 Projection of Lines, myself Mr. S. P. Mankani, assistant professor, department of mechanical engineering, wall change institute of technology. At the end of this lecture students will be able to solve problems on projection of lines inclined to any given plane. So now the given problem line AB 75 millimeter long and 45 degree inclination with VP and its front tube makes 55 degree with HP and A is 10 millimeter above the HP and 15 millimeter in front of the VP. Find its inclination with HP. So first work is always you start with the XY line. After drawing the XY line you are expected to see the given dimension of a position of a point A. Point A is 10 millimeter above the HP and 15 millimeter in front of the VP. In this case you have studied the detail so 10 millimeter above the XY line and 15 millimeter below the XY line. Position of the point above the horizontal reference plane and position of the point in front of the vertical plane. You are going to be locating this as a A dash mark and this as a A mark. So now this is a 45 degree angle he has given 45 degree inclination with the VP the first line 45 degree inclination with the VP just by keeping A as a position with the protractor you have to draw this as angle as a 45 degree in the downward direction and this is 45 degree angle you have taken. The length is given as 75 millimeter 75 millimeter length is given you take it from this particular point as a position from this particular point to draw this extended line as 75 millimeter that is a location of a B1 point similarly you go it in the front tube side next. So now the same procedure you are going to bring this point in the upward direction wherever it will cut the locus of this A point locus of this A point that gives the A dash and this up to this particular point it gives the front view length of a line keeping this A as a position and you are going to take it as the given angle as the 55 degree angle given angle as 55 degree angle just you are going to draw this as a line. So now here you think it as the given angle 55 degree angle 55 degree with HP that is a front view is making an angle he has given front view is making an angle means here this angle is not a true inclination it is a apparent inclination that is the reason you are going to be taken this angle with the front view directly here. So now just you are drawn this as a line in the upward direction then keep the compass here take it this position draw the arc toward this direction which is a 55 degree angle line angle it is going to cut somewhere here draw the arc it will cut this particular point. So now this is A dash and B dash that gives the front view length A dash and B dash that gives the front view length same as this length then you draw this locus of this particular point B locus of this particular point B similarly whatever the locus point is here ok procedure is exactly similar to the previous problem. So now you are drawn this as a locus of this particular point. So now this one is 75 millimeter given in the problem keep the compass here take it 75 millimeter length then you cut it this particularly locus of B point. So wherever it will cut that gives the B1 dash B1 dash ok this point is A dash B1 dash is the true length is the true length and whatever this angle is there what is this angle this angle is theta you have to measure by keeping the protect here and whatever the angle is you are going to get it that is expected in the problem inclination with HP find it is inclination with HP this is the expected in the problem. Ok so now bring this particularly B1 dash point in the downward direction it is going to cut the locus of B1 locus of B1. So this projection you are going to bringing it in the downward direction with the intention that to get the A and B that is a top view A and B as a top view ok you are going to join this as a A B point B as the top view length top view length of the line even you can bring it in the similar way you can bring it by keeping this point as a reference point and this particular point as a B1 point bring it in the downward direction. So it will come up to this particularly point ok. So you bring it in the downward direction wherever this position of this A comes so that locus point wherever it will cut keep that as a reference point keep this compass here and take it this length and you draw the arc you will get it the same point you will get the same point either you can get it directly from here or you can bring this projector in the downward direction by keeping this point here and you rotate it you will get this as a top view length. So this is a front view length and top view length you are expected to draw this front view length as well as a top view length as a dark line and this true length in the front view as well as true length in the top view as you are going to draw this as a medium thickness rest of all the lines you are going to draw it as a construction work that is a thin lines so now we are going with the one more problem. So here front view of a line AB is 50 degree inclined to XY and measures 55 millimeter long while its top view is 60 degree inclined with XY line. So here just to think it what exactly this 50 degree and what exactly this 60 degree what is this 50 degree and what is this 60 degree so here if you read the problem front view of a line AB is 50 degree inclined to XY line means front view of a line AB means this is a apparent inclination you are going to be deciding with the base on this particular word as if the given angle is a apparent inclination means 50 degree with the XY line and that is a front view line is making an angle of 50 degree means it comes where exactly it comes above the XY line or below the XY line it is a apparent angle it comes front view line AB with XY line it comes as a above the XY line and the 60 degree angle comes below the XY line if the end point A is 10 millimeter above the HP and 15 millimeter in front of the VP so where exactly these points are coming if you are going to draw this as a XY line here if you are going to draw this XY line here where exactly the location of this particular point 10 millimeter and 15 millimeter will come point A 10 millimeter above the horizontal reference plane means you have to measure the XY line from XY line 10 millimeter above and 10 15 millimeter below so that you are going to locate the point so now you have to conclude this one with the solution so what exactly are located now position of A you have taken 10 millimeter above the horizontal plane and 50 millimeter below the reference line XY that is in front of the vertical plane okay this is 50 degree as he has given 50 degree and similarly are expected to draw here also this is the reference point you have taken draw the reference point this is locus of B point then keep the compass here and you are going to getting this particular laser on this locus now you can refer the rest of the problem step by step thank you