LESSON 2 Preparation of working drawings from models and Isometric views

1.1.INTRODUCTION

The working drawing must be prepared from the model or isometric views of the object to easily understand the views of the object. In the initial stages the drawing should be always soft so that the lines are thin, faint and easy to erase without forming any black smudges.

1.1.1.To prepare a working  drawing from the isometric view

( View animation)

  • To prepare a working drawing from the model, the model is carefully examined and kept in a suitable position for sketching the front view.

  • All other views are then sketched free hand and with suitable proportion on a pad.

  • Measurements and sizes are inserted in the free hand sketch.

  • Special instructions and notes are also to be included.

  • The over all dimensions of the views has to be determined first.

  • Suitable scale has to be selected so that all the views are positioned suitably in the drawing sheet or in the working space of the system.

While drawing the orthographic views we have to consider that,

  • The top view and the front view lie in the same line vertically.

  • The front view and the side views are always in line horizontally.

  • The length and height of the object are commonly given by the Front view, the length and the width are given by the top view and the width and height are given by the side view.

  • If a surface is parallel to a vertical or horizontal plane, its projection on the plane will give its true dimension and shape 

  • The centre lines of all the views are to be drawn.

  • When a cylindrical part or hole is seen as circle in the particular view, two centre lines intersecting at right angles to each other has to be drawn at the centre of the circle.

  • When the cylindrical part or hole is seen as a rectangle in the particular view, one centre line has to be drawn passing through its axis.

In a drawing,

  • A full line has to be shown before showing a dashed line or any other line

  • A dashed has to be shown before a centre line

  • The details are to be given in all the views .

  • All the hidden corners or part of the model are shown in dashed lines.

  • The dimension has to be given in all the views so that the complete details of the entire model can be understood.

  • Repetition of same dimensions in two views may be avoided.

 

1.1.2.To prepare a working  drawing from the isometric view,

(View animation)

  • The direction from which the object has to be seen for its front view has to be indicated by means of an arrow.

  • Then by considering that the object is either in first quadrant or third quadrant, the overall dimensions of the required views is to be calculated and rectangles are to be drawn on the  planes on which the view is to be projected pertaining to these dimensions.

  • The front view has to be completed and other views may be made by looking in directions parallel to the other two axes.

  • All holes or grooves are assumed to be drilled or cut right through.

  • Surfaces which are parallel to the direction of vision will be seen and drawn as straight lines.

  • Edges which are parallel to the direction of vision will be seen and drawn as points.

  • Suitable radii may be assumed for small curves and fillets.

  • Drawing has to be checked thoroughly and it should be complete in all respects with dimensions, scale etc.,

Last modified: Monday, 16 September 2013, 5:04 AM