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  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    DMM 2412

    METROLOGY

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    Table o f Contents

    CHAPTER 1 Fundamentals Of Metrology

    1.1 WHAT IS METROLOGY 2.1 NEEDS AND FUNCTIONS OF INSPECTION 3.1 OBJECTIVES OF METROLOGY 4.1 PRINCIPLES OF METROLOGY

    CHAPTER 2 Basic Inspection and Procedures

    2.1 INTRODUCTION 2.2 TESTING AND ITS PROCEDURES 2.3 TYPES OF MEASUREMENTS 2.4 FACTORS IN SELECTING TESTING INSTRUMENT 2.5 CALIBRATION 2.6 CARE OF MEASURING INSTRUMENTS

    CHAPTER 3 Measurement Errors

    3.1 INTRODUCTION 3.2 FACTORS AFFECTING THE ACCURACY OF A MEASURING SYSTEM 3.3 TYPES OF ERRORS 3.4 SOURCES OF MEASUREMENT ERRORS

    CHAPTER 4 Vernier Caliper

    4.1 INTRODUCTION 4.2 PARTS OF A VERNIER CALIPER 4.3 MEASURING ACCURACY 4.4 READING THE SCALE 4.5 DIAL CALIPER 4.6 DIGITAL CALIPER 4.7 DEPTH VERNIER CALIPER 4.8 APPLICATIONS OF VERNIER CALIPER

    CHAPTER 5 Micrometer

    5.1 INTRODUCTION 5.2 EXTERNAL MICROMETER 5.3 DEPTH MICROMETER 5.4 INTERNAL MICROMETER 5.5 SPECIAL TYPES OF MICROMETERS

    CHAPTER 6 Mechanical Dial Indicator

    6.1 INTRODUCTION 6.2 PRINCIPLE OF A DIAL INDICATOR (PLUNGER TYPE) 6.3 PARTS OF A DIAL INDICATOR 6.4 HOW DOES A DIAL INDICATOR WORK 6.5 MEASURING ACCURACY 6.6 READING THE SCALE 6.7 GUIDELINES WHEN USING DIAL INDICATOR 6.8 SOURCES OF ERRORS 6.9 APPLICATIONS OF DIAL INDICATOR

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    CHAPTER 7 Gauge Block

    7.1 INTRODUCTION 7.2 TYPES AND GRADES 7.3 STANDARD SET OF GAUGE BLOCKS 7.4 TO DETERMINE THE GAUGE BLOCKS COMBINATION 7.5 CHECKING SURFACE FLATNESS OF GAUGE BLOCKS 7.6 GAUGE BLOCK APPLICATIONS 7.7 MAINTENANCE AND CARE OF GAUGE BLOCKS

    CHAPTER 8 Surface Plate Inspection

    8.1 INTRODUCTION 8.2 WHAT IS A SURFACE PLATE 8.3 ADVANTAGES OF GRANITE SURFACE PLATE 8.4 CARE OF SURFACE PLATE 8.5 SOURCES OF ERRORS 8.6 SURFACE PLATE ACCESSORIES OR HOLDING DEVICES 8.7 PRINCIPLES OF SURFACE PLATE INSPECTION 8.8 EXAMPLES OF HOLDING DEVICES USED IN CONJUNCTION WITH A SURFACE PLATE

    CHAPTER 9 Instruments for Testing Angles

    9.1 INTRODUCTION 9.2 TESTING ANGLES

    9.3 EXAMPLES OF APPLICATION 9.4 CALCULATION METHOD

    CHAPTER 10 Gauges

    10.1 INTRODUCTION 10.2 ADVANTAGES OF GAUGES 10.3 DISADVANTAGES OF GAUGES 10.4 FACTORS IN SELECTING MATERIALS FOR GAUGES 10.5 MATERIALS FOR GAUGES 10.6 TYPES OF GAUGES

    CHAPTER 11 Profile Projector

    11.1 INTRODUCTION 11.2 APPLICATION 11.3 TEST PROCEDURES 11.4 DIFFERENT STANDARD OVERLAY CHARTS 11.5 TYPES OF MEASUREMENT 11.6 MAINTENANCE OF OPTICAL COMPONENTS

    CHAPTER 12 Surface Roughness Measurement

    12.1 INTRODUCTION 12.2 SURFACE TEXTURE MEASUREMENT 12.3 DEFINITIONS OF SURFACE ROUGHNESS TERMS 12.4 WAVE LENGTH LIMIT C 12.5 BASIC TERMS OF SURFACE TEXTURE 12.6 EFFECTS OF VARIOUS CUT-OFF VALUES 12.7 DEFINITION OF SURFACE PARAMETERS 12.8 ADDITIONS TO THE SURFACE SYMBOL

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    12.9 CHOICE OF THE WAVELENGTH LIMIT C 12.10 INSTRUMENTS FOR TESTING ROUGHNESS

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    FUNDAMENTALS OF METROLOGY

    CHAPTER 1

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    1.1 WHAT IS METROLOGY Metrology is the science of measurement. However, we have to go one step ahead and must also deal with the correctness of measurement. We have to observe whether the measuring result is given with the sufficient correctness and accuracy for the particular need or not. Thus, in industrial terms metrology is primarily concerned with methods and techniques of measurement based on agreed units and standards. The practice of metrology involves precise measurement, which requires the use of apparatus and equipment to permit the degree of accuracy required to be obtained. In a broader sense, metrology is not limited to length measurement. It is also concerned with the industrial inspection and its various techniques from the raw material to the finished product or even assembled parts.

    1.2 NEEDS AND FUNCTIONS OF INSPECTION

    a. To determine good or bad parts Our five senses are basically instruments, which are used to inspect certain objects based on observation, curiosity or enjoyment. We can use our nose to smell (i.e. to check) whether there is a gas leak. We can use our tongue to taste whether the food is good or bad. In industrial terms, inspection basically is defined as the function of comparing or determining the conformance of a product to specifications or requirements. In other words, the function of inspection is to inspect a product in order to determine whether it is good or bad, and whether it can be accepted or whether it has to be rejected. More specifically, inspection refers to the measurement, visual assessment or testing of a product, process or the act of making a product.

    b. To achieve interchangeability Nowadays many new production techniques have been developed and products are being manufactured in large scale due to low-cost methods of mass production. It is very essential that products must be fit and mate if any product is chosen at random for interchangeability purposes. Thus, to achieve interchangeability of products, inspection has to be performed sufficiently and this can be done either by measuring or gauging. The gauging method is very economical for mass production.

    c. To improve and develop precision measuring instruments Inspection also led to the development of precision measuring instruments and improvements of inspection methods due to demands of high accuracy and precision works or products. Inspection has also created a spirit of competition and led to the production of quality products on a large scale basis by eliminating variations, thus improving processing techniques.

    d. To support the manufacturing department Inspection also supports the manufacturing department by designing and maintaining a system that assesses the quality levels of the work that is done, and the products that are made, according to objectified standards of measurement criteria.

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    1.3 OBJECTIVES OF METROLOGY a. To ensure the products designed are within the process and measuring instrument

    capabilities available in the plant. b. To determine the process capabilities and ensure that these are better than the

    relevant parts tolerances. c. To determine the measuring instrument capabilities and ensure that these are

    adequate for their respective measurements. d. To minimize the cost of inspection by effective and efficient use of available

    facilities, and to reduce the cost of rejects and rework through application of Statistical Process Control Techniques.

    e. Standardization of measuring methods: This is achieved by laying down the inspection methods for any product right at the time when the production technology is prepared.

    f. Maintenance of the accuracy of measurement: This is achieved by periodical calibration of all measuring instruments used in the plant.

    1.4 PRINCIPLES OF METROLOGY

    a. Fundamental Units and Standards To determine whether the parts meet the requirements or specifications, we need to perform measurement to collect the data or information. Of course, we need both measuring unit and measuring instrument according to standards before we can start to take any measurement. Units are defined and expressed in standards. Units are the language of measurement and must be constant. The measuring unit of length is Meter. Originally, in 1889 a meter is defined as the distance between two lines on a specific bar which is made of platinum-iridium rod to represent the length of a meter. Thirty of these bars are manufactured. One was kept at the International Bureau of Weights and Measures in Paris as the international standard. The others were sent to laboratories around the world. However, this standard bar has its limitation. It is not stable and constant due to the effect of temperature and environmental factors. Thus, in 1960 a Meter was redefined as 1,650,763.73 wavelengths of a particular orange light emitted by the gas krypton 86. Again, in 1983 the meter was redefined in terms of speed of light. The new definition says: The meter is defined as the length of path traveled by light in vacuum during a time interval of 1/299,792,458 of a second.

    b. Units used in Metrology The units used are laid down in the International Units System (S.l = System International) as shown in the table in the following page.

    Quantity Units SymbolsLength meter m Mass kilogram kg Time second s

    Thermodynamic Temperature Kelvin K Electric Current Ampere A

    Table 1.1 List of Basic SI Quantities, Units and Symbols

  • UNIVERSITI MALAYSIA PAHANG FACULTY OF MECHANICAL ENGINEERING

    Prefixes Symbol Multiplier Meaning Giga G 1000000000 109 billion Mega M 1000000 106 million kilo k 1000 103 thousand

    Hekta H 100 102 hundred Deka Da 10 101 ten deci d 0.1 10-1 tenth centi c 0.01 10-2 hundredth milli m 0.001 10-3 thousandth micro 0.000001 10-6 millionth

    Table 1.2 List of Prefixes c. Derived Units and Conversions The units derived from the basic unit of meter are kilometer, decimeter, centimeter, millimeter, micrometer, and nanometer.

    1 km = 1000 m 1 m = 10 dm = 100 cm = 1000 mm 1 dm = 10 cm = 100 mm 1 cm = 10 mm 1 mm = 1000 m

    Convert the following for length into values in mm. 0.05m = 0.05 x 1000 = 50 mm 0.88 dm = 0.88 x

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