Important Definitions

IMPORTANT DEFINITIONS

`Development of surface' of a solid may be defined as the process of opening out all the surfaces of a three dimensional body onto a flat plane.

Development of surface can be obtained for a full solid (or) only for the lateral surface (ie., surfaces parallel to the axis) of solid. Development of full solid is normally known as `Total Development of surface' and the development of lateral surface is known as 'Lateral development of surface' of solid. (If it is not mentioned in a problem, always draw the lateral development of surface only).

The plane surface so obtained by opening out all the surfaces of a three dimensional body is known as `Pattern' (or Development). It is to be noted here while fabricating a solid, the pattern of the solid, ie., layout of the plane area which may be cut into number of pieces of appropriate shapes and sizes, is to be prepared first on a paper and then the sheet metal is cut according to the pattern. While cutting the metal sheet proper allowances for the lap and seams are to be added to the inside pattern for cutting and welding. However, these allowance are not considered in the worked out examples presented in this textbook since it may leads confusion at this initial stage. But the students are advised to make models of the solids after drawing the pattern with sufficient overlaps for cutting and welding.