(BQ) Part 2 book "Textbook of engineering drawing" has contents: Devlopment of surfaces, intersection of surfaces, isometric projection, oblique and perspective projections, conversion of isometric views to orthographic views and vice versa, freehand sketching,.and other contents. | CHAPTER 7 Devlopment of Surfaces Introduction A layout of the complete surface of a three dimentional object on a plane is called the development of the surface or flat pattern of the object. The development of surfaces is very important in the fabrication of articles made of sheet metal. The objects such as containers, boxes, boilers, hoppers, vessels, funnels, trays etc., are made of sheet metal by using the principle of development of surfaces. In making the development of a surface, an opening of the surface should be determined fIrst. Every line used in making the development must represent the true length of the line (edge) on the object. The steps to be followed for making objects, using sheet metal are given below: 1. 2. 3. 4. 5. 6. Draw the orthographic views of the object to full size. Draw the development on a sheet of paper. Transfer the development to the sheet metal. Cut the development from the sheet. Form the shape of the object by bending. Join the closing edges. Note: In actual practice, allowances have to be given for extra material required for joints and bends. These allowances are not cosidered in the topics presented in this chapter. Methods of Development The method to be followed for making the development of a solid depends upon the nature of its lateral surfaces. Based on the classillcation of solids, the folloiwing are the methods of development. 1. Parallel-line Development It is used for developing prisms and single curved surfaces like cylinders in which all the edges / generators of lateral surfaces are parallel to each other. 2. Radial-line Development It is employed for pyramids and single curved surfaces like cones in which the apex is taken as centre and the slant edge or generator (which are the true lengths)as radius for its development. Textbook of Enginnering D r a w i n g - - - - - - - - - - - - - - - - - - Develop[ment of Prism To draw the development of a square prism of side of base 30mm .
