This document provides instructions for experiments to be conducted in a metrology lab. It includes 10 experiments involving calibration of measurement tools like micrometers and dial gauges using slip gauges, measurement of angles using a bevel protractor and sine bar, measurement of gear features, surface roughness, and more. The document was prepared by B.Sudarshan, Assistant Professor of Mechanical Engineering, for students to record their experiment details, objectives, theories, procedures, observations and results.

1. Prepared by B.Sudarshan, (Ph.D.), Asst.Proffesor, Department of Mechanical engineering, GITAMUNIVERSITY.
METROLOGY LAB MANNUAL
GITAM UNIVERSITY
GST, BENGALURU
Name:……………………………………………………………………………………
Regd.No:………………………………………………………………………………..
Semester:……………………………………………………………………………….
Branch:…………………………………………………………………………………..

2. SUDARSHAN, B. 1
LIST OF EXPERIMENTS
1. Calibration of micrometer and dial gauge by using slip gauges.
2. Measurement of angle gauges by using bevel protractor and sine bar.
3. Measurement of taper angle of v-groove by vernier height gauge.
4. Measurement of central distance between two holes by using vernier height gauge.
5. Gear metrology to find module, addendum, dedendum, pitch circle diameter, tooth width and
pressure angle to given a spur gear.
6. To check roundness and concentricity of spigot.
7. To check straightness of surface plate by using spirit level and autocollimator.
8. Study of flatness of slip gauges by using monochromatic check lite.
9. Tool maker’s microscope: to study screw thread profile (major dia, minor dia, pitch, thread angle)
and tool angles.
10. Measurement of surface roughness by using stylus method.

3. SUDARSHAN, B. 2
EXP1a: CALIBRATION OF MICROMETER USING SLIP GAUGES
Aim: To calibrate the micrometer using slip gauges
Apparatus: Micrometer, slip gauges
Objectives:
1. To know the use and working of slip gauges
2. To know the classification and working of slip gauges
Theory: Slip gauges are end standards used in linear measurements. They are used in workshop for work
where a tolerance as low as 0.001mm is needed. Slip gauges were invented by Swedish engineer, C.E.
Johnson, so they are also called Johnson gauges. Slip gauges are rectangular blocks, made of high grade
steel, having cross section about 30mmX10mm. These blocks are made into required sizes and hardened
to resist wear and allowed to stabilize so as to relieve internal stresses. This prevents occurrence of size
and shape variations. After hardening the blocks, measuring faces are carefully finished to fine degree
of surface finish, flatness and accuracy. This high grade surface finish is obtained by superfinishing
process known as lapping.
Wringing of slip gauges:
The measuring face of the gauges is flat and it possesses high surface finish. If two slip gauges are forced
against each other on measuring faces, because of contact pressure, gauges stick together and
considerable force is required to separate these blocks. This is known as wringing of slip gauges. Thus,
wringing refers to condition of intimate and complete contact and of permanent adhesion between
measuring faces. Slip gauges are wrung to build desired dimension. Slip gauges are wrung together by
hand and no other external means. Figure shows 1) Parallel wringing of slip gauges and 2) Cross
wringing of slip gauges.
In cross wringing – the two slip gauges are first cleaned to remove dirt and then they are placed together
at right angles in the form of cross and then rotated through 90o
, while being pressed together. This
method causes less rubbing of surfaces. Almost any dimension may be built by suitable combination of
gauges. Wringing phenomenon is purely due to surface contact and molecular adhesion of metal of
blocks. Hence, ―wringing is defined as the property of measuring faces of gauge blocks of adhering,
by sliding or pressing the gauge against measuring faces of other gauge blocks or reference faces or
datum surfaces without the use of external means.
Uses/Applications of slip gauges
1. as a reference standard.
2. for verification and calibration of measuring apparatus.

4. SUDARSHAN, B. 3
3. for adjustment of indicating devices.
4. for direct measurement.
5. for setting of various types of comparators.
6. Micrometers are used to measure the small or fine measurements of length, width, thickness and
diameter of the job.
Determining the dimension of 29.758mm by M45 slip gauge set:
Rule 1:-Minimum number of slip gauges should be used to build dimension.
Rule 2:- Always start with the last decimal place.
Hence to build the dimension of 29.758 we need slip gauges of 20mm, 6mm, 1.7mm,
1.05mm and 1.008mm.

5. SUDARSHAN, B. 4
Procedure of performing experiment:
(1) Clean the fixed vice and micrometer
(2) Clamp the micrometer in vice putting cushioning material between micrometer and jaws of vice to
protect the micrometer from probable damage due to clamping force.
(3) Make pile of gauge blocks and insert between two anvils of the micrometer and take reading.
(4) Increase the value of gauge blocks pile and take next few readings.
(5) Then decrease the value of gauge blocks pile and take same readings in decreasing order.
(6) Tabulate the readings
(7) After cleaning the place the gauge blocks should be placed in their respective places.

6. SUDARSHAN, B. 5
Plot the Graphs:
(1) Slip gauges combination – Micrometer average
(2) Slip gauges combination – Error
(3) Micrometer average reading – correction
Result:
The given micrometer has been calibrated using M87 slip gauge set.

7. SUDARSHAN, B. 6
EXP.1b. CALIBRATION OF DIAL GAUGE BY USING SLIP GAUGES.
AIM: To calibrate the given mechanical comparator with respect to a standard reference i.e. Slip gauge
set and to draw the calibration curve.
MEASURING INSTRUMENTS & TOOLS:
1. Mechanical comparator (Dial gauge)
2. Slip gauge set
3. Comparator stand
4. Surface plate
THEORY:
Measuring instruments in usage will acquire certain errors due to wear and tear. So every instrument
should be checked periodically to find out the errors and assess the accuracy. Comparing the reading of
the instrument with a standard reference does this. This type of inspection is known as calibration.
Depending on the type of instrument the standard reference is selected, against which the error of the
instrument is evaluated. Since the error cannot be eliminated from the instrument, corresponding
correction is applied to the measured reading of the instrument. Since the wear and tear of the instrument
is not uniform, the error in the measured value will be different at different ranges of the instrument. To
apply correction for the various readings in the range of the instrument, a calibration curve is to be drawn.
Calibration curve is the curve drawn between the error and the instrument reading. The error at any stage
of the instrument can be either positive or negative. The correction to be applied for a positive error is
negative and vice – versa.
CONSTRUCTIONAL DETAILS & APPLICATIONS:
Figure1: Dial gauge set up

8. SUDARSHAN, B. 7
PROCEDURE:
1. The dial gauge was mounted securely on the stand.
2. The base of the stand was cleaned and free movement of the dial gauge plunger was ensured.
3. Slip gauges are degreased and an initial reading was set by selecting a suitable slip gauge so that the
plunger of the dial gauge just slide on the top surface.
4. Dial gauge reading with initial set up was adjusted to read zero
5. A small increment was given to the initial size of the slip gauge by combination of slip gauges and
was placed under the dial gauge plunger by lifting it. The corresponding reading is noted down.
6. The procedure was repeated for different sizes of slip gauges within the range of the dial gauge and
reading were tabulated and corresponding errors were found.
7. A graph is plotted against dial gauge reading and error obtained
PRECAUTIONS:
1. The dial gauge should be clamped to the stand properly so that the plunger is vertical to the base.
2. The slip gauge set should be degreased properly.
3. The plunger of the dial gauge should be handled gently.
4. The dial gauge reading was set to zero after giving slight initial compression to the plunger.
5. Slip gauges should be increased in size with regular increments within the range of dial gauge.
6. Slip gauges should be wringing properly for various combinations.
OBSERVATIONS:
Least count of Mechanical comparator =
S.No Mechanical
comparator
reading
X mm
Slip gauge
reading
Y mm
Error
E = X - Y
Correction
C mm
GRAPH:
1. C versus X
Result:

9. SUDARSHAN, B. 8
VIVA QUESTIONS
1. Explain about Linear measurement?
2. What is difference between accuracy and repeat which?
3. What is the use of comparator?
4. Classify comparators?
5. Explain tolerance?
6. Explain limits?
7. What is surface plate?
8. Comparators are used in which type of production?
9. What is the basic comparator?

10. SUDARSHAN, B. 9
EXP.2a. MEASUREMENT OF ANGLE GAUGES BY USING BEVEL
PROTRACTOR AND SINE BAR
AIM: To find out the various angles of the given specimen using universal bevel protractor
MEASURING INSTRUMENTS & TOOLS:
Universal bevel protractor with accessories
THEORY: The bevel protractor is used to measure the various angles of both small and large
components with accuracy up to 5 minutes. The design of the universal bevel protractor type had
considerably increased the scope of angular measurement with the adjustable blades and the protractor
can be indexed through 3600. The same basic principle as in the other Vernier scales was used in this
instrument.
CONSTRUCTIONAL DETAILS & APPLICATIONS:
Figure 2: Universal bevel protractor
LEAST COUNT: The vernier scale of the protractor had 24 equal divisions with 12divisions on each
side of zero. On each side 12 divisions are marked from 0-60 and occupying 23 divisions on the main
scale. Each division on vernier scale measures 23/12o
.Therefore least count is the difference between
one main scale division and one vernier scale division [2o
– 23/12o
= 1/12o
= 5’] Once the least count was
known the method of taking the reading is as usual.
PROCEDURE:
1. The appropriate size blade to suit the given job was fixed and locked.
2. The job / component was placed by touching the reference face and the movable blade.
3. The blade was locked after ensuring the proper contact on the two faces of the job.

11. SUDARSHAN, B. 10
4. The reading was noted down corresponding to the zero of the vernier scale.
(M.S.R + V.S.C x 1/12)
5. The procedure was repeated to find out all the required angles.
PRECAUTIONS:
1. The blades should be fined tightly without any play.
2. Blade should be clamped only after ensuring the contact of the blade over the entire length of the
component.
3. The instrument should be cleaned before and after use.
4. Vernier coincidence should be taken without parallax error
OBSERVATIONS:
SPECIMEN – 1:
θ1 =
θ2 =
θ3 =
SPECIMEN – 2:
θ1 =
θ2 =
θ3 =
RESULT:
The angles of the various corners of the given specimen were found to be as follows.
θ1 =
θ2 = , θ3

12. SUDARSHAN, B. 11
EXP.2b. MEASUREMENT OF TAPER ANGLES – SINE BAR
AIM: To find out the taper angle of a given specimen using sine bar
MEASURING INSTRUMENTS & TOOLS:
1. Sine bar
2. Dial gauge
3. Dial gauge stand
4. Slip gauge set
5. Surface plate
THEORY & PRINCIPLE: The high degree of precision available for linear measurement in the form
of slip gauges can be utilized for the measurement of angles with the aid of a very simple and best
measuring tool known as sine bar. The principle involved in this measurement was that the sine bar, slip
gauges and the datum surface i.e. surface plate on which they lay form a right-angled triangle. The sine
bar forms as hypotenuse of the right-angled triangle and the slip gauges form the side opposite to the
required angle. If θ is the angle to be measured and if H is the height of slip gauge and L is the length of
the sine bar, from the right-angled triangle.
Sin θ =
𝐻
𝐿
PROCEDURE:
1. The surface plate was considered as the datum to conduct the experiment.
2. The component whose angle is to be checked was mounted securely on the sine bar and both are
placed on the surface plate.
3. The sine bar along with the component was set at an approximate angle by placing a known size of
slip gauge at one end of the sine bar, so that the tapered side of the component is made parallel to the
surface plate.
4. The dial gauge mounted on a suitable stand was placed adjacent to the sine bar so that the plunger just
slides on the surface of the component. At one end the dial gauge was adjusted to read zero.
5. The same dial gauge was placed at the other end of the component and the reading is noted.
6. The height of slip gauges under the sine bar was adjusted until the dial gauge read zero at both ends
of the component and the corresponding slip gauge size was noted down.
7. The acute angle made by the sine bar with the surface plate is the taper angle of the component, which
was measured by using the following formula.
θ = 𝑆𝑖𝑛 − 1
𝐻
𝐿

13. SUDARSHAN, B. 12
PRECAUTIONS:
1. The surface plate, slip gauge set and sine bar should be degreased properly.
2. The dial gauge should be clamped to the stand properly so that the plunger is vertical to the base.
3. The dial gauge plunger should be handled gently and the gauge was set to zero after giving slight
initial compression to the plunger.
4. The slip gauges should be placed gently under the roller of the sine bar.
OBSERVATIONS:
Length of the sine bar = L mm
Height of the slip gauges = H mm
CALCULATIONS:
The Taper Angle θ = 𝑆𝑖𝑛 − 1
𝐻
𝐿
RESULT:
Taper angle of the specimen ‘θ’ =
Figure 3: Experiment Setup of Sine Bar

14. SUDARSHAN, B. 13
EXP.3. MEASUREMENT OF TAPER ANGLE OF V-GROOVE BY
VERNIER HEIGHT GAUGE
AIM: To measure the angle of V-groove of a given V-block by using two cylindrical rollers of different
diameters.
MEASURING INSTRUMENTS & TOOLS:
1. V- Block with clamps
2. Surface Plate
3. Vernier Height Gauge
4. Vernier Calipers
5. Rollers of three different diameters
THEORY: Many methods were available to measure the angle of V- groove depending upon the size
of the groove, location and accuracy of the groove. Two rollers of different diameters should be used for
the measurement of the angle. This roller method is suitable to measure if the component height is within
the range of vernier height gauge. The accuracy of measurement in this method depends up on the roller
sizes and type of V-groove surface.
The parameters required were roller dimensions and the heights of those rollers from the reference when
they were placed in the V-groove. An expression was derived for the V groove angle θ in terms of the
roller diameters and heights of those rollers from reference plane.
θ = V-groove angle
d2 & d1 = Diameters of the two rollers
h2 & h1 = Height of the rollers
PROCEDURE:
1. The diameters of the three rollers were found using the vernier calipers (i.e. d1, d2 & d3mm)
2. The components with V-groove were placed on a properly cleaned and dust free surface plate.
3. The rollers with diameter ‘d1’ was clamped in V-groove.
4. The vernier height gauge was placed on the surface plate and was adjusted to read zero when the
scriber is touching the surface plate.

15. SUDARSHAN, B. 14
5. The height of the roller was measured using vernier i.e. ‘h1’
6. The roller with diameter ‘d1’ was replaced by roller with diameter ‘d2’ and the height ‘h2’was found.
7. The procedure was repeated for roller with diameter d3 and height h3 was found.
8. The reading related to all the three rollers were tabulated.
9. The V-groove angle was calculated thrice with the three possible combinations of the three rollers.
10. The average of the three values of was calculated.
PRECAUTIONS:
1. The rollers in the V-groove should not move while the height is measured.
2. The scriber edge of the vernier height gauge should just touch the surface of the roller while measuring
the height.
3. The diameters and height of the rollers were found at three different places and the average diameter
and height were found.
4. The readings should be taken without parallax error.
RESULT: Average angle of the V-groove of the given V-block was found to be…………………….
OBSERVATIONS:
Least count of the vernier calipers =
Least count of the vernier height gauge =
MEASUREMENT OF ROLLER DIAMETERS:
S.No Roller
diameter
Trial – 1
mm
Trial – 2
mm
Trial – 3
mm
Average
mm
1 d1
2 d2
3 d3
4 d4
CALCULATIONS:

16. SUDARSHAN, B. 15
ROLLER HEIGHT MEASUREMENT:
S.No Roller diameter Trial – 1 (mm) Trial – 2 (mm) Trial – (3 mm) Average
(mm)
1 h1
2 h2
3 h3
4 h4

17. SUDARSHAN, B. 16
EXP.4. MEASUREMENT OF CENTRAL DISTANCE BETWEEN
TWO HOLES
AIM: To measure the central distance between the two holes of the template using vernier height gauge.
MEASURING INSTRUMENTS & TOOLS:
Vernier height gauge
Surface plate
Angle plate with clamps
Bevel protractor
THEORY: Vernier height gauge will be used to measure and mark vertical distances above a reference
surface with the help of knife edge or lever type dial indicator fitted to the measuring jaw. With this
capability the utility of vernier height gauge can be extended to measure the central distance between
the two holes of a template. The template should have two adjacent sides corrected to right angle
accurately, which will be the reference sides.
Figure 4: Vernier Height Gauge

18. SUDARSHAN, B. 17
PROCEDURE:
1. The template sides were checked for 90o angle using a bevel protractor.
2. Any two sides at right angle were selected and the template was fixed to the angle plate so that one of
the sides under consideration touching the surface plate.
3. The heights of the lowest and highest points of the two holes under consideration were found using
vernier height gauge with reference to the surface plate.
4. The procedure was repeated and the heights of the same holes were measured with reference to the
second side of the template.
5. All the readings were tabulated and central distance between the two holes was found by finding the
coordinates of the same holes.
PRECAUTIONS:
1. Vernier height gauge should be set to read zero on the surface plate.
2. The template should be clamped properly to angle plate to ensure the plan of the plate perpendicular
to the surface plate.
3. Care should be taken while seeing the coincidence of the knife edge with the edges of the holes.
OBSERVATIONS:
L.C of the vernier height gauge =

19. SUDARSHAN, B. 18
EXP.5: GEAR METROLOGY TO FIND MODULE, ADDENDUM, DEDENDUM,
PITCH CIRCLE DIAMETER, TOOTH WIDTH AND PRESSURE ANGLE TO
GIVEN A SPUR GEAR
AIM: To determine the gear tooth thickness and pressure angle for the given spur gear using gear tooth
micrometer / David brown base tangent micrometer.
MEASURING INSTRUMENTS AND TOOLS:
1. Base tangent micrometer
2. Vernier caliper
THEORY: Spur gear is a machine element, which is used to transmit both motion and power between
two shafts whose axis are parallel. The nomenclature of a spur gear can be explained with help of the
figure and is as follows.
Pitch circle diameter: It is the diameter of the pitch circle. Which by pure rolling action would produce
the same motion as the toothed gear? The size of the gear usually specified by Pitch circle diameter
Module: It is the ratio of the Pitch circle diameter in a millimeter to the number of teeth or it is the length
of the Pitch circle diameter per tooth. It is usually denoted by ‘m’.
Addendum: It is the radial distance of the tooth from the pitch circle to the top or tip of the tooth.
Dedendum: It is the radial distance of the tooth from the pitch circle to the bottom of the tooth.
Tooth thickness: It is the width of the tooth measured along the pitch circle
Blank diameter: This is the diameter of the blank from which gear is cut.
SIGNIFICANCE OF PRESSURE ANGLE: When a pair of gear wheels are in mesh the teeth on two
gears will have contact along a common tangent to their base circles, which is referred as line of contact
or line action. Since this line of contact is the common generator of involute profile for both gears, the
load and pressure between the gears will be transmitted along this line. The angle between this line of
action and the common tangent to the pitch circles at the pitch point is called pressure angle. The standard
values for pressure angle φ are14 ½o and 20o
.
PRINCIPLE: The principle involved in this experiment was the principle of base tangent method. This
is the popular method for checking the gear wheel parameters. In this method the length of the base
tangent was measured covering different numbers of teeth i.e 2, 3 and 4nos. of teeth. If x, y and z are the
lengths of the base tangents corresponding to different no.of teeth i.e. l, m and n, then the base circular
pitch can be calculated. Further the pitch circle diameter was found with an assumption that the gear has
addendum equal to one module. Knowing the base circle diameter and pitch circle diameter, both
pressure angle and tooth thickness was calculated using relevant formula.
PROCEDURE:
1. The spur gear to be checked was cleaned.
2. The no. of teeth on the spur gear were counted i.e. ‘N’
3. The outer diameter of the gear was found using vernier caliper (Do
)
4. Using the base tangent micrometer the distance covered by 2, 3 and 4 nos. of teeth was found i.e. x,
y and z respectively.

20. SUDARSHAN, B. 19
5. The readings were tabulated and the calculations were done to find the pressure and ‘’and gear
tooth thickness ‘W’.
PRECAUTIONS:
1. The base tangent micrometer should be handled properly so that the flanged anvil had contact on the
tooth profile close to the pitch circle.
2. The readings should be taken without parallax error.
GEAR PROFILE FIGURE:
EXPERIMENTAL SETUP:
Figure 5: Gear tooth measurement methods

21. SUDARSHAN, B. 20
OBSERVATIONS:
Least count of vernier caliper =
Outer Circular diameter of gear (Do
) =
No of teeth on gear N =

22. SUDARSHAN, B. 21
EXP. 6: TO CHECK ROUNDNESS AND CONCENTRICITY OF SPIGOT
AIM: To check the given cylindrical specimen for roundness and find the run out from the graphical
representation.
MEASURING INSTRUMENTS AND TOOLS:
1. Bench centers
2. Dial indicator
3. Dial indicator stand
THEORY: In any manufacturing industry the accuracy and precision of the assembly’s made will
depend on the geometrical tolerance and dimensional tolerance of the various components involved in
the assembly. Geometrical tolerances are related to the shape of the component and dimensional
tolerances are related the size of the components. Some of the geometrical tolerances are: 1) Straightness
2) Roundness 3) Parallelism 4) Squareness 5) Flatness. For cylindrical elements and shafts roundness
and parallelism are more important.
Hence cylindrical components should be checked for roundness and parallelism and run out should be
found. The reference that was considered is intrinsic datum.
ROUNDNESS: It is the condition of surface of revolution. An element is said to be round if all the
points on the surface intersecting with any plane perpendicular to a common axis and passing through a
common center are equidistant from the axis.
EXPERIMENTAL SETUP:
Figure 6: Bench Centers
PROCEDURE:
1. The cylindrical mandrel was set on the bench centers and free rotation was ensured.

23. SUDARSHAN, B. 22
2. The dial gauge was fixed to the magnetic stand and was placed behind the specimen so that the probe
just touch the surface of the specimen at the highest point by having initial compression.
3. At least 5 circles were marked along the length of the specimen to check roundness.
4. At each circle after adjusting the dial gauge to read to zero with initial compression the specimen is
rotated once and change in the dial gauge reading was noted at 4 to 6different points.
5. The procedure was repeated at all the 5 circles and the readings were tabulated to find the out of
roundness.
6. For all the 5 circles the readings of dial gauge were plotted graphically and the run out was found. The
maximum run out of the 5 circles will be the run out of the specimen.
RESULT: Run out of the given specimen was found to be ____________
VIVA QUESTIONS
1. Define Random?
2. What is Dial indicator?
3. Explain working principle of dial indicator?
4. What is Straight ness?
5. What is parallelism?
6. What is squareness?
7. For cylindrical elements which parameters are most important?

24. SUDARSHAN, B. 23
EXP.7. TO CHECK STRAIGHTNESS OF SURFACE PLATE BY USING SPIRIT LEVEL
AND AUTOCOLLIMATOR
Aim: To check the Straightness & flatness of the given component by using Autocollimator.
Apparatus: Autocollimator, work piece/ object to be tested.
Theory:
Definition of straightness-a plane is to be said straight over a given length. If the variation or distance of
its point from two planes perpendicular to each other and parallel to the generation direction at of the
line remain within specified tolerance limits. The reference planes being so chosen that there intersection
is parallel to the straight line joining two points suitably located on the line to be tested and two points
being close ends of the length to be measured.
Principle of the Autocollimator: A cross line ―target‖ graticule is positioned at the focal plane of a
telescope objective system with the intersection of the cross line on the optical axis, i.e. at the principal
focus. When the target graticule is illuminated, rays of light diverging from the intersection point reach
the objective via a beam splitter and are projected from the objective as parallel pencils of light. In this
mode the optical system is operating as a―collimator‖.
A flat reflector placed in front of the objective and exactly normal to the optical axis reflects the parallel
pencils of light back along their original paths. They are then brought to focus inthe plane of the target
graticule and exactor coincident with its intersection. A proportion of the returned light passes straight
through the beam splitter and the return image of the target cross line is therefore visible through the
eyepiece. In this mode, the optical system is operating as a telescope focused at infinity.
If the reflector is tilted through a small angle the reflected pencils of light will be deflected by twice the
angle of tilt (principle of reflection) & will be brought to focus in the plane of target graticule but linearly
displaced from the actual target cross lines by an amount 2θ* f.
An optical system of an auto collimator consists of a light source, condensers, semi reflectors, target
wire, collimating lens and reflector apart from microscope eyepiece. A target wire takes place of the
light source into the focal plane of the collimator lenses. Both the target wire and the reflected image are
seen through a microscope eyepiece. The eye piece incorporates a scale graduated in 0.05mm interval
and a pair of parallel setting wires which can be adjusted. Movements of wires are effected through a
micrometer, one rotation of the drum equals to one scale division movement of the wires. The instrument
is designed to be rotated through 90 degrees about its longitudinal axis so that the angles in both
horizontal &vertical planes are measured.
Autocollimators: It is an instrument designed to measure small angular deflections & maybe used in
conjunction with a plane mirror or other reflecting surface. An automator is essentially an infinity
telescope & a collimator combined into one instrument. This is an optical instrument used for the
measurement of small angular differences. For small angular measurements, autocollimator provides a
very sensitive and accurate approach. Auto collimator is essentially an infinity telescope and a collimator
combined into one instrument.

25. SUDARSHAN, B. 24
The principle on which this instrument works is given below. O is a point source of light placed at the
principal focus of a collimating lens. The rays of light from O incident on the lens will now travel as a
parallel beam of light. If this beam now strikes a plane reflector which is normal to the optical axis, it
will be reflected back along its own path and refocused at the same point O. If the plane reflector be now
tilted through a small angle 0, then parallel beam will be deflected through twice this angle, and will be
brought to focus at O‘ in the same plane at a distance x from O. Obviously
‘OO’= X = 2θ.f, where f is the focal length of the lens.
Applications:
1. To find the control line & alignment of circular & flat surfaces in machining.
2. Alignment of beams & columns in construction buildings / industries, steel structures.
3. In measuring the straightness, flatness and parallelism, these can be used.
Procedure:
(1) Make the distance of 100mm internal on the work piece.
(2) Set the cross wire so that two cross will coincide.
(3) Set the mirror so that the cross wire will be visible
(4) Move the reflector on next 100mm mark and adjust it to see reflection of cross wire.
(5) Take the reading of reflected crosswire deviated or moved up or down. Measure the distance between
two crosswire.
Figure 7: Autocollimator

26. SUDARSHAN, B. 25
Figure 8: Experimental setup of autocollimator
Table: Observations
SL
No.
Bridge Length
(Base length of
the reflector)
Cumulative
Bridge length
(Position of the
reflector)
Micrometer final
reading
(Autocollimator)
Difference
from previous
Position
(X in seconds)
Deviation
for
each 100mm
(Ѳ in
degrees)
1
2
3
4
Calculation:
Tan  = X / 100
X = (100 x Tan) x 1000 in Microns
Where X = Level at position B with respect to position A
 = Angle/Deviation in degrees/ Seconds (1 Degree = 60 Minutes, 1 Minute = 60 Seconds).

27. SUDARSHAN, B. 26
Result:
The values are analyzed and necessary modification of the surface may be recommended based on the
accuracy required on flatness. If the values observed from the micrometer are varying linearly then
straightness/flatness can be judged.

28. SUDARSHAN, B. 27
EXP. 8: STUDY OF FLATNESS OF SLIP GAUGES BY USING
MONOCHROMATIC CHECK LITE
Aim: To measure the flatness of a given surface by using the optical flat.
Apparatus: Optical flat, monochromatic light source, dry soft cloth, cleaning agent.
Theory: Light band reading through an optical flat, using a monochromatic light source represent the
most accurate method of checking surface flatness. The monochromatic light on which the diagrammatic
interpretations of light wave readings are based comes from a source, which eliminates all colours except
yellowish colour. The dark bands viewed under the optical flat are not light waves. They simply show
where interference is produced by reflections from two surfaces. These dark bands are used in measuring
flatness. The band unit indicates the level of the work that has risen or fallen in relation to the optical
flat, between the centre of one dark band and the center of the next dark band.
The basis of comparison is the reflected line tangent to the interference band and parallel to the line of
contact of work and the optical flat. The number of bands intersected by the tangent line indicates the
degree of variation from the true flatness over the area of the piece. Optical flats are used to check flatness
when surface to be tested shine and smooth i.e. Just like a mirror.
Optical flats are cylindrical piece made up of important materials such as quartz. Specification ranges
from 25mm by 38mm (dia x Length) to 300mm by 70 mm. Working surface are finished by lapping and
polishing process where as cylindrical surface are finished by grinding.
Applications:
1. Optical flats are used for testing the measuring surfaces of instruments like micrometers, measuring
anvils & similar other devices for their flatness &parallelism.
2. These are used to calibrate the standard gauges, like slip gauges, angle gauges &secondary gauges in
the workshops.
3. In measuring the curvatures like convex and concave for surfaces of the standard gauges.
Observations:
1. Monochromatic yellow light source is used for conducting this experiment.
2. Wavelength of Monochromatic source of light.
λ /2 = __________ mm. Where λ = 0.0002974 mm

29. SUDARSHAN, B. 28
Figure 9: Experimental setup of monochromatic light

30. SUDARSHAN, B. 29
Procedure:
1. Clean the surface to be tested to become shiny and wipe if with dry clean cloth
2. Place the optical flat in between flatness of work piece to be tested and monochromatic
Sources of light i.e. on the work piece.
3. Both parts and flat must be absolutely clean and dry.
4. After placing optical flat over work piece switch on the monochromatic source of light and
Wait until getting yellowish or orange colour.
5. Apply slight pressure over optical and adjust until getting steady band approximately parallel to the
main edges.
6. Count the number of fringes obtained on the flat with the help of naked eye and calculates the flatness
error
Tabular Column:
SL No. Type of
optical flats
No. of fringes
observed
‘N’
Flatness
error
Remark on type
of surface
with sketch
1 Straight(Slip
gauge)
2 Concave
3 Convex
Calculations:
Flatness error = N x λ /2
Results:
Measured the flatness of a given surface by using the optical flats.

31. SUDARSHAN, B. 30
EXP.9. TOOL MAKER’S MICROSCOPE: TO STUDY SCREW THREAD
PROFILE (MAJOR DIA, MINOR DIA, PITCH, THREAD ANGLE) AND TOOL
ANGLES.
Aim: Measurement of thread parameters by using Tool maker microscope.
Apparatus: Toolmaker microscope, vernier calliper and pitch gauge.
Theory:
Tool maker‘s microscope is versatile instrument that measures by optical means with no pressure being
involved. It is thus a very useful instrument for making measurements of small and delicate parts. Centre
to centre distance of holes in any plane and other wide variety of linear measurements and accurate
angular measurements. A Tool maker‘s microscope has optical head which can be moved up or down
the vertical column and can be clamped at any height by means of a clamping screw. The table which is
mounted on the base of the instruments can be moved in two mutually perpendicular horizontal
directions (longitudinal and lateral) by means of accurate micrometers screws having thimble scale and
vernier. A ray of light from light source is reflected by a mirror through 900. It is then passes through a
transparent glass plate (on which flat parts may be placed). A shadow image of the outline or contour of
the work piece passes through the objective of the optical head and is projected bya system of three
prisms to a ground glass screen. The screen can be rotated through 3600 the angle of rotation is read
through an auxiliary eyepiece.
For taking linear measurements the work piece is placed over the table. The microscope is focused and
one end of the work piece is made to coincide with cross line in the microscope (by operating
micrometers screws). The table is again moved until the other end of the workpiece coincide with the
cross line on the screen and the final reading taken. From the final reading the desired measurement can
be taken.
To measure the screw pitch, the screw is mounted on the table. The microscope is focused (by adjusting
the height of the optical head) until a sharp image of the projected contour of the screw is seen on the
ground glass screen. The contour is set so that some point on the contour coincides with the cross line
on the screen.

32. SUDARSHAN, B. 31
Figure 10: Tool Makers Microscope
Observations:
1 Least Count of vertical slide micrometer = 1 MSD/ No. of divisions on thimble
= 0.0005 mm or 5 microns.
2 Least Count of horizontal slide micrometer = 1 MSD/ No. of divisions on thimble
= 0.0005 mm or 5 microns.
Tabular Column:

33. SUDARSHAN, B. 32
Angle Measurement:
Angles are measured with the angle dial using the following procedure
1. Align an edge of the work piece with the cross – hair reticle.
2. Align the end edge with the center of the cross – hair; turn the angle dial to align the cross
– hair with the other edge of the work piece.
3. Take readings from the angle dial.
Objectives:
1. After performing this experiment, you should be able to
2. Appreciate the importance of precision measurement,
3. Know how precise measurements can be taken with this instrument,
4. Explain the field of application/working of this instrument, and
5. Understand the principle of working of tool room microscope.
Applications:
1. Precision tools making of cutting tools.
2. In jigs and fixtures for accuracy measurement, this can be used.
3. In assembly & matching of components.
4. In precision machining
5. In jewelries applications.
Procedure:
1. Note the least count of the micrometers.
2. Dimensions of the screw thread whose elements have to be measured are noted.
3. Place or fix the screw thread on XY stage (stage glass) of the tool maker‘s microscope.
4. Align a measuring point on the work piece with one of the cross hairs.
5. Take the reading from the micrometer head.
6. Move the XY stage by turning the micrometer head and align another measuring point with the same
cross hair and take the reading at this point.
7. Difference between the two readings represents the dimension between the two measuring points.
8. Repeat the experiment for different screw thread.

34. SUDARSHAN, B. 33
Results:
The following parameters are found that;
1. Outside dia. = _____________mm
2. Inside dia. = _____________mm
3. Pitch = _____________mm
4. Helix angle = _____________ Degrees

35. SUDARSHAN, B. 34
EXP.10a. MEASUREMENT OF SURFACE ROUGHNESS BY USING STYLUS
METHOD
Aim: To measure surface roughness parameter as per ISO Standards
Apparatus: Mitituyo make surface roughness tester, Calibrated specimen, Surface plate, Specimen
Procedure:
1. Connect Ac adopter to the measuring instrument & Switch on the power supply
2. Attach the drive detector unit & connect to all the cable connection as shown when mounting the detector to
the drive unit, take care not to apply excessive force to the drive unit.
3. Adjust or modify the measurement condition such as sample length, number samples, Standard required for the
measurement
4. Calibrate the instrument using standard calibration piece
5. Carefully place the detector on the work piece. Care should be taken to see that work piece &detector are aligned
properly
6. Press the start button to measure the work piece & result are displaced on the console
7. Press print button to take the print out.
Applications:
1. Taly surf is the dynamic electronic instrument used on the factory floor as well as in the laboratory.
2. To find out the surface roughness of the machines & components.
3. To check the accuracy of the cast iron, granites used in workshops for checking the surface finish &
flatness.
Figure11: Taly surf

36. SUDARSHAN, B. 35
Figure12: Experimental setup for Taly surf
Tabular column:
Sl. no Specimen Ra value R z value R q value
1
2
3
4
Results: Surface roughness checked for different specimens by Tally surf.

37. SUDARSHAN, B. 36
EXP. 10b.MEASUREMENT OF SURFACE ROUGHNESS USING MECHANICAL
COMPARATOR
Aim: To measure the surface roughness of the components by using mechanical comparator (dial gauge)
& also Acceptance/Rejections of the specimen test will be conducted. To compare the dimensions of
given mass produced product with designed tolerance standard by using mechanical comparator.
Apparatus: 20 No‘s of product to be tested, Mechanical comparator with dial gauge and slip gauges for
setting standard.
Theory:
Comparator is the instrument used to compare the unknown dimension with one of the reference standard
known as designed specification. The purpose of comparator is to detect and display the small difference
between the unknown and the standard. The deviation in size is detected as the displacement of sensing
device. The important and essential function of the instatement is to magnify the small input to
displacement. The magnification required is greater than 1000: 1. The relationship between the input and
output affected by the readings in the direction of input and this reveals that the movement should not
have any backlash. The major disadvantage of mechanical comparator is that, it is very difficult to
recompute the arrangement for the adjustment of magnification. Dial gauge is one of the Mechanical
components which are used in laboratories. It has contact tip, graduated circular scale, plunger and
clamp. Dial gauge works on the rack and pinion principle.
Applications:
1. Mechanical comparators are most widely used tools of dimensional measurements in metal – working
production.
2. These are instruments for comparative measurements where the linear movement of a precision
spindle is amplified and displayed on a dial or digital display.
3. Measurements of heights & levels by using combination of surface plate & dial gauges. Use of
measurement by accurate slip gauges
4. In mechanical industries, acceptance & rejections of the components will be checked by the
mechanical comparators.
Observations:
1. Name of the product to be tested = ------------------------------------
2. No of product to be tested = ------------------------------------
3. Size of standard slip gauge used = ------------------------------------ mm
4. Least count of the comparator = ------------------------------------ mm.
5. Specified designed dimensions with tolerance = ------------------------- mm ± ------ µ
6. No. of components rejected during the test = --------------------------
7. No. of components accepted during the test = --------------------------

38. SUDARSHAN, B. 37
Figure13: Experimental setup for mechanical comparator

39. SUDARSHAN, B. 38

40. SUDARSHAN, B. 39
Procedure
1. Clean the sensors of the comparator and the surface table of the comparator.
2. Note down the actual measurement of each product by micrometer.
3. Slip gauge of specified basic size is placed on the surfaces of comparator table and here slip gauge
serves as a setting standard have specified size.
4. Adjust the tolerance read needles to the specified size on either side of the zero reading by using screw
knobs provided on the comparator.
5. Adjust the comparator needle, which is reading actual dimension to zero reading by using
Corresponding knobs (vertical movement)
7. After initial adjustment of comparator remove the setting standard.
8. Place the given product for test in-between the sensors and surface of Comparator table.
9. Note down the readings of dial indicator provided in comparator. If the readings are within the
tolerance needles the product can be accepted if it lies outside the tolerance Needle the product can be
rejected.
10. The product following within certain tolerance ranges are grouped together according to Sequence
of test and tabulated in the tabular column.
11. The above procedure is repeated for all products.
Results:
The given components are tested by mechanical comparator or a dial gauge by using slip gauges as
standards.