Engineering Drawing (General Engineering) (SSC JE)

The surface roughness on a drawing is represented by triangles. These are classified into four groups
The ISO has recommended a series of preferred roughness values and corresponding roughness grade numbers. These grade numbers are used to specify surface roughness on drawings.

The point of intersection of given line, produced or extended if necessary, where it meets one of the principal planes is called its trace.
• The point of intersection of a given line if extended with the H.P is called the horizontal trace. It is usually denoted by H.T or H.
• The point of intersection of a given line if extended with the V.P is called the vertical trace and is usually denoted by V.T or V.

In orthographic projection, the projectors are parallel to each other and also perpendicular to the plane but in oblique projection, the projectors are inclined to the plane of projection and projectors are parallel to each other.
• In orthographic projection each projection view represents two dimensions of an object..

A circle will appear on an isometric drawing as an ellipse. It can be derived by using fourcentre method. In this method, a given circle is enclosed by a square.

A food chain is a series of organism feeding on one another, a food web consists of a number of interlinked food chain.
• Food chain and food webs play a very important role in the ecosystem because energy flow takes place through them, nutrient cycle takes place through them and it helps to maintain ecological balance.

The front view and top view of a line both lie above the xy line, the line is isolated in second quadrant. In the second quadrant, view above the horizontal plane and behind the vertical plane.