Guide to Engineering Metrology Carl Hitchens MSc. CEng FIMechE Technical contributions: S. Cavill, R. Smalley and P. Hulme Version 4 TABLE OF CONTENTS Introduction.............................................................................................................................................. 3 Dimensional Metrology ............................................................................................................................ 4 SI units, the international system ............................................................................................................ 5 The 10% Rule ......................................................................................................................................... 7 Hand Tools .............................................................................................................................................. 8 Abbe’s Principle .................................................................................................................................... 11 Accuracy and Precision ......................................................................................................................... 12 Measurement Process .......................................................................................................................... 13 Calibration ............................................................................................................................................. 16 Traceability ............................................................................................................................................ 17 Design for Inspection ............................................................................................................................ 18 Measurement Strategy .......................................................................................................................... 20 Measurement System Analysis ............................................................................................................. 21 Uncertainty ............................................................................................................................................ 29 Introduction to GD&T (Geometric Dimensioning and Tolerancing) ...................................................... 32 Variations of Form Rule #1: Envelope Principle Taylor Principle ............................................................. 33 Material Condition Modifiers ................................................................................................................................ 34 Bonus Tolerance ......................................................................................................................................................... 34 Regardless of feature size (RFS).......................................................................................................................... 37 Virtual Condition ........................................................................................................................................................ 37 Datum ............................................................................................................................................................................. 38 Airy and Bessel points ........................................................................................................................... 40 Inspection Methods for GD&T ............................................................................................................... 41 Straightness Feature ................................................................................................................................................. 41 Flatness Feature ......................................................................................................................................................... 44 Circularity (Roundness) Feature ......................................................................................................................... 46 Cylindricity Feature ................................................................................................................................................... 46 Profile of a Line Feature .......................................................................................................................................... 49 Profile of a Surface Feature .................................................................................................................................... 51 Angularity ...................................................................................................................................................................... 52 Perpendicularity ......................................................................................................................................................... 55 Parallelism..................................................................................................................................................................... 58 1 C. Hitchens The contents of this document should not be reprinted or redistributed. Position ..........................................................................................................................................................................60 Concentricity (Coaxiality) Feature ...................................................................................................................... 61 Symmetry ...................................................................................................................................................................... 62 Runout Feature ........................................................................................................................................................... 63 Total Runout Feature ................................................................................................................................................ 63 Inspection Gauges ................................................................................................................................ 66 Threads ................................................................................................................................................. 67 Coordinate Measuring Machine ............................................................................................................ 71 Coordinate Measuring Machines and GD&T .................................................................................................. 75 On-Machine Probing ............................................................................................................................. 77 Large Volume Metrology ....................................................................................................................... 83 Laser Tracker .............................................................................................................................................................. 83 Optical Tracking ......................................................................................................................................................... 85 Auto Collimator, Optical Alignment Telescope and Inclinometer .......................................................... 86 Autocollimator ............................................................................................................................................................ 86 Optical Alignment Telescope ................................................................................................................................. 86 Inclinometer ................................................................................................................................................................. 87 Non-Contact Measurement and Scanning Instruments ........................................................................ 88 Laser Line Scanners and laser strip scanners ................................................................................................88 Structured light .......................................................................................................................................................... 89 Photogrammetry ....................................................................................................................................................... 90 Inspection Process for Scanning Instruments ....................................................................................... 92 Reverse Engineering ............................................................................................................................. 94 Manufacturing Process Capabilities .................................................................................................... 100 Bibliography ........................................................................................................................................ 102 2 C. Hitchens The contents of this document should not be reprinted or redistributed. INTRODUCTION Metrology is the science of measurement and the understanding of a measurements quantity and quality. Quality is shown by providing evidence of traceability and accuracy. Measurements should be repeatable, reproducible and reliable and the engineer making these measurements should have an understanding