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Darshan Institute of Engineering & Technology

Certificate

This is to certify that Mr./Ms.____________________________________

Enrollment No. ________________ Branch: - Mechanical Engineering

Semester: IV has satisfactory completed the course in the subject Mechanical

Measurements and Metrology (2141901) in this institute.

Date of Submission: - __________________________

Staff in Charge Head of Department

DARSHAN INSTITUTE OF ENGG. & TECH.

Department of Mechanical Engineering

B.E. Semester – IV

Mechancial Measurement and Metrology (2141901)

List of Experiments

Sr.

No. Title

Date of

Performance

Date of

submission Sign Remark

1. Preparatory Activity

2. Practice of Measurement with

Vernier caliper


Micrometer


Vernier Height Gauge

5. Practice of measurement with slip

gauge

6. Practice of calibration with slip

gauge

7. Practice of measurement with bevel

protector

8. Practice of measurement with sine

bar

9. To study about roughness of

surfaces.

10. To study about limit gauges.

Mechanical Measurement & Metrology (2141901) Prepared By: Paras G.Vegada

Darshan Institute of Engineering & Technology, Rajkot Page1.1 Department of Mechanical Engineering

EXPERIMENT – 1

AIM: Preparatory Activity

1.1. DEFINE FOLLOWING TERMS

Measurement: It is the process by which one can convert physical parameters to

meaningful number.

Instrument: It may be defined as a device for determining the value or magnitude of

a quantity or variable.

Metrology: It is the science of measurement. The purpose of this discipline is to

establish means of determining physical quantities, such as dimensions, temperature,

force, etc. or, the design of comparison process for measurements.

Instrumentation: It is a collective term for measuring instruments used for indicating,

measuring and recording physical quantities

Standards: A known set of dimensions, or ideals to compare others against.

Standards are the basis for all modern accuracy. As new methods are found to make

more accurate standards, the level of accuracy possible in copies of the standard

increase, and so on. A well-known metric standard is the metric 1m rod.

Inspection: Procedure in which a part or product feature, such as a dimension, is

examined to determine whether or not it conforms to design specification

Accuracy: It is defined as the closeness with which the reading approaches an

accepted standard value or true value.

Precision: It is the degree of reproducibility among several independent

measurements of the same true value under specified conditions. It is usually

expressed in terms of deviation in measurement.

Repeatability: It is defined as the closeness of agreement among the number of

consecutive measurement of the output for the same value of input under the same

operating conditions. It may be specified in terms of units for a given period of time.

Reliability: It is the ability of a system to perform and maintain its function in routine

circumstances. Consistency of a set of measurements or measuring instrument often

used to describe a test.



1.2. TYPES OF ERRORS

Systematic Errors: These errors include calibration errors, error due to variation in the

atmospheric condition Variation in contact pressure etc. If properly analyzed, these

errors can be determined and reduced or even eliminated hence also called

controllable errors. All other systematic errors can be controlled in magnitude and

sense except personal error.

These errors results from irregular procedure that is consistent in action. These errors

are repetitive in nature and are of constant and similar form.

Random Errors: These errors are caused due to variation in position of setting

standard and workpiece errors. Due to displacement of level joints of instruments,

due to backlash and friction, these error are induced. Specific cause, magnitude and

sense of these errors cannot be determined from the knowledge of measuring system

or condition of measurement. These errors are non-consistent and hence the name

random errors.

Environmental Error: These errors are caused due to effect of surrounding

temperature, pressure and humidity on the measuring instrument. External factors

like nuclear radiation, vibrations and magnetic field also leads to error. Temperature

plays an important role where high precision is required. E.g. while using slip gauges,

due to handling the slip gauges may acquire human body temperature, whereas the

work is at 20°C. A 300 mm length will go in error by 5 microns which is quite a

considerable error. To avoid errors of this kind, all metrology laboratories and

standard rooms worldwide are maintained at 20°C.

1.3. UNIT CONVERSION

Unit conversion of length, area and volume are given as follows:

Table 1.1 Unit Conversion of Length

cm m km in ft

1Centimeter 1 10-2 10-5 0.3937 3.281 X 10-2

1 Meter 100 1 10-3 39.37 3.281

1 Kilometer 105 1000 1 3.937 X 10-4 3281

1 Inch 2.540 2.540 X 10-2 2.540 X 10-3 1 8.333 X 10-2

1 Foot 30.48 0.3048 3.048 X 10-4 12 1



Table 1.2 Unit Conversion of Area

m2 cm2 ft2 in2

1 Square Meter 1 104 10.67 1550

1 Square cm 10-4 1 1.076 X 10-3 0.1550

1 Square Foot 9.290 X 10-2 929.0 1 144

1 Square Inch 6.452 X 10-4 6.452 6.944 X 10-3 1

Table 1.3 Unit Conversion of Volume

m3 cm3 liter ft3 in3

1 Cubic Meter 1 106 1000 35.31 6.102 X 10-4

1 Cubic cm 10-6 1 1.0 X 10-3 3.531 X 10-8 6.102 X 10-2

1 Liter 1.00 X 10-3 1000 1 3.531 X 10-2 61.02

1 Cubic Foot 2.832 X 10-2 2.832 X 104 28.32 1 1728

1 Cubic Inch 1.639 X 10-5 16.39 1.639 X 10-2 5.787 10-4 1

1.4. GEOMETRICAL SYMBOLS

Types of Tolerance Geometric Characteristics Symbol

Form Straightness

Form Flatness

Form Circularity

Form Cylindricity

Profile Profile of a line

Profile Profile of a surface

Orientation Perpendicularity

Orientation Angularity

Orientation Parallelism

Location Symmetry

Location Positional tolerance



Location Concentricity

Runout Circular runout

Runout Total runout


Department of Mechanical Engineering Page 2.1 Darshan Institute of Engineering & Technology, Rajkot

EXPERIMENT – 2

AIM: Practice of Measurement with Vernier caliper

2.1. INTRODUCTION

Vernier caliper is used to take internal as well as external linear dimensions of a

product such as length, width, diameter, height, thickness etc.

Construction and Working principle:

In vernier caliper there are two scales which can slide on each other. The graduations

on these two scales are having very minor difference. One of the scales is called main

scale and another is called vernier scale. This kind of arrangement provides accurate

measurement

(a)

(b)

Figure 2.1 Vernier caliper



2.2. MATERIAL

The vernier caliper is made out of 440C grade stainless steel. It is suitable because of

its superior wear resistance, hardness and a high ultimate tensile strength which

makes it able to withstand high stresses. In addition its ability to resist corrosion makes

it a popular choice.

2.3. LEAST COUNT

It is the smallest measurement which can be taken by vernier caliper.

Least count =Measurement of small division on main scale

total number of division on vernier scale

Smallest measurement on main scale is 1 mm and total 50 divisions on vernier scale.

Least count of this type of vernier is 1/50 = 0.02 mm.

2.4. PROCEDURE

Study the given vernier caliper and recognize its various parts.

Understand the vernier principle and calculate its least count.

Check errors, if any (zero adjustment)

Read the instrument for at least three random vernier positions.

Measure the samples at the indicated places and record dimension as per standard

Performa given.




Checking for zero error Observed reading Corrected reading

3.14 cm

(No zero error

correction

required) The two zero marks coincide no zero

error Reading = 3.14 cm

3.17 cm –

(+0.03)=3.14 cm

(The positive zero

error is

subtracted from

the reading)

Zero mark on vernier slightly to the

right –

Positive zero error of +0.03 cm

Reading = 3.17 cm

3.11 cm – (-

0.03)=3.14 cm

(The negative zero

error is added to

the reading)

Zero mark on vernier slightly to the

left –

negative zero error of -0.03 cm

Reading = 3.11 cm



Observations:

Range: __________________ mm

Least Count (L.C.):____________________ mm

Error of Vernier = __________________ mm

Observation Table:

Sr.

No

.

Object

feature

Main

Scale

Reading

(A)

Division of

Vernier Scale

Matching

with Main

Scale Division

(n)

Vernier

Scale

Reading

(B=n*LC)

Total

(C’=A+B)

Average

(C)

Corrected

Reading

(C-Error)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.



Observations:

Range: __________________ mm

Least Count (L.C.):____________________ mm

Error of Vernier = __________________ mm

Observation Table:

Sr.

No

.

Object

feature

Main

Scale

Reading

(A)

Dial reading

(n)

Vernier

Scale

Reading

(B=n*LC)

Total

(C=A+B)

Average

(C)

Corrected

Reading

(C-Error)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.



DRAWING OF GIVEN JOB

Mechanical Measurement & Metrology (2141901)

Department of Mechanical Engineering Prepared By: Paras G.Vegada Darshan Institute of Engineering & Technology, Rajkot Page 3.1

EXPERIMENT – 3

AIM: Practice of Measurement with Micrometer

3.1. INTRODUCTION

It is a precision measuring instrument having accuracy of 0.01 mm and working on

screw and nut principle.

3.2. WORKING PRINCIPLE

Micrometer is working on screw and nut principle. Spindle of the micrometer are

having threads of 0.5 mm pitch. The spindle is moving in fixed nut. Thimble is joined

with spindle. On the periphery of thimble 50 divisions are marked. By rotating the

thimble to 1 rotation (50 divisions), spindle can be moved forward or backward by 0.5

mm. So when thimble revolves by one division it moves forward or backward by 0.5/50

= 0.01 mm. This is the accuracy of measurement by micrometer.

3.3. CONSTRUCTION

Outside Micrometer:

Different parts of outside micrometer are explained as below:

Body or Frame: It is a U or C shaped frame made out of light alloy steel, cast steel or

malleable cast iron.

Anvil and Spindle: Fixed anvil is on left side of the frame whereas spindle is having

threads of 0.5 mm pitch. Spindle and anvil are made out of high grade tool steel and

job is held in between them.

Spindle clamp or lock nut: Lock nut is provided to hold the spindle at specific location.

Barrel and thimble: Reference line and main scale are provided on barrel. Thimble is

in cylindrical form attached with spindle. There are 50 divisions on thimble equally

spaced on periphery of the same. It is also called as circular scale.



(a)

(b)

Figure 2.1 Outside micrometer

Ratchet or friction stop: It is used to provide suitable pressure on the job to get

accurate reading. When spindle touches surface of the job, ratchet stop automatically

slips with typical noise. This will indicate the operator to stop applying pressure on the

job.

Inside Micrometer:

Different parts of inside micrometer are explained as below:

Measuring head (Micrometer unit): It consists of a barrel and a thimble similar to the

outside micrometer. It has no frame and spindle.

Extension rods: A series of extension rods are provided in order to obtain a wide

measuring range.

Spacing collar: These are intended for smaller adjustments in the range of

measurement. The ends of the spacing collars are well finished by lapping and are flat

and mutually parallel and square to the axis

Handle: For measuring bores of comparatively small diameters, a handle is provided

which can be screwed into a radial hole in the barrel.



Least Count:

Least count =Pitch of spindle screw

No. of division on circular scale

=0.5

50= 0.01 mm

3.4. PROCEDURE

1. Study the given Micrometer and recognize its various parts. Understand the

Micrometer and Calculate its Least Count. Check for Errors, if any. Read the instrument

for at least three random spindle positions.

Figure 2.2 Inside micrometer

3.5. PRECAUTIONS IN THE USE OF MICROMETER

1. First clean the micrometer by wiping of oil dirt, dust and grit etc.

2. Clean the measuring faces of the anvil and spindle with a clean piece of paper or cloth.

3. Set the zero reading of the instrument before measuring.

4. Hold the part whose dimension is to be measured and micrometer properly. Then turn

the thimble with forefinger and thumb till the measuring tip just touches the part and

find adjustment should be made by ratchet so that uniform measuring pressure is

applied.

5. While measuring dimensions of circular parts, the micrometer must be moved

carefully over representative arc so as to note maximum dimension only.




Checking for zero error Observed reading Corrected reading

2.25 mm

(No zero error

correction required) Zero mark on thimble scale

coincides with datum line on the

main scale and reading on main

scale is 0, Zero error

Reading = 2.0 + 0.25

= 2.25 mm

2.32 mm –

(+0.07)=2.25 mm

(The positive zero

error is subtracted

from the reading)

Zero mark on datum line can be

seen– Positive zero error of +0.07

mm

Reading = 2.0 + 0.32

= 2.32 mm

2.23 mm – (-

0.02)=2.25 mm

(The negative zero

error is added to

the reading)

Zero mark on datum line cannot

be seen – negative zero error of -

0.02 mm

Reading = 2.0 + 0.23

= 2.23 mm



Observations:

Range: __________________ mm

Least Count (L.C.):____________________ mm

Error of Micrometer = __________________ mm

Observation Table of outside micrometer:

Object

Feature

Sr.

No.

Main

Scale

Reading

(A)

Division of

Circular

Scale

Matching

with Main

Scale

(n)

Micrometer

Scale

Reading

(B=n*LC)

Total

(C’=A+B)

Average

(C)

Corrected

Reading

(C-Error)



Observations of Vernier micrometer:

Range: __________________ mm

Least Count (L.C.):____________________ mm

Error of Micrometer = __________________ mm

Observation Table:

Object

Feature

Sr.

No.

Main

Scale

Reading

(A)

Division

of

Circular

Scale

Matching

with

Main

Scale

(n)

Micrometer

Scale

Reading

(B=n x LC of

thimble)

Vernier scale

reading(C=n x

LC of Vernier

scale)

Total

(D=A+B+C)

Average

(E)

Corrected

Reading

(E-Error)

Conclusion:



EXPERIMENT – 4

AIM: Practice of Measurement with Vernier Height Gauge

4.1. INTRODUCTION

Vernier height gauge is similar to vernier caliper but in this instrument the graduated

bar is held in a vertical position and it is used in conjunction with a surface plate. The

vernier height gauge is designed for accurate measurement and marking of vertical

height above a surface plate datum. It can also be used to measure differences in

heights by taking the vernier scale reading at each height and determining the

difference by subtraction. Vernier height gauge works on the Vernier principle.

4.2. CONSTRUCTION

Figure 2.3 Vernier Height Gauge

A vernier height gauge consists of (i) a finely grow and lapped base. The base is massive

and robust in construction to ensure rigidity and stability. A vertical graduated beam

or column supported on a massive base (iii) Attached to the beam is a sliding vernier

head carrying the vernier scale and a clamping screw. (iv) An auxiliary head which is



also attached to the beam above sliding vernier head. It has fine adjusting and

clamping screw. (v) A measuring jaw or a scriber attached to the front of sliding

vernier.

Least Count:

Least count =Measurement of small division on main scale

total number of division on vernier scale

=1

50= 0.02 mm

4.3. PROCEDURE

Clean the working platform and put the vernier height gauge on it.

Fix the measuring jaw of the vernier height gauge.

Clean the measuring jaw of the vernier height gauge.

Loosen the locking screw of the height gauge.

Clean the measuring surface of the item being measured with clean cloth (or soaked

with cleaning oil.

Make the measuring jaw and platform surface gently touch.

Get the reading from the vernier height gauge.

4.4. PRECAUTIONS IN THE USE OF VERNIER HEIGHT GAUGE

1. The measuring jaw should have a clear projection from the edge of the beam at least

equal to the projection of the base from the beam.

The upper and lower gauging surfaces of the measuring jaw shall be flat and parallel

to the base. The scriber should also be of the same nominal depth as the measuring

jaw so that it may be reversed.

The projection of the jaw should be at least 25mm.

The slider should have a good sliding fit for all along the full working length of the

beam



Observations:

Range: __________________ mm

Least Count (L.C.):____________________ mm

Error of Vernier Height Gauge = __________________ mm

Observation Table:

Sr,No. Object

Feature

Main

Scale

Reading

(A)

Division of

Vernier Scale

Matching

with Main

Scale

(n)

Vernier

Scale

Reading

(B=n*LC)

Total

(C’=A+B)

Average

(C)

Corrected

Reading

(C-Error)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.



Conclusion:



EXPERIMENT – 5

AIM: Practice of measurement with slip gauge

5.1. INTRODUCTION

Slip gauges are rectangular blocks of high grade steel with exceptionally close

tolerances. It can also be made of tungsten carbide. These blocks are suitably

hardened through out to ensure maximum resistance to wear. They are then stabilized

by heating and cooling successively in stages so that hardening stresses are removed,

after being hardened they are carefully finished by high grade lapping to a high degree

of finish, flatness and accuracy. For successful use of slip gauges their working faces

are made truly flat and parallel. The slip gauge having a cross section of about 9mm X

30mm for sizes up to 10mm and 9mm X 35mm for larger sizes.

Figure 2.6 Slip gauge

5.2. GRADE OF SLIP GAUGE

Indian standard specifications for slip gauges (IS 2984-1966) specifies grade as follows:

Grade 00: These are placed in the standard room and used for highest precision work.

Grade 0: is used in Laboratories and tool room which serves as standard for

periodically checking the accuracy of Grade I & grade II gauges.

Grade I: It is of higher accuracy and used in inspection departments.

Grade II: These are used in workshops during actual production of components, tools

and gauges.



5.3. SLIP GAUGE SET

Slip gauges are generally available in sets. The following two sets of slip gauges are in

general uses as follows.

Normal set (M-45)

Range (mm) Increment (mm) No. of pieces

1.001 to 1.009 0.001 9

1.01 to 1.09 0.01 9

1.0 to 1.9 0.1 9

1.0 to 9.0 1.0 9

10.0 to 90.0 10.0 9

Total 45 Pieces

Special set (M-87)


1.001 to 1.009 0.001 9

1.01 to 1.49 0.01 49

0.5 to 9.5 0.5 19

10.0 to 90.0 10.0 9

1.005 - 1

Total 87 Pieces

Set (M-112/1)


1.001 to 1.00 0.001 9

1.01 to 1.49 0.01 49

0.5 to 24.50 0.5 49

25.00 to 100.00 25.00 4

1.0005 - 1

Total 112/1 Pieces



5.4. WRINGING OF SLIP GAUGE

Wringing is the process of sliding two blocks together so that their faces lightly bond.

One slip gauge is oscillated slightly over the other gauge with a light pressure

One gauge is then placed at 900 to other by using light pressure and then it is rotated

until the blocks one brought in one line.

In this way air is expelled out from between the gauge faces causing the gauge blocks

to adhere. The adhesion is caused partly by molecular attraction and partly by

atmospheric pressure.

5.5. SELECTION OF SLIP GAUGE FOR GIVEN DIMENSION:

Take the following things into account when selecting gauge blocks:

Use the minimum number of blocks whenever possible.

Select thick gauge blocks whenever possible.

Select the size from the one that has the least significant digit.

5.6. PRECAUTION

1. Remove protective coating applied to it with petrol.

2. Clean gauges to be used with soft linen cloth.

3. During the actual use, the fingering of lapped faces should be avoided.

4. Use the standard wringing process for assembly.

5. If during wringing process, any sign of roughness or scratching is felt the process of

wringing should be stopped and faces examined for burns or scratches.

6. After use of slip gauge, it should not be left wrung together.



Exercises:

Select most appropriate Slip gauges for following dimensions.

34.4785 72.9825 26.1535 29.758

43.716 92.357 59.316



EXPERIMENT – 6

AIM: Practice of calibration with slip gauge

6.1. INTRODUCTION

1. Vernier Caliper 2. Outside Micrometer 3. A set of slip Gauges

6.2. PROCEDURE

1. Check the Micrometer for smooth running over its whole range.

2. Clean its anvils carefully.

3. Set the micrometer on its stand horizontally with anvils upwards.

4. Allow the micrometer to cool to the ambient temperature for 10 minutes.

5. Close the micrometer anvils and take the zero error reading.

6. Clean the slip gauges which are to be used for measurements.

7. Take reading with various slips starting from minimum to maximum at equal intervals.

8. Tabulate the readings and plot the graph of normal reading (slip gauge reading) v/s

error.

9. Interpret the graph.

10. Report the same procedure for vernier caliper.



Observations:

Outside Micrometer

Range = ________________mm

Least count = ________________mm

Zero Error = ________________mm

Correction = ________________mm

Observation Table:

Sr.

No.

Slip Gauge

Value

mm

Micrometer

Reading

mm

Error

mm

Sr.

No

.

Slip Gauge

Value

mm

Micrometer

Reading

mm

Error

mm

1. 9.

2. 10.

3. 11.

4. 12.

5. 13.

6. 14.

7. 15.

8. 16.



Vernier Caliper:

Range = ________________mm

Least count = ________________mm

Zero Error = ________________mm

Correction = ________________mm

Observation Table:

Sr.

No.

Slip Gauge

Value

mm

Vernier

Caliper

Reading

mm

Error

mm

Sr.

No.

Slip Gauge

Value

mm

Vernier

Caliper

Reading

mm

Error

mm

1. 9.

2. 10.

3. 11.

4. 12.

5. 13.

6. 14.

7. 15.

8. 16.

Conclusion:



EXPERIMENT – 7

AIM: Practice of measurement with bevel protector

7.1. INTRODUCTION

A (universal) bevel protractor is used to measure angles of objects. You might see it

used with various objects, including jigs, and when producing engineering/machine

drawings.

7.2. CONSTRUCTION

Various Components of Bevel Protectors are given as follow:

Body: It is designed in such a way that its back is flat and there are no projections

beyond its back so that when the bevel protector is placed on its back on a surface

plate there shall be no perceptible rock. The flatness of the working edge of the stock

and body is tested by checking the squareness of blade with respect to stock when

blade is set at 900.

Figure 3.1 Bevel Protector



Stock: The working edge of the stock is about 90 mm in length and 7 mm thick. It is

very essential that the working edge of the stock be perfectly straight and if at all

departure is there, it should be in the form of concavity and of the order of 0.01 mm

maximum over the whole span.

Blade: It can be moved along the turret throughout its length and can also be reversed.

It is about 150 or 300 mm long, 13 mm wide and 2 mm thick and ends beveled at

angles of 450 and 600 within the accuracy of 5 minutes of arc. Its working edge should

be straight upto 0.02 mm and parallel upto 0.03 mm over the entire length of 300 mm.

It can be clamped in any position.

Actual Angle Attachment: It can be readily fitted into body and clamped in any

position. Its working edge should be flat to within 0.005 mm and parallel to the

working edge of the stock within 0.015 mm over the entire length of attachment.

The bevel protectors are tested for flatness, squareness, parallelism, straightness and

angular intervals by suitable methods.

Least Count:

The vernier scale has 12 divisions each side of the centre zero. These 12 divisions

occupy the same space as 23 degrees on the main scale. Therefore each division of

the vernier is equal to 1/12 of 230 or

0

12

111

. Since 2 divisions on the main scale equals

2 degrees of arc, the difference between 2 divisions on the main scale and one division

on the vernier scale is 20-

0

12

111

= 1/120= 5 minutes of arc.

7.3. PROCEDURE

The given work piece is cleaned before taking measurement.

The fixed blade of the bevel protractor is made to coincide with the reference surface

of work piece.

Move the movable blade of protractor to coincide with outer surface.

The angle between the blades is taken from protractor after noting main scale and

vernier scale reading.



Figure 3.2 How to read Bevel Protector

7.4. PRECAUTIONS IN THE USE OF BEVEL PROTECTOR

Angle of instrument must coincide with the angular scale

Clean the measuring faces with paper or cloth. Keep the instrument in the box

properly.

Set the zero reading of the instrument before measuring

Gripped the instrument to the measuring face exactly




Observations table of bevel protector:

Range: __________________

Least Count (L.C.):____________________

Error of Bevel Protector = __________________

Sr No. Object

Feature

Main Scale

Reading

(A)

Division of

Vernier Scale

Matching

with Main

Scale Division

(n)

Vernier

Scale

Reading

(B=n*LC)

Total

(C’=A+B)

Average

(C)

Corrected

Reading

(C-Error)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.



Conclusion:



EXPERIMENT – 8

AIM: Practice of measurement with sine bar

8.1. INTRODUCTION

A sine bar consists of a hardened, precision ground body with two precision ground

cylinders fixed at the ends. The distance between the centers of the cylinders is

precisely controlled, and the top of the bar is parallel to a line through the centers of

the two rollers. The dimension between the two rollers is chosen to be a whole

number (for ease of later calculations) and forms the hypotenuse of a triangle when

in use.

When a sine bar is placed on a level surface the top edge will be parallel to that

surface. If one roller is raised by a known distance, usually using gauge blocks, then

the top edge of the bar will be tilted by the same amount forming an angle that may

be calculated by the application of the sine rule.

Apparatus:

Sine bar, Slip gauge, Surface Plate, Clamps Lightening work piece, Dial indicator with

stand, Taper work pieces

8.2. WORKING PRINCIPLE

Sine bar is based upon laws of trigonometry. To set a given angle one roller of the bar

is placed on the surface plate and the combination of slip gauges is inserted under the

second roller as shown in the figure 8.1 If h is the height of the combination of the slip

gauges, l is the distance between roller centers,

Then, θ = sin-1 (h/l)

The angle can be measured as a function of sine. Thus, it is called sine bar.

8.3. CONSTRUCTION

It consists of a steel bar and two rollers. The sine bar is made of high carbon, high

chromium corrosion resistant steel, suitable hardened precision ground and

stabilized. The rollers are of accurate and equal diameters. They are attached to the



bar at each end. The axes of these rollers are parallel to each other and upper surface

of the bar.

Figure 8.1 Sine Bar

l = distance between centres of ground cylinders

h = height of the gauge blocks

𝜃 = the angle of the plate

8.4. PROCEDURE

The sine bar is made to rest on surface plate with rollers contacting the datum.

Place the component on sine bar and lock it in position.

Lift one end of the roller of sine bar and place a pack of slip gauge, underneath the

roller.

The dial gauge is set at one end of the work and move along the upper surface of the

component.

If there is a variation in parallelism of the upper surface of the component and the

surface plate, it is indicated by the dial gauge.

The combination of slip gauge is so adjusted that the upper surface of the component

is truly parallel with the surface plate.

The angle of the component is then calculated by the relation 𝜃 = sin−1(ℎ𝑙⁄ )



8.5. LIMITATIONS

Sine bar is reliable for angles less than 150, and becomes increasingly inaccurate as the

angle increases. It is impractical to use sine bars for angle above 450.

It is physically clumsy to hold in position.

Slightly errors of the sine bar cause larger angular errors.

Size of the parts which can be impacted by sine bar is limited.

8.6. SOURCE OF ERROR

1. Error in distance between roller centers.

2. Error in parallelism between the gauging surface and plane of roller axes.

3. Error in parallelism of roller axes with each other.

4. Error in flatness of the upper surface of the bar.

Observation of sine bar:

Sr. No. Object

Feature

Slip gauge height,

h

Distance between

roller(l) Angle

1 𝜃1

Calculation:

sin 𝜃 =ℎ

𝑙

∴ 𝜃 = sin−1 (ℎ

𝑙)

= ________

Observation of sine bar:

Sr. No. Object

Feature Reading (R1) Reading (R2)

Distance between

roller(l) Angle

1 𝜃1

Calculation:

sin 𝜃 =R1 − R2

𝑙

∴ 𝜃 = sin−1 (R1 − R2

𝑙)

= ________



Conclusion:



EXPERIMENT – 9

AIM: To study about roughness of surfaces.

9.1. INTRODUCTION:

Surface finish is the most important property of any industrial product, as it describes

its surface texture. It determines the deviations from the nominal surface described

by an engineering drawing.

9.2. SURFACE TEXTURE:

The surface texture may be defined as “The characteristic quality of an actual surface

due to small departures from its general geometrical form which, occurring at regular

or irregular intervals, tend to form a pattern or texture on the surface.”

9.2.1 Element of Surface Texture:

Figure 9.1 the general character of a machined surface, highly magnified which in

general can be considered a pattern of hills and valleys.

Figure 9.1 Elements of surface texture

Roughness (Primary Texture): The surface irregularities of small wavelength are

known as roughness or primary texture. Waviness



(Secondary Texture): The surface irregularities of considerable wavelength of a

periodic character are known as waviness or secondary texture.

Flaws: there are surface irregularities which occur at one place or at relatively

infrequent or widely varying intervals in a surface. Lay: It is the direction of the

‘predominant surface pattern’ ordinarily determined by the method of production

used.

9.3. SURFACE ROUGHNESS TESTER:

Principle:

When the stylus is moved over the surface which is to be measured, the irregularities in the

surface texture are measured and it is used to assess the surface finish of the work piece.

Figure 9.2surface roughness tester

Working:

The stylus type instruments consist of skid, stylus, amplifying device and recording device. The

skid is slowly moved over the surface by hand or by motor drive. The skid follows the

irregularities of the surface and the stylus moves along with skid.

When the stylus moves vertically up and down and the stylus movements are magnified,

amplified and recorded to produce a trace. Then it is analyzed by automatic device.

Indication of Surface Roughness Symbols Used:

As per IS:969 surface texture specified by indicating the following main characteristics

in the symbols:

1. Roughness value i.e. Ra value in 𝜇𝑚.

2. Machining allowance in mm.

3. Sampling length or instrument cut-off length in mm.



4. Machining/production method, and

5. Direction of lay in the symbol form as =, ⊥, X, M, C, R.

Figure 9.3 Indication of surface roughness



Ra Value and Grade Number:

Table 9.1 Ra value and grade number


Darshan Institute of Engineering & Technology, Rajkot 10.1


EXPERIMENT – 10

AIM: To study about limit gauges.

10.1. INTRODUCTION:

Gauging, done in manufacturing processes, refers to the method by which it is

determined quickly whether or not the dimensions of the checking parts in

production, are within their specified limits.

It is done with the help of some tools called gauges. A gauge does not reveal the actual

size of dimension.

High carbon and alloy steels have been the principal material used for many years.

Objections to steel gauges are that they are subjected to some distortion because of

the heat treating operations and that their surface hardness is limited.

These objections are largely overcome by the use of chrome plating or cemented

carbides as the surface material. Some gauges are made entirely of cemented carbides

or they have cemented carbides inserted at certain wear points

10.2. LIMIT GAUGE:

A gauge having arrangement for checking maximum and minimum limits of product is

called limits gauge. Having two members of different size called as ‘Go’ and ‘No Go’

members. Length of ‘Go’ member is larger because it has to pass through or above the

product for checking.

Quantity of product getting accepted through ‘Go’ member is generally larger than

quantity rejected by ‘No Go’ member. Therefore, ‘Go’ member is having excessive

wear and tear and that is why it needs larger bearing surfaces.

10.2.1 Plug gauge

This gauge is used to check internal details of the product such as hole diameter. It is

manufactured from hardened steel which can resist wear during checking. ‘Go’

member of plug gauge will have dimension equal to lower limit of hole dimension.

‘No Go’ member will have dimension equal to higher limit of the hole dimension.

Different types of plug gauges are shown in figure 10.1.




(a)Double ended limit plug gauge (b) Progressive limit plug gauge

(c) Single ended limit plug gauge

Figure 10.1 Types of plain plug gauges

10.2.2 Snap and ring gauge

They are used to check the external details of the product such as diameter of the

shaft, thickness of block etc.

Snap gauge is used to check cylindrical as well as non-cylindrical work pieces. Ring

gauge is used only for cylindrical work pieces.

Adjustable snap gauge can check different sized within some limit but it is costlier than

simple snap gauge. ‘Go’ member of snap or ring gauge will have dimension equal to

higher limit of shaft and ‘No Go’ member will have dimension equal to lower limit of

the shaft.

Figure10.2 Snap gauge and ring gauge




10.2.3 Taper Gauges:

The most satisfactory method of testing a taper is to use taper gauges. They are also

used to gauge the diameter of the taper at some point.

Taper gauges are made in both the plug and ring styles and, in general, follow the

same standard construction as plug and ring gauges. A taper plug and ring gauge is

shown in Figure 10.3.

Figure 10.3 Taper plug and ring gauges

10.2.4 Thread Gauges:

Thread gauges are used to check the pitch diameter of the thread. For checking

internal threads (nut, bushes, etc.), plug thread gauges are used, while for checking

external threads (screws, bolts, etc.), ring thread gauges are used.

Common types of thread gauges are shown in following figure 10.4.

Figure 10.4 Thread plug and ring gauges

A Go thread plug gauge checks that the internal thread fits the counterpart external

thread.

Thus it checks that the minimum pitch diameter has been maintained, which includes

the effects of pitch, flank angle and thread profile deviations, which apparently reduce




the pitch diameter. It also checks that the minimum major diameter has been

maintained. This gauge does not check the minor diameter of the internal thread.

A No Go thread plug gauge checks that the specified maximum pitch diameter has not

been exceeded.

10.2.5 Thread pitch gauge:

Thread pitch gauges are used as a reference tool in determining the pitch of a thread

that is on a screw or in a tapped hole.

This tool is not used as a precision measuring instrument. This device allows the user

to determine the profile of the given thread and quickly categorize the thread by

shape and pitch.

Figure 10.5 Thread pitch gauge

10.2.6 Radius gauge:

Radius gauges require a bright light behind the object to be measured. The gauge is

placed against the edge to be checked and any light leakage between the blade and

edge indicates a mismatch that requires correction.

Every leaf has a different radius. The material of the leaves is stainless steel. It is of

two types: 1. Internal 2. External. It is used to check the radius of inner and outer

surfaces.

Figure 10.6 Radius gauge

https://en.wikipedia.org/wiki/Thread_pitch_gauge

https://en.wikipedia.org/wiki/Thread_pitch_gauge




10.2.7 Feeler gauge:

A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in

engineering to measure the clearance between two parts.

They consist of a number of small lengths of steel of different thicknesses with

measurements marked on each piece.

They are flexible enough that, even if they are all on the same hinge, several can be

stacked together to gauge intermediate values.

Figure 10.7 Filler gauge

10.2.8 Wire gauge:

In commerce, the sizes of wire are estimated by a device, also called gauges, which

consist of plates of circular or oblong form having notches of different widths around

their edges to receive wire and sheet metals of different thicknesses.

Each notch is stamped with a number, and the wire or sheet, which just fits a given

notch, is stated to be of, say, No. 10, 11, 12, etc., of the wire gauge.

Figure 10.8 Wire gauge

https://en.wikipedia.org/wiki/Tool

https://en.wikipedia.org/wiki/Engineering

https://en.wikipedia.org/wiki/Gauge_(engineering)

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