts at the b-tech level this is when I say this I say this for myself I do not expect you to become experts after you b-tech on the other hand I expect you to get exposed to a lot of subjects you guys are going to be doing 6 courses a semester starting your second year. So, we will expose you to a lot of subjects and expose you really really a lot. So, this is what we do at the b-tech level this is what I do at the b-tech level expose you guys it is up to you whether you would want to become an exporter not at the end of b-tech if not not a problem definitely you have got something called the master's program definitely have something called a PhD program where you learn to where you learn more about any subject of your choice. So, do not expect yourself to become experts of subjects after you b-tech it is totally fine no no a lot and it is ok for you not to know everything it is perfectly ok. We give you hints we give you hints it is up to you how to use the hints for your treasure hunt I will talk about section of assembly today. So, this is the example that your 6.3 problem number 6.3 of your six lab this example pertains that. So, feel free to make sketches if you want to. So, you got four parts base plate you got two brackets you got a pulley and you got a shaft once again you got a base plate you got two brackets you got a pulley and a shaft you need to arrange them together into an assembly into a sensible assembly and show the sectioned front view full top view and I am not sure if I asked you to show the profile view did I anybody having a manual did I ask you to show the profile view as well no just the full top view and section by the way in all the examples that you have seen today and the previous lecture which view did I section was it always the front view or some examples top view some examples profile view just the front view what front only the front view null examples yeah why not top why not profile why only front why only front why not top why not profile priority FTP. So, front view is the top most priority view then comes the top view then comes the profile view. So, you would want to show as much details as possible with as much clarity as possible in the front view and then comes the top view and then comes the profile view right. So, by convention this is my impression by convention that people tend to section front views mostly really have I seen somebody section the top view and the profile view alright. So, these four parts base plate you got dimensions 150 by 80 four holes four arcs there is a little groove here there is something over here something over here where would the brackets go where would the brackets go here or here look at the dimension look at this dimension where would the brackets go. So, I will give you a hint the brackets will go over here one here the other one here. So, this guy is going to go just like that and if you flip this guy they come here between the two brackets you have a pulley which is supported by the shaft. So, let me start drawing do you have any questions so far any questions how I wish I could be sitting on there and dozing off it is like a puzzle for you I have given you different parts you need to fit them together you got the numbers you got the numbers dimensions what is the best way to assemble these guys together. So, that makes sense study this problem when you are working on your sketches anyhow. So, I will start drawing I would want all eyes on the screen things are going to get nice and messy at the same time. So, if you think about this all you need to do when you are drawing the sectioned view of the assembly is to just cut and paste the respective front views nicely cut and paste the respective front views this is what I am doing the base plate do not worry about the dimensions do not worry about the projections as yet base plate quite simple you got two cylindrical voids and then you got a bracket on the left a bracket on the right I am going to go a little slow got the ribs on the bracket center line two little holes in the bracket counter sunk or counter bow a cylindrical void to allow the shaft to go in on both sides the center line I think your brackets are done you start working with the shaft. So, this is your shaft a little taper on both sides and then you start drawing the pulley that is to be housed over the shaft. So, I am a little careful here I am not showing all the details that you actually see in the respective front views there are certain lines which are going to be missing of course, because I have taken the section plane and I have cut the entire assembly half and half what this how is it is. So, I got the base plate there I got bracket one over here bracket two over here flipped I got my shaft over here over which I got the pulley of course, everything is sectioned. So many lines messy enough messy capital M capital E capital S capital S capital Y or I the soccer guy Lionel messy. This is where things start getting beautiful wait and watch hatching lines or hash lines at 45 degrees the distance between two hash lines is almost uniform the brackets are sectioned differently the left bracket positive 45 degrees the right bracket negative 45 degrees or 135 degrees you would want to avoid something like this in your diagram is to be perfect and then you start hatching the base plate again 45 degrees, but with a larger spacing between the hash lines the pulley again larger spacing minus 45 degrees messy and beautiful yes no was that why larger spacing these are 4 different components these are 4 different components they have to be shown using different hashed lines 45 degrees less spacing 45 degrees minus 45 degrees less spacing plus 45 degrees more spacing minus 45 degrees more spacing. So, people tend to use you know 30 degree hash lines 60 degree hash lines at times. So, there are different conventions that people tend to follow do a little bit of reading it is a different component it is perfectly for you to want this to be positive 45 degrees want this to be negative 45 all you need to show using hash lines is that these are different components 4 different components the ribs are not hashed the shaft is not hashed and then I am going to be introducing fasteners a bolts they will not be hashed good enough they should be lighter than the solid line. So, maybe 2 h so, this is where you can practice your art in technical drawing. So, make this as beautiful as you can then what so, as I said I mean people tend to follow different conventions. So, at times people tend to use hatching so, that they are like 2 hashed lines which are very close to each other separated by a gap followed by 2 again closely placed hash lines you can vary the degree. So, I actually have chosen plus 45 and minus 45, but you can work with plus 30 minus 30 plus 60 minus 60 do not make them vertical because they get confused with you get confused with these lines do not make them horizontal does not make sense slightly slanted. So, the range is 32 45 30 60 all right nuts and bolts so, people use different conventions I am going to be introducing you to one of them of course, for the bolt you got the head which is hexagonal nature you can actually have square heads also there are different kinds of bolts. And then the shank of the bolt you can have a part of that threaded or you can have the entire shank threaded and people so, what people do is people say well this is the hexagonal bolt with some nominal diameter D. So, they would give you the diameter of the shank the outer diameter of the shank D and you have to figure out well by convention the size of this bolt depends on D the minor diameter of the threads that also depends on D this guy here that depends on D I will show you have one of the conventions at people tend to follow. So, start with the top view so, imagine that you are looking at the bolt from this direction in the top view start with a circle with 1.8 times D where D is the diameter of the shank draw hexagon lab 1 the vertex to vertex distances 2 times D the face to face distances 1.8 times D your top view is not yet over but, I have started with the front view take the projections this distance here this distance here is usually taken as 0.7 times D everything is with regard to over respect to the nominal diameter of the shank this angle is 30 degrees draw horizontal. So, you get 3 points 1 2 3 1 2 3 1 2 3 with these 3 points in the respective regions rectangular regions draw 3 arcs. Now, look at this guy here and try to compare this guy with this guy what would this arc correspond to what would this arc correspond to may be essentially the projection of this arc over here. So, this nut is chamfered so, will be projection of this arc this here would be projection of this arc and this arc will be the projection of this one here draw vertical lines draw the shank of the bolt diameter D. So, that measures the outer portion of the threads just follow this you would also be given the length of the bolt and the threaded length L T by convention. So, this angle is 45 degrees this angle is 45 degrees this little taper down here by convention we represent the threads by 2 solid lines and 2 thick solid lines and 2 thin solid lines and this distance between 2 thin solid lines is 0.8 D. So, these guys they represent the outer portion of the threads they represent the inner portion of thread this is just one of the conventions that people follow there are many other conventions. So, those in mechanical you will be learning a lot more in 251 you mean 251 this one in the top view in the top view of course, this is symmetric rather this is axis symmetric look at the way I am representing the threads in the top view the nominal diameter thing is a dotted circle of diameter D that is the outer portion of the thread the inner portion of the thread is represented by 3 quarters of a circle it is a broken circle and they are dotted because they are hidden of course, they are dotted because they are hidden. So, if you were to show the bottom view of the bolt in these 2 circles they would have been solid of course, there will be a bigger circle nicely nice or not no boring too many ratios to work with this one diameter of this is D diameter of this is they should be they should be they should they should. So, what is the impression here boring nice too many numbers boring fine too many numbers. How many of those who say it is boring are in mechanical engineering good luck with your 251 then you know I have the advantage of having a mic. So, I can reach you guys, but people who are asking questions peers of yours who are asking questions to me if you can lend a polite ear to them not only will you be able to hear my answer if I am ready to give that you will also be able to hear the questions yes it corresponds to the chamfer on the net. So, chamfer on the head of the nut. So, see how this is made. So, it is not a regular hexagonal structure. So, there is something some manufacturing operation that has happened on the head of the nut head of the nut through which these portions they have gotten smoothened in some sense good question. As far as the drawing is concerned as far as this convention is concerned pitch is not the information that we provide, but the only information that we provide with the nut is the nut has this normal diameter D through which you get the other features the length of the shank the threaded length and the pitch or may be pitch is also part of the convention. This one this one what should be alright. So, did I ask you to draw the bolt also with your assembly view look at question number 6.3 did I yes or no no yes or no no you guys also lucky just in case just in case if I need to show the assembly the full section assembly along with the two bolts on the left and on the right. Oh by the way before before I go there the nut is going to be something very similar to the head of the bolt just that this part will also appear over here. So, chamfering at both the ends of the nut alright. So, this is how the final full section assembly looks like I am a little curious I am a little curious what was that for I mean are you trying to appreciate my drawing over here or what no anyhow ok yeah repeat your question please hold on hold on and can you be a little louder they are not important for what just two or three minutes I will be done I am going to say this in Hindi or maybe not you are doing five one or two five one or two what is that is that a mechanics course or what mechanics guys come on come on come on come on I am not as exposed as you are come on come on anyhow. So, if I talk about mechanics there is something called a reference frame ok. So, whenever I make a statement I make a statement relative to some context ok. So, the statement that you were making well some politicians will say that I have been miscoted. So, I have been miscoted I am without politics. So, when I say they are not important I speak in relation to with respect to sectioning ok. So, in sectioning I have to make a judgment as to which parts I need to section and which parts I do not need to section because if I keep on sectioning everything then there is no point ok. So, that statement is in relation to sectioning of course, nothing both are important right yeah they represent both think about that they represent both it is a tight fit sorry sorry sorry sorry. So, it is this threading that is important not this one. So, this one the bolt is nicely able to get in ok. So, there is no threads there are no threads over here ok. So, there is some clearance the bolt is nicely able to smoothly able to come in and then it gets fastened over here. So, sorry I mistook your question they were just going inside ok. So, if you think about that then look at look at this portion of drawing look at this portion of drawing ok. So, the nut and the bolt they both have interlocking threads thank you I was groping for that word they have interlocking threads. So, the solid line at the outer side and the thin solid line at the inner side they both represent the inner as well as the outer threads right think about that alright. So, before I leave the floor if you draw the full assembly of this this is how your full sectional front view will look like and that is how your top view will look like and just appreciate the clarity at the bottom and the complexity at the top clarity at the bottom complexity at the top 2 c words ok.