5. Linear Measurements_1.pptx

Linear Measurements
By: Mudit M. Saxena
Dept. of Mech. Engg.

Content
• Definition
• Types of Linear Measurement
• Linear Measuring Instrument
– Steel Rule, Calipers, Vernier Caliper, Vernier Height Gauge,
Vernier Depth Gauge, Micrometer, Vernier Micrometer –
Principle, Construction, Error, Bore Gauge, Telescopic
Gauge, Slip Gauges, Dial indicators : Construction &
Working, Comparators
2
By: Mudit M. Saxena, Dept. of Mech. Engg., ITE, Indus University

• Miscellaneous Linear measuring instruments like bore
gauge, telescopic gauge, slip gauges, Dial indicators :
Their construction & Working
• Comparators
• Calibration of various linear measuring instruments
• Applications, Advantages & Limitations of commonly
used linear measuring instruments.
Content
3

Introduction
• Linear measurement applies to the measurement of lengths,
diameters, heights and thickness including external and internal.
• Line measuring instruments are designed either for the line
measurements or end measurement.
4

Classification of Linear Measuring Instrument
• The instrument used for linear measurement can be
classified as
– Direct Measuring Instrument
– Indirect Measuring Instrument
• Direct Measuring Instruments are further classified
as
– Graduated – Rules, vernier calliper, dial indicators etc.
– Non-graduated – Callipers, thickness gauge, slip gauge etc.
–
• Direct Measuring Instruments are also classified as
– Non-precision Instruments – Rules, callipers etc.
– Precision Instruments
5

Least Count
• The least count of any measuring equipment is the
smallest quantity that can be measured accurately
using that instrument.
6

Engineer’s Steel Rule
• Steel rule is a line measuring device.
• It compares an unknown length to be measured with
the previously calibrated length.
• It is made of hardened steel or stainless steel,
having equally spaced lines engraved on it.
• They are manufactured in different sizes; 150, 300,
600 or 1000 mm length.
• It is graduated in ½ mm in some portion and 1 mm
on the other.
• Reading accuracy of steel rule is 0.5mm in metric
system and 1/64” in British system.
7

• Desirable qualities of the steel rule:
– Made of good quality steel.
– Clearly engraved lines.
– Optimum thickness.
– Chrome plated to prevent corrosion and protection against staining.
– Its faces should be machine ground.
8

• Precautions while using steel rule
– The ends of the rule preserved from wear.
– The rule should never be used for cleaning between parts or as a
substitute of for screw driver, otherwise its edges and ends will be
damaged.
– Do not place a steel rule with any cutting tools.
– Apply a thin layer of oil when not in use.
– To avoid parallax error, while making measurements, eye should
be directly opposite and 90o to the mark on the part to be
measured.
– While measuring, the graduation lines should be as close as
possible to the faces being measured.
9

Callipers
• Caliper are simple measuring instruments used to
transfer measurement from a steel rule to objects, and
vice versa.
• It is used to measure the diameter of a circular part.
• Calipers are of different types depending on the type of
the joint and the shape of the leg .
10

Callipers
• The calliper consists of two legs
and a hinged at top.
• The legs of the calliper are made
from carbon and alloy steel.
• They are identical in shape.
11

• Callipers can be classified as
– Firm joint calliper
– Spring type calliper
Callipers
12

Callipers
• Firm Joint (Fixed Joint ) Calliper
– Firm joint calliper work on the friction created at
the junction of legs.
– In the case of firm joint calipers, both legs are
pivoted at one end.
– To take measurement of a workpiece, the caliper
is opened roughly to the required size.
– Fine setting is done by tapping the caliper lightly
on a wooden surface.
– They can be used to measure inside as well as
outside diameter.
– They are available in the nominal sizes of 100,
150, 250 and 300 mm.
13

Callipers
• Spring Calliper
– Improved version of firm joint calliper.
– The legs of spring callipers are made from
suitable steel alloy.
– The two legs carry a curved spring (tension)
(carbon spring steel) at a top, fitted in the
notches, applying pressure on the legs.
– A screw is fixed in one leg and made to pass
through the other.
– It is provided with a knurled nut for making
adjustment.
– Available in sizes of 75, 100, 150, 250 and
300 mm.
14

Callipers
Firm Joint Calliper Spring Calliper
15

Callipers
• Outside and Inside Calliper
– Out side and inside callipers are differentiated by the shape of
the legs.
– Callipers used for out side measurements are known as out side
calipers.
– The callipers used for internal measurements are known as
inside caliper.
– Calliper are used along with steel rule ,and the accuracy is
limited to 0.5 mm.
16

• Callipers can also be classified according to their use
– Outside Calliper
– Inside Calliper
– Transfer Calliper
– Odd Leg Calliper
Callipers
17

Callipers
Outside / Inside Calliper
Specification
Maximum length to be
measured
Length in mm Length in in
150 6'
175 7'
200 8'
250 10'
300 12'
400 16”
18

Callipers
• Transfer Calliper
– Transfer callipers are used for measuring chamfered
grooves or flanges.
– A screw attaches a small auxiliary leaf to one of the
legs.
– The leaf is locked to the leg.
– The legs may be opened or
closed as needed to clear the obstruction.
– The legs are then brought back and locked to the
leaf, restoring them to the original setting.
19

Callipers
• Odd Leg Calliper
– Oddleg callipers / Hermaphrodite calipers or
Oddleg ennys, or Ol' Jennysare generally
used to scribe a line a set distance from the
edge of workpiece.
– The bent leg is used to run along the
workpiece edge while the scriber makes its
mark at a predetermined distance, this
ensures a line parallel to the edge.
– The uppermost caliper has a slight shoulder
in the bent leg allowing it to sit on the edge
more securely, the lower caliper lacks this
feature but has a renewable scriber that can
be adjusted for wear, as well as being
replaced when excessively worn.
20

Vernier Callipers
• Vernier Calliper
• Working Principle
• “The difference between two scales or divisions which are nearly equal but not
quite alike , used for obtaining small difference in measurement.”
21

Vernier Callipers
• Construction
22

Vernier Callipers
o Construction
23

Vernier Callipers
• Construction
Parts Function/s
Outside calliper jaws Use to close around the outside of an object.
Inside calliper jaws Fit into the hole or slot and measure the inside dimension.
Coarse locking screw Both locking screw loose the lower jaw, free to move.
Initially close the jaws loosely around the object.
Final locking screw Locks the lower jaw so that the calliper can be removed from the object to
read.
Fine adjustment
thumbscrew
Allows the jaws to be closed to a sung fit.
Main scale Calibrated on L shaped framed fixed jaw.
Vernier scale Slides over a main scale.
The two jaws coincides the zero setting.
Depth probe Use to measure the depth of the cavity.
24

Vernier Callipers
o Measurement Application/s
• Use to measure internal and external dimensions.
• Use to measure the depth of the cavity.
25

Vernier Callipers
• Measurement Application/s
26

Vernier Callipers
• Specification/s
• Vernier callipers are specified according to the length.
27

Vernier Callipers
• Least count
• Least count of the vernier calliper is the difference between the one main scale
division and same vernier scale division.
• In vernier caliper, main scale division (49mm) are divided in to 50 equal part in
the vernier scale.
• 1 main scale division = 1 mm
• 1 vernier scale division = 49/50 mm
• Therefore, least count = 1 – 49/50 = 1 / 50 mm = 0.02 mm
28

Vernier Callipers
• Reading the vernier scale (procedure)
• The reference point is the 0 on the vernier scale.
• Read the number of divisions on the main scale.
• Locate the line of coincidence.
• The line of coincidence is the line on the vernier scale that coincides with a line
on the main scale.
• Total reading = Main scale reading + vernier scale reading * least count
29

Vernier Callipers
• Reading the vernier scale (procedure)
 Check the vernier caliper correctly so it reads zero when the jaws are closed. If
not, find the error.
 Close the jaws around the object but do not over tighten. The jaws should exert a
firm pressure on the object.
 Lock both the screws to tight the caliper jaws and then remove from the object.
can be removed from the object and read without worrying if the jaws will shift
position.
30

Vernier Callipers
• Example of Reading
• Main scale reading = 35 mm
• Vernier scale reading = 20 mm
• Total reading = 35 + 20*0.02 = 35.40 mm.
31

Vernier Callipers
32

Vernier Callipers
• Calculate the total reading
33

Vernier Callipers
34

Vernier Callipers
• Types of vernier calliper
• According to the least count
• Vernier Calliper with 0.02mm least count
• According to the recommendation by Indian Standard
• Type A – both the sides for internal and external measurement
• Type B – Internal measurement are made by adding width to the
internal measuring jaws
• Type C – Dial or digital measurement unit is attached
35

Vernier Callipers
• Types of vernier calliper
36

Vernier Callipers
• Errors in vernier measurement
• Due to play sliding jaw on the scale.
• Worn or warped sliding jaw frame surface.
• Due to wear or warping of the jaws.
• Incorrect reading of the vernier scale.
• Due to its size and weight.
37

Vernier Callipers
• Precautions to be taken in vernier measurement
• Check the zero error before use.
• The line of measurement must coincide with the line of scale.
• The caliper should not tilted or twisted.
• The plane / surface of the measuring jaws must be perpendicular to the center
line of the work piece.
• Should not over tight the jaws of the work piece.
• Grip the instrument near the jaw.
• Use corrective or magnifying glass to overcome the imperfect vision.
• Avoid parallax or reading error.
38

Vernier Height Gauge
• Vernier Height Gauge
• A height gauge is a measuring device used either for
determining the height of something, or for repetitious
marking of items to be worked on.
• It is similar to vernier calliper but in this the graduated scale
is held in vertical position.
39

• “The difference between two scales or divisions which are
nearly equal but not quite alike , used for obtaining small
difference in measurement.”
40

• Construction
• The main parts of a vernier height gauge are
• Base
• Beam
• Vernier slide
• Fine setting device / screw
• Vernier plate
• Locking screws
• Scriber
41

• Vernier Height gauge
• Construction
Parts Function/s
Base A base is massive and robust in construction to ensure rigidity and stability.
Beam A vertical graduated beam supported on massive base, supports vernier
slide and vernier scale.
Vernier Slide Mounted on beam and carries vernier scale.
Fine Setting Device Screw operated and used to adjust the height
Vernier Plate Vernier scale is engraved on it.
Locking Screw Used for fine adjustment and locking.
Scriber Used for zero setting and height measurement
42

• Measurement Application /s
• Use to measure and mark vertical
heights above a surface of datum plate.
• Use to measure difference in heights by
taking vernier scale reading.
• Use in quality inspection department for
checking the dimensional correctness.
43

• Specification
• Vernier height gauges are specified according to its range
of measurement.
Sr. No. Range, mm Range, in
1 0 – 150 0 - 6
2 0 – 300 0 - 12
3 0 – 450 0 – 18
4 0 – 600 0 – 24
5 0 – 1000 0 – 40
6 0 - 1500 0 - 60
44

• Types of vernier height gauge
• There are two types of height gauges:
• Vernier height gauges
• Dial or electronic height gauges
45

• Vernier height gauges -
• The vernier height gauge has the additional refinement of a vernier
scale for greater accuracy in reading or setting the tool.
46

• Dial or electronic height gauges
• The dial or electronic height gauge has a dial or digital
readout that gives the measured height.
47

• Precautions to be taken in vernier height gauge
measurement
• The beam should be sufficiently rigid square with the base.
• .The upper and lower gauging surface of the measuring jaws shall be flat and
parallel to the base.
• Keep the instatement in the case when not in use.
• It should be tested for straightness, squareness and parallelism of the working
faces of the beam.
• The springing of the measuring jaw should always be avoided.
48

Vernier Depth Gauge
• Vernier Depth Gauge
• A depth gauge is a measuring device used to measure the
depths of hole, slots and recesses, to locate center
distances etc.
49

Vernier Depth Gauge
• “The difference between two scales or divisions which are
nearly equal but not quite alike , used for obtaining small
difference in measurement.”
50

Vernier Depth Gauge
o Construction
1. Base
2. Graduated Beam (Main Scale)
3. Clamping screw
4. Fine Adjustment Mechanism
5. Vernier Scale
51

Vernier Depth Gauge
• Construction
Parts Function/s
Beam It the fixed unit and serves as a datum for measurement
Graduated Beam The beam with the main scale graduations is the sliding member
Clamping Screw Close the base loosely around the object.
Fine Adjustment Screw For measurement after tightening the clamping screw
Vernier Scale Vernier scale is engraved on it.
52

Vernier Depth Gauge
• Measurement Application /s
• Use to measure depth of holes recesses, slot and step.
53

Vernier Depth Gauge
• Specification
• Vernier depth gauges are specified according to its range of
measurement.
Sr. No. Range,
mm
Range,
in
1 0 – 150 0 - 6
2 0 – 300 0 - 12
3 0 – 450 0 – 18
4 0 – 600 0 – 24
5 0 – 1000 0 – 40
6 0 - 1500 0 - 60
54

Vernier Depth Gauge
• Reading the vernier depth gauge
(procedure)
• The base should be firmly held against the
reference surface.
• Lower the graduated beam into the cavity until it
contacts the bottom surface of the cavity.
• Do the base loosely around the job using clamping
screw.
• Tight the holding using fine adjustment screw.
• Remove the instrument from the cavity.
• Take reading in the same way as the vernier
calliper.
55

Vernier Depth Gauge
• Vernier depth gauges
• Dial or electronic depth gauges
56

Micrometer
• Micrometer
• “When a screw is turned through nut through one revolution, it advances one
pitch distance i.e. one revolution of screw corresponds to a linear movement of a
distance equal to pitch of the thread.”
57

Micrometer
• Micrometer
• Construction
58

Micrometer
• Micrometer
• Construction
Parts Function/s
Frame U or C shaped steel frame holds all the parts together.
Frame gap permits the maximum diameter or length of the job to
be measured.
Anvil Fixed to frame protruding 3 mm from left and of the same
diameter as spindle.
The shiny part that the spindle moves toward, and that the
sample rests against.
Spindle Movable measuring face with the anvil
Cylindrical shaped part that the thimble causes to move toward
the anvil.
Barrel / Sleeve The stationary round part with the linear scale on it.
Thimble The part that one's thumb turns. Graduated markings on
cylindrical surface.
Rachet Screw Device on end of handle that limits applied pressure by slipping at
a calibrated torque. 59

Micrometer
• Micrometer
• Measurement Application/s
• Use to measure the length dimensions between two parallel / end surfaces on
the outer / inner side of an object or feature.
60

Micrometer
• Micrometer
• Specification/s
• Micrometers are specified according to maximum dimension it can hold in
between anvil and spindle.
61

Micrometer
• Micrometer
• Specification/s
• Micrometers are specified according to maximum dimension it can hold in
between anvil and spindle.
62

Micrometer
• Micrometer
• Least count
• Least count of micrometer is the smallest
division it can measure.
• If the circumference of the screw is divided into
number of equal parts “n” and the pitch is “p”,
then
• Least count = p / n
• Either by increasing the number of divisions on
the circumference or by reducing the pitch, least
count can be improved.
• Example –
• Pitch of the screw = 0.5 mm
• Divisions on circular scale = 50
• Least Count = 0.5 / 50 = 0.01 mm
63

Micrometer
• Micrometer
• Reading the micrometer
(procedure)
• Select the micrometer of the desired range
depending upon size of the workpiece.
• Check the micrometer for zero reading.
• For 0 – Maximum size range, check by
contacting the faces.
• For others, check by placing a master
gauge of required shape.
• The zero on the thimble should coincide with
the reference line on main scale. If not, use
special spanner provided to do the same.
• The main scale on barrel has 1 mm interval
divisions above reference line and 0.5 mm
interval lines below the reference line.
64

Micrometer
• Micrometer
• Reading the micrometer (procedure)
• Hold the workpiece between the faces of the anvil and spindle till the anvil and
spindle surfaces touches the workpiece.
• Make fine adjustment with rachet.
• Take the reading on main scale for both above and below the reference line.
• Take thimble reading which coincide with reference line on the sleeve.
• Total reading = Main scale reading + Least Count * Reading on thimble
65

Micrometer
• Micrometer
• Assume the least count of the
micrometer be 0.01 mm.
• A = Main scale reading above ref.
line
• = 5 mm
• B = Main scale reading below ref.
line
• = 0.50 mm
• C = Reading on circular scale
• = Least count * Line of
coincidence
• = 0.01 * 37
• = 0.37 mm
• Total Reading = A + B + C
• = 5.87 mm
66

Micrometer
• Micrometer
• Assume the least count of the micrometer be 0.01 mm
67

Micrometer
• Micrometer
• Assume the least count of the micrometer be 0.01 mm
68

Micrometer
• Micrometer
• Types of micrometer
• Micrometers may be classified as
• Outside micrometer
• Inside micrometer
• Vernier Micrometer
• Screw thread micrometer
• Depth gauge micrometer
69

Micrometer
• Micrometer
• Outside Micrometers
• Outside micrometer use to measure the outside diameter and thickness of
parts.
70

Micrometer
• Micrometer
• Outside Micrometers
• Outside micrometer use to measure the outside diameter and thickness of
parts.
71

Micrometer
• Micrometer
• Inside Micrometers
• Inside micrometer use to measure the inside dimensions of the parts.
• Use to precisely measures holes and slots.
72

Micrometer
• Micrometer
• Vernier calliper principle is applied to micrometer.
• The objective is to increase its accuracy.
• The vernier scale is engraved on the micrometer barrel.
• The 10 divisions on the vernier scale equal to 9 divisions thimble.
73

Micrometer
• Micrometer
• One division on vernier scale = 9 / 10 of that of the thimble.
• One division on thimble = 0.01 mm (generally)
• Therefore least count according to the principle of vernier calliper is as
follow:
• Least count = 0.01 – 9 / 10 * 0.01 = 0.001 mm
74

Micrometer
• Micrometer
• Screw Thread Micrometer
• Use to measure the pitch diameter of the screw thread.
• The screw thread micrometer has a 60-degree pointed spindle and a double V-
shaped swiveling anvil.
• When the micrometer is set at zero, the pitch line of the spindle and anvil
coincide
75

Micrometer
• Micrometer
• Precautions to be taken in micrometer
• Clean the micrometer by wiping of oil, dirt, dust etc.
• Clean measuring of the anvil and the spindle.
• Set the zero reading of the instrument before measuring.
• Hold the part and micrometer properly.
• Micrometer must be moved out carefully to note the reading.
76

Micrometer
• Micrometer
• Screw Thread Micrometer
• When the micrometer is measuring the thread, it is measuring along the pitch
diameter of the thread
• It is important to make sure that the screw thread micrometer will fall within the
screw pitch range of a particular thread.
77

Micrometer
• Micrometer
• Errors in micrometer
• Lack of flatness anvil / spindle surfaces.
• Accurate setting of the zero reading.
• Accurate reading of the final dimension.
• Accurate reading of fraction reading.
• Applying too much pressure on the thimble.
• Wear of the anvil surfaces, threads on spindle due to constant use.
• Wear of rachet mechanism / locking arrangement.
78

Advantages & Limitations
79

Miscellaneous Linear Measuring Instruments
• Bore Gauge
• Introduction
• A bore gauge is a convenient tool used for accurately measuring holes.
• Types
• Telescopic Bore Gauge
• Dial Bore Gauge
80

• Bore Gauge
• It is also called as ‘Telescopic gauge’.
• It consists of handle with rods in the tube at one end and working screw at other
end.
• The rods with spherical contacts can slide within the tube and are forced apart by
internal spring.
• The locking screw can lock the rods at any desired position.
81

• Bore Gauge
• The rods are pressed closer and are inserted into the hole to be measured such
that the both the ends of the rods touch the internal surface.
• Lock the position.
• Take the gauge out of the hole.
• The dimension across the rods is measured by micrometer or vernier calliper.
82

• Bore Gauge
• Telescopic Bore Gauge - Specification
• They are specified according to their range of measurement as follows
• A – 8 mm to 12.7 mm
• B – 12.7 mm to 19 mm
• C – 19 mm to 32 mm
• D – 32 mm to 54 mm
• E – 54 mm to 90 mm
• F – 90 mm to 150 mm
83

• Bore Gauge
• Dial Gauge
• It is an instrument used to measure small variation in linear measurement.
• It is named so because the results are displayed by mean of dial.
• The main functions of the dial indicators:
• To measure the length
• To determine the errors in geometrical forms.
84

• Bore Gauge
• Dial Gauge
• The various parts o ft he dial gauge are as follows:
85

• Bore Gauge
• Dial Gauge
• A plunger can move upward and downward.
• This movement is converted in the rotary movement f the dial by gear train.
• The dial is divided into 100 divisions.
• One complete revolution corresponds 1 mm movement of the plunger.
86

• Bore Gauge
• Dial Gauge
• Application / s
87

• Slip Gauge
• Introduction
• Slip gauges are known as gauge blocks.
• They are also known as Johansson blocks.
• They are a precision grounded and lapped length measuring standard.
• They are used as a reference for the setting of measuring equipment used in
machine shops,
• They are used to check linear tolerances in the range of 0.001 mm to 0.0005
mm.
88

• Slip Gauge
• Introduction
• These are mostly available in rectangular, square or round in shape.
• They are commonly available in sets.
• Each block in a set has a given thickness or length marked on it.
• These gauges mostly come in 32 mm x 9 mm size.
• High quality steel or tungsten carbide is used to manufacture these gauges.
89

• Slip Gauge
• Introduction
90

• Slip Gauge
• Types
• Slips gauges are usually of three types:
• Master Blocks – Used in air conditioned laboratories.
• Inspection Blocks – Used in air conditioned laboratories.
• Working Blocks – Used for general purpose.
• Accuracy in measurement of the slip gauges are given in table
91

• Slip Gauge
• Types
• Classification of slip gauges according to purpose
92

• Slip Gauge
• Example
• A common gauge block contains 81 to 88 blocks ranging from 0.5 mm to 100
mm thickness.
• A M88 Grade – I slip gauge set contains 88 blocks as per the details given
below:
93

• Slip Gauge
• Example
• A common gauge block contains 81 to 88 blocks ranging from 0.5 mm to 100
mm thickness.
• A M88 Grade – I slip gauge set contains 88 blocks as per the details given
below:
94

Calibration of Various Linear Measuring Instruments
• Calibration
• According to The Automation, System and Instrumentation
Dictionary, the word calibration is defined as
• “A test during which known quantities of the measurement are applied to
the transducer and the corresponding output reading are recorded under
specified conditions.”
• The calibration range is defined as “the region between the
limits within which the limit is measured, received or
transmitted, expressed by stating the lower and upper range
values.”
95

• Why Calibration is required?
• Instrument error can occur due variety of factors – dirt,
usage of time, process change, environment etc.
• So, it is required to make sure the instrument is providing
the accurate indication of the measurement.
96

• Calibration of Vernier Calliper
• Measuring Equipment Required
• Gauge blocks
97

• Following procedure describes the steps taken when
calibrating vernier calliper gauges of any dimension using
the DIN 862 standard.
• Cleaning
• The measuring surfaces are cleaned using petroleum ether. Any
grit or other particles are also cleaned from the scale.
• The surfaces are wiped afterwards using the tougher side of a
chamois leather (or special synthetic cloth).
• Minor damages on guides or measuring surfaces are repaired
using special fine grindstone.
98

• Temperature Variation
• The temperature of the gauge is stabilized at 20oC ± 1oC for 5
hours.
99

• Calibration
• Visual Inspection
• Measuring surfaces are checked to see if there are any
scratches which may impede calibration.
• Classical scale is checked for any marking points or
numbers on the scale which may be missing or worn.
• Dial scale is checked for the straightness of the pointer
and its distance from the scale.
• Digital scale is checked for numerical legibility and for any
scratches on the display.
• The numbers must be clearly visible in each measuring
position.
100

• Calibration
• Functional Check (Parallelism of Measuring
Surfaces)
• The parallelism is checked by observing the air slot when
measuring surfaces are in contact.
• It should not change if the gauge is fixed.
101

• Calibration
• Functional Check (Measurement of Deviations)
• Deviations of gauges with measuring range 0 - 150 mm
are checked using gauge blocks of the dimension.
• Deviation of inside measure is checked at the value 50
mm using gauge ring (for all measuring ranges).
102

Comparators
• Comparators are precision measuring equipment mainly
consisting of sensing, indicating or displaying units whose
purpose is to detect variation in a specific distance w.r.t
reference.
• In length measurement, it serves the following functions –
• Locating the object under test on a reference plane with end of the
distance to be measured
• Holding the comparator I a positive position from the reference plane, with
the effective movement of the spindle.
103

• Comparators are classified as –
• Mechanical Comparators
• Optical Comparators
• Pneumatic Comparators
• Electrical & Electronics Comparators
• Fluid displacement comparators
Comparators
104

• Mechanical Comparators –
• Dial Indicator
• Micrometer Dial Comparator
• Johansson Mikrokator
• Sigma Mechanical Comparator
Comparators
105

• Micrometer Dial Comparator
– It is used for rapid measurement of diameters of cylindrical parts, shafts,
bolts, shanks, etc. and measurement and checking of thickness and length.
– It consists of a dial as a comparator, which is integrated into frame.
– The procedure for noting the reading is similar to the procedure of reading a
micrometer.
Comparators
106

• Johansson Mikrokator
– It is one of the important type of mechanical comparators.
– It is developed by Swedish Engineer, H Abramson and developed by C
E Johansson Ltd.
– It works on the principle of a button spin-ning on a loop of string.
– A twisted thin metal strip carries at the center of its length a very light
pointer made of thin glass.
– The two halves of the strip from the center are twisted in opposite
directions so that any pull on the strip will cause the center to rotate.
– One end of the strip is fixed to the adjustable cantilever strip and the
there end is anchored to the spring elbow, one arm of which is carried
on the measuring plunger.
Comparators
107

Comparator
108

Comparator
• As the measuring plunger moves either upwards or downwards, the elbow
acts as a bell crank lever and causes twisted strip to change its length thus
making it further twist or untwist.
• Thus the pointer at the center of the twisted strip rotates by an amount
proportional to the change in length of strip and hence proportional to the
plunger movement.
• The amplification depends upon the rate of amplification and the scale used.
109

Comparator
• Sigma Mechanical Comparator
• It consists of a plunger attached to a rectangular bar which is supported at its
upper and lower ends by flat steel springs (split diaphragms)
• Plunger carries the knife edge
110

Assignmenmt 2
Q 1. What are linear measurements. How linear measuring intruments can be
classified ?
Q 2. What is least count ? How least count of vernier calipers is calculated ?
Q 3. What are callipers ? How they are classified ?
Q 4. Explain the parts and their functions of vernier callipers.
Q 5. What are the errors in vernier callipers.
Q 6. Give an example of calculating least count of micrometer.
Q 7. Explain the parts and their functions of vernier hight guage.
Q 8. write the parts and their functions of vernier depth guage.
Q 9. what are the type of micometrs ?
Q 10. What are the errors in micrometer ?
Q 11. Explain telescopic bore guage with a neat diagram.
Q 12. What are slip guages ? How they are classified ?
Q 13. How vernier callipers are calibrated ?
Q 14. Explain the parts and functions of a Micrometer.
Q 15. What are the comarators ? How they are classified.
111

5. Linear Measurements_1.pptx

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5. Linear Measurements_1.pptx