Problem 4.1 Projection of Straight Lines – A line AB is 80 mm long. It is perpendicular to profile plane. The point A is 40 mm above H.P. and 30 mm in front of V.P. Draw the projections.

Procedure:

Step-1 Draw a horizontal line, which is x-y line of some suitable length.

Step-2 Mark a point a’ at the distance 40 mm above the x-y line. And draw a horizontal line from the point a’. This is locus of the point a’. Then from the point a’ draw a line of the length equal to its true length, which is 80 mm parallel to the x-y line. The end point of this line is marked as b’. This is elevation line in front view.

Step-3 Mark a point a at the distance 30 mm below the x-y line. And draw a horizontal line from the point a. This is locus of the point a. Then from the point a draw a line of the length equal to its true length, which is 80 mm parallel to the x-y line. The end point of this line is marked as b. This is plan line in top view.

Step-4 As line is perpendicular to profile plane its projection on profile plane will be a point or point view. This is marked as a1 b1 in figure above. This shows projection of profile plane of the given line AB.

Step-5 As line is perpendicular to one plane it will be parallel to both other plane. As theory says “if one line is making an angle of 90 degree with one of three principal planes then it will make zero degree with other two planes.”

Step-6 Give the dimensions by any one method of dimensions and give the notations as shown into the figure. And make a list of the True Length & Angles made by the line AB as shown into the figure.