Metrology and instrumentation lab manual

INDEX
Sr.
No.
Name of Practical Page
No.
Date of
Practical
Date of
Submission
Remarks
1. Use of linear measuring instruments
like vernier calliper and micrometer.
2. Use of height gauge and depth gauge.
3. Measurements with the help of
combination set and bevel protractor.
4. Angle measurement by use of sine bar
and slip gauges.
5. Measurement of centre distance
between two pins using slip gauges.
6. Checking of flatness using Dial
indicator.
7. Measurement of taper by standard balls
and rollers.
8. Measurement of thread parameters by
using Tool makers microscope.
9. Measurement of gear elements by
using gear tooth vernier.
10. Measurement of profile by profile
projector.
11. Measurement of surface roughness of a
surface.

Pracitcal – 1
Aim : Use of linear measuring instruments like Vernier Caliper and Micrometer.
Apparatus used : Vernier Caliper, Micrometer, specimen.
Diagram :
Fig.1. Vernier Caliper
Main Parts of Vernier Caliper :
1. Main Scale 6. Internal Jaws
2. Vernier Scale 7. Stem / Blade
3. Fixed Jaw 8. Locking Screw
4. Movable Jaw 9. Fine Adjustment Screw
5. External Jaws
3 5 4 2
7
6 8
1
9

Fig.2. No Zero Error
Fig.3. Positive Zero Error
Fig.4. Negative Zero Error
Observations and Calculations:
1. Least Count :
Least Count of main scale = Value of one main scale division = ………………
Total Number of divisions on vernier scale (n) = ……………….
Length of vernier scale (l) = ……………………………
Least Count of vernier scale = Value of one vernier scale division = l/n = …………..
Least Count of Vernier Caliper (L.C.) = … M.S.D. – …V.S.D.= ………………………...

2. Zero Error :
Sr.
No.
Main Scale
Reading
(in mm)
Vernier Scale Reading Zero Error =
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
Vernier Scale Reading = Coinciding
Division of Vernier Scale X Least Count
of Vernier Caliper
(in mm)
Mean zero error = ……………………………………..
3. Observation Table for ………… of specimen :
Sr.
No.
Main Scale
Reading
(in mm)
Vernier Scale Reading Total Reading =
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
of Vernier Caliper
(in mm)
Mean value of ………………of specimen is = …………………………………
Correct Reading = Mean value of Total Reading ± Mean Zero Error =.………………
Result : The average …….. (length, depth, diameter etc.) of the specimen is ……….

Pracitcal – 1
Aim : Use of linear measuring instruments like Vernier Caliper and Micrometer.
Apparatus used : Vernier Caliper, Micrometer, specimen.
Theory : Vernier Caliper : Vernier Caliper was invented by French mathematician
Pierre Vernier in 1631. It is used to measure the linear dimensions like length, depth,
diameter of an object, both internally and externally.
Principle : The principle used in vernier caliper is that using two scales of different
least count we can measure the least difference between divisions of two scales
used.
Constructional and Functional detail :
Main Scale : This scale is marked in inches and metric units. Its least count is 1mm,
1/40 inches for metric and inches scales respectively. Its maximum measuring range
may be upto 150 mm or 300 mm.
Vernier Scale : This scale is also marked in inches and metric units, but its size is
less than the main scale. Its least count and measuring range depends on the
construction of vernier caliper.
Fixed Jaw : This jaw is fixed to the main scale and does not move during
measurement.
Movable Jaw : This jaw is fixed with vernier scale and can move during
measurement.
External Jaws : These jaws are used for measurement of external dimensions.
Internal Jaws : These jaws are used for measurement of internal dimensions.
Stem / Blade : It is used for measuring the depth.
Locking Screw : It is used to block the movable part to allow easy transfer of
measurement.
Fine Adjustment Screw : It faclitate for repeated measurement of an object from
different sides, with in some tolerance limit.
Least Count : It is the minimum quantity which can be measured accurately by an
instrument , is called as least count of that instrument. The least count of vernier
caliper is the difference between least count of two scales used.
To find least count of vernier caliper, first check the least count of main scale. The
least count of main scale is the value of one main scale division.Then count the total
number of divisions (say n) on vernier scale and the note the length (l) of vernier
scale by observing its last division which coincide with main scale.

Therefore, Least Count of Vernier Scale = l/n
Forward Vernier Scale :
(1M.S.D. > 1V.S.D.); Least Count = Main Scale Division – Vernier Scale Division
Backward Vernier Scale :
(1V.S.D. > 1M.S.D.); Least Count = ..x..Main Scale Division – Vernier Scale Division
Vernier Caliper may be constructed based on forward vernier scale or backward
vernier scale
Zero Error : When fixed jaw and movable jaw of vernier caliper are closed together,
but the zero mark of vernier scale does not coincide with zero mark of main scale
then it is said that instrument has zero error. No zero error condition is shown in
Fig. 2.
Zero Error is of two types: (i) Positive Zero Error (ii) Negative Zero Error
Positive Zero Error : If the zero mark of vernier scale lies right to zero mark of main
scale on closing the jaw together, then it is called as positive zero error (Fig.3).This
error is finally subtracted from the measurement.
To find this error, close the jaws of vernier caliper and note the reading of main scale
division which is left to zero mark of vernier scale and also note the vernier scale
division which coincides with division on main scale. The vernier scale division is
multiplied by the least count of vernier caliper. The positive zero error is obtained by
adding this product with the main scale reading.
Negative Zero Error : If the zero mark of vernier scale lies left to zero mark of main
scale on closing the jaw together, then it is called as negative zero error (Fig.4). This
error is finally added to the measurement.
To find this error, close the jaws of vernier caliper and note the vernier scale division
which coincides with division on main scale. The vernier scale division is subtracted
from the total number of divisions on vernier scale. The difference is then multiplied
by the least count of vernier caliper to obtained negative zero error.
Procedure : 1) First find the least count of vernier caliper.
2) Check the zero error in the instrument. If any, then calculate the mean zero error.
3) Mark the reference point on specimen for measurement.
3) Fix the specimen between the jaws and Lock the measurement by tightening of
locking screws. Note the main scale reading (i.e. main scale division, left to the
vernier scale zero division).

4) Now examine the vernier scale division which coincide with the main scale
division. Multiply the vernier scale division with the least count of vernier caliper, to
find vernier scale reading.
5) To find total reading, add main scale reading with vernier scale reading.
6) Repeat the above procedure and note atleast three reading from different sides of
the specimen at marked point.
7) Record the noted reading in tabular form and find the mean value of total reading.
8) To find correct reading, add or subtract the mean zero error from the total reading
according to the type of zero error.
Result : The average ………..(length, depth, diameter etc.) of the specimen is ……..
Precautions : 1) There should not be any play between movable jaw and vernier
scale.
2) Zero error of instrument must be check before any measurement.
3) Measuring jaws should be flat and free from any type of wear & tear.
4) Measuring jaws must be kept perpendicular to the specimen’s longitudinal centre
line.
5) The coinciding division of vernier scale must be check carefully. For this
magnifying glass may be used.

Diagram :
Fig.3. Micrometer
Parts of Micrometer :
1. Frame 6. Thimble
2. Anvil 7. Main Scale
3. Spindle 8. Base line on main scale
4. Lock Nut 9. Circular Scale
5. Sleeve /Barrel 10. Rachet
Fig.4. No Zero Error Fig.5. Positive Zero Error Fig.6. Negative Zero Error
3
5
4
2 7
6
8
1
9 10

1. Least Count :
Lead of screw (l) = ……………………………
Total Number of divisions on cicular scale (n) = ……………….
Least Count of micrometer (L.C.) = . Lead of screw .
Total Number of divisions on circular scale
Therefore, L.C. = l/n = ……………………………….
.2. Zero Error :
Sr.
No.
Main Scale
Reading
(in mm)
Circular Scale Reading Zero Error =
Main Scale Reading
+ Circular Scale
Reading
(in mm)
Coinciding
Division of
Circular Scale
Circular Scale Reading = Coinciding
Division of Circular Scale X Least
Count of Micrometer
(in mm)
Mean zero error = ……………………………………..

Sr.
No.
Main Scale
Reading
(in mm)
Circular Scale Reading Total Reading =
Main Scale Reading
+ Circular Scale
Reading
(in mm)
Coinciding
Division of
Circular Scale
Circular Scale Reading = Coinciding
Division of Circular Scale X Least
Count of Micrometer
(in mm)
Correct Reading = Mean value of Total Reading ± Mean Zero Error = ………………
Result : The average …….. (length, depth, diameter etc.) of the specimen is ……….

Theory : Micrometer : Micrometer is also known as Screw Gauge.Micrometer
Screw was first invented by an English astronomer William Gascoigne. It was used
in telescope in 1638 to measure the angular distances between stars and the relative
size of celestial objects. It is used to measure the external dimensions of an object
Principle : Micrometer works on the principle of a screw. If a screw makes a single
rotation in a nut then its linear movement will be equal to the pitch of screw thread. If
cirular scale is used on screw head, then we can measure the distance moved by
screw in one division rotation.
Frame : It is thick, “C” shape like body of micrometer which is used to hold the anvil
and barrel in their place.
Anvil : It is the fixed part mounted on one end of frame which is exactly parallel to
spindle. Anvil face supports the specimen being measured, at one end.
Spindle : It is the cylindrical part which moves linearly by the rotation of thimble. It is
used to grip the specimen between anvil and spindle.
Lock Nut : It blocks spindle rotation for easy transfer of measurement.
Sleeve / Barrel : It is cylindrical body which is fixed to frame and covers the screw
mechanism. Main scale is engraved on it. Sleeve can be adjusted for zero error
removal. Vernier scale is also engraved on sleeve in vernier micrometer.
Thimble : It is the cylindrical part of micrometer through which measring screw is
rotated. Circular scale is engraved on it.
Main Scale : This scale is engraved on stationary barrel.
Circular Scale : This scale is engraved in circular shape on thimble body.
Base line on main scale : It is reference line which is engraved longitudinally on
barrel.
Rachet : Rachet is fixed adjacent to thimble at one end of micrometer. It helps to
grip the specimen between anvil and spindle with sufficient applied force.
Least Count : The minimum measurement made by an instrument is called as least
count of that instrument. The least count of micrometer is defined as the linear
advancement of screw in single division rotation on circular scale.
To find least count of micrometer, rotate thimble for one complete rotation and note
the linear movement of spindle on main scale. The linear movement of spindle in one
rotation of thimble will be equal to the lead (l) of screw. Count total number of
divisions (n) on circular scale. Then

Least Count of micrometer = . Lead of screw .
Total Number of divisions on circular scale
Therefore, L.C. = l/n
Zero Error : When both anvil and spindle faces of micrometer are closed together,
but the zero mark on circular scale doen not coincide with the base line mark of main
scale, then it is said that instrument has zero error.
Positive Zero Error : If zero mark of circular scale remains below the base line mark
of main scale when anvil and spindle face touch each other, then it is called as
positive zero error (Fig. ).This error is finally subtracted from the measurement.
To find this error, close the anvil and spindle face together and note the reading on
main scale. Check the cicular scale division which coincide with the base line of main
scale. Multiply this division with the least count of micrometer and add this product to
main scale reading, to find positive zero error.
Negative Zero Error : If zero mark of circular scale lies above the base line mark of
main scale when anvil and spindle face touch each other, then it is called as
negative zero error (Fig. ).This error is finally added to the measurement.
To find this error, close the anvil and spindle face together and note the reading on
main scale. Check the cicular scale division which coincide with the base line of main
scale. Subtract this value from the total number of divisions on circular scale. Multiply
this difference with the least count of micrometer and add this product to main scale
reading, to find negative zero error.
Zero Error Removal : To remove zero error, the barrel of micrometer can be rotated
in either direction with the help of adjustment key, to match zero mark of cicular
scale with base line mark on barrrel.
Backlash Error : Due to wear and tear of threads, the screw get loosen in the
cylindrical frame nut. Consequently spindle remains stationary for small rotation of
thimble. The error caused due to this, is called as backlash error. To avoid this error,
thimble should be rotated in same direction only.
Procedure : 1) First find the least count of micrometer.
Zero error can be removed by adjusting the barrel with key.
4) Fix the specimen between the anvil and spindle with the help of rachet. Lock the
measurement by rotating lock nut.

5) Note the main scale reading (i.e. main scale division, left to the circular scale).
6) Now examine the circular scale division which coincide with the base line of main
scale. Multiply the circular scale division with the least count of micrometer, to find
circular scale reading.
7) To find total reading, add main scale reading with circular scale reading.
10) To find correct reading, add or subtract the mean zero error from the total
reading according to the type of zero error.
Result : The average ………..(length, diameter etc.) of the specimen is ……………
Precautions : 1) Face of anvil and spindle should be clean.
3) While measurement, the rotation of circular scale should be in same direction to
avoid backlash error.
4) Circular scale rotation should be done through rachet for firmly gripping of
specimen.
5) The coinciding division of cicular scale must be check carefully.
P V
12 8

Pracitcal – 2
Aim : Use of height gauge and depth gauge.
Apparatus used : Vernier Height Gauge, Depth Gauge (Vernier depth gauge, Depth
Micrometer, Depth gauge dial indicator), specimen.
Diagram :
Fig.1. Vernier Height Gauge
Main Parts of Vernier Height Gauge :
1. Base 7. Scriber Clamp
2. Beam 8. Set Screw
3. Slider 9. Magnifying Lens
4. Main Scale 10. Magnifying Lens Support
5. Vernier Scale 11. Fine Adjustment Screw
6. Jaw 12. Locking Screw
7. Scriber 14. Main Scale Adjustment Screw
10
11
12
7
6
4
5
3
8
2
1
9
3

1. Least Count :
Length of vernier scale (l) = ……………………………
Least Count of vernier scale = Value of one vernier scale division = l/n = …………..
2. Zero Error :
Sr.
No.
Main Scale
Reading
(in mm)
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
of Vernier Caliper
(in mm)
Mean zero error = ……………………………………..

3. Observation Table for height of specimen :
Sr.
No.
Main Scale
Reading
(in mm)
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
of Vernier Caliper
(in mm)
Mean value of height of specimen is = …………………………………
Result : The average height of the specimen is ………………………….

Pracitcal – 2
Aim : Use of height gauge and depth gauge.
Apparatus used : Vernier Height Gauge, Depth Gauge (Vernier depth gauge, Depth
Micrometer, Depth gauge dial indicator), specimen.
Theory : Vernier Height Gauge : Vernier Height Gauge is the further extension of
vernier caliper.It is used to measure the height of an object. It also acts as scriber to
assist marking of heights.
Principle : Vernier Height Gauge is based on the principle of vernier caliper.
According to the principle of vernier caliper, if we use two scales of different least
count we can measure the least difference between divisions of two scales used.
Base : The heavy bottom part of vernier height gauge which stand upon the surface
plate is called as base. It is made up of cast iron. It ensures the rigidity and stablility
of the vernier height gauge.
Beam : It is rectangular cross sectional component which is fixed vertically to the
base. It includes a printed scale in both inches and metric format.
Slider : It is moving component of vernier height gauge which slides over the beam.
Vernier scale is engraved on it.
Main Scale : This scale is attached on beam . It is marked both in inches and metric
units. Its least count is 1mm, 1/40 inches for metric and inches scales respectively.
Vernier Scale : This scale is engraved on slider. It is also marked in inches and
metric units, but its size is less than the main scale. Its least count and measuring
range depends on the construction of vernier height gauge.
Jaw : It is the projection which fixed to the slider at one end while its other free end
is parallel to base. The free end is used to clamp the scriber.
Scriber : It is the sharp pointer which assist marking on workpieces.
Scriber Clamp : Scriber clamp holds the scriber at free end of jaw.
Set Screw : It assist to adjust and fix the sciber, at desired position in scriber clamp.
Magnifying Lens : It assist to read the coinciding division of vernier scale.
Magnifying Lens Support : It is the guideway on slider which support and guide
magnifying lens.

Locking Screw : It is used to block the slider to allow easy transfer of
measurement.
Main Scale Adjustment Screw : It assist the zero error removal of vernier height
gauge.
heigt gague is the difference between least count of two scales used.
To find least count of vernier caliper, first check the least count of main scale. The
least count of main scale is the value of one main scale division.Then count the total
number of divisions (say n) on vernier scale and the note the length (l) of vernier
scale by observing its last division which coincide with main scale.
(1V.S.D. > 1M.S.D.); Least Count = Vernier Scale Division – Main Scale Division
Vernier Height Gauge may be constructed based on forward vernier scale or
backward vernier scale
Zero Error : When scriber touches the ground plane, but the zero mark of vernier
scale does not coincide with zero mark of main scale then it is said that instrument
has zero error.
Positive Zero Error : If zero mark of vernier scale lies above to the zero mark of
main scale when scriber touches the ground plane, then it is called as positive zero
error.This error is finally subtracted from the measurement.
To find this error, bring down the scriber to its lowest position and touch it with
ground plane. Note the reading of main scale division which is below the zero mark
of vernier scale. Examine the vernier scale division which coincide with main scale
division. Multiply the vernier scale division with least count of vernier height gauge
and add this product with main scale reading to obtain positive zero error.
Negative Zero Error : If zero mark of vernier scale lies below to the zero mark of
main scale when scriber touches the ground plane, then it is called as negative zero
error.This error is finally added to the measurement.
To find this error, bring down the scriber to its lowest position and touch it with
ground plane. Note the vernier scale division which coincides with division on main

scale. The vernier scale division is subtracted from the total number of divisions on
vernier scale. The difference is then multiplied by the least count to obtained
negative zero error.
Zero Error Removal : To remove zero error, the main scale of vernier height gauge
can be slide to up or down on beam, with the help of main scale adjustment screw.
Procedure : 1) First find the least count of vernier height gauge.
2) Place the vernier height gauge on surface plate. Check the zero error in the
instrument. If any, then calculate the mean zero error. Zero error can be removed by
adjusting main scale by main scale adjustment screw.
3) For marking purpose, the slider is set to pre-determined height and corresponding
marking on specimen is done by sliding sharp edge scriber.
4) For measurment, mark the reference point on specimen. Lock the measurement
by tightening of locking screws.
5) Note the main scale reading (i.e. main scale division, below to the vernier scale
zero division).
division. Multiply the vernier scale division with the least count of vernier height
gauge, to find vernier scale reading.
Result : The average height of the specimen is ………………
Precautions : 1) Zero error of instrument must be check before any measurement.
2) Scriber must be grip firmly to avoid its springing while measurement.
3) The working surface of scriber should be flat and parallel to the base.
4) For marking, scriber should be slide in one direction only.
5) The coinciding division of vernier scale must be check carefully. For this

Diagram :
Fig.3. Vernier Depth Gauge
Parts of Vernier Depth Gauge :
1. Sliding Head 5. Vernier Scale
2. Base 6. Clamping Screws
3. Beam 7. Fine Adjustment Scerw
4. Main Scale
2
4
1
6
7
3
5

3. Observation Table for depth of specimen :
Sr.
No.
Main Scale
Reading
(in mm)
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
of Vernier Caliper
(in mm)
Mean value of depth of specimen is = …………………………………
Result : The average depth of the specimen is ………………………….

Theory : Vernier Depth Gauge : Vernier depth gague is the design modification of
vernier caliper for depth measurement. It is commonly used to measure depth of
holes, slots and counterbores etc.
Principle : Vernier depth gauge is based on the principal of vernier caliper i.e. by
using two scales of different least count we can measure the least difference
between divisions of two scales used.
Sliding Head : It carries a engraved vernier scale and can slide over the beam. It is
designed to bridge holes and slots for measurement.
Base : The lower face of sliding head which rests over the surface is called as base.
Beam : It is flat vertical component of depth gauge which is attached at right angle to
the base. It carries the main scale engraved on it.
Main Scale : This scale is marked in inches and metric units. Its least count is 1mm,
1/40 inches for metric and inches scales respectively. Its maximum measuring range
may be upto 150 mm or 300 mm.
Vernier Scale : This scale is also marked in inches and metric units, but its size is
less than the main scale. Its least count and measuring range depends on the
construction of vernier depth gauge.
Clamping Screw : It is used to block the sliding head to allow easy transfer of
measurement.
depth gauge is the difference between least count of two scales used.
To find least count of vernier depth gauge, first check the least count of main scale.
Then count the total number of divisions (say n) on vernier scale and the note the
length (l) of vernier scale by observing its last division which coincide with main
scale.

Zero Error : When base of the depth gague is placed over the surface plate and
bottom of beam is made to touch the surface plate, but the zero mark on vernier
scale doen not coincide with the zero mark of main scale, then it is said that
instrument has zero error.
Positive Zero Error : If zero mark of vernier scale lies above the zero mark of main
scale when both base and beam touch the surface plate, then it is called as positive
zero error .This error is finally subtracted from the measurement.
To find this error, place the depth gauge on surface plate such that bottom of beam
touch the surface plate. Then note the reading on main scale. Check the vernier
scale division which coincide with the main scale. Multiply this division with the least
count of depth gague and add this product to main scale reading, to find positive
zero error.
Negative Zero Error : If zero mark of vernier scale lies below the zero mark of main
scale when both base and beam touch the surface plate, then it is called as negative
zero error .This error is finally added to the measurement.
To find this error, place the depth gauge on surface plate such that bottom of beam
touch the surface plate. Then note the reading on main scale. Check the vernier
scale division which coincide with the main scale. Subtract this division from the total
number of divisions on vernier scale and multiply this result with the least count of
depth gague and add this product to main scale reading, to find negative zero error.
Procedure : 1) First find the least count of vernier depth gague.
3) Place the depth gague over hole such that base rests horizontally over the surface
and beam can freely slide into the hole.
4) Allow the beam to move down freely such that beam touch the bottom of hole.
5) Lock the measurement by tightening of clamping screws. Note the main scale
reading (i.e. main scale division, below to the vernier scale zero division).
division. Multiply the vernier scale division with the least count of vernier depth
gauge, to find vernier scale reading.

8) Repeat the above procedure and note atleast three reading by changing the
position of base from left to right.
Result : The average depth of the specimen is ……..
Precautions : 1) There should not be any play between sliding head and vernier
scale.
3) The reference surface on which the depth gauge base is rested must be
satisfactorily true, flat and parallel to horizontal.
4) While measurement the base of depth gauge must contact with the reference
surface.
5) The coinciding division of vernier scale must be check carefully.

Pracitcal – 3
Aim : Measurements with the help of combination set and bevel protractor.
Apparatus used : Combination Set, Bevel Protractor, Surface plate, specimen.
Diagram :
Fig.1. Use of Combination Set Square Head
Main Parts of Combination Set Square Head :
1. Square Head 5. Steel Rule/Blade
2. Spirit Level 6. Scriber
3. Adjustable knob 7. Specimen
4. Gauging surfaces anvil or shoulder
5
4
6
3
7
1
2

1. Least Count :
Least Count of groove scale is ...............
2. Zero Error :
Sr. No. Grooved Scale Reading
(in mm)
Mean zero error = ……………………………………..
Sr. No. Grooved Scale Reading
(in mm)
Result : The average ……….(height, depth, thickness etc.) of the specimen is ……..

Diagram :
Fig.2. Use of Combination Set Protractor Head
Main Parts of Combination Set Protractor Head :
1. Protractor Head 5. Steel Rule/Blade
3. Gauging surfaces 7. Locking Screw
4. Protractor scale disc
1. Least Count :
Least Count of protractor scale is ...............
2. Zero Error :
Sr. No. Protractor Scale Reading
(in degree)
Mean zero error = ……………………………………..
2
6
3
5
1
4
7

3. Observation Table for angle of specimen :
Sr. No. Protractor Scale Reading
(in degree)
Mean angle of specimen is = …………………………………
Result : The average angle of the specimen is ……..
Diagram :
Fig.3. Use of Combination Set Centre Head
Main Parts of Combination Set Centre Head :
1. Centre Head 4. Steel Rule/Blade
3. Gauging surfaces
3
5
2
4
1

Diagram :
Fig.4. Vernier Bevel Protractor
Main Parts of Vernier Bevel Protractor :
1. Body 8. Blade
2. Adjustable knob for blade 9. Acute angle attachment
3. Working Edge 10. Slow motion device
4. Stock 11. Vernier Scale
5. Turret 12. Eye Piece
6. Protractor/Main scale 13. Clamp
7. Locking Nut
5
10
00
6
11
2 8
3
9
3
4
1
7
12
13

1. Least Count :
Total angle of vernier scale (α) = ……………………………
Least Count of vernier scale = Value of one vernier scale division = α /n = …………..
2. Zero Error :
Sr.
No.
Main Scale
Reading
(in degree)
Main Scale Reading
+ Vernier Scale
Reading
(in degree)
Coinciding
Division of
Vernier Scale
of Vernier bevel protractor
(in degree)
Mean zero error = ……………………………………..
Sr.
No.
Main Scale
Reading
(in degree)
Main Scale Reading
+ Vernier Scale
Reading
(in degree)
Coinciding
Division of
Vernier Scale
of Vernier bevel protractor
(in degree)
Result : The average angle of the specimen is ……….

Pracitcal – 3
Aim : Measurements with the help of combination set and bevel protractor.
Apparatus used : Combintion Set, Bevel Protractor, Surface plate, specimen.
Theory : Combination Set : Combination set consists of a grooved scale, square
head, protractor head and centre head. According to use Square head, protractor
head and centre head are fixed in the groove of scale for different measurements.
Square Head: Square head is used to check the squareness as well as the depth of
a component. It can be used to scribe lines at an angle of 45 degrees. Generally its
least count is 0.5mm.
Spirit Level : It is fitted in the square head body and used to check the parallelism of
surfaces.
Adjustable Knob: It is used to adjust and lock the grooved scale at desired position.
It carries a slot in which grooved scale is fitted.
Gauging surfaces: These are the working edges of the square head which contacts
with the specimen. These gauging surfaces makes 450, 900 angles with the grooved
scale.
Steel Rule/ Blade: Steel rule is grooved at centre and is engraved in mm scale.
Generally its least count is 0.5mm.
Scriber: It is an accessory which is provided in some of square heads and can be
used for scribing lines.
Protractor Head: It is used to measure the angle of specimen. Generally its least
count is 1 degree. It carries a circular slot in which the protractor scale disc rotates. It
is marked to read the coinciding division.
Protractor Scale disc : This circular disc fitted in the circular slot of protractor head
casing and carries a protractor scale 0-1800 engraved on it. Its least count is 1
degree.
Centre Head : Centre Head is used to find the centre of circular bar. Its gauging
surfaces are at 90 to each other. With adjustable knob, grooved scale is fitted in the
slots of centre head.

Zero Error :
Square Head : Fix the grooved scale with adjustable knob on square head and
place it over the surface plate such that end of scale along with gauging surface
touches the plate. Lock the adjustable knob and read the scale. If scale reads zero
then there is no zero error.
Protractor Head : Fix the grooved scale with adjustable knob on Protractor head
and place it over the surface plate such that bottom edge of scale touches the plate.
Lock the adjustable knob and read the protractor scale. If scale reads zero then
there is no zero error.
Procedure :
Square Head:
1) Fix the scale in square head and check the zero error.
3) Put the specimen over the surface plate.
4) Place the gauging surface over the specimen and loosen the adjusting knob such
that grooved scale slides down till it touches the surface plate or bottom of specimen.
5) Push the blade at top with light pressure to ensure its true contact with bottom.
Now lock the adjusting knob and read the scale.
6) Repeat the above procedure and note at least three reading from different sides of
Result : The average ……….(height, depth, thickness etc.) of the specimen is ……..
Protractor Head:
1) Fix the scale in protractor head and check the zero error.
3) Put the specimen over the surface plate.

4) Hold the specimen gently between gauging surface and grooved scale as shown
in figure 2.
5) Now lock the adjusting knob and read the coinciding division of protractor scale.
6) Repeat the above procedure and note at least three reading from different sides of
Result : The average angle of the specimen is ................................
Centre Head:
1) Fix the scale in centre head.
2) Place the specimen beneath the scale such that it touches both the gauging
surfaces of centre head.
3) In this position scribe the line on specimen along the scale.
4) Now scribe another two lines by rotating specimen to different positions.
5) All three lines will coincide at one point which will be the centre of specimen.
Precautions : 1) Surface of specimen should be clean before measurement.
2) Loosen the locking screw before any measurement to prevent lock damage.
4) While measurement the gauging surface must contact truly with the specimen
surface.
5) The coinciding division of scale must be check carefully.

Theory : Vernier Bevel Protractor : Bevel protractor is an angular measuring
instrument. It consists of graduated scale on circular arc and adjustable leg. Its least
count is 1°. Vernier bevel protractor is more accurate than simple bevel protractor
due to attached vernier scale. It can read upto 5 minutes of arc.
Principle : Vernier bevel protractor is based upon the vernier principle. It consists of
two scales main scale and vernier scale. Generally it follows backward vernier scale
in which value of one vernier scale division is more than the value of one main scale.
Body: It is consists of circular base plate which is extended to the stock and acute
angle attachment. Main scale is engraved on the body.
Scale: Protractor scale is engraved on the body. This is called as main scale. One
main scale division can read upto 1°.
Working Edge: Grounded flat portion of stock act as working edge for
measurement.
Stock: It is the extended part of main base plate on which edge is grounded.
Swivel Plate/Turret: It is circular plate which is pivoted at centre on the base plate.
It carries vernier scale on it.
Protractor/Main Scale: Main scale is graduated in 0-360° angle on base plate in the
form of circular arc. Its least count is 1°.
Locking Nut: It is used to mount the acute angle attachment on body.
Blade: These are 150 or 300 mm long, 15 mm wide and 2mm thick steel bar which
carries a groove at centre and is fixed on the turret with adjustable knob. Its end are
bevelled at 45° or 60°.
Adjustable Knob: It is used to adjust and lock the blade at convenient position on
turret.
Acute Angle Attachment: It is used for measurement of very small angles.
Slow Motion Device: It controls the rotation the turret and helps to fix the turret at
convenient position with fine adjustment.
Eyepiece: It is fitted on the body. It magnifies the view to assist reading accurately.
Vernier Scale: Vernier scale is engraved on turret. It is graduated in 12 divisions on
each side of zero.
Clamp: It locks the turret at desired position while measurement.

Least Count : It is the minimum angle measurement of vernier bevel protractor.
To find least count of vernier bevel protractor, first check the least count of main
scale. The least count of main scale is the value of one main scale division. Then
count the total number of divisions (say n) on vernier scale and the note the total
angle (say α) inscribed by vernier scale.
Therefore, Least Count of Vernier Scale = α /n
Least count is calculated as the minimum difference between the divisions of two
scales.
Zero Error : When both blade and working edge of stock touches the surface plate
then it is said that instrument has zero error.
Since vernier scale divisions are on the both sides of zero mark, so nature of zero
error depends upon the rotation of turret while measurement.
Positive Zero Error : For clockwise rotation of turret, if zero mark of vernier scale
lies right to the zero mark of main scale when blade touches the surface plate, then it
is called as positive zero error. This error is finally subtracted from the measurement.
To find this error, note the reading of main scale division which is left to the zero
mark of vernier scale. Examine the vernier scale division which coincide with main
scale division. Multiply the vernier scale division with least count of vernier bevel
protractor and add this product with main scale reading to obtain positive zero error.
Negative Zero Error : For clockwise rotation of turret, if zero mark of vernier scale
lies left to the zero mark of main scale when blade touches the surface plate, then it
is called as negative zero error. This error is finally added to the measurement.
To find this error, note the reading of main scale division which is right to the zero
mark of vernier scale. Examine the vernier scale division which coincide with main
scale division. Multiply the vernier scale division with least count of vernier bevel
protractor and add this product with main scale reading to obtain negative zero error.
Procedure :
1) Firstly fix the blade in turret and check the zero error.
3) Put the specimen over the surface plate and loosen the clamp of turret.

4) According to shape, place the bevel protractor over specimen such that both
blade and working edge of stock touches the measuring surfaces of specimen.
5) Carefully check the rotation of turret in clockwise or anticlockwise and lock the
clamp in this position.
6) For clockwise turret rotation, examine the main scale reading which lies left to the
zero mark of vernier scale.
division. Multiply the vernier scale division with the least count of vernier bevel
protrator, to find vernier scale reading.
10) Record the noted reading in tabular form and find the mean value of total
reading.
Result : The average angle of the specimen is ................................
Precautions : 1) Surface of specimen should be clean before measurement.
2) Loosen the turret clamp before any measurement to prevent lock damage.
4) While measurement the gauging surface must contact truly with the specimen
surface.
5) The coinciding division of scale must be check carefully and avoid parallax error.

According to shape, different positions of Vernier Bevel Protractor

Vernier Caliper may be constructed based on forward vernier scale or backward
vernier scale
Zero Error : When fixed jaw and movable jaw of vernier caliper are closed together,
then it is said that instrument has zero error.No zero error condition is shown in
Fig. 2.
Positive Zero Error : If the zero mark of vernier scale lies right to zero mark of main
scale on closing the jaw together, then it is called as positive zero error (Fig.3).This
error is finally subtracted from the measurement.
To find this error, close the jaws of vernier caliper and note the reading of main scale
division which is left to zero mark of vernier scale and also note the vernier scale
division which coincides with division on main scale. The vernier scale division is
multiplied by the least count of vernier caliper. The positive zero error is obtained by
adding this product with the main scale reading.
Negative Zero Error : If the zero mark of vernier scale lies left to zero mark of main
scale on closing the jaw together, then it is called as negative zero error (Fig.4). This
error is finally added to the measurement.
To find this error, close the jaws of vernier caliper and note the vernier scale division
which coincides with division on main scale. The vernier scale division is subtracted
from the total number of divisions on vernier scale. The difference is then multiplied
by the least count of vernier caliper to obtained negative zero error.
Procedure : 1) First find the least count of vernier caliper.
3) Fix the specimen between the jaws and Lock the measurement by tightening of
locking screws. Note the main scale reading (i.e. main scale division, left to the
vernier scale zero division).

Pracitcal – 4
Aim : Angle measurement by use of sine bar and slip gauges.
Apparatus used : Sine bar, slip gauges set, dial indicator, dial indicator stand,
surface plate, angle plate, clamp, vernier height gauge, specimen.
Diagram :
(a) (b)
(c) (d)
Fig.1. Different uses of sine bar

Observation Table for height of specimen :
Length of sine bar (L) = .................................
Least count of vernier height gauge = .............................
Sr.
No.
Heights
Sin(α)=H/L α = Sin-1 (H/L)
H1 H2 H = H1- H2
Result : The average angle of the specimen is ………………………….

Pracitcal – 4
Aim : Angle measurement by use of sine bar and slip gauges.
Apparatus used : Sine bar, slip gauges set, dial indicator, dial indicator stand,
surface plate, angle plate, clamp, vernier height gauge, specimen.
Theory : Sine bar : Sine bar is used for precise measurement of small angular
dimensions. It is used in conjunction with slip gauges or vernier height gauge. Sine
bar is made of high carbon, high chromium corrosion resistant steel. It carries two
equal diameter cylinders which are fixed at the ends. Relief holes are provided on
sine bar to reduce its weight and to assist clamping of sine bar on angle plate.
Length of sine bar is measured as the centre to centre distance between two
cylinders. Sine bar is available in 100mm, 150mm, 200mm or 300mm length.
Sine bar works on the principle that if hypotenuse of right angle triangle is kept
constant then different angle can be obtained just by varying the height of
perpendicular.
Slip Gauges : Slip gauges are used as calibration standards for vernier calliper,
micromter and for angular measurement in conjunction with sine bar. Gauge blocks
are made of hardened steel which are grounded, stabilized and lapped to certain
thickness. When lapped blocks are made to slide over one another it adheres to
each other. This process of joining is called as wringing. For stacking, minimum
number of slip gauges should be used to reduce dimensional error.
Procedure : 1) First clean the sine bar, surface plate and specimen for dirt, if any.
Note the length of sine bar.
2) For small jobs, place the sine bar over the measuring surface of specimen such
that its one end touches the surface plate, as shown in figure1 (a). Angle plate
should be used to support sine bar.
3) Make a stack of slip gauges on other end till it touches the sine bar roller. For big
size specimen, slip gauges may be stacked at both the ends of sine bar, as shown in
figure 1(b).
4) Very small specimen may directly be placed over the sine bar as shown in
figure1 (c). The top surface of specimen should be checked with the dial indicator for
its parallelism with the surface plate.
5) For large size specimen, sine bar should be placed inverted as shown in
figure 1(d). Vernier height gauge is used to check the height of roller.
6) By light gap method, check the contact between sine bar and specimen. The
contact should be perfectly true.

7) Note the heights (H1, H2) of slip gagues which are stacked at ends. The height
difference is calculated as H = H1- H2. Find the Sin(α)=H/L and calculate the angle α.
8) Repeat the above procedure and note atleast three reading of the specimen at
marked point.
Result : The average angle of the specimen is ………………
Precautions : 1) Sine bar should be used for angles below 45 degree only.
2) Angle plate and clamps must be used to support the sine bar and specimen.
3) All the instruments must be clean properly before use.
4) Minimum number of slip gauges should be used.
5)The coinciding division of vernier scale must be check carefully. For this

Practical – 5
Aim : Use of slip gauges in measurement of centre distance between pins.
Apparatus used : Slip gauges set, slip gauge accessories set, scale, specimen.
Diagram :
Fig.1. Use of slip gauge accessory/holder
Slip gauge set:
Thickness range Step Total

Sr. No. Total thickness of slip gauges
Mean distance between two points of the specimen is = ………………………………
Result : The average distance between two points of the specimen is ………………

Practical – 5
Aim : Use of slip gauges in measurement of centre distance between pins.
Apparatus used : Slip gauges set, slip gauge accessories set, scale, specimen.
Theory : Slip Gauges : Slip gauges are known as Johansson gauges. Slip gauges
are used as calibration standards for vernier calliper, micrometer and for angular
measurement in conjunction with sine bar. Gauge blocks are made of hardened steel
which are grounded, stabilized and lapped to certain thickness. When lapped blocks
are made to slide over one another it adheres to each other. This process of joining
is called as wringing. For stacking, minimum number of slip gauges should be used
to reduce dimensional error.
Slip gauges are available in different grades. These gauges are reference,
calibration, inspection and working grades. The tolerance of reference grade and
working grades are close to ±0.05 μm and ±0.25 μm respectively. One slip gauge set
may contain 10, 18, 32,47,78,87,122 slip gauge pieces.
Slip Gauge Accessory: Slip gauges accessory is designed to improve the use of
slip gauges. These are available in different designs. These accessories extend the
slip gauge use to measure not only thickness but also internal & external diameter of
cylindrical objects and height of specimen.
Procedure : 1) First clean the slip gauge accessory, surface plate and specimen for
dirt, if any.
2) Select the slip gauge accessory according to the nature of surface of specimen.
3) Note pin thickness if measuring internal dimensions.
4) Hold the specimen between two pins and measure the approximate gap between
pin with the help of scale.
5) Insert slip gauges in the gap created between two pins on slip gauge holder.
6) Note the thickness of slip gauges thickness and add pin thickness for internal
measurement.
7) Repeat the above procedure and note at least three reading of the specimen at
marked point.
Result : The average distance between two points of the specimen is ………………

Precautions : 1) Select the appropriate pin set according to surface of specimen.
2) Excessive pressure on slip gauge should be avoided.
4) Minimum number of slip gauges should be used.
5) Slip gauge should be carefully inserted along its thickness only.

Practical – 6
Aim : Checking of flatness using Dial indicator.
Apparatus used : Dial Indicator, Dial indicator stand, Surface Plate, specimen.
Diagram :
Fig.1. Flatness check by Dial Indicator
Least Count of Dial Indicator = ...........................
Observation table:
Sr.
No.
Maximum Reading Minimum Reading Flatness
X (mm) Y (mm) X-Y (mm)
Flatness of the specimen is = ………………………………
Result : The average flatness of the specimen is ………………

Practical – 6
Aim : Use of comparator for measurement.
Apparatus used : Dial Indicator, Dial Indicator stand, Slip Gauges set, Supports, specimen.
Theory : Flatness : A surface is said be flat if all the points on surface lies between two parallel
planes, drawn in the direction of plane and separated by tolerance limit.
Dial Indicator : Dial indicator is a sensitive instrument which is used to check very small variation
in sizes. Generally its least count is 0.01mm. Dial indicator is used as a mechanical comparator.
It consists of plunger, main dial with long hand needle and counter dial with short hand needle.
Plunger slides in the stem for any variation in measurement and this variation is further magnified
with rack & pinion arrangement which finally show on the dial. Counter dial needle moves one
division when long hand needle completes its one rotation on the main dial.
Procedure : 1) First clean the slip gauge, surface plate and specimen for dirt, if any.
2) Fix the dial indicator on the dial indicator stand.
3) Place the support on surface plate and check its height. Height of all support should be equal.
4) Mark at least two mutually perpendicular lines on the working surface.
Now lower down the dial indicator till its plunger knob touches the top of slip gauges stack as
shown in fig .1.
5) Now place the measuring surface inverted over the supports as shown in Fig .1.
6) Touch the plunger knob on the measuring surface and set dial indicator to show zero reading.
7) Further raise the dial indicator to set an initial compression of 2 to 3mm.
8) Now lock the dial indicator in its position on the dial indicator stand.
9) Move the dial indicator beneath the specimen and maintain contact with measuring surface.
10) Note the maximum and minimum reading of dial indicator during movement along the marked
lines of measuring surface.
11) Find the difference between maximum and minimum reading.
12) Repeat the above procedure and note at least three reading of the specimen at marked point.
13) Keep reading in tabular form and find the mean value of flatness .
Result : The average flatness of the specimen is ………………
Precautions : 1) Plunger knob should be free from wear.
2) Excessive pressure on slip gauge should be avoided.
4) Excessive movement of plunger knob should be avoided to set initial compression.
5) Avoid sudden jerk of plunger while replacing specimen with the standard specimen.

Practical – 7
Aim : Measurement of taper by standard balls and rollers.
Apparatus used : Measuring pin/roller set, Inspection gauge ball set, Slip gauge set,
Depth micrometer, Vernier Calliper, Surface Plate and Specimen.
Diagram:
i) External Taper ii) Internal Taper
Fig.1. Measurement of Taper i) External Taper ii) Internal Taper
Least Count of Vernier Calliper (L.C.) = ...........................
Least Count of Depth Micrometer (L.C.) = ...........................
Observation table for External Taper Measurement :
Sr.
No.
Diameter of
Measuring Roller
L1 L2 Slip Gauge Height
(H)
tan(𝛼) =
L2 − L1
𝐻
𝛼 = tan−1
L2 − L1
𝐻
(mm) (mm) (mm) (mm) (degree)
Mean External taper angle of the specimen is = ………………………………

Observation table for Internal Taper Measurement :
Sr.
No.
Diameter of
Gauge Ball
Radius of
Gauge Ball
Depth sin(𝛼)
=
(𝑟2 − 𝑟1)
((ℎ1 − ℎ2) − (𝑟2 − 𝑟1))
𝛼
= sin−1
(𝑟2 − 𝑟1)
((ℎ1 − ℎ2) − (𝑟2 − 𝑟1))
D1
(mm)
D2
(mm)
r1
(mm)
r2
(mm)
H1
(mm)
H2
(mm)
(degree)
Mean Internal taper angle of the specimen is = ………………………………
Result : 1) The average External Taper angle of the specimen is ………………
2) The average Internal Taper angle of the specimen is ………………

Practical – 7
Aim : Measurement of taper by standard balls and rollers.
Apparatus used : Measuring pin set, Inspection gauge gall set, Slip gauge set, Depth
micrometer, Vernier Calliper, Surface Plate and Specimen.
Theory : Taperness: A job is said to be taper if its lateral dimensions varies uniformly
when measured along the length of job. For conical shape job, taperness is defined in
terms of conicity “K”.
Conicity “K” = (D-d)/L
where D= Large end diameter of job, d = Small end diameter of job, L= Length of job.
or taper is defined as half of conicity, if α = half of taper angle, then tanα= (D-d)/2L
Procedure : (External Taper)
1) First clean vernier calliper jaws, surface plate and specimen for dirt, if any.
2) Calculate the least count of vernier calliper and check its zero error, if any.
3) Place the specimen vertically on surface plate such that its small end faces the
surface plate as shown in Fig. 1(i).
4) Pick the suitable set of measuring roller, note its diameter and place one roller each
adjacent to the smaller end of job.
5) Now measure end to end distance between two rollers by using vernier calliper and
note this reading as L1.
6) Remove the roller and make slip gauges stack of equal height (say H) at adjacent to
the taper specimen, one on each side.
7) Now use the same roller as used in above procedure and place one roller each on
top of slip gauge stack.
8) Measure end to end distance between two rollers by using vernier calliper and note
this reading as L2.
9) Apply formula as tan(𝛼) =
L2−L1
𝐻
and calculate taper angle 𝛼.
10) Repeat the above procedure and note at least three reading of the specimen.
11) Record the noted reading in tabular form and find the mean value for taper angle.

(Internal Taper):
1) First clean depth micrometer, surface plate and specimen for dirt, if any.
2) Calculate the least count of depth micrometer and check its zero error, if any.
3) Place the specimen vertically on surface plate such that its small end faces the
surface plate as shown in Fig. 1(ii).
4) Insert a suitable size ball such that it gets stick in the taper. Note ball diameter as
D1.
5) Measure depth from top surface to ball with the help of depth micrometer. Note this
depth as H1.
6) Now remove the inserted ball and insert second ball of larger diameter in the taper.
Note second ball diameter as D2.
7) Measure depth from top surface to second ball with the help of depth micrometer.
Note this depth as H2.
8) Apply formula as sin(𝛼) =
(𝑟2−𝑟1)
((ℎ1−ℎ2)−(𝑟2−𝑟1))
and calculate taper angle.
14) Repeat the above procedure and note at least three reading of the specimen.
15) Record the noted reading in tabular form and find mean value of taper angle 𝛼.
Result : 1) The average External Taper angle of the specimen is ………………
2) The average Internal Taper angle of the specimen is ………………
Precautions : 1) Measuring roller should properly contact with specimen.
2) Use minimum number of slip gauges.
3) Use rachet to avoid excessive pressure while measuring depth.
4) For blind hole taper, ball should not rest on the bottom.
5) Abrupt change in cross section may cause error in measurement.

Practical – 8
Aim : Measurement of thread parameters by using Tool makers microscope.
Apparatus used : Tool Makers Microscope and Specimen.
Diagram:
Fig.1. Tool Makers Microscope
Fig.2. Various Positions of cross mark line
Least Count of Micrometer = ...........................
Least Count of Protractor Scale = ...........................
Major Diameter:
Initial reading of micrometer (I.R.) = ........................
Final reading of micrometer (F.R.) = ........................
Major Diameter = F.R. – I.R. = .............................

Minor Diameter:
Minor Diameter = F.R. – I.R. = .............................
Pitch (p) :
Pitch = F.R. – I.R. = .............................
Thread Angle :
Thread Angle = F.R. – I.R. = .............................
Helix Angle (α):
Helix Angle = F.R. – I.R. = .............................
Slope(m) :
Slope = tan(α) =
Number of start (n) and effective diameter(d) :
Slope =
𝑛𝑥𝑝
𝜋𝑥𝑑
=
n = ................, d = ..............................
Form of thread = ...........
Result : Thread parameters:
Major Diameter = ............, Minor Diameter = .............., Pitch = ......................
Thread Angle = ............, Helix Angle = .............., Slope = ......................
Number of start = ............, Effective Diameter = .............., Form of thread = ...........

Practical – 8
Aim : Measurement of thread parameters by using Tool makers microscope.
Apparatus used : Tool Maker’s Microscope and Specimen.
Theory : Tool Makers Microscope: Tool Makers Microscope is an optical device
which is used to examine different thread parameters. It consists of hollow base which
encloses the light source. Work table is mounted over the base which can slide in two
directions with the help of micrometer. Vertical column is attached to the base which
supports the optical head.
Tool maker microscope consists of two micrometer, used to measure table slide in
longitudinal and transverse direction. Cross line are marked on glass screen which
can be rotated through 360o angle. Rotation of cross line mark can be measured by
protractor scale which is engraved on the optical head.
A light ray from source passes through the lens and reflected by mirror towards the
work table. These light rays transmitted through transparent glass table and passes
through the contour of thread specimen. The reflected image is received by optical
head and examined through the eye piece.
Procedure :
1) First connect the tool maker microscope to power supply.
2) Calculate the least count of micrometer and protractor scale.
3) Set the protractor scale to zero reading.
4) Place the thread specimen on glass table and observe its image through the eye
piece.
5) Adjust optical head height by knob to observe sharp edges of threaded specimen.
6) Adjust cross mark such that its horizontal line touches the crests of threaded
specimen as shown in Fig.2.
7) Note initial reading of micrometer and rotate the micrometer till horizontal line
touches the crests on opposite end.
8) Note micrometer reading as final reading. Difference between final and initial
reading is observed as major diameter of threaded specimen.
9) Repeat the above procedure to determine linear dimensions like minor diameter
and pitch.
10) For angular measurement, adjust the cross line mark along the one edge of thread
as shown in Fig.2 and note protractor scale reading as initial reading.

11) Rotate the cross line mark through protractor scale and adjust it on the adjacent
edge of thread. Note the protractor scale reading as final reading.
12) Difference between protractor scale readings observed as thread angle.
13) Similarly use the protractor scale to find the helix angle. Further calculate slope
and find out the number of start, effective diameter of threaded specimen.
14) Observe carefully crests to examine thread form.
Result : Thread parameters:
Major Diameter = ............, Minor Diameter = .............., Pitch = ......................
Thread Angle = ............, Helix Angle = .............., Slope = ......................
Number of start = ............, Effective Diameter = .............., Form of thread = ...........
Precautions : 1) Threaded specimen should properly clamp on table .
2) Coinciding line of cross mark should be checked carefully.
3) Avoid backlash error in micrometer.
4) Thread axis should be parallel to glass plate.
5) Carefully read the protractor scale.

Practical – 9
Aim : Measurement of gear elements by using gear tooth vernier.
Apparatus used : Gear Tooth Vernier, vernier calliper and Spur gear specimen.
Diagram:
Fig.1. Gear Tooth Vernier
Main Parts of Vernier Caliper :
1. Beam 7. Vernier Scale
2. Horizontal Slider 8. Auxiliary Slide
3. Vertical Slider 9. Tongue/ Blade
4. Fixed Jaw 10. Locking Screw
5. Moveable Jaw 11. Fine Adjustment Screw
6. Main Scale
9
1
3
6
8
4
2 7
5
11
10

Least Count of vernier calliper = .......................
Least Count of Gear tooth vernier = .......................
Zero Error = ......................
Total number of teeth on gear (T) = ..........................
Outside diameter of gear (O.D.) = ............................
Pitch Circle Diameter (D) =
𝑇𝑋𝑂.𝐷.
𝑇+2
= ......................
Module (m) =
𝐷
𝑇
= ......................
Addendum = m = ......................
Dedendum = 1.157xm = ......................
Clearance = 0.157xm = ......................
Circular Pitch = πxm = ......................
Diametral Pitch =
1
𝑚
= ......................
Observation Table :
Sr.
No.
Main Scale
Reading
(in mm)
Main Scale Reading
+ Vernier Scale
Reading
(in mm)
Coinciding
Division of
Vernier Scale
of Gear tooth Vernier
(in mm)
Mean gear tooth thickness is = …………………………………
Correct Reading (t) = Mean Gear tooth thickness ± Mean Zero Error =.……………
Theoretical gear tooth thickness (t’) = Dsin(90/𝑇) = ........................
Percentage error in gear tooth thickness = [
(𝑡′−𝑡)𝑥100
𝑡′
] = .................
Result : The average gear tooth thickness is .................and percentage error is .....

Practical – 9
Aim : Measurement of gear elements by using gear tooth vernier.
Apparatus used : Gear Tooth Vernier, vernier calliper and Spur gear specimen.
Theory : Gear Tooth Vernier : Gear tooth vernier is used to check the chordal
thickness of gear tooth. It is based on the vernier principle. It carries two arms:
horizontal and vertical. On vertical arm tongue is set for addendum size and tongue
rests over top of tooth during measurement. In this position, horizontal arm jaws are
used to measure the chordal tooth thickness along the pitch circle, as shown in
Fig.1.
Beam: Beam is made of steel in form of L shape which carry horizontal and vertical
arm. Vertical arm is further projected to form fixed jaw.
Horizontal Slider: It slides over the horizontal arm of beam and carry vernier scale.
Vertical Slider: It slides over the vertical arm of beam and carry vernier scale.
Fixed Jaw: It is stationary jaw which fixed to the beam body.
Moveable Jaw: Moveable jaw is fixed to the horizontal slider.
Main Scale : It is engraved over the beam in inches and metric units. Its least count
is 0.5mm, 1/40 inches for metric and inches scales respectively. Its maximum
measuring range may be upto 40 mm.
Vernier Scale : It is engraved over horizontal as well as vertical slider in both inches
and metric units, but its size is less than the main scale. Its least count and
measuring range depends on the construction of vernier caliper.
Auxiliary Slide: It slides over the beam along with slider and carry fine adjustment
screw.
Tongue/ Blade: It is attached to the vertical slider. It rests over top of gear tooth
during measurement.
Locking Screw : It blocks movable jaw movement which prevent disturbance in
measurement.
Fine Adjustment Screw : It faclitate for repeated measurement of an object and to
set the gear tooth vernier in close tolerance limit.

Procedure : 1) First find the least count of vernier calliper and gear tooth vernier.
2) Count the total number of teeth on gear and note down the reading.
3) Calculate pitch circle diameter and find out module value.
4) Set addendum size on vertical arm equal to module value and lock the vertical
arm in this position.
5) Now place the gear tooth vernier on gear such that tongue rests over the top of
tooth as shown in Fig. 1.
6) Clamp the tooth with in horizontal arm jaws and lock the reading.
7) Repeat the above procedure to determine at least three readings of gear tooth
thickness.
8) Note down the reading in tabular form and calculate the average value.
9) Calculate theoretical thickness and compare it with average tooth thickness to find
percentage error.
10) Percentage error should be within tolerance limits.
Result : The average gear tooth thickness is .................and percentage error is .....
Precautions : 1) Gear specimen should be clean before measurement.
2) There should not be any play between slider and beam.
3) Zero error of instrument must be check before use.
4) Carefully set the addendum on vertical arm.
5) Repeat the practical for different teeths.

Practical – 10
Aim : Measurement of profile by profile projector.
Apparatus used : Profile Projector, Gear specimen (Involute and cyloidal profile) ,
glass plate.
Diagram:
Fig.1. Profile Projector
Result : Observed Gear profiles i)........................ ii) ...............................

Practical – 10
Aim : Measurement of profile by profile projector.
Apparatus used : Profile Projector, Gear specimen (Involute and cyloidal profile) ,
glass plate.
Theory : Profile Projector : Profile projector is an optical instrument which is used
to examine complex contour of different objects like screws, gear or other
regular/irregular shapes. It consists of high intensity light source from which light ray
fall over contour surface of objects and get passed through transparent glass plate.
Further these rays incident on the magnifying lens and travels towards the reflector.
Reflector reflects these rays to projection screen and form the contour image over
the screen. Magnification may be 10X, 25X and 50X etc. Profile projector may have
graduated scale over the projection screen for angular measurement. For linear
measurement micrometers are attached to table.
Procedure : 1) First clean the projection screen, glass plate, specimen and
magnifying lens for dirt, if any.
2) Calculate the least count of measuring scales.
3) Place the glass plate over the table.
4) Select a suitable magnifying lens and fix it in the profile projector.
5) Connect the profile projector to power supply and turn on power supply.
6) Adjust focus by moving table up or down till sharp image form over screen.
7) Micrometer may be used for linear measurement while angular measurement can
be taken from graduated screen.
8) Trace paper can be used to draw the profile of complex shapes and can be used
for further calculation.
Result : Observed Gear profiles i)........................ ii) ...............................
Precautions : 1) Specimen should be free from dust & dirt.
2) Read the scale carefully.
3) Switch off power supply when not in use.

Practical – 11
Aim : Measurement of surface roughness of a surface.
Apparatus used : Surface roughness tester and specimen.
Diagram:
Fig.1. Surface Roughness Tester
Observation Table :
Sr.
No.
Specimen Roughness Parameters
Ra (µm) Rq (µm) Rz (µm)
Result : Maximum rough surface is ................... and smooth surface is ....................

Practical – 11
Aim : Measurement of surface roughness of a surface.
Apparatus used : Surface roughness tester and specimen.
Theory : Surface Roughness Tester : Surface roughness tester is used to
numerically evaluate the roughness of surface. It carries a stylus probe which slides
over the specimen surface. Stylus movement is recorded and amplified by different
methods of measurement. Working principle of surface roughness tester may be
mechanical, electrical and pneumatic type. Some of common roughness parameters
are Ra, Rq and Rz. Generally surface roughness is measured in µm.
Procedure : 1) First clean the standard and specimen surfaces for dirt, if any.
2) First set up the connections between stylus and control unit.
3) Connect control unit to power supply and switch on the control unit.
4) Place stylus probe in horizontal position over the standard specimen and do
calibration of roughness tester.
5) Now replace the standard specimen with specimen to be measured.
6) Set various test/display conditions in the control unit.
7) Start the test and stylus will slide over the specimen surface.
8) Control unit displays profile of surface being measured.
9) Calculated values of various roughness parameters are shown on the display
screen in the end of test.
10) Note various roughness parameters for given surface and repeat the above
procedure for different specimen surfaces.
11) Examine the maximum rough and smooth surfaces from noted readings.
Result : Maximum rough surface is ................... and smooth surface is ....................
Precautions : 1) Stylus probe should be parallel to the surface to be measured .
2) Ensure good contact between stylus and surface throughout travel of probe.
3) Carefully set the measuring parameters.

VIVA-VOCE
Practical-1
Vernier Calliper
Q1. Which type of measurement is done by Vernier Calliper.
Ans. Linear measurement (External, internal and depth)
Q2. Name important parts of Vernier Calliper.
Ans. External measuring jaws, Internal measuring jaws, Stem, Main Scale, Vernier
Scale, Locking Screws, Fine adjustment screw.
Q3. What is the value of least count of Vernier Calliper.
Ans. 0.02 mm.
Q4. Define Least count.
Ans. It is the minimum quantity which can be measured accurately by an instrument ,
is called as least count of that instrument.
Q5. Name different types of Vernier Scale.
Ans. Forward Scale ( 1MSD> 1VSD), Backward Scale (1MSD < 1VSD)
Q6. Define Zero error in Vernier Calliper.
Ans. When fixed jaw and movable jaw of vernier caliper are closed together, but the
zero mark of vernier scale does not coincide with zero mark of main scale then it is
said that instrument has zero error.
Q7. Name different types of zero errors in vernier calliper.
Ans. Zero Error is of two types: (i) Positive Zero Error (ii) Negative Zero Error
Q8.

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