support your answer with the help of diagram. dis will give a clear view.i hope u know dis... but in 2 angle projection both the views(front and top) will be in the top of the xy plane and in 4th angle projection both the views (front and top) will be in the bottom of the xy plane... since both the views will be in one side of the xy plane, its not possible to draw... both views will merge... due to which we are not usibg 2 an 4th ange projection. First and third angle projections depict a 3D object in a 2D yet second and fourth angle projections show one view of the object. Why rotating in clockwise?/why not anticlockwise? Therefore the 2nd angle projection system is not used. 1st angle projection is a type of orthogonal projection system where the object is placed in the first quadrant in such a way that it lies in between the observer and the plane of projection. Either way it was been around before all of us even the good DrD. Some times the questions make us to think about the topics which are not present in any book. (edited). same logic is applied to third angle where p.p. In first-angle projection, the object is conceptually located in quadrant I, i.e. 7.23 select the correct front view Join Yahoo Answers and get 100 points today. The front, side and plan views have drawn around the 3D shape. Again, as the observer is normally supposed to look from the right side of the quadrant to obtain the front view, in this method, the projection plane comes in between the observer and the object. Modern orthographic projection is derived from Gaspard Monge's descriptive geometry. In other words first and third angle projections are more elaborate than second and fourth angle projections. it floats above and before the viewing planes, the planes areopaque, and each view is pushed through the object onto the plane furthest from it. The â¦ it is positioned below and behind the viewing planes, the planes are transparent, and each view is pulled onto the plane closest to it. "First angle was the norm until 60 years ago. i.e the object behind vertical plane and below the horizontal plane. 1. When we turn the adjacent plane by 90 degree to see the top view, the front and top views are overlap to each other. is in V.P. why we are not use bottom view for describe standard projection method. Overlapping projection views create confusion in the drawing. Thus, I would exchange the labels for the 2nd and 4th quadrant. The reason why 2nd and 4th angle are not used is that all details except the outer perimeter will be hidden lines. Which of the following is NOT correct for Post-tension concrete. The only difference is that in 4th angle of projection the object is in between the observer and plane. When I look at the quadrant labels in the original question, I see that the labelling convention at at least some of you are familiar with is not the one I know. Third-angle projection is often considered to be more intuitive than first-angle projection. So, just for the simplicity of drawing the orthographic views, we prefer first angle projection. Based on the above schematic, Answer the following:? As per discussion we not use 2nd and 4th angle projection method because of in both method front and top view are comes in either top of xy plane or bottom of xy plane. First of all, we use first angle and third angle projection because it is assumed that the Horizontal plane is rotated CLOCKWISE to bring them in the same plane (for drawing purpose) and if we use second or fourth angle projection , then the Horizontal and vertical views will overlap , creating confusions in their ... Firstly,you understand the concept behind the angle projection system. It took me a while to find some place that explained where the terms came from, which is done on the site below and the pages before and after although a lot of places state that the second and fourth are not useful. difference between first and third angle Symbol of projection. Ah, once again, we have a communication gap!! The same problem occurs in 4th angle of projection. with this method you can give a drawing to anybody and they will be able to interpret what the part looks like. The object is positioned at the front of a vertical plane and top of the horizontal plane. In 2nd angle projection system, the plane is in between object and observer. The second angle quadrant and fourth angle quadrant are combination of first and third angle projections and cause confusion to the reader. The projections obtained on VP and We get overlapped Projections. We consider that horizontal plane rotates in clockwise direction after having projection on it. As Mr Karim has rightly answered,In second and fourth angle projection viewing and projected plane are different than that of first and third angle projection,There is possibility that the one projection may overlap the other one creating confusion to understand the drawing. Therefore the 2nd angle projection system is not used to draw engineering drawings. if consider bottom view in 1st and 3rd angle projection method then front and bottom view are comes in either top of xy plane or bottom of xy plane. so again this problem same as 2nd and 4th angle projection method only difference in view front view instead of bottom view. hence we never use those methods. Monge defined a reference system of two viewing planes, horizontal H ("ground") and vertical V ("backdrop"). Well I have never heard that thing before, Could you please provide some documentation/, , the object is conceptually located in quadrant, through the object onto the plane furthest from it. Hereâs an infographic further detailing the concept While third-angle projections are prevalent in the USA and Canada, First-Angle projection is more popular in Europe and Asia. Thus both 1st angle and 3rd angle projection will be replaced by 2nd angle and 4th angle projection. (a) First angle projection (b) Third angle projection (c) Second angle projection (d) Fourth angle projection 9) The recommended symbol for indicating the angle of projection shows two views of the frustum of a (a) Square Pyramid (b) Triangular pyramid (c) Cone (d) Any of these 10) For the object shown in Fig. it is positioned, onto the plane closest to it. Overlapping projection views create confusion in the drawing. If you rotate the HP Counter clockwise, then the views will overlap in case of first and third angle projection, and then the second and fourth angle projections will be favourable. I found the best explanation of angle projections I have even come across. towards 2nd quadrant.Then we rotate the view in H.P. On 1/15/2015 at 9:24 PM, sibonelonxumalo said: Why first angle and third angle projection method is used in machine design and why second and fourth angle method is not used? In the third angle projection method, the object is assumed to be in the third quadrant. Very often FEA (finite element analysis) is applied to a solid model, which by the way uses the same 6 named views. Engineering Drawing is the language of Engineers. (note changing viewer's position will also change the orientation of quadrants. is in H.P. hence in first angle where p.p. In second and fourth angle method, top view and front view overlaps. In the third angle projection right view is on right side of front view with the top view sitting at the top of the front view. as opaque then only first view can be drawn as object is visible from both sides in first quadrant only and not in any other ( for second quadrant vertical opaque plane is between object and viewer hence front view can not be drawn & for fourth quadrant opaque horizontal plane is between object and viewer hence top view cant be drawn. in second and fourth angle projection due to this process horizontal and vertical plane will overlap with each other. in either a first or third angle projection and show each side of a design without perspective, ie a 2D drawing of a â¦ In 2nd angle projection system, object is in 2nd quadrant.The plane is in between object and observer. Does canada use second angle projection in printreading. First Angle Projection is one of the ways of representing three-dimensional objects with respect to two dimensions which is commonly used in Europe and most of the world except the United States. (Mnemonic: an "actor on a stage". (top view) are obtained, to draw it in 2d we have to bring F.V. It doesn't matter which angle of projection is used because 2nd and 4th angle projection will resemble with 1st and 3rd, Posted October 24, 2015 Do I need a voltage regulator when converting ac voltage from an adapter to dc? according to me,i don't know whether I'm right or not but we don't use 2nd angle projection cos it doesn't show the whole image properly.the side plane obstructs most of the object.and if u cant see the object as much as possible,its not worth the hard work u do in converting a 3D object 2 2D.something opposite is the case with the 4th angle,u cant see the side or front plane easily so things get messed up. & 3rd. Third angle projection & Third angle projection symbol In this, the object is imagined to be placed in the third quadrant. The section continues onto the next page but only adds that expensive mistakes have been made confusing the two systems. In this projection technique, placing the object in the third quadrant puts the projection plane between the viewer & the objec t and is shown in figure 3. To understand why the 2nd and 4th angle projection system are not used.As per rule of projection when horizontal plane is rotated 90 degree in clockwise direction, top and front view will overlap. In Third Angle Projections We get exactly opposite of this. Neither is more right or wrong than the other, but it points to the need to communicate carefully. why should not revolve horizontal pane in anti clockwise direction to get second and fourth angle projections. Not much science about it, just that it will be completely confusing. Second-angle and fourth-angle projection also are defined, but do not result in useful images. Hi, It is very simple, first consider this. The labelling sequence shown in the question moves clockwise from the first quadrant; the convention that I (and I suspect others in the USA at least) am familiar with is the opposite. However if we took the dis-ambiguous piece like a pencil the top view is not important.On the other hand to make dice it is paramount for the CNC operator to follow the 6 side rule...Since the onset of solid modeling the are many more view applications especially in the hollow solid body forms or in our case the view from inside the piece looking out at an interference fit. 1) That if this happens, both fv and tv coincides with each other in 2 and 4 angle projection ( both view come above or below x axis) as said by abdul karim. The rule for this is we move the view in H.P. As I mentioned before, It is assumed that the HP is rotated clockwise. Orthographic projection is the method of representing three-dimensional objects in two-dimensions and the object is the view in parallel lines that are perpendicular to the drawing plan. the object behind vertical plane and below the horizontal plane. To draw a projection of any object first we need to place this object in any quardrant then fit a source of light in front, above or any angle you want. Well I have never heard that thing before, Could you please provide some documentation/citation. Really i am interested in the giving the answer but i am not sure of the answer, i am seeing such questions after 6 years, i am working in manufacturing side but never think of that. The only difference is that in 4th angle of projection the object is in between the observer and plane. That's why we can't draw second and fourth angle projection. An Alternative method The Third Angle Projection or First Angle Projection, different countries and regions typically use one method or the other although this can depend on a companyâs customer. Upload or insert images from URL. i.e. You cannot paste images directly. Please promote this website as a good source of knowledge in the field of mechanical engineering. The observation is done from right as indicated in Figure.Once the F.V. into V.P. (Mnemonic: a "shark in a tank"), NOTED ON PRINTS TO INDICATE PROJECTION USED, second and fourth angle not used because in these projections are overlap (front &top) /(plan,elevation). in order to draw the projection with ref to xy line the verticle plane needs to be rotated in 3rd and 1st angle we get the projections above n below the xy line .. now if the object is kept in 2nd or 4th angle by rotating the plane wont give the other view.. practically speaking take your notebook hold it in your hand opened in L shape and just think a bit .. its easy lolz, 2nd. Can some one here explain this engineering question, some thing that resonant? I recall in my early years wondering about 1st and third angle projection. clockwise and observe it from right. In 2nd angle projection system, object is in 2nd quadrant.The plane is in between object and observer. are working drawings. Good luck in the Craft ....Merry Christmas....From the E.. Why is second and fourth angle projection is notin used in engineering? Here the object is assumed to be in the third quadrant. vice versa for third angle. when I do drawings of complex nature I name each view such as "View in Direction 'A'" and so on. Below is an example of First Angle projection. As both the views lies on either side of x-line in first & third angle, we make use of these methods. The views come like this in the first angle projection starting from top left, clockwise, Right view, Front view, and Top view. I want the side drawing to be on the same side as the view it is showing not behind. In this projection technique, Placing the object in the third quadrant puts the projection planes between the viewer and the object and is shown in figure. Still have questions? What happen to number two? is in V.P. October 1, 2013. Types of Orthographic projection systems are first angle and third angle projection. There is a rule that hp must be rotated 90 degree clockwise. Pasted as rich text. The multi-view drawing for the point P lying in the second quadrant is shown in figure 4. For 1st angle projection system, we place object in 1st quadrant, for 2nd angle projection system, we place object in 2nd quadrant and so on. so if you are considering p.p. Since these are only relative to the object and not to the drawing one could as easily perform an isometric view on any angle with the same accuracy or for that matter all 6 angle named views. Why does amperage increase when voltage decreases? plane. (Mnemonic: an "actor on a stage". we all type fast and this increase chance of mistakes during typing. For 1st angle projection system, we place object in 1st quadrant, for 2nd angle projection system, we place object in 2nd quadrant and so on. Similarly when the object is placed in the 4th quadrant both top and front view will overlap. The principle of first-angle projection â¦ A shadow will occur in the opposite side of the light source which will represent the projection of that object. this is the most puzzling question...at least for an undergraduate student like me.. awaiting a â¦ Yes we can use second angle and fourth angle projection but in that case we need to rotate horizontal plane of projection in counterclockwise direction. Firstly,you understand the concept behind the angle projection system. The first angle projection is approved internationally except the United States and in this projection the object is placed â¦ In the first angle projection system, the object placed in the first quadrant and in third angle projection system the object placed in the third quadrant. Orthographic projections. is in H.P. But in this both it is very easy to read the drawing. The same problem occurs in 4th angle of projection. 'Rooting hard for you': Trump may end WH tradition If behind, it should show hidden lines. For giving ur such a passelating comments. Clear editor. This set of Engineering Drawing Multiple Choice Questions & Answers (MCQs) focuses on âFirst Angle Projection Methodâ. You will get both of views overlapped Observe carefully for 2nd angle projection 71. The same with the fourth angle, it is not used in multiview projections. Why, when I was learning to write, it was still done with a stylus pressed into damp clay (later to be fired); papyrus and ink had not yet been invented! Observe carefully for 2nd angle projection 70. (Mnemonic: a "shark in a tank"), It is standard throughout Europe and Asia (excluding Japan, Y14.3-2003 specifies it as the default projection system), Japan (, B 0001:2010 specifies it as the default projection system) Canada, and Australia. It is located in the second quadrant. Suddenly a circuit carries a current 20 times the normal current. and T.V. First Angle Projection : In the first angle projection, the object is placed in the 1st quadrant. I am not sure if the 60 refers to the original 1911 printing or the 7th Ed (1947) that I have. I took a photo of the page. First angle projection system is widely used in European countries. In 1st angle projection the object is kept in _____ a) 1st quadrant b) 2nd quadrant c) 3rd quadrant d) 4th quadrant View Answer Display as a link instead, × clockwise and observe it from right. What is the function of cooling tower in thermal power plant? Hence second angle projection Technic is not followed anywhere for engineering drawing. very good job. F.V. When We Turn Horizontal Plane to 90â². in order to draw the projection with ref to xy line the verticle plane needs to be rotated in 3rd and 1st angle we get the projections above n below the xy line .. now if the object is kept in 2nd or 4th angle by rotating the plane wont give the other view.. practically speaking take your notebook hold it in your hand opened in L shape and just think a bit .. its easy lolz I have one query about projection method.