The technique used to determine the size of any component in terms of standard units is called measurement. eg, Linear measurement applies to measure the length, thickness, diameter, height, etc., covering both internal and external features. When any measurement is carried out, the magnitude of a quantity (length, mass, time, etc.) to be measured is expressed in terms of a fixed predetermined magnitude of the same quantity. This fixed predetermined magnitude is called the unit of quantity.
Working in a workshop, while making jobs or manufacturing machine parts, some sizes are given in the drawing such as length, breadth, height, diameter, thickness, radius, angle, etc. To make the same size and shape of the job, it is essential that it should be correctly measured. Since their production depends upon these sizes. Making of some special type of parts or jobs as per drawing in a workshop, we have to measure and inspect so for that some instruments are required which are known as measuring tools eg., rules, beam type tools, micrometers are examples of measuring tools whereas dial indicators and other precise indicators are examples of instruments. By using measuring tools, we can make a comparison between two jobs and identify which one is small or large. So, measurement with some specified tools is an important factor that must be applied before starting the job.
In this chapter, we will discuss about the measurement, measuring tools, and their types and parts to expand the related terms, etc.
Measurement
The process of measurement involves the comparison of the measured value with another similar value accepted as standard. The accuracy of a workpiece depends upon the quality of measurement. The main kinds of measuring processes are as follows.
(i) Linear Measurement
The measurement in a straight line is known as linear measurement. In this measurement, the measuring tools are used such as steel rule, vernier caliper, micrometer, etc.
(ii) Angular Measurement
The measurement of an angle created by two lines is called angular measurement. It is normally measured by try square, angle gauge, vernier bevel protractor, sine bar, etc.
(iii) Radial Measurement
It includes the measurement of round, spherical, or semi-spherical jobs. It is normally measured by plug gauge, ring gauge, radius gauge, etc.
(iv) Plain Surface Measurement
The measurement of surface accuracy is called plain surface measurement. They are used as surface plates, surface gauges, straight edges, dial test indicators, vernier height gauges, etc.
Methods of Measurement
The making of parts or jobs in the workshop according to their sizes, requires some measuring tools with proper knowledge of it. Without proper knowledge, the worker or engineer is not perfect. There are three systems to measure any job discussed as follows.
(i) Direct Measurement
In this system, the job is directly measured by measuring tools such as steel rule, micrometer, vernier caliper, bevel protractor, etc.
(ii) Indirect Measurement
In this system, we have a helping tool with the main measuring tool. The job is measured by the main tools such as a caliper, telescope gauge, divider, etc., and the final reading can be taken with the help of measuring tools such as the steel rule.
(iii) Comparative MeasurementÂ
In this system, the measurement of a job is known by comparing it with a masterpiece.
System of Units
A system of measurement is a set of units of measurement that can be used to specify anything which can be measured. It is divided into different forms, which are given below.
(i) British System
It is also called as FPS (Foot Pound Second) system. Here foot, pound, and second are the fundamental units of length, mass, and time respectively. It was normally used in British and its allied countries.
(ii) CGS System
It means that Centigrade Gram Second system. This system is normally used in our daily life. In this system, length is measured in centimeters, weight in grams, and time in seconds.
(iii) Metric System
In this system, Metre, Kilogram, and Second are the fundamental units of length, mass, and time respectively. It is recognized by the International Standard Organisation (ISO). This system is also called the MKS system.
(iv) SI Units
The International System of Units is the modern form of the metric system, and it is the world’s most widely used system of measurement.