FORM MEASUREMENTS

FORM MEASUREMENTS METHODS

1. UNIT 4 FORM MEASUREMENT Principles and Methods of straightness – Flatness measurement – Thread measurement, gear measurement, surface finish measurement, Roundness measurement – Applications.

2. APPLICATIONS

3. 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.

4. GEOMETRICAL FEATURES The measurement of Straightness Flatness Squareness Parallelism Roundness Circularity Cylindricity

5. FORM MEASUREMENT INCLUDES Screw thread measurement Gear measurement Radius measurement Surface Finish measurement Straightness measurement Flatness measurement roundness measurement

6. 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 .

7. 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

8. Straightness Measurement

9. 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

10. Spirit level indicator

11. Spirit level indicator

12. 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:

13. Straight edge equipment

14. 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

15. TEST PROCEDURE

16. METHODS Beam comparator is used for flatness testing Flatness measuring by using interferometry(NPL) Using laser interferometer Using electromechanical gauges. Autocollimator

17. Beam comparator Electromechanical gauge

18. NPL FLATNESS TESTER

19. SURFACE PLATES Used as reference datum plane Act as a master pattern Different materials like cast iron granite glass block

20. PARALLELISM Two lines or planes or surfaces are parallel to each other. It is defined as angle between two surfaces of a sample specimen.

21. AUTO COLLIMATOR

22. 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.

23. Types of irregularities O vality L obing

24. 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

25. Diametral method

26. Circumferential confining gauge

27. Rotating on centers

28. Three point probe

29. V-Block method

30. Roundness measuring spindle

31. Overhead method Rotating table

32. 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

33. SCREW TERMINOLOGY

34. NOMENCLATURE Major diameter of nominal diameter (d) Minor diameter or core diameter or root diameter (d c ) Pitch diameter or effective diameter ( d p ) Pitch(p) Lead: lead=pitch Crest root

35. Depth of thread Flank Angle of thread Screw thread: Flank angle Helix angle Addendum Deddendum tan α = p/ π d

36. 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

37. Different Types of Thread profiles:- Square Threads. V-threads. ACME Threads Buttress Threads. Whitworth threads Thread Conventions

38. ACME threads Buttress threads

39. Square Threads V- threads

40. MEASUREMENT OF VARIOUS ELEMENTS OF THREAD MAJOR DIAMETER MINOR DIAMETER EFFICTIVE DIAMETER PITCH THREAD ANGLE AND FORM

41. MEASUREMENT OF MAJOR DIAMETER ORDINARY MICROMETER BENCH MICROMETER

42. MEASUREMENT OF MINOR DIAMETER

43. 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 metho d

44. One wire method

45. Two wire method E=T+P where , T=M-2d

46. THREE WIRE METHOD

47. THREAD MICROMETER METHOD

48. Measurement of pitch TOOLMAKERS MICROSCOPE

49. THREAD GAUGES

50. ADJUSTABLE THREAD GAUGES

51. FLOATING CARRIAGE MICROMETER

52. SURFACE FINISH MEASUREMENT Surface texture Primary texture or roughness Secondary texture or waviness The factors to be affected cutting speed feed depth of cut

53. Properties of the work piece Tool materials Types of machine tool Quality of the machine tool

54. ANALYSIS OF SURFACE FINISH For determining the surface tecture Peak to valley height method The average roughness method Form factor or bearing curve

55. Peak to valley method

56. Centre line average method

57. RMS METHOD

58. TEN POINT HEIGHT METHOD

59. Stylus probe instrument

60. Profilometer

61. Tomlinson surface meter

62. Taylor- hobson taly surf

63. Talysurf layout

64. GEAR PROFILE

65. Gear tooth vernier caliper

66. Base tangent method

67. Gear rolling test

68. Parkinson gear tester

69. Involute checking

70. CONSTANT CHORD METHOD