UNIT II

UNIT II
LINEAR AND ANGULAR
MEASUREMENTS
1

Linear measurement
• Linear measurement applies to measurement of
lengths, diameters, heights, and thickness
including external and internal measurements.
• The line measuring instruments have series of
accurately spaced lines marked on them, e.g.
scale. The dimension to be measured is aligned
with the graduations of the scale.
• Linear measuring instruments are designed either
for line instruments, the measurement is taken
between two end surfaces as in micrometers, slip
gauges etc
2

LIST OF METERS
accelerometer physical, accelerations
actinometer heating power of sunlight
alcoholmeter alcoholic strength of liquids
altimeter altitudes
ammeter electric current
anemometer windspeed
astrolabe latitude and altitude of celestial bodies
audiometer hearing
barkometer tanning liquors used in tanning leather
barometer air pressure
bettsometer integrity of fabric coverings on aircraft
bevameter mechanical properties of soil
3

bolometer electromagnetic radiation
Brannock Device measuring shoe size
breathalyzer breath alcohol content
caliper distance
calorimeter heat of chemical reactions
cathetometer vertical distances
ceilometer height of a cloud base
chronometer or clock time
clap-o-meter volume of applause
compass direction of North
colorimeter color
creepmeter
slow surface displacement of an active geologic fault in
the earth
declinometer magnetic declination
densimeter specific gravity of liquids
4

Micrometer readings
• Using the first example seen below:
1. Read the scale on the sleeve. The example clearly
shows12 mm divisions.
2. Still reading the scale on the sleeve, a further ½ mm
(0.5) measurement can be seen on the bottom half
of the scale. The measurement now reads 12.5mm.
3. Finally, the thimble scale shows 16 full divisions
(these are hundredths of a mm).
• The final measurement is 12.5mm + 0.16mm =
12.66mm
• Total reading=(MSR+SD+TSRXLC)=(12+0.5+16X0.01)
12

TERMINOLOGY
• BACK LASH: lack of motion of spindle
• MEASURING RANGE: total travel of spindle
• CUMULATIVE ERROR: deviation of
measurement from nominal dimension
13

USEAGE OF THREAD MICROMETER
21

SLIP GAUGES
• Most accurate form of representing size by
means of two parallel surfaces.
• Set of blocks with standard length
• They can be joined together by a process
called WRINGING
• Comparators are used to calibrate the slip
gauges
24

CLASSIFICATION
• AA- used to calibrate the inspection blocks and very
high precision gauging.
• A- used as tool room standards for setting other
gauging tools
• B- used as workshop standards for precision
measurement.
• Grade 2: It is a workshop grade slip gauges used for
setting tools, cutters and checking dimensions
roughly
• Grade 1: tool room for precision works
• Grade 0: setting or calibrating of instruments
• Grade 00: standard labs
25

Slip gauges in mm Graduation in mm No of pieces
1.001-1.009 0.001 9
1.01-1.09 0.01 9
1.1-1.9 0.1 9
1.0-9.0 1 9
10-90 10 9
Total 45

It is manufactured in standard sets of 32
pieces, 45 pieces, 56pieces & 88 pieces
26

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 gives the information about the
products which may be either within the
prescribed limit or not.
27

• 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.
28

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.
• If we use any measuring instruments to check these
dimensions, the process will consume more time. Still
we are not interested in knowing the amount of error
in dimensions.
• It is just enough whether the size of the component is
within the prescribed limits or not. For this purpose,
we can make use of gauges known as limit gauges.
29

The common types are as follows:
• 1) Plug gauges.
• 2) Ring gauges.
• 3) Snap gauges.
31

• The ends are hardened and accurately finished by
grinding. One end is the GO end and the other end is
NOGO end.
• Usually, the GO end will be to the lower limit size of the
hole and the NOGO end will be equal to the upper limit
size of the hole
• If the size of the hole is within the limits, the GO end
should go inside the hole and NOGO end should not go.
• If the GO end and does not go, the hole is under size and
also if NOGO end goes, the hole is over size. Hence, the
components are rejected in both the cases.
33

TAPER PLUG GAUGE
• 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.
• They are various types taper plug gauges are available as
shown in fig. Such as
• 1) Taper plug gauge-plain
• 2) Taper plug gauge-tanged.
• 3) Taper ring gauge-plain
• 4) Taper ring gauge-tanged.
35

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.
• The periphery of the ring is knurled to give more grips
while handling the gauges. We have to make two ring
gauges separately to check the shaft such as GO ring
gauge and NOGO ring gauge.
• But the hole of GO ring gauge is made to the upper
limit size of the shaft and NOGO for the lower limit.
• While checking the shaft, the GO ring gauge will pass
through the shaft and NOGO will not pass.
• To identify the NOGO ring gauges easily, a red mark or
a small groove cut on its
36

SNAP GAUGES
• Snap gauges are used for checking external
dimensions. They are also called as gap
gauges. The different types of snap gauges are
38

Progressive type snap gauge
43

APPLICATIONS OF LIMIT GAUGES
• 1. Thread gauges
• 2. Form gauges
• 3. Screw pitch gauges
• 4. Radius and fillet gauges
• 5. Feeler gauges
• 6. Plate gauge and Wire gauge
46

GAUGE DESIGN
• DESIGN OF PLUG GAUGES:
• GO- lower limit
• NO GO- upper limit
• GO end diameter, D1 = (k+z) ± H/2
• NOGO end diameter D2= G ± H/2
Where k – Lower limit
z – Wear allowance
H/2 – Manufacturing allowance
G – Upper limit
47

Checking of slip gauges for surface quality
48

COMPARATOR
• Comparators are one form of linear
measurement device which is quick and more
convenient for checking large number of
identical dimensions.
• Comparators normally will not show the actual
dimensions of the work piece. They will be
shown only the deviation in size.
• This cannot be used as an absolute measuring
device but can only compare two dimensions.
49

CLASSIFICATION
The comparators are classified according to the
principles used for obtaining magnification. The
common types are:
1) Mechanical comparators
2) Electrical comparators
3) Optical comparators
4) Pneumatic comparators
50

• For magnifying small deviations
• The method of magnifying small movement of the
indicator in all mechanical comparators are effected
by means of levers, gear trains or a combination of
these elements.
• These are mostly used for inspection of small parts
machined to close limits.
• A dial indicator or dial gauge is used as a mechanical
comparator
52

• The dial is graduated into 100 divisions
• A full revolution of the pointer about this scale
corresponds to 1mm travel of the plunger
• a turn of the pointer be one scale division
represents a plunger travel of 0.01mm.
53

PROCEDURE
• Let us assume that the required height of the
component is 32.5mm.
• Initially this height is built up with slip gauges. The
slip gauge blocks are placed under the stem of the
dial gauge.
• The pointer in the dial gauge is adjusted to zero. The
slip gauges are removed.
• Now the component to be checked is introduced
under the stem of the dial gauge. If there is any
deviation in the height of the component, it will be
indicated by the pointer.
54

• Chennai is one of the six regional meteorological
centres (RMCs) of the India Meteorological
Department (IMD) and is responsible for the weather-
related activities of the southern Indian peninsula
comprising the states of Andhra
Pradesh, Karnataka, Kerala, Tamil Nadu and the union
territories of Andaman and Nicobar, Lakshadweep
Islands and Puducherry.
• The other regional centres are located
at Kolkata, Guwahati, Mumbai, Nagpur and New
Delhi.[1]
• Established in the later part of the 18th century, the
Chennai meteorological centre is considered one of the
first modern astronomical-cum-meteorological
observatory in the East, way before the establishment
of the Indian Meteorological Department in 1875.[2]
56

• seismological observatories were established at Chennai,
Thiruvananthapuram and Visakhapatnam under Global
Seismological Network (GSN).
• In addition, an observatory under World Wide Standardised
Seismological Network (WWSSN) functions
at Kodaikanal and a broadband system functions at Mangalore.
• The hydrology section at RMC Chennai periodically inspects
about 2,000 rainguage stations maintained by organisations
such as railways and state governments.
• The Cyclone Detection Radar Station in Chennai is located at
the Port Trust Building of the Chennai Port.
• Data from this Doppler radar is currently being used by
the Chennai airport.[6] The aviation weather forecasting
activities, which are required by pilots and airport authorities,
are controlled and coordinated by the Aerodrome
Meteorological Office at Chennai Airport in Meenambakkam.
57

• Since 1978, Agromet Advisory Units are
functioning at RMC Chennai and other
meteorological centres under it.
• These units regularly issue Agromet Advisory
Bulletins twice a week benefiting the farming
community in their respective states.
• More than 1,400 personnel including 300
officers work in various offices under Regional
Meteorological Centre, Chennai which
includes 3 meteorological centres, 1 area
cyclone warning centre, 1 cyclone warning
centre, 6 cyclone detection radar stations and
17 aviation meteorological offices
58

REED TYPE MECHANICAL
COMPARATOR
59

• In this type of comparator, the linear movement of the
plunger is specified by means of read mechanism.
• The mechanism of this type is illustrated in fig. A
spring loaded pointer is pivoted. Initially, the
comparator is set with the help of a known
dimension
• Eg. Set of slip gauges as shown in fig. Then the
indicator reading is adjusted to zero.
• When the part to be measured is kept under the
pointer, then the comparator displays the deviation of
this dimension either in ± or— side of the set
dimension.
60

An electrical comparator consists of
the following three major part such as
1) Transducer
2) Amplifier
3) Display device as meter
62

• If the armature is centrally located between the coils,
the inductance of both coils will be equal but in
opposite direction with the sign change.
• Due to this, the bridge circuit of A.C. wheat stone
bridge is balanced. Therefore, the meter will read
zero value.
• But practically, it is not possible. In real cases, the
armature may be lifted up or lowered down by the
plunger during the measurement. This would upset
the balance of the wheat stone bridge circuit.
63

• Due to this effect, the change in current or potential
will be induced correspondingly. On that time, the
meter will indicate some value as displacement.
• This indicated value may be either for larger or
smaller components. As this induced current is too
small, it should be suitably amplified before being
displayed in the meter.
64

CHECKING OF ACCURACY
• To check the accuracy of a given specimen or work,
first a standard specimen is placed under the plunger.
• After this, the resistance of wheat stone bridge is
adjusted so that the scale reading shows zero.
• Then the specimen is removed. Now, the work is
introduced under the plunger.
• If height variation of work presents, it will move the
plunger up or down.
• The corresponding movement of the plunger is first
amplified by the amplifier then it is transmitted to the
meter to show the variations.
• The least count of this electrical comparator is
0.001mm (one micron).
65

BEVEL PRTRACTOR
• OBJECTIVE
It is used for measurement of angles between
two faces of component
72

CONSTRUCTION
• A vernier bevel protractor is attached with acute angle
attachment. The body is designed its back is flat and no
projections beyond its back.
• The base plate is attached to the main body and an adjustable
blade is attached to the circular plate containing Vernier scale.
• The main scale is graduated in degrees from 0° to 90° in both the
directions. The adjustable can be made to rotate freely about the
center of the main scale and it can be locked at any position.
• For measuring acute angle, a special attachment is provided. The
base plate is made flat for measuring angles and can be moved
throughout its length.
• The ends of the blade are beveled at angles of 45° and 60°. The
main scale is graduated as one main scale division is 1° and
Vernier is graduated into 12 divisions on each side of zero.
73

SINEBAR
OBJECTIVE
• Used to measure angle very accruately
• Locate the work piece to a given angle with very
high precision.
• Sine bar is high precision and accurate
instrument.
• It uses sine principle
• Sine angle = Perpendicular/Hypotenuse
= h/l
83

CONSTRUTION
• Generally, sine bars are made from high
carbon, high chromium, and corrosion
resistant steel.
• These materials are highly hardened and
stabilized.
• In sine bars, two cylinders of equal diameter
are attached at lie ends with its axes are
mutually parallel to each other.
84

• They are also at equal distance from the
upper surface of the sine bar mostly the
distance between the axes of two cylinders is
100mm, 200mm or 300mm.
• The cylindrical holes are provided to reduce
the weight of the sine bar.
85

WORKING PRINCIPLE
• The working of sine bar is based on
trigonometry principle. To measure the angle
of a given specimen, one roller of the sine bar
is placed on the surface plate and another
one roller is placed over the surface of slip
gauges.
86

• I. To set at a given
angle 0, first h’ of slip
gauge is calculated by the
formula Sin 0= h/L
• ii. After calculating the
height ‘h’. the required
height h’ is made by
using suitable slip gauge
combinations.
• iii. After this, one of the
rollers is placed on the
top of the sine bar and
the other one is placed
on the top of the slip
gauge combination.
87

LIMITATIONS OF SINE BAR
1) Sine bars are fairly reliable for angles than
2) It is physically difficult to hold in position.
3) Slight errors in sine bar cause larger angular errors.
4) A difference of deformation occurs at the point of
roller contact with the surface plate and to the gauge
blocks.
5) The size of parts to be inspected by sine bar is limited
94

SOURCES OF ERRORS IN SINE BAR
) Error in distance between roller centers.
2) Error in slip gauge combination.
3) Error in checking of parallelism.
4) Error in parallelism of roller axes with each other.
5) Error in flatness of the upper surface of sine bar.
95

TWO FREQUENCY LASER
INTERFEROMETER
97

TWYMAN-GREEN INTERFEROMETER
98

TWYMAN-GREEN INTERFEROMETER
99

AUTOCOLLIMATOR
OBJECTIVE
• Auto-collimator is an optical instrument
used for the measurement of small angular
differences, changes or deflection, plane
surface inspection etc.
• For small angular measurements,
autocollimator provides a very sensitive and
accurate approach.
• An autocollimator is essentially an infinity
instrument
100

BASIC PRINCIPLE
• If the light source is placed in the flows of a
collimating lens, it is projected as a parallel
beam of light.
• When this beam is made to strike a plane
reflector, kept normal to the optical axis, it is
reflected back along its own path and brought
to the same focus.
• If the reflector is tilted through a small angle
‘0’ the parallel beam is reflected twice the
angle and is brought to focus in the same
plane as the light source
101

FUNCTIONAL VIEW OF AUTOCOLIMATOR
102

• X= 2 ‘0’. f
• f= focal length of the lens
• 0 = fitted angle of reflecting mirror
106

WORKING OF AUTO-COLLIMATOR
• There are three main parts in auto-collimator.
• 1. Micrometer microscope.
• 2. Lighting unit and
• 3. Collimating lens
107

• Fig shows a line diagram of an auto-
collimator. A target graticule is positioned
perpendicular to the optical axis.
• When the target graticule is illuminated by a
lamp, rays of light diverging from the
intersection point reach the objective lens via
beam splitter.
• From objective, the light rays are projected as
a parallel rays to the reflector.
108

• A flat reflector placed in front of the
objective and exactly normal to the optical
axis reflects the parallel rays of light back
along their original paths.
• They are then brought to the target graticule
and exactly coincide with its intersection. A
portion of the returned light passes through
the beam splitter and is visible through the
eyepiece.
109

• If the reflector is tilted through a small angle,
the reflected beam will be changed its path at
twice the angle. It can also be brought to target
graticule but linearly displaced from the actual
target by the amount 2 x f.
• linear displacement of the graticule image in the
plan tilted angle of eyepiece is directly
proportional to t
• he reflector. This can be measured by optical
micrometer. The photoelectric autocollimator
is particularly suitable for calibrating polygons,
for checking angular indexing and for checking
small linear displacements.
110

APPLICATIONS OF AUTO-COLLIMATOR
1) Measuring the difference in height of length
standards.
2) Checking the flatness and straightness of
surfaces.
3) Checking square ness of two surfaces.
4) Precise angular indexing in conjunction with
polygons.
5) Checking alignment or parallelism.
6) Comparative measurement using master angles.
7) Measurement of small linear dimensions.
8) For machine tool adjustment testing.
111

UNIT II

More Related Content

Similar to UNIT II (20)

More from BALASUBRAMANI220670 (9)

Recently uploaded (20)

UNIT II