metrology laboratory iii b.tech i semester · pdf fileexperiment - 4 bevel protractor and sine...

DEPARTMENT OF MECHANICAL ENGINEERING

Department of ME, SVCET, CHITTOOR

SRI VENKATESWARA COLLEGE OF ENGINEERING & TECHNOLOGY (AUTONOMOUS)

Accredited by NBA, NAAC & AICTE New Delhi (Affiliated J.N.T. University, Ananthapuramu)

Department of Mechanical Engineering R.V.S. NAGAR, CHITTOOR

METROLOGY LABORATORY

III B.TECH – I SEMESTER (2015-16)

Name of the student : …………………………………………….

Roll No. : …………………………………………….

Year : …………………. Semester ……………

Department : …………………………………………….



INDEX

S. No. Date of

experiment Name of the experiment Signature



Experiment - 1

VERNIER CALIPERS

Aim: To measure the length, height and diameter using vernier calipers.

Apparatus: vernier caliper, slip gauges, round rod.

Principle: Vernier Calipers is the most commonly used instrument for measuring outer and inner diameters. It

works on the principle of Vernier Scale which is some fixed units of length (Ex: 49mm) divided

into 1 less or 1 more parts of the unit (Ex: 49mm are divided into 50 parts). The exact measurement

with up to 0.02mm accuracy can be determined by the coinciding line between Main Scale and

Vernier Scale.

Total Reading = M.S.R + L.C * V.C

Where:

M.S.R – Main Scale Reading

L.C – Least Count

V.C – Vernier Coincidence

Procedure: 1. The Least Count is to be determined as L.C= 1MSD - 1VSD = 1- 49/50 =0.02mm.

2. The workpiece is placed between the jaws of Vernier Calipers correctly.

3. The reading on Main scale which is just behind the first Vernier Scale Division is noted as Main

Scale Reading.

4. The Division on Vernier Scale which coincides with the line on Main Scale is noted down as

Vernier Coincidence.

5. The length, height and diameter can be calculated using the given Formula.

Precautions: 1. Clean the measuring faces with paper or cloth.

2. Make sure the workpiece axis is perpendicular to the Vernier Calipers.

3. The calipers should not be fitted or twisted.

4. Don’t apply pressure on jaws.



Calculations:

For length measurement

Sl. No. MSR VSR VSR*LC TR=MSR+(VSR*LC)

(mm)

1.

2.

3.

4.

For height measurement


(mm)

1.

2.

3.

4.

For diameter measurement


(mm)

1.

2.

3.

4.



Result: Physical quantities like length, height and diameter of the given specimens are measured using

vernier calipers.



Experiment - 2

MICROMETER

Aim: To measure the length and diameter using micrometer.

Apparatus: Micrometer, slip gauges, round rod.

Principle: Micrometer is one of the most common and most popular forms of measuring instrument for precise

measurement with 0.01mm accuracy. It works on the principle of screw and nut. We know that

when a screw is rotated through one revolution it advances by one pitch distance i.e. one rotation of

screw corresponding to a linear movement of a distance equal to pitch of the screw thread.

Procedure: 1. The least count is to be determined.

2. The workpiece is placed between the two anvils after the instruments are adjusted for zero error.

3. Work piece is held strongly without applying any pressure on the instrument.

4. The value of the main scale is noted down. The main scale division just coincides with the index

line.

5. Take the thimble scale reading (TSR) which coincides with the reference line on the sleeve.

Length/diameter of the work piece = main scale reading + L.C. * TSR

Precautions: 1. Clean the measuring faces of paper or cloth.

2. Set the zero reading of the instrument to before measuring.



Result: Physical quantities like length and diameter of the given specimens are measured using micrometer.



Calculations:

For length measurement

Sl. No. MSR TSR TSR*LC TR=MSR+(TSR*LC)

(mm)

1.

2.

3.

4.

For diameter measurement

Sl. No. MSR TSR TSR*LC TR=MSR+(TSR*LC)

(mm)

1.

2.

3.

4.



Experiment - 3

GEAR TOOTH VERNIER

Aim: To measure the thickness of gear teeth at the pitch line or chordal thickness of teeth and the distance

from the top of a tooth the chord i.e. Addendum using gear tooth caliper.

Apparatus: Gear tooth vernier caliper, Spur gear of known module, surface plate.

Theory: Tooth thickness is the arc distance measured along the pitch circle from its intercept with one flank

to its intercept with the other flank of the tooth.

Tooth thickness = π m/2 where m is the module

m=D/N

N=no. of teeth

D=Pitch circle diameter of the gear.

Addendum is the radial distance from the tip of a tooth to the pitch circle. In the most of the cases, it

is sufficient to measure the chordal thickness i.e. the chord joining the intersection of the tooth

profile with the pitch circle because it is difficult to measure length of the arc directly.

Figure: Chordal thickness method

Now, from figure

W = AB = 2AD

angle, AOD = θ = 360/4T



where T = number of teeth,

w = 2 AD = 2 x A O sin θ

i.e. , w = 2R sin 360/4T (R = Pitch circle radius)

Module m=P.C.D/No. of teeth

= 2R/T

Therefore, R = Tm/2

and w = 2 Tm/2 . sin (360/4T)

i.e. , w = T. m sin (90/T)

Also from figure

d = OC – BD

But OC = OE + addendum = R + m

= Tm/2 + m

and OD = R cos θ

= Tm/2 cos (90/T)

Therefore, h= Tm/2 + m - Tm/2 cos (90/T)

i.e. , = Tm/2 (1+ 2/T - cos (90/T))

or = m + Tm/ 2 (1 - cos (90/T))

Procedure: 1. The given gear caliper is held over the gear and the slide is moved down so that it touches the

top of the gear tooth.

2. The jaws are made to have contact with the tooth on either side by adjusting the knob.

3. The reading on vertical scale i.e. addendum is noted down.

4. The reading on horizontal scale i.e. tooth thickness is noted down.

5. The above procedure is repeated for three times and readings are noted.

Precautions: 1. Clean the measuring faces of paper or cloth.

2. Set the zero reading of the instrument to before measuring.

Result: The addendum and tooth thickness of spur gear are measured using gear tooth vernier caliper.



Calculations:

For tooth thickness


(mm)

1.

2.

3.

4.

For addendum


(mm)

1.

2.

3.

4.



Experiment - 4

BEVEL PROTRACTOR AND SINE BAR

Aim: To measure the angle of the given workpiece using bevel protractor and sine bar.

Apparatus: Sine bar, workpiece, dial gauge, slip gauges, bevel protractor.

Theory:

Sine bar

The sine principle uses the ratio of the length of two sides of a right triangle in deriving a given

angle. The accuracy with which the sine principle can be put to use is dependent in practice, on

some form of linear measurement. The sine bar in itself is not a complete measuring instrument.

Sine bars in conjunction with slip gauges constitute a very good device for the precise measurement

of angles. The arrangement is based on the fact that for any particular angle θ the sides of a right

angled triangle will have precise ratio, i.e., Sin θ = h/L

If h and L could be measured accurately, θ can be obtained accurately. The value of h is built-up by

slip gauges and value L is constant for a given sine bar.

Bevel protractor

A universal bevel protractor is used to measure angles between two planes. This consists of stem,

which is rigidly attached to main scale and a blade, which is attached to the vernier scale and can be

rotated to read angles. To improve the accessibility, the blade can also slide. It should be noted that

the divisions on the main scale is in degrees and that the fractional divisions of degrees are minutes

(i.e. with 60 minutes/degree, denoted).

Procedure:

Sine bar 1. Place the work piece/wedge above the sine bar and make it horizontal with the base.

2. The dial gauge is then set at one end of the work moved along the upper surface of the

component.

3. If there is any variation in parallelism of the upper surface of the component and the surface

plate, it is indicated by the dial gauge.

4. The combination of the slip gauges is so adjusted that the upper surface is truly parallel with the

surface plate.

5. Note down the values of the slip gauges.

6. Calculate the angle using θ=Sin-1(h/L)

7. Repeat the procedure 3 or 4 times and take the average.



Calculations:

For sine bar

Sl. No. HEIGHT(h) LENGTH(L) ANGLE, θ=Sin-1(h/L)

1.

2.

3.

4.

For bevel protractor

Sl.

No.

TRIAL-1 TRIAL-2 TRIAL-3 TRIAL-4 ANGLE OBTAINEDBY BEVEL

PROTRACTOR=(90- θ)

1.

2.

3.

4.



Bevel protractor

1. The least count is calculated by knowing the value of the smallest division on the main scale and

number of division on the vernier scale.

2. To measure angle between two planes, rest the stem on one of the planes (reference plane).

3. Rotate the blade such that blade is flush with second plane.

4. Readings are taken after ensuring that the stem and blade are in flush with the two planes.

5. Lock the protractor at this point and note down the readings.

Precautions: 1. The sine bar should not be used for angle greater than 600 because any possible error in

construction is accentuated at this limit.

2. A compound angle should not be formed by misaligning of work piece with the sine bar. This

can be avoided by attaching the sine bar and work against an angle plate.

3. As far as possible longer sine bar should be used since using longer sine bars reduces many

errors.

Result: The angle of the given specimen is measured using bevel protractor and sine bar.



Experiment - 5

ALIGNMENT TESTS ON LATHE

Aim: To perform alignment tests on lathe.

Apparatus: Dial gauge, test mandrel, spirit level.

Procedure: 1. True running of head stock centre:

The feeler of dial indicator should be pressed perpendicular to the taper surface of the head

stock spindle and spindle is rotated. The deviation is indicated by dial gauge given the trueness of

centre. Permissible error is 0.01 mm.

2. True running of taper socket in main spindle:

The test mandrel is held with its taper shank in the head stock spindle socket. The dial gauge

is mounted on the saddle such that its feeler touches the test mandrel then the saddle is travelled

longitudinally along the bed ways and the readings are taken. Permissible error is 0.02 mm.

3. Movement of upper slide parallel with main spindle in vertical plane:

The test mandrel is fitted in to the spindle. The dial gauge is clamped on the upper slide such

that its feeler touches the top surface of the test mandrel. The slide is traversed along the mandrel

and readings are taken. Permissible error is 0.02 mm.

4. True running of locating cylinder of main spindle:

The dial gauge is mounted on the bed such that its feeler touches a point on main spindle.

Then the main spindle is rotated by hand and readings of dial gauge are taken. Permissible error is

0.01 mm.

Precautions: Before conducting the alignment test, it is essential to check the flatness by using the spirit level.



Calculations:

True running of head stock centre

Position 1 2 3 4

Error

True running of taper socket in main spindle

Position 1 2 3 4

Error

Movement of upper slide parallel with main spindle in vertical plane

Position 1 2 3 4

Error

True running of locating cylinder of main spindle

Position 1 2 3 4

Error



Result: Alignment tests are performed on lathe and observed that the errors are within the permissible

values.



Experiment - 6

ALIGNMENT TESTS ON MILLING MACHINE

Aim: To perform alignment tests on milling machine.

Apparatus: Dial gauge, test mandrel, spirit level.

Procedure: 1. Flatness of work table in longitudinal and transverse direction:

A spirit level is placed directly on the table at points about 25 to 30 cm apart, at A, B, C for

longitudinal tests and D, E and F for the transverse test. Then readings are noted. Permissible error

in longitudinal and transverse is ±0.04 mm.

2. True running of internal taper of main spindle:

The test mandrel is held with its taper shank in the main spindle socket. The dial gauge is

mounted on the table such that its feeler touches the test mandrel. Spindle is rotated and dial gauge

readings are noted at two different positions. Permissible error is 0.02 mm.

3. Parallelism of the work table surface to the main spindle:

The table is adjusted in the horizontal plane by a spirit level and is then set in its mean

position longitudinally. The mandrel is fixed in the spindle taper. Dial gauge is mounted on the

table such that its feeler touches the lower surface of the mandrel Readings are taken at two

positions by moving the stand of the dial gauge. Permissible error is 0.02 mm.

Precautions: Before conducting the alignment test, it is essential to check the flatness by using the spirit level.



Calculations:

Flatness of work table in longitudinal and transverse direction

Position A B C

Error

Position D E F

Error

True running of internal taper of main spindle

Position 1

Point 1 2 3

Error

Position 2

Point 1 2 3

Error

Parallelism of the work table surface to the main spindle

Position 1

Point 1 2 3

Error

Position 2

Point 1 2 3

Error



Result: Alignment tests are performed on milling machine and observed that the errors are within the

permissible values.



VERNIER CALIPERS

MEASUREMENT OF THICKNESS OF PLATE USING VERNIER CALIPERS



DIAL INDICATOR



SINE BAR

MEASUREMENT OF ANGLE USING SINE BAR

metrology laboratory iii b.tech i semester · pdf fileexperiment - 4 bevel protractor and sine...

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