Form Measurement Principles and Methods Guide
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FORM MEASUREMENTS METHODS
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Form Measurement Principles and Methods Guide
- 1. UNIT 4 FORM MEASUREMENT Principles and Methods of straightness – Flatness measurement – Thread measurement, gear measurement, surface finish measurement, Roundness measurement – Applications.
- 2. APPLICATIONS
- 8. INTRODUCTION • Threads are of prime importance, they are used as fasteners. • It is a helical groove, used to transmit force and motion. • In plain shaft, the hole assembly, the object of dimensional control is to ensure a certain consistency of fit. • The performance of screw threads during their assembly with nut depends upon a number of parameters such as the condition of the machine tool used for screw cutting, work material and tool.
- 9. GEOMETRICAL FEATURES • The measurement of • Straightness • Flatness • Squareness • Parallelism • Roundness • Circularity • Cylindricity
- 10. FORM MEASUREMENT INCLUDES • Screw thread measurement • Gear measurement • Radius measurement • Surface Finish measurement • Straightness measurement • Flatness measurement • roundness measurement
- 11. STRAIGHTNESS MEASUREMENT • A line is said to be straight over a given length, if the variation of the distance of its from two planes perpendicular to each other and parallel to the general direction of the line remains within the specified tolerance limits. • The tolerance on the straightness of a line is defined as the maximum deviation in relation to the reference straight line joining the two extremities of the line to be checked.
- 12. • Important geometrical parameter of machines • Example: shaping machine-guideways • Shortest distance between the two lines – straight line • Ray of light, liquid level • It is a qualitative measure of a surface • Straightness measuring system should be in line with functional point – called Bryan’s principle
- 14. METHODS OF STRAIGHTNESS SPIRIT LEVEL: • Inspecting the horizontal surfaces • Finding direction and magnitude of minor deviation from nominal condition • The bubble will move from its position along the radius of the angle of tilt. • Ether, alcohol, benzol- low viscosity fluid • Having graduated scale
- 18. STRAIGHT EDGES: • With the help of surface plates and sprit levels straight edges are used for checking straightness and flatness • Flat – sectioned measuring instrument • Made up of steels • Straight edges are used for testing large areas of surface • Painted surfaces are used to measure straightness LASER MEASURING SYSTEM:
- 20. FLATNESS MEASUREMENT • Minimum distance between the two planes, which will cover all irregularities of the surface to be tested • Best-fit plane between two standard reference plane one above and one below the plane surface to be tested • Deviation of the surface from the best fitting plane
- 22. TEST PROCEDURE
- 23. METHODS • Beam comparator is used for flatness testing • Flatness measuring by using interferometry(NPL) • Using laser interferometer • Using electromechanical gauges. • Autocollimator
- 26. SURFACE PLATES • Used as reference datum plane • Act as a master pattern • Different materials like cast iron granite glass block
- 27. PARALLELISM • Two lines or planes or surfaces are parallel to each other. • It is defined as angle between two surfaces of a sample specimen.
- 28. AUTO COLLIMATOR
- 29. ROUNDNESS MEASUREMENT • Measure of how closely the shape of an object approaches the circle. • All points of cross sections are equal distant to a common surface.
- 30. Types of irregularities Ovality Lobing
- 31. Methods of roundness measurement • Diametral method • Circumferential confining gauge • Rotating on centers • V- Block • Three point probe • Roundness measuring spindle • Reference circle • Roundness measuring machines
- 32. Diametral method
- 36. V-Block method
- 38. Overhead method Rotating table
- 40. THREAD MEASUREMENT • Helical structure • To convert rotational movement into linear movement • Helical ridge produced by forming a continuous helical groove of uniform section • To transmit power and motion
- 45. NOMENCLATURE • Major diameter of nominal diameter (d) • Minor diameter or core diameter or root diameter (dc) • Pitch diameter or effective diameter (dp) • Pitch(p) • Lead: lead=pitch • Crest • root
- 46. • Depth of thread • Flank • Angle of thread • Screw thread: • Flank angle • Helix angle • Addendum • Deddendum tan α= p/π d
- 47. TYPES OF THREAD • British association thread • Whitworth (bsw) threads • Metric thread • It is necessary to measure the following – Major diameter – Minor diameter – Effective diameter – Pitch
- 48. Different Types of Thread profiles:- 1. Square Threads. 2. V-threads. 3. ACME Threads 4. Buttress Threads. 5. Whitworth threads Thread Conventions
- 51. MEASUREMENT OF VARIOUS ELEMENTS OF THREAD • MAJOR DIAMETER • MINOR DIAMETER • EFFICTIVE DIAMETER • PITCH • THREAD ANGLE AND FORM
- 52. MEASUREMENT OF MAJOR DIAMETER • ORDINARY MICROMETER • BENCH MICROMETER
- 56. MEASUREMENT OF EFFECTIVE DIAMETER • Effective diameter measurement is carried out by following methods. 1. One wire, 2. Two wires, or 3. Three wires method. 4. Micrometer method
- 58. One wire method
- 59. Two wire method E=T+P where, T=M-2d
- 66. Measurement of pitch TOOLMAKERS MICROSCOPE
- 69. THREAD GAUGES
- 72. SURFACE FINISH MEASUREMENT • Surface texture • Primary texture or roughness • Secondary texture or waviness • The factors to be affected cutting speed feed depth of cut
- 73. • Properties of the work piece • Tool materials • Types of machine tool • Quality of the machine tool
- 74. ANALYSIS OF SURFACE FINISH • For determining the surface tecture • Peak to valley height method • The average roughness method • Form factor or bearing curve
- 75. Peak to valley method
- 76. Centre line average method
- 77. RMS METHOD
- 78. TEN POINT HEIGHT METHOD
- 80. Profilometer
- 83. Talysurf layout
- 88. GEAR PROFILE
- 90. Gear tooth vernier caliper