Tool Design and Metrology

1. ME351:TOOL DESIGN AND
METROLOGY
1
Metrology is the science of measurement, embracing
both experimental and theoretical determinations at
any level of uncertainty in any field of science and
technology. (General Conference on Weights and Measures,
CGPM)

2. 2
Pager device Electronic Typewriter
Audio cassette and player
Coordinate
Measuring
Machine

3. 3
Optical
Profilometer

4. 4
Gear Inspection Machine

5. 5
Laser calibration of CNC machine table

6. ME351: Tool Design and Metrology
 General measurement
concepts
 Principles of measurement,
 Standards of measurement
 Linear and Angular
Measurements
 Limits, Fits of Tolerances as
per I.S.
 Gauge Design
 Measurements of Flatness
 Inspection of threads
 Measurement of surface
finish,
 Comparators
6

7. Books:
1. Metrology and Measurement
Anand K. Bewoor, Vinay A. Kulkarni
Published by Tata McGraw-Hill Education Pvt. Ltd., 2009
ISBN 10: 0070140006 / ISBN 13: 9780070140004
2. Engineering Metrology by K. J. Hume, Macdonald
3. Handbook of Surface Metrology
by David J. Whitehouse (Author)
7
 Mid-term: 30
 End Sem: 50
 Lab:20
 Pass Marks: 35

8. Metrology: Introduction
 Metrology is the science of measurement
 Dimensional metrology is that branch of Metrology which deals
with measurement of “dimensions” of a part or workpiece
(lengths, angles, etc.)
 Dimensional measurements at the required level of accuracy
are the essential link between the designers’ intent and a
delivered product.
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9. Principal fields of Metrology
 Establishing units of measurement and their standards such as
their establishment, reproduction, conservation, dissemination
and quality assurance.
 Measurement methods and estimation of their accuracy.
 Measuring instruments
 Design, manufacturing and testing of gauges of all kinds
 Observers’ capabilities to make measurements
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10. Types of Metrology
 Scientific/Fundamental Metrology: Deals with the organization
and development of measurement standards and their
maintenance (Reference standard metrology)
 Industrial Metrology: To ensure adequate functioning of
measuring instruments used in industry.
 Legal Metrology is concerned with the accuracy of
measurement for the general good of the society.
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11. Some Important Standards
 ASTM: American Society for Testing and Materials
 JIS: Japanese Industrial Standards
 DIN: Deutsches Institut für Normung (German Institute for
Standardization)
 AISI: American Iron and Steel Institute
 ANSI: American National Standards Institute
 BS: British Standards
 SAE: Society of Automotive Engineers
 NIST: National Institute of Standards and Technology
11

12. Need of inspection
 Ensure the material, parts and components conform to the
established standards.
 Meet the interchangeability of manufacture
 Finding the problem area for not meeting established
standards
 To produce parts with acceptable quality with reduced scrap.
 Purchase good quality of raw materials, tools and equipment
 Take necessary efforts to measure and reduce the rejection.
 Judge the possibility of rework of defective parts and re-
engineer the process. 12

13. Basic Measurement Devices
 Surface Plates
 Test Stands
 Dial Gages
 Micrometers and Vernier
 Gage Blocks
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Dial Gauge

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15. 15
Source: Mitutoyo

16. 16
Digital
Micrometer
Outside calliper
Inside Calliper
Odd leg Calliper

17. 17

18. Spirit level
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19. Dimensional Metrology Needs
 Linear measurements
 Angular measurements
 Geometric form measurements
 Roundness
 Straightness
 Cylindricity
 Flatness, etc
19

20. Dimensional Metrology Needs
 Geometric relationships
 Parallel, perpendicular, etc.
 Concentric, runout, etc.
 Controlled surface texture
 Geometric Dimensioning and Tolerancing (GDT)
 Standard symbols, etc., on part drawings.
20

21. Some important terms
 Measurand
 Resolution
 Accuracy
 Precision
 Repeatability
 Sensitivity
 Drift
 Error
 Calibration
 Range
 Readability
 Response time
 Stability
 Testing
 Traceability
 Uncertainty
21

22.  Measurand is the quantity to be measured.
 Resolution is the smallest change of the measured quantity
which changes the indication of a measuring instrument. This is
also known as the sensitivity of the instrument.
 Accuracy is the closeness between a test result and the
accepted reference value.
 Precision is the closeness of agreement between independent
test results obtained under stipulated conditions. This is also
referred as the repeatability of the instrument.
 Sensitivity
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23.  Drift is a slow change of a metrological characteristic of a
measuring instrument.
 Error is the deviation of the measured value from the true
value.
 Absolute error: │True value – Measured value│
 Relative error:
│True value – Measured value│/│True value│
 %age error: Relative error X 100
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24. 24
 Calibration is a documented comparison of the measurement
device to be compared against a traceable reference
standard/device.
 Range is the capacity within which an instrument is capable of
measuring.
 Readability refers to the ease with which the readings of a
measuring instrument can be read.
 Response time is the time taken for measuring device, when
subjected to a changes in input signal, to change its state by a
specified fraction of its total response to that change.

25.  Stability refers to the ability of a measuring instrument to constantly maintain
its metrological characteristics with time.
 Testing is a technical investigation to ascertain the functionality of a product.
 Traceability means that a measured result can be related to the stated
reference, usually national or international standards through an unbroken
chain of comparison, all having stated uncertainty.
 Uncertainty of measurement is a parameter, associated with the result of a
measurement that characterizes the dispersion of the values that could
reasonably be attributed to the measurand.
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26. Factors affecting accuracy
 Standards of calibration for setting accuracy
 Workpiece control during measurement
 Inherent characteristics of measuring instrument
 Inspector (Human factor)
 Environmental conditions: Noise, vibration, temperature,
humidity, electrical parameter variations, adequate lighting,
atmospheric refraction, clean surrounding.
To ensure higher accuracy during measuring, the above sources of
error are required to be analyzed frequently and necessary steps
should be taken to eliminate them. 26

27. 27

28. Standards of Measurements
 Metre is accepted as the fundamental unit of linear
measurement.
 The wavelength of monochromatic light, is used as the
fundamental unit of measurement.
 A metre is defined as 1650763.73 wavelengths of the orange
radiation in vacuum of krypton-86
28
Iodine stabilized helium-neon laser

29. Three types of measurement standards are used:
i. Line standard
ii. End standard
iii. Wavelength standard
29
14th October: International Standards Day

30. Line Standard
 The international Bureau of weights and measures (CIPM:
comite International des Poids et Measures) established the
metre as the linear measuring standards in the year 1875.
 The metre is the distance between the centre portions of two
lines engraved on the polished surface of a bar made up of
platinum(90%) iridium (10%) alloy having a unique cross-
section (web).
 The web section gives maximum rigidity and economy in the
use of the expensive material.
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31. 31
International
prototype metre
The distance between
inscribed lines on a bar
under certain conditions of
temperature (0 °C and
normal atmospheric
pressure) and support (10
mm diameter rollers at 589
mm apart).

32. End standard
 End standards are used for all practical measurements in
workshops and general use in precision engineering in standard
laboratories.
 These are in the form of end bars and slip gauges.
 These are used to set the reference dimension in various
measurements.
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33. 33
Source: Mitutoyo

34.  End bars made of steel having cylindrical cross-section of 22.2
mm diameter with the faces lapped and hardened at the ends
are available in sets of various lengths.
 Parallelism of the ends is within few tenths of micro-meters.
 End bars are made from high-carbon chromium steel, ensuring
that faces are hardened to 64 HRC (800 HV)
 The bars with a round section of 30 mm are used for greater
stability.
34

35.  Slip gauges are practical end standards.
 Slip gauges are rectangular blocks of hardened and stabilized
high-grade cast steel or zirconium oxide (ZrO2) having thermal
expansion coefficients of 11.5X10-6 K-1 and 9.5X10-6 K-1
respectively.
 Cross-section 9 mm wide and 30 to 35 mm long.
 Slip gages are available in three grades of accuracies [IS 2984]:
35
Grade 0
(Reference)
Grade 1
(Inspection)
Grade 2
(Workshop)

36. Errors in Measurement
 Absolute error Relative error
Static error
a) Reading error (parallax error)
b) Alignment error ( the axis of the measuring instrument and the
line of measurement should coincide)
c) Characteristic error (Linearity, repeatability, hysteresis,
resolution etc.)
d) Environmental error (surrounding temperature, pressure and
humidity on the measuring system)
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37. 37
Loading error Parallax error
e) Loading error (entrapment of dirt, chips, burrs etc. between the
datum and workpiece; improper contact)

38. Errors in measurement
 Dynamic error (caused by time variation in the measurand)
Controllable/Systematic errors (Bias): These errors are regularly
repetitive in nature and follow a definite pattern. They include
the following errors:
a) Calibration error
b) Stylus pressure error (uniform pressure is desirable)
c) Avoidable error (due to parallax, non-alignment of workpiece
centers, loading error etc.)
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39. Random/chance errors: These errors are accidental,
non-consistent in nature. They cannot be eliminated
since no definite cause can be located.
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40.  Formally agreed by the 11th General Conference on Weights
and Measures (CGPM) in 1960, the SI is at the centre of all
modern science and technology. The definition and realization
of the base and derived units is an active research topic for
metrologists with more precise methods being introduced as
they become available.
 There are two classes of units in the SI: base units and derived
units. The base units provide the reference used to define all
the measurement units of the system, whilst the derived units
are products of base units and are used as measures of derived
quantities.
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41. The Seven ‘SI’ Base units
 The ampere (A) - Unit of measurement of electric current
 The kilogram (kg) - Unit of measurement of mass
 The metre (m) - Unit of measurement of length
 The second (s) - Unit of measurement of time
 The kelvin (K) - Unit of measurement of thermodynamic
temperature
 The mole (mol) - Unit of measurement of amount of substance
 The candela (cd) - Unit of measurement of luminous intensity
41

42. SI Base units
Name Symbol Measure Current (2005) formal definition[1] Dimension
symbol
metre m length
"The metre is the length of the path travelled by light in
vacuum during a time interval of 1 Ú 299792458 of a
second."
17th CGPM (1983, Resolution 1, CR, 97)
L
kilogram kg mass
"The kilogram is the unit of mass; it is equal to the mass of the international
prototype of the kilogram."
3rd CGPM (1901, CR, 70)
M
second s time
"The second is the duration of 9192631770 periods of the radiation corresponding
to the transition between the two hyperfine levels of the ground state of the
caesium 133 atom."
13th CGPM (1967/68, Resolution 1; CR, 103)
"This definition refers to a caesium atom at rest at a temperature of 0 K."
(Added by CIPM in 1997)
T
ampere A electric current I
kelvin K thermodynamic
temperature
Θ
mole mol amount of
substance
N
candela cd luminous
intensity
J
42

43. Linear Measurement Instruments
 Steel Rule
 Inside, Outside and Odd-leg calliper
 Vernier calliper (Modified anvil for gear measurement)
with dial, digital vernier
 Vernier height gauge
 Vernier depth gauge
 Micro-meter (Modified anvil for gear measurement, thread
measurement)
 Depth micro-meter
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44. 44
Digital
Micrometer
Outside calliper
Inside Calliper
Odd leg Calliper

45. 45
Vernier Height
gauge
Surface Plate

46. 46
Vernier depth gauge
Depth
micrometer

47. 47
Gear tooth
vernier
Vee wedge pieces contacting minor
diameter

48.  Protractor
 Squares
 Vernier bevel protractor
 Combination Set
 Angle gauges
 Sine bar
 Sine centre
 Autocollimator/ Angle dekkor
 Micro-meter clinometer
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Angular Measurement Instruments

49. Autocollimator
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50. 50
Autocollimator
Reflecting
mirror unit

51. Working Principle of Autocollimator
 When a monochromatic light source’s beam of light rays is
made to fall on a beam deflector, it deflects the beam into 90
degree towards the converging lens. The converging lens made
the beams parallel and throws it to the object or reflecting
surface. The beam deflector should be kept near the converging
lens’s focus to keep the light beam parallel. The parallel rays
are then made to fall on a reflecting surface or an object. The
rays reflect back and proceed along the same path, in opposite
direction,
 if there is no angular deviations on the object’s surface,
eventually converge at the receiver kept at the focal distant
from the converging lens. If the object is inclined at angle α
then the reflected ray makes an angle 2α with the incident
beam.
51

52. Application of Autocollimator
 Checking flatness of machine tool beds and slide ways.
 Measuring very small angle with high precision.
 Verifying parallelism
 Checking the column’s squareness in relation to the base.
 Examining the flatness of bed plates and table tops.
 Checking for small linear shifts.
Advantages of Autocollimator
 Very high accuracy.
 Ability to measure wide range angle.
 Easy to set up and operate.
 Calibration at the level of international standards.
 Result can be seen directly on the screen.
52

53. Disadvantage of Autocollimator
 Regular maintenance is required
 Measurements require much time.
 For the detector to trace the sample, it has to be cut and
processed.
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54. 54
Vernier bevel protractor
Combination Set

55. 55
Micrometer
Clinometer

56. Specification of Linear Tolerances
56

57. Angular Specifications
57

58. Angular Tolerances
58

59. Flatness Specification
59

60. Flatness Tolerances
60

61. Straightness Specification
61

62. Straightness Tolerance
62

63. Roundness Specification
Roundness applies to every section
63

64. Roundness Tolerances
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65. Surface Profile Without Datums
65

66. Line Profile Without Datums
66

67. Surface Profile with Datums
Profile of a line with datums is similar
67

68. Surface Profile with Datums
68

69. Cylindricity Specifications
69

70. Cylindricity Tolerances
70

71. Surface Texture Specification
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72. Surface Texture
72

73. Perpendicularity Specification
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74. Perpendicularity Measurements
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75. Parallelism Specification
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76. Parallelism Measurements
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77. Concentricity Specification
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78. Concentricity Tolerances
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79. Concentricity Measurements
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80. Concentricity Measurements
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81. Circular Runout Specifications
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82. Circular Runout Tolerances
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83. Total Runout Specifications
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84. Total Runout Tolerances
84

85. Position Specifications
85

86. Position Tolerances
86

87. Simulated Datum
87

88. Datum Selection
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89. 89
Single Angle Sine
Table made generally
as per IS-5939-1970
Compound Angle Sine
Table made generally
as per IS-5943-1970

90. THANK YOU
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