17.1 Introduction

In many ways, learning to read a drawing is the same as learning to read a language. Blueprint

is the common name of the copies taken from an original drawing, usually drawn on a tracing

paper. The copies may be obtained by way of reprographic processes, viz., blueprinting, ammonia

printing, xerox copying, copy of a photo film, etc., but the colour of the print has nothing to do

with the name “blueprint”.

For blueprint reading and understanding the drawing, one must have a thorough

knowledge of the principles of drawing and orthographic projections. The knowledge of various

manufacturing processes and the sequence of operations required to obtain the finished shape,

intended by the designer, also helps in interpreting the drawings.

In this chapter, the examples chosen help providing guidelines to enable students to

understand the shape and size of a component, in the case of component drawings, and also its

location, in the case of assembly drawings. While reading the drawings, the details such as

shape, size, through dimensions, notes and material to be used, and additional notes to the

workman on machining, surface finish, tolerances, etc., are to be noted carefully.

17.2 Examples

17.2.1 Rear Tool Post

Rear tool post is generally used on capstan lathes, mainly for parting-off operations. It is fixed

on the cross-slide in the slots, provided at the rear side of the lathe. Study the drawing shown

in Fig. 17.1 and answer the following :

1. What is the overall size of the tool post?

— 102mm × 70mm × 62mm

2. How many bolts are provided for fixing the tool, and what is the size of each bolt?

—3, M10

3. What type of tool can be used with it?

— Parting tool

4. What is the maximum height of the tool holder?

— 25mm

5. How many screws are provided to locate the tool?

— 2

6. How is the tool holder fixed to the cross slide?

— By 2 Nos. of M6 Hex. socket headed set screws

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