When you have read this chapter, you should understand:

■ What is meant by linear measurement ■ How to make linear measurements ■ What is meant by angular measurement ■ How to make angular measurements ■ The correct use of measuring equipment ■ How to identify and select marking out tools for making lines ■ How to identify and select marking out equipment for providing guidance ■ How to identify and select marking out equipment for providing support ■ How to identify and select different types of datum ■ The need for templates ■ The techniques for marking out templates ■ The methods of manufacturing templates for sheet, plate and structural

components ■ What materials are used for templates ■ The tools and instruments that are used for making templates ■ The care of measuring and marking out equipment

5.1 Introduction

Measuring can be considered to be the most important process in engineering. Without the ability to measure accurately, we cannot:

■ Mark out components ■ Set up machines correctly to produce components to the required size and shape ■ Check components whilst we are making them to ensure that they fi nally end up

the correct size and shape ■ Inspect fi nished components to make sure that they have been correctly manufac-

tured. This is particularly important for large fabrications that have to be assembled on site

5.2 Linear measurement

Fabrication, sheet metal and welding engineers rarely have to work to the fi ne limits and close tolerance of size that the mechanical engineer requires: the exception being when fi tted bolts are required when assembling structures. When you measure length, you measure the shortest distance in a straight line between two points, lines or faces. It doesn’t matter what you call this distance (width, thickness, breadth, depth, height and diameter) it is still a measurement of length.