Linear Measuring Instruments ,Vernier Caliper

1. S.DHARANI KUMAR
Asst.professor
Department of Mechanical
Engineering
SRI ESHWAR COLLEGE OF
ENGINEERING ,COIMBATORE
,INDIA
UNIT-2
LINEAR AND ANGULAR
MEASUREMENTS

2. UNIT-II
LINEAR AND ANGULAR
MEASUREMENTS
• Measurement systems are mainly used in industries for quality control
management.
• quality control engineers are applying some the measuring systems
such as linear and angular measurements.

3. Measurements
• Measurement systems are mainly used in industries for quality control.
• Often widely using measurements are
• Linear Measurement
• Angular measurement

4. Linear and Angular Measurement
The Linear Measurement includes measurements of length, diameters,
heights and thickness.
The Angular measurement includes the measurement of angles or
tapers.

5. Angular measurement is another important element in measuring.
This involves the measurement of angles of tapers and similar surfaces.
In angular measurements types of angle measuring devices are used.
They are angle gauges corresponding to slip gauges and divided scales
corresponding to line standards. The most common instrument is sine bar.
The main difference between linear and angular measurement is that no
absolute standard is required for angular measurement.

6. Dimensions
A very common measurement is that of dimensions, i.e., length, width,
height of an object
Dimensions of the measuring instruments are classified as follows
Low resolution devices (up to 0.25mm)
Medium resolution devices (up to 0.0025mm)
High resolution devices (less than microns)

7. Low resolution devices
Steel rule
Steel rule with assistance of
Calipers
Dividers &
Surface gauges
Thickness gauges

8. Medium resolution devices
Micrometer
Micrometer with assistance of
Telescoping
Extendable ball gauges
Vernier calipers
Dial indicators
Microscope

9. High resolution devices
Gauge blocks
Gauge block with assistance of
Mechanical comparator
Electronic comparator
Pneumatic comparator
Optical flats

10. Linear Measuring Instruments
Steel Rule
Calipers are of two types : spring type and firm joint type.
Vernier caliper
Micrometer
Slip gauge or gauge blocks
Optical flats
Interferometer
Comparators

11. Steel Rule

12. Calipers
Calipers are used for measurement of the parts, which cannot be
measured directly with the scale.
Calipers are of two types : spring type and firm joint type.

13. Outside Spring Calipers

14. Inside Spring Calipers

15. Firm joint calipers are of following types :
• (i) Outside caliper
• (ii) Inside caliper
• (iii) Transfer caliper
• (iv) Hermaphrodite caliper

16. Outside Firm Joint Caliper

17. Inside Firm Joint Caliper

18. Transfer Caliper

19. Hermaphrodite Caliper

20. Divider

21. Vernier caliper
• Components of vernier calipers are
• Main scale
• Vernier scale
• Fixed jaw
• Movable jaw
• Types of vernier calipers
• Type A vernier caliper
• Type B vernier caliper
• Type C vernier caliper

22. Type A Vernier Caliper

23. Vernier caliper
VERIER CALIPER WITH 0.02MM LEAST COUNT IS GENERLY USED IM
WORK SHOP.
In this Vernier caliper main scale division (49mm) are divided in to 50 equal
part in the Vernier scale.
i.e. 1 main scale division =1 mm
(MSD)
1. Vernier scale division =4950 mm
(VSD)
Least count is 1mm – 4950 =150 mm
THE DIFFERENCE BETWEEN 1.MSD and 1. VSD=0.02MM

24. Example
Main scale reading =35mm
The vernier division coinciding with the main scale is the 20th
division. Value=20 multiplied by 0.02=0.40mm.
Total reading is 35mm+0.40= 35.40mm
35.40 mm

25. Type B Vernier Caliper

26. Vernier Caliper – Type C

27. VERNIER CALIPER
• Vernier calipers are available in size of 150 mm, 225
mm, 900 mm and 1200 mm.
• The selection of the size depends on the measurements to
be taken.
• Vernier calipers are precision instruments, and extreme
care should be taken while handing them.

29. VERNIER HEIGHT GAUGE
The main parts of a vernier height gauge and
their function are given.
1.base
2. beam
3.vernier slide
4. fine setting device
5. vernier plate
6. locking screws
7. scriber

30. Vernier Depth Gauge
• A vernier depth is very commonly used precision
instrument for measuring depth of holes recesses, slot
and step.
• Its construction and method of reading are similar to
those of a vernier caliper.

32. VERNIER DEPTH GAUGE
 Base
 Graduated beam
 Clamping screw
 Fine adjustment mechanism
 Vernier scale

34. MICRO METER
 A micro meter is a precision instrument used to
measure a job, generally within an accuracy of
0.01mm.
Micrometer used to take the outside measurements are
know as outside micrometer.

35. PARTS OF MICROMETER
Frame
Anvil and spindle
Screwed spindle
Graduated sleeve or barrel
Ratchet or friction stop
Spindle clamp

37. Major divisions = 10 x 1.00 mm= 10.00mm
Minor divisions = l x 0.50mm = 0.50mm
Thimble divisions = 16 x 0.0lmm = 0.16mm
Reading = 10.66mm

38. Stick Micrometers
Inside Micrometer Caliper

39. Depth micrometer

40. Screw Thread Micrometer Caliper

41. Inside Micrometer Caliper
Measuring the Inside Diameter of a Hole by an
Inside Micrometer (1) Micrometer, (2) Anvil, (3)
Handle and (4) Extension Rod

42. V-anvil Micrometer Caliper

43. Blade Type Micrometer

44. Digital Micrometer

45. Classification of Comparator
1. Mechanical Comparator: It works on gears pinions, linkages,
levers, springs etc.
2. Pneumatic Comparator: Pneumatic comparator works by using
high pressure air, valves, back pressure etc.
3. Optical Comparator: Optical comparator works by using lens,
mirrors, light source etc.
4. Electrical Comparator: Works by using step up, step down
transformers.
5. Electronic Comparator: It works by using amplifier, digital
signal etc.

46. Mechanical Comparator -Dial Indicator

47. • They are designed for use on a wide range of standard measuring
devices such as dial box gauges, portal dial, hand gauges, dial depth
gauges, diameter gauges and dial indicator snap gauge.
• Applications:
1. Comparing two heights or distances between narrow limits.
2. To determine the errors in geometrical form such as ovality,
roundness and taper.
3. For taking accurate measurement of deformation such as in
tension and compression.
4. To determine positional errors of surfaces such as parallelism,
squareness and alignment.
5. To check the alignment of lathe centers by using suitable
accurate bar between the centers.

48. Mechanical Comparator
–Reed type Comparator

49. Mechanical Comparator
- Johansson Mikrokator
or

50. Advantages of Mechanical Comparator:
1. They do not require any external source of energy.
2. These are cheaper and portable.
3. These are of robust construction and compact design.
4. The simple linear scales are easy to read.
5. These are unaffected by variations due to external source of
energy such air, electricity etc.
Disadvantages:
1. Range is limited as the pointer moves over a fixed scale.
2. Pointer scale system used can cause parallax error.
3. There are number of moving parts which create problems due to
friction, and ultimately the accuracy is less.
4. The instrument may become sensitive to vibration due to high
inertia.

51. Electrical Comparators

52. Advantages:
1. Measuring units can be remote from indicating units.
2. Variable sensitivity which can be adjusted as per requirement.
3. No moving parts, hence it can retain accuracy over long periods.
4. Higher magnification is possible as compared to mechanical
comparator.
5. Compact sizes of probes arc available.
Disadvantages:
1. The accuracy of working of these comparators is likely to be
affect due to temperature and humidity.
2. It is not a self contained unit; it needs stabilized power supply for
its operation.
3. Heating of coils can cause zero drifts and it may alter calibration.
4. It is more expensive than mechanical comparator.

53. Optical Comparators

54. • The actual difference x between the two dimensions is amplified by a
lever to give an angular displacement theta of a pivoted mirror.
• The reflected ray is deflected through an angle 2 theta from the original
line and gives a reading of X on the scale.
• The main advantage of an optical comparator is that it is capable of giving
higher degree of magnification due to reduction of moving members and
better wear resistance qualities.

55. Pneumatic Comparators (Solex Gauge):

56. LIMIT GAUGES
• A limit gauge is not a measuring gauge. Just they are used as
inspecting gauges.
• The limit gauges are used in inspection by methods of attributes.
• This procedure is mostly performed by the quality control department
of each and every industry.
• Limit gauge are mainly used for checking for cylindrical holes of
identical components with a large numbers in mass production.

57. Purpose of using limit gauges
• Components are manufactured as per the specified tolerance limits, upper
limit and lower limit.
• The dimension of each component should be within this upper and lower
limit.
• If the dimensions are outside these limits, the components will be rejected.
The common types are as follows
1. Plug gauges.
2. Ring gauges.
3. Snap gauges.

58. PLUG GAUGES

59. Solid type. For sizes up to 10mm

60. Renewable type

61. Fastened type:

62. Flat type

63. 63
Thread Plug Gauges

64. Taper plug gauge
1. Taper plug gauge — plain
2. Taper plug gauge — tanged.
3. Taper ring gauge plain
4. Taper ring gauge — tanged
• Taper plug gauges are used to check tapered holes. It has two check lines. One
is a GO line and another is a NOGO line.
• During the checking of work, NOGO line remains outside the hole and GO
line remains inside the hole.

65. Taper plug gauge — plain

66. Taper ring gauge plain

67. Taper plug gauge — tanged.

68. Taper ring gauge — tanged

69. RING GAUGES
• Ring gauges are mainly used for checking the diameter of shafts having a central
hole.
• The hole is accurately finished by grinding and lapping after taking hardening
process.
• But the hole of GO ring gauge is made to the upper limit size of the shaft and
NOGO for the lower limit

70. 70
Thread Ring Gauges

71. 71
Snap Gauges
• One of most common types of comparative measuring instruments
• Faster to use than micrometers
• Limited in their application
• Used to check diameters within certain limits by comparing part size to preset
dimension of snap gauge

72. 72
Snap Gauges
• Have C-shaped frame with adjustable gauging anvils or rolls
set to "go" and
"no-go" limits
of the part
• Several styles

73. Snap, Gap or Ring
Gauges

74. Adjustable Type
Gap Gauges

75. FEELER GAUGE
• A feeler gauge (also known as a
thickness gauge) is an accurately
manufactured strip of metal that is used
to determine the gap or clearance
between two components.

76. Radius Gauge
• A radius gauge is a tool used to measure the radius of an object.
76

77. Thread Pitch Gauge
• It used to quickly determine the pitch of various threads by matching
the teeth on the leaves with teeth on the work.
77

78. Angular measurement devices
1.Linear standard angular measurements
• Protractors
• Universal bevel protractor's
2.Measurement of inclines
• Spirit level
• Clinometer
3.Angle comparators

79. Vernier Bevel Protractor

80. Universal Bevel Protractor

81. Applications

83. Spirit Level
• Spirit level is one of the most commonly used instruments for inspecting the
horizontal position of surfaces and for evaluating the direction and magnitude of
minor deviation from that nominal condition.
• It is filled almost entirely with a liquid, leaving a small space for the formation of an
air or gas bubble .
• Generally, low viscosity fluids, such as ether, alcohol or benzol, are preferred for
filling the vial
• The liquid due to its greater specific weight tends to fill the lower portion of the closed
space.

84. • Inclination of a surface can be known from the deviation of the bubble from
its position when the spirit level is kept in a horizontal plane
• To reduce the effect of heat transfer in handling spirit levels are made of a
relatively stable casting and are equipped with thermally insulated handles.

85. Clinometer
• A clinometer is a special case of application of spirit level for measuring,
in the vertical plane, the incline of a surface in relation to the basic
horizontal plane, over an extended range.
• The angle of inclination of the rotary member carrying the level relative to
its base is measured by this circular scale.
• It used to determine the include angle of two adjacent faces of work piece.
• clinometers with 10’ graduations are available.

86. Applications clinometer
• It used check the angular faces and relief angles on large cutting tools
and milling cutter inserts.
• Measurement of an incline plane with respect to a horizontal pane.
• Measurement of the relative position of two mutually inclined surfaces

89. Sine Bar

91. Use of Sine Bar
1. Measuring known angles or locating any work to a given angle.
2. Checking of unknown angles.
3. Checking of unknown angles of heavy component.

92. 1.Measuring known angles or locating any work to a given
angle

93. 2. Checking of unknown angles

94. 3.Checking of unknown angles of heavy component
Component
Vernier
Height Gauge
Reading R1Reading R2
Dial Test
Indicator a
Fiducial
Indicator
Fig. 2.25 Use of Sine bar with large work piece

96. Modifications in sine bar
1. Sine table
2. Sine center

97. 1. Sine table

98. 2. Sine center

99. Advantages of sine bar:
1. It is used for accurate and precise angular measurement.
2. It is available easily.
3. It is cheap.
Disadvantages:
1. The application is limited for a fixed center distance between two
plugs or rollers.
2. It is difficult to handle and position the slip gauges.
3. If the angle exceeds 45°, sine bars are impracticable and inaccurate.
4. Large angular error may results due to slight error in sine bar.

101. Sources of Error in Sine Bars
• Error in distance between roller centers.
• Error in slip gauge combination used for angle setting.
• Error in parallelism between gauging surface and plane of roller axes.
• Error in equality of size of rollers and cylindrical accuracy in the form
of the rollers.
• Error is parallelism of roller axes with each other.
• Error in flatness of the upper surface of the bar.

102. Autocollimators
The two main principles used in an autocollimator are
• (a) the projection and the refraction of a parallel beam of light by a lens,
and
• (b) the change in direction of a reflected angle on a plane reflecting
surface with change in angle of incidence.

103. 1.Reflector is at 90 Ѳ with the Direction of Rays

104. 2. Reflector is not at Right Angles to the Direction of the
Rays

106. Tool Makers Microscope