Download - Metrology Lab -Manual

Metrology lab manual….

Ravi.K, Dept. of I&P Engg., PESCE, Mandya, Karnataka

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Metrology Laboratory

Subject code: Duration of Exam: 3Hours

1. Calibration of micrometer using slip gauge or height master.

2. Calibration of Vernier caliper using slip gauge or height master.

3. Calibration of height gauge using slip gauge or height master.

4. Calibration of straight edge by Wedge method.

5. Measurement of dovetail angle and checking the taper angle of taper plug.

6. Angle measurement using – Combination sets, Universal bevel protector, Optical bevel protector,

Sine bar and Since Center.

7. Screw thread measurement using – Two wire method, three wire method, Pitch gauge and Profile

projector.

8. Auto Collimator

9. Gear tooth measurement using – Gear tooth Vernier Caliper, Constant chord method

10. Calibration of Height gauge

11. Profile Projector andTool Maker Microscope

12. Study and measurement of surface finish by surface finish tester,

13. Roundness or Circularity testing.



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Expt. No – 01

CALIBRATION OF MICROMETER

Theory:

Write brief theory about slip gauges; classification, specification, uses and care to be taken before and

after using.

A micrometer is used to measure the external diameter of small cylinders, sphere etc.

It has a V – shaped structure to which a handle is attached. Two anvils are fixed to the inner

surface of the block. The job to be measured is placed between the anvils and held in position by

rotating the handle. The end of the screw forms one measuring tip and the other measuring tip is

constituted by a stationary anvil in the base of the frame. The screw is threaded for certain distance and

plain for the remaining distance. The screw’s plain portion is called ‘sleeve’ and its end is the

measuring surface.

Procedure:-

1. Find out the least count of the given instrument.

2. Clean the micrometer stand so that there are no burrs on the anvils. Clean the measuring faces

of micrometer with a cleaning cloth.

3. Fix the micrometer to the stand horizontally, to avoid manual errors during handling.

4. Check for zero errors of micrometer by closing the micrometer to ‘0’ and note down the zero

error, if any (ex.: -0.01mm or + 0.01mm)

5. The selected (values) standard step gauges are taken and cleaned with a cloth and arranged in

such a way that there would be no gap (wringing phenomenon) and placed between the anvils.

6. The readings shown by the micrometer are noted and compared with the actual reading of slip

gauges.

7. Error and percentage error are calculated results and calculations are tabulated in the tabular

column.

8. The experiment is repeated for different readings of slip gauges (minimum 10 readings).

Note: Always complete the entire range of the instrument by selecting appropriate values unless

specified



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Aim: To calibrate the given Micrometer using slip gauges.

Apparatus Used:

thimbleondivisionsofNo.Total thimbleoftion moved/rota Distance

Slip gauge set, Micrometer, Micrometer stand, cleaning cloth

Least count =

=

∴LC = ______mm

Zero Error = ______mm

Tabulation

Sl.No Actual Reading Micrometer Reading Error Percentage Error

Specimen calculation: -

Actual reading of slip gauge (x)

Micrometer reading

Error = Micrometer reading - Actual reading

Percentage error = readingActual

Error



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Expt. No – 02

CALIBRATION OF VERNIER CALIPER

Aim: To calibrate the given Vernier calipers using given slip gauges.

Theory: Vernier calipers are used to measure the outside diameter as well as inside diameter of

cylinders. All parts of the instrument are made of good quality steel. It is commonly used in machine

shop to measure the diameters of work piece.

Apparatus: Vernier Caliper, Slip gauges, cleaning cloth

Procedure:-

9. Find out the least count of the given instrument.

10. Clean measuring faces of Vernier caliper with a cleaning cloth.

11. Check for zero errors of Vernier caliper by closing the micrometer to ‘0’ and note down the

zero error, if any (ex.: -0.02mm or + 0.02mm)

12. The selected (values) standard step gauges are taken and cleaned with a cloth and arranged in

such a way that there would be no gap (wringing phenomenon) and placed between the jaws.

13. The readings of Vernier are noted and compared with the actual reading of slip gauges.

14. Error and percentage error are calculated results and calculations are tabulated in the tabular

column.

15. The experiment is repeated for different readings of slip gauges (minimum 10 readings).

Note: Always complete the entire range of the instrument by selecting appropriate values unless

specified

L.C. = 1 M.S.D – 1 V.S.D. (consider the coinciding divisions of main and Vernier)

= _______mm

Zero Error = ______mm

Tabulation

Sl No Actual Reading Reading of Caliper Error Percentage Error

Specimen Calculation:

Error = Reading of caliper - Actual reading



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Percentage error = readingActual

Error

Sl.

No

Actual

(m)

Instrument reading in (mm) Error % Error

M.S.D V.S.D. T.R

Given Calculated from Vernier Given –

cal

Given cal given

1



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CALIBRATION OF CALIPERS

Procedure:

1. The least count of the instrument is calculated

2. Standard slip gauges of known values are taken cleaned properly and arranged in such a way

that these should be no air gap between them.

3. The micrometer readings are noted and compared with actual results.

4. Reading are tabulated in the tabular column

5. Procedure is repeated for different values gauges.

CALCULATIONS: -

Least count of Dial Gauge = scaledialonmoveddivisionsofNo

scalemainonmadedivisionsofNoorrotation )(1

= 1/100 = 0.01mm

Least count of calibration tester = rotationsdismicrometerondivisionsofNo

scalemainonmovedceDis tan

= 500

5.0 = 0.001mm

Actual Disc Reading = Dial Gauge Reading x L.C

Correct disc reading (Instrumental Reading)= Micrometer disc reading ± Instrumented error given in

chart

Error = Actual Reading – Instrumental Reading

% Error = 100xreadingActual

Error

Sl.

No

Dial gauge

Reading x LC

mm

Micrometer disc

reading x LC

(0.001) mm

Instrumental

Error from

chart

Instrumental

reading

Error % Error



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Exp. No: 03

CALIBRATION OF DIAL GAUGE

AIM: - Calibration of dial gauge using dial indicator.

Apparatus: - Dial gauge, dial calibration tester.

Theory:- Dial indicators are instruments used for making and checking linear measurements. These

require less skill than other precision instruments for their usage, like plug gauges, gap gauges,

micrometers and Vernier scales etc. Dial indicators are smaller indicating devices containing a

graduated dial lever magnification system. These are generally used as comparators is compare a part

to a master setting. Some indicators known as dial micrometers or dial thickness gauge are however,

also used for actual measurements when dial indicator is used as an essential part in the mechanism of

any set up for compassion measurement purposes it is referred to as dial gauge.

Most of the dial indicators take the form of a circular or semicircular scale upon which a pointer

fives a direct indication of the movements of a contact arm or a spindle small changes of dimensions of

the component in contact with the spindle are made to assume large proportions to scale by employing

some mechanical reading to be obtained.

A dial indicator by it self is not of much use unless it is properly mounted and set before using

for inspection purpose. By mounting a dial Indicator on any suitable base and with various attachments

it can be used on thousands of special gauges which manufacturers them selves design to meet the

requirement of the job.

Procedure: - 1. The L.C of the dial indicator is calculated

2. The L.C of calibration tester is calculated.

3. Rotate the dial tester circular disc to touch the points of contact of dial indicators & lock the

spindle.

4. Now loosen the 3 screws under the disc of dial tester and make the disc reading zero and again

tighter the screws.

5. Now make the reading of dial indicator zero.

6. Fix the pointer to some specified reading and take the disc reading.

7. Rotate the disc for 10mm displacement and take the disc reading.

The instrument error is noted from the chart and total error is calculated.



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Experiment No –4

CHECKING OF STRAIGHT EDGES BY WEDGE METHOD

Aim: To check the straightness of the straight edge by wedge method.

Apparatus : Straight edge with blade width not less then 6mm, surface plate to accommodate the

straight edge, slip gauges, dial indicator, support blocks.

Theory Straight edges: These are used for checking the straightens and flatness of parts in conjunctions

with the surface plates, spirit levels and the flatness of a surface background or by a light coat of

prussian blue on the work surface.

These may be made of steel or cast iron. Steel straight edges are available up to 2 m length and

may be rectangular in section with beveled edge. C. I straight edges, are made up to 3 m length and

widely used for testing machine tool slide ways. They are heavily ribbed and bow–shaped (camel back

construction) to prevent distortion. These are provided with feet for rest when they are idle to prevent

distortion. Feet are placed at points of minimum deflection.

According to IS: 2220 – 1962, straight edges are of two grades; Grade A for inspection and

Grade B for workshop purposes. These are of rectangular cross section and the side faces of the straight

edge are straight parallel and also square with the working surfaces. When the straight edge is

supported at minimum natural deflection points (Airy points) over the span, i.e., at a distance of 2/9

total length of straight edge from each end or 0.5541 span, the error in the straightness of the working

faces over its whole length should not exceed (2 + 101) microns for Grade A and (5 + 101) microns for

Grade B; where is the length in meters.

The straight edges are classified as follows:

1. Tool – maker’s straight edge.

2. Wide – edge straight edge,

3. Angle straight edge.

Procedure:

The distance of support points is calculated (i.e., 2/9 of total length of straight edge from each

end, or 0.5541 span). The straight edge is divided into convenient equal number parts (measuring

accuracy increases with maximum number of parts), which contains the support points also. The



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Erro

r (µ)

surface plate, straight edge and support blocks are cleaned. The straight edge is supported over the

blocks at the calculated distance. Any convenient intended slope (by allowing, say 0.05 mm difference

in height for each point) is introduced at the support points using slip gauges. If the surface is flat and

the straight edge is having true edges, then the gap between the successive points will vary by the

intended difference in height.

Slip gauge for the required dimension for the start point is set below the straight edge so that the

gauge is inserted with free force. Repeat this at each point (by increasing the height of gauges with

respect to the slope set earlier) throughout the length of the straight edge. If any difference is noted at

any point, the value of slips may increase or decreased. The difference between the nominal and

measured difference in heights at various points is the error.

In another method, dial gauge is set below the straight edge so that the plunger is in its middle

position and the readings were taken at each point. The measurements were made throughout the length

of the straight edge. The difference between the nominal and measured difference in heights at various

points is the error.

Position Nominal Slips (mm) Actual Slips (mm) Error

+

-

Position (mm)



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Experiment - 5

Measurement of External Taper

Aim : To measure the external taper angle of given specimen

Apparatus : Tapered specimen (preferably a plug gauge), Surface plate, Slip gauge set, Standard

rollers of equal size, Vernier caliper / Micrometer.

L.C of the instrument (Vernier caliper /Micrometer) : _____________________

Procedure : Clean the specimen surface with a clean cloth and place it on the surface plate.

Select 2 set slip gauges (each set of equal size) of different height and two equal size

standard rollers. Position the slip gauges at each side of upper end (h1) of specimen and

place the rollers. Note down the reading over the rollers. Repeat the above step at lower

end (h2)

)hh(2ll

2tan

21

21

−−

=θ

of the specimen with another set of slip gauge.

Now using the equation given below, calculate the taper angle of the specimen.

Select another set of slip gauges, which ranges between the first 2 sets. Keeping

one of the first set readings as first reading, take the second reading with this set of slip

gauges and rollers. Calculate the angle to prove that the taper of the specimen is uniform

and more accurate.

l1

l2

h2

h1 2θ

Slip gauge

Standard rollers

Plug gauge



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Measurement of Dovetail Angle

Aim : To Determine the Included Angle of an Internal Dovetail

Apparatus : Tapered specimen (dovetailed), Surface plate, Slip gauge set, Standard rollers of equal

size, Vernier caliper / Micrometer.

L.C of the instrument (Vernier caliper /Micrometer) :

In dovetail, the sloping sides act as guide and prevent the lifting of the female mating part

during mating operation. The angle which the sloping face makes with an imaginary vertical centre

plane is important in case of dovetail. For measuring this angle we require two pins of equal size, slip

gauges and micrometers. First the two pins are placed touching both the sides of dovetail as shown in

fig. above and distance l1 is measured across pins with a micrometer. Then the pins are raised on two

sets of equal slip gauge blocks. Here care should be taken that the pins do not extend above the top

surface of dovetail. Again distance l2

h2

ll

ACBC

12 −

=

across the pins is measured. Let the height of the slip gauges be

h.

Then tan A=

Thus knowing l2, l1 and h, the angle A can be calculated.

This method is also suitable for measuring the angle of a taper plug gauge or any round or flat tapered

work which can be placed on a surface.

Std. Rollers

l1

h A B

A

C

l2

Slip

gauges



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EXPERIMENT NO. 6

Aim: To find out the unknown angle and set up the given angle

Use of Slip Gauge, Sine Bar & Sine Centre (Measurement of Angle)

Theory : Write theory about Sine bars and centres

Introduction: - Instruments used for measuring angles.

1. Vernier bevel protractor / Mechanical bevel protractor

2. Optical bevel protractor.

3. Optical dividing head.

4. Sine bars/Centres.

SINE – BARS

Sine bars used in conjunction with slip gauges, to provide precise measurement of angles. These

are used either to measure the angles or for setting up any work to given angle very accurately. The size

of sine – bar / center is defined by the center distance between two rollers (100, 200, 300mm).

To Measure The Known Angle.

Angle Sine LH Where H = Height of the slip gauge to be used

L = Length of the sine bar.

Thus knowing θ, h can be found out

H = SIN θ * L

The measure unknown angle Place the sine bar on a surface plate. The work piece is placed on the sine bar and clamped. Set

a dial indicator at one end of the work and move to the other end and note the deviation.

If the deviation noted down by the dial indicator is the “δh” over the length of ‘l’ of the job,

then the height of the slip gauges by which it should be adjusted is equal to

1L*hδ

Now place the slip gauge of ‘H’ under one side of the rollers. Again move dial indicator over

the work and note the deviation. Repeat the step to obtain the required height. Slip gauges are so



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adjusted that dial indicator reads zero across the work surface. Now calculate the angle. H may

include (h1 + h2+ ….._ or (h1 – h2 - …) so on.

Experiment No. 7

MEASUREMENT OF SCREW THREAD USING TWO WIRES & MICROMETERS

(FLOATING CARRIAGE THREAD MEASURING MACHINE)

Aim: To find out the parameters of screw thread using two-wire method.

Apparatus: Floating carriage thread measuring machine work piece, standard wires, standard prism,

and standard gauge for the work piece.

Theory: Errors of thread: The errors of thread covers following elements major dia, minor diameter

pitch and flank angle.

In mass production system all these elements must be checked. Errors in major & minor diameter will

cause interference with the making…….. and the component will be weak in strength. Errors on the

between the flanks. Pitch and angle errors cause progressive --- and interference on assembly.

There are many methods for checking the elements of thread.

1. The micrometer method

2. Two wire and three wire method.

Best size wire: This wire has the dia, which makes contact with the flanks of the thread on

effective dia, or pitch line. The best wire is always to be used for effective diameter and for this

condition the wire touches the flank at mean diameter line within – 1/5 of flank length.

Floating carriage thread measuring m/c (floating carriage diameter measuring machine) has a

rigid base and two carriages which can float transversely and longitudinally on the to slide (transverse

direction) at one end a micrometer with large drum is fixed and its reads 0.0002mm. at the other end a

fiducial indicator is fixed which is a spring loaded instrument with 1 zero setting facility.

Procedure:

1. Fix the workpiece/ between centres.

2. Take the readings for major diameter over the work piece.

3. Insert the standard measuring pins into the threads of workpiece and take the reading.

4. Now insert the standard prism into the threads of workpiece and take the readings

5. Now remove the work piece and fix the Master cylinder between the centres.

6. Repeat the steps 1- 4

7. Using the equations find out the actual values of the workpiece.



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To find major Diameter

F = D± (Rs ~ Rw)

D = Diameter of the standard.

Rs = Reading over the standard.

Rw = Reading over the workpiece

For Effective dia.

E = D± [(Rs – P) ~ Rw]

Rs – Reading over the standard with standard wire

Rw – Reading over the standard work piece with stander wire

P = Sin 60 * p – d (where sin60 is the angle of thread - metric)

p = Pitch of the thread

d = Mean dia of the standard wires.

For minor dia

C = D ± [Rs ~ Rw]

Rs = Reading over the standard with standard prism

Rw = Reading over the standard work piece with standard prism



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EXPERIMENT NO – 8

USE OF AUTO COLLIMATOR TO CHECK FLATNESS & ALIGNMENT

Aim: To determine parallelism, perpendicularity of given specimen using auto collimator.

Apparatus Required:

1. Auto collimator.

2. Surface plate.

3. Highly polished mirror.

4. Try square.

Theory:

1. Cares to be taken while using auto collimator.

2. Different methods straightness measurement.

3. Use of feeler gauge for straightness measurement.

4. What are straight edges and what for it is used?

5. Applications of auto collimator.

PRINCIPLE OF MEASUREMENT:

The optical arrangement adapted for auto collimator is as shown in the fig. Light rays from the

light source will be reflected partially in the optical axis by the half – reflecting layer in the prism.

Then, passing through the objective the light rays become parallel and reach the mirror ‘M’ placed at a

distance in front of the objective. The light beam thus, reflected back by the mirror surface will pass

through the objective again and further through the half reflecting layer in the prism, forming an image

S1 of the crtoss hair S on the reticule.

If the mirror tilted by a minute angle of ‘0’ from position A to B, the reflected beam, being

inclined ‘20’, will re – enter the objective, causing a displacement of ‘d’ to the image of the cross hair.

This interrelation can be expressed by the formula.

d = f, Tan 20 = 2. f.0

Where,

‘f’ is the focal length of the objective. By reading the value of ‘d’ with the scale provided on the

article the tilt angle of the mirror can be determined. In the auto collimator model 6D, 2 vertical and

Horizontal scales are engraved at right angles on the reticule with one division of 1’ minute and the

fractional value of 1’ can be read out down to 0.5” by moving the retails precisely with the micrometer.

INITIAL SETUP:

1. Set the compensator ring to 100.



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2. Set the reading of the micrometer to ‘zero’

3. Place the reflecting mirror on the work piece to be tested at a distance between 0.9 to 1.4 mts.

4. Approximately align the collimator such that the green light is visible in the reflecting mirror when

viewed from one side of the collimator tube.

5. Get the cross wire in the field of view by swinging the collimator tube along vertical and horizontal

axis.

Note: While swing the collimator tube, at most care must be taken as there are chance of

collimator tube hitting the surface plate and may cause damage. After getting the cross – wires in

the filed of view lock the all-locking knobs firmly.

6. Using the fine adjustment knobs provided at the bottom of the collimator bracket, bring the cross –

wires to align at the centre of the scale. Then the measurements are made as explained below.

READING AND CALCULATIONS: (For straightness Measurements)

1. Set the successive measuring points at some interval and call such points as A,B,C,D………. in the

order from the auto collimator.

2. Move the mirror across various distance and make auto collimations at respective points in the

tabular column, with the help of the auto collimator scale and the micrometer scale and the

micrometer. This represents the differences in ‘0’ from thee zero position with plus or minus sign

according to the moving direction of the cross – wire from thee zero position.

3. Find the amount the linear variation corresponding to the angular values using the relation.

h =L Sin0

Where,

h = difference in height between two successive points.

L = Length of successive measuring points.

0 = Angle noted between two successive points

Then tabulate the readings of h, in the tabular column.

4. Write the accumulated values in the next row and draw a graph with successive lengths on x = axis

and the accumulated reading at different points on Y – axis.

5. Join the ends points by a straight line and tilt this line such that it becomes parallel to the x – axis.

(As shown if fig.)

Now Transfer the perpendicular heights from this line to get the total deviation present on the

component. The height between peak points on positive and negative co – ordinates will indicate the

error of straightness.

Position L Angle θ Difference from Last reading (θn -θ1

Linear displacement L*θ*0.000005 mm )

Cumulative error



17

Mm Min&secs.



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Experiment No. 9

TESTING OF GEARS

Aim: To test the given Gear using Gear Tooth Vernier Caliper

Theory: The sources of error are generally due to the methods of manufacturing.

1) Reproducing method and

2) Generating method.

The errors are profile error, pitch error, tooth thickness error, cyclic error, periodic error, run out

error, radial run out, eccentricity error, tooth alignment error.

Testing of Gear is determination of then various elements in which the errors are caused due to

manufacturing erros.

Profile, Spacing, Pitch, run out or eccentricity, tooth thickness, lead backlash.

The inspection consists of carrying out the running test of gear with another gear which is more

accurate and is known as master gear.

The rolling test can be done using the machine “Double flank gear Tester” (similar parkinson Gear

tester) When two gears are engaged in a tight mesh (double flank), then the errors in tooth from pitch

and concentricity will cause the variation of centre distance.

It consists of a base two anvils, one fixed and the other movable are mounted on it. The movable anvil

is spring loaded and or dial gauge is fixed against it.

The master gear is mounted on the spindle on fixed anvil and gear to be tested is mounted on the

movable anvil. The gears rotated by hand and variations in dial gauge are observed.

Composite error: This is the centre distance variation in one complete revolution of the gear under test.

Tooth to tooth error: Is is the centre distance variation as the gear is rotated through any increment of

n360°

MEASUREMENT OF GEAR ELEMENTS

Aim: To measure the different elements of given gear

Apparatus:

1. Gear tooth Vernier caliper

2. Span Micrometer

3. Outside Micrometer

4. Double Flank Gear Tester

5. Dial Gauge



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Theory:

1. Different elements of gear

2. Different type of error

A gear is defined by the number and the form of its teeth. The tooth from is given by the

geometry of the gear blank, the flank line and the tooth profile. The flank line is the line of intersection

of the tooth flank with a basic circle dia equal to the pitch circle diameter. The flank lines are parallel to

the gear axis.

In gear it is necessary to realise the individual errors so that the gear production can be controlled

and also for the inspection of high quality gears, such as standard gears and gear cutting tools.

Some of the individual errors are:

1. Variation of pressure angle from one tooth to another that is variation base circle dia.

2. Errors of the involute profile of the tooth.

3. Pitch are tooth thickness error

4. Error of flanks in respect to gear axis

5. Pitch error

6. Concentricity error

7. Accumulative of a span gear

Basic elements of a span gear

1. Pressure angle

2. Circular pitch

3. Tooth thickness

4. Crest circle dia

5. Root circle dia

Procedure: Observe and note the basic data

Number of teeth, N = Pressure Angle α = (usually 14.5° or 20°)

Module m = (Do -= m (N + 2)

1. measurement of tooth thickness using gear tooth vernier caliper. The G.T.V caliper measure

chordal thickness. The measuring principle is based upon the determination of the exact depth h

from the crest of the tooth at which the chordal thickness should be measured.

The variable slide is to set the depth ‘d’ and horizontal slide is used to obtain the thickness at that

position.

The chordal addendum or depth (d) to be set on the vertical slide of the caliper is obtained using the

equation

d(Theoretical) = N m/2 || 1+2 /N-Cos (90/N)||



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d chordal thickness, W (Theoretical) = Nm Sin (90/N)

Where N = no. of tooth of gear, m = Module

2. Measuring of tooth span using span micrometer.

The simplest method of measuring the tooth thickness and its allowance is by using the tooth

span micrometer. Its consists of two flat parallel axis-, the distance between them (W) includes a no of

teeth ‘N’ such that the measuring points lie on a line tangent to the base circle. Therefore the tooth span

‘W’ consists of base pitches and the tooth thickness at the bas circle and can be calculated for span gear

using the equation.

Tooth span W = Nm Cos φ || tan φ - φ - II /2N+II S/N ||

Where φ is pressure angle, S = no. of teeth selected



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Experiment No – 10

Calibration of Height gauge using Height Master Height Master General Description Height Master is termed as Height Micrometer. It is an instrument comprising of a robust housing, which carries a vertical movable column, positioned by a micrometer screw. Measuring is provided by regularly spaced, alternate measuring faces, and the datum plane (Generally a Granite Plate). ADITYA MAKE Height Masters are available in two models. Heavy duty Height Master HM1: Least count 0.001mm

Specifications (Functional Parameters) Heavy Duty HM1 • Measuring range 5 – 310mm • Least count 0.001 mm • Minimum reading with counter 0.01 mm • Travel of micrometer head 20 mm • Pitch of micrometer head 0.5 mm • Height of measuring blocks 20 mm • Travel of reference line 360° • Minimum reading on housing scale 5 mm • Weight 26 Kg • Support pads Tungsten Carbide • Overall accuracy / performance test ± - 0.003 mm • Parallelism over entire length of blocks 0.001 mm • Accuracy of micrometer head ± 0.0015 mm

MEASURING ELEMENTS: These are gauge blocks stacked and fixed in a block holder in a staggered manner.

• In the staggered type of gauge block stack, two measuring faces, one facing up and the other facing down, are provided side by side on the same plane. The bottom block gauge is of 9.5 mm. 5 mm step is provided in the Heavy Duty model to get measuring range of 5 – 310 mm and 5 – 310 mm for Light Duty Mode.

• Block Gauges are manufactured from High Carbon High Cromium (HCHC) Steel, are hardened and stabilised to 60 +/ -2 HRC.

• The sliding of the stack is effected by precision feed screw mechanism of a micrometer head. • Top block is not a measuring face. This is attached with a seal.

INSTALLATION & PERFORMANCE TEST Make the performance test of the Height Master placed on a surface plate as follows:

1. Wipe off anti – corrosive oil from the measuring faces of blocks and clean the surface plate. 2. Using the reference blocks of 10 mm, Zero set the Height Master as mentioned below:

a) Referring to Fig. 4a & 4b and using lever type dial indicator, level the upper face of the bottom block to the height of the reference block. In this setting, the bottom block must be elevated up to the height of the reference block by rotating the micrometer head clockwise.

b) Check to be sure that the Zero line of the thimble coincides with the datum line of the reference ring. If it is deviated, rotate the reference ring with its clamp loosen to have the datum line aligned with the zero line. Then, lock the clamp to fix the reference rin.



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Fig Note: Make sure the zero point setting before using Height Master.

3. With the bottom block leveled to the height of the reference block, the counter should read just 0.00 mm. If deviation is observed on the counter indication. Refer to ADJUSTMENT.

4. Rotate the micrometer head to make sure that the range of its stoke is 20mm. • Around both the ends of stroke, top and bottom, care must be taken to rotate the micrometer

head slowly. Note: Never have the lower face of the bottom block touched on the surface plate; touch will occur in setting the measuring faces at height of 30 mm, 50 mm, 70 mm and so on as shown in fig. 5a so in order to obtain such height, elevate up the gauge block stack by 20 mm as shown in fig. 5b Fig 5. While rotating the micrometer head, make sure that there is no uneven gap between the thimble

and the reference ring. The gap between the two has been adjusted to about 0.2 mm before shipment. If uneven gap or noise by contacting the two is observed while rotating the micrometer head, refer to ADJUSTMENT

HEIGHT MEASUREMENT AND READING. As shown in Fig. 6 height measurement with the use of a Height Master is to transfer the height (H) of the workpiece by means of lever head or test indicator to the Height Master by setting its gauge block exact to the height (H).

For measuring height above 310 mm, i.e., the measuring range of the Height Master. Riser blocks are available in two sizes, 150 mm & 300 mm to extend the range up to 610 mm maximum.

Fig READING OF METRIC HEIGHT MASTER

a) First Step: Reading on reference scale. Reading is made in the unit of 10 mm on the reference scale. In Fig. 7, ‘A’ face in between 70 mm and 80 mm graduation is read as 70 mm in height and B – face as 50 mm

b) Second Step: Reading on counter. Counter reads to 0.01 mm. Fig. 8a / 8b represents 7.85

c) Third Step: Reading on micrometer head. Heavy Duty Model One division on thimble represents 0.001 mm. In Fig. 9a the datum line of the reference ring coincides with the fourth line of the thimble counted from the nearest taller line on the left side of the datum line. In this case, the reading is 4 x 0.001 mm = 0.004 mm. If the datum line does not coincide with the line on thimble, the line nearest to the datum line should be taken in counting. For the Light Duty ref. Fig. 9b datum line on the reference ring Coincides with the second line of the thimble, counted from nearest taller line on the left side of the datum line. In this case, the reading is 2 x 0.002 = 0.004 mm.



23



24

Experiment – 11

USE OF TOOL MAKERS MICROSCOPE & PROFILE PROJECTOR Aim: To Measure the thickness, taper, radius of curvature, thread element etc.

PROFILE PROJECTOR

Write theory

Light system

In contour illumination the light passes through the object to produce dark image of the image

contour. By this source we can easily measure the external dimension of the object.

In a surface illumination light reflects over the object and again reflect back to the screen. Here

we can see the surface texture of the object. This is also very useful for comparison.

The screen has two cross hairlines marked on its centre which represents X and Y co –

ordinates with respect to the movement of micrometer stage. Measurements are taken with one edge of

the object coinciding with the respective cross hairline and then the micrometer is rotated to bring the

other edge of the object to coincide with the same cross hairline. When point contact method is needed

the axis (intersection point) of the co – ordinates is selected. (Eg: Circle, radius by 3 points method and

Angles by 4 point method or when used with Data processor).

The screen also has graduated protractor rings for angular measurement through 360°. By

rotating the protractor we can set the cross hairline parallel to the object side and get the differential

readings. The work will be held on micrometer stage and focused on the screen by means of vertical

movement of stage until a sharp image of the object is obtained.

Types of Measurements:

1. Thickness = 2 point / line reference. 2. Diameter / radius = 3 point / point reference. 3. Thread measurement = Major diameter, Minor diameter, Pitch and Angle. 4. Angle measurement = i) Using protractor ring

ii) Using point measurement system.

5. Measurement using Data processor.

( )[ ])(2

)()((

1221

221

221

22

22

21

21

yxyxyyxxyxyx

R−

−+−++=



25

Radius measurement by 3 point method

( )( ) ( ) ( )[ ]( )1221

221

221

22

22

21

21

2 YXYXYYXXYXYX

R−

−+−++=

P0 = X0,Y0

P1 = X1,Y1

P2 = X2,Y2

P1 = P1 - P0 (i.e., X1 – X0, Y1 – Y0)

P2 = P2 - P0 (i.e., X2 – X0, Y2 – Y0)



26

TOOL MAKERS MICROSCOPE

Write theory

Light system

In contour illumination the light passes through the object to produce dark image of the image contour. By this source we can easily measure the external dimension of the object.

In a surface illumination light reflects over the object and again reflect back to the screen. Here we can see the surface texture of the object. This is also very useful for comparison.

The eyepiece has cross hairlines marked on its centre which represents X and Y co – ordinates

with respect to the movement of micrometer stage. Measurements are taken with one edge of the object

coinciding with the respective cross hairline and then the micrometer is rotated to bring the other edge

of the object to coincide with the same cross hairline. When point contact method is needed the axis

(intersection point) of the co – ordinates is selected. (Eg: Circle, radius by 3 points method and Angles

by 4 point method or when used with Data processor).

The protractor eyepiece has a graduated scale above the main eyepiece tube, which can be

rotated by a knob beneath the eyepiece housing for angular measurement through 360°. On the smaller

eyepiece minute Vernier scale is marked with 1’ accuracy. By rotating the protractor we can set the

cross hairline a shore Fogbows I D parallel to the object side and get the differential readings. The

work will be held on micrometer stage and focused on the screen by means of vertical movement of

stage until a sharp image of the object is obtained.

Types of Measurements:

6. Thickness = 2 point / line reference. 7. Diameter / radius = 3 point / point reference. 8. Thread measurement = Major diameter, Minor diameter, Pitch and Angle. 9. Angle measurement = i) Using protractor ring

ii) Using point measurement system.

10. Measurement using Data processor.



27

Experiment No.12

MEASUREMENT OF SURFACE FINISH

PERTH-O-METER Aim: To measure the surface roughness of given object

Apparatus: Perthometer, surface plate, object

Perthometer is an Electronic-measuring Instrument for the surface roughness value of technical

surfaces. It consists the following parts:

1. Pick Up : - This is a sensing device (probe) which has skid and stylus (Stylus is a

diamond pointer)

2. Drive Unit : - Guides and moves the pickup during the traverse over the measuring surface in

required direction at constant speed.

3. Perthometer : - Provides the readout of the computed surface roughness values (Ra, Rz, Rmax). It

consists of Magnification selector switch, Traverse length selector switch, Roughness

selector switch and instrument zero tuner.

Working The styles is made to move across the surface of specimen and the Mechanical /Electrical transformer generates electrical signals of the effective surface. These signals are then amplified, filtered and transmitted to the connected indicating / recording unit. Parameters Total traverse length (Tl

: )

This the total distance that the styles can travel

Cut-off length (Pre–traverse length) (Cl

:

)

This is the first part of the traverse length which is disregarded for the measuring process, (It is also known as cut – wave length).

Measuring length (Ml

: )

This is the actual length for which the results are computed and displayed on the indicator( i.e M1 = T1 – Cl

Effective surface (P)

) : This is a close representation of the real surface obtained by the styles

during setup. This effective surface always includes surface roughness and forms the basis for all further analysis.

Average roughness (Rz

: )

This is the arithmetical average of the five single roughness of single measuring traverse length (Tl

Maximum Roughness (R

). (The perthometer divides total measuring length into 5 equal part for analysis).

: max)

This is the biggest of the single roughness depth of measuring length (Ml

Arithmetical mean deviation (R

).

a

: )

This is the arithmetical average value of the departure of the profile above and below the reference line within the measuring length.



28

Calibration:

Position pick–up on the calibration master and align the stylus such that it is parallel with the face of calibration master, using height adjustment on drive unit.

Position stylus immediately behind the measuring groove. Set the Surface value selector in position P, Magnification switch in position P = 10 / um ( for pickups with range 250µm P = 1µm as per the manufacturer’s specification). Push calibration master towards drive unit until stylus has reached centre of measuring groove. Indicator should give reading as per value on calibration master. If not adjust the meter to required value with instrument zero, with the help of a screwdriver. Pull calibration master back to original position and ensure that indicator return to zero.

Procedure Place the object on the surface plate. Set the Surface value selector in position P, Magnification switch in position P = 10 /um (for

pickups with range 250µm P = 1µm as per the manufacturer’s specification). Position the stylus over the object and align the stylus such that it is parallel with the face of the

object, with the help of height adjustment knob (this can be monitored through the monitor which indicates the position of the stylus on the measuring surface, i.e., when the stylus is set parallel to the measuring face, the indicator in the monitor moves to the centre of the white area)

Using zero adjustment knob, set the meter to ‘0’. Now set the surface value selector to Ra , range to required magnification on Ra Select the traverse length, note down the cut-off length.

side.

Push the press button to start measurement Note down the readings of Ra, Rz and Rmax Repeat the measurements for different traverse lengths.

by selecting the surface value selector knob.

Sl. No.

Magnification (µ)

Traverse length

(Tl

Cut-off length

(C)mm l

Measuring length M

)mm l = (Tl – Cl

Surface roughness )

mm R Ra (µ)

Rz (µ)

max (µ)



29

Experiment No-13

Measurement of Roundness using V-Block Method Out of roundness of mechanical parts could be due to poor bearings in the lathe grinding wheel spindle, or to deflection of the work piece as the tool is brought to bear on it. Shafts which are ground between centers or deflection of the shaft. A round bar or ring type part held in a chuck for grinding or turning is compressed at the points of contact giving rise to stresses in the material. When it is removed from the chuck the stress in the material will be released, giving rise to lobes. Drawn or extruded parts takes their shapes from the dies, and roundness checks on the parts cannot only any imperfections which cause scoring along the surface. A worn tool or one not set correctly could produce chatter marks. Generally a part is said to be round in a specific cross section if there exists within that section of a point (centre) from which all other on the periphery are equidistance. The cross section is therefore a perfect circle. The out of roundness is specified as the difference in distance of points on the periphery from the centre. But to specify out of roundness of an irregular profile it is possible if we can find a centre from which to make the measurements. So finding a centre of the part is an important part of roundness testing. There are many method of testing roundness of a part.

1. Vee block method three-point method. 2. Bench centre method. 3. Stylus method turn table or pick up rotation method.

The following are the essential features, which need to be incorporated in a roundness-measuring instrument. Since roundness is normally measured by rotation either the part itself can be rotated against a

fixed measuring device, or the measuring device can be rotated around the stationery part. The axis of rotation must be independent of the part being measured because when the part

itself is used as one of the bearing surfaces for rotation, the irregularities on that surface cause the whole part to move up an down make simple & accurate measurements of roundness impossible.

Type of measuring devices. In bench type measurements a simple dial indicator is adequate but in an instrument capable of

very accurate rotation, a non-mechanical gauge is employed. This can be in the form of an electrical transdrecer (pick – up)

Indicator. Any measuring device must have an indicator from which the measurements can be read.

Roundness tester sometimes have a meter but is gives a fluctuating reading an used for setting up only. As such a graph is provided result to get more information about the roundness this datum is the axis of rotation of the spindle.

Roundness measuring in instruments are of two basics types. in one (Rotation pick up) type the part is stationery and pick up revolves about is and in other type (Turntable type) the work piece rotates.

Rotating pick up type In this type the spindle has only to carry the light, constant load of pickup High accuracy is

therefore can be obtained. The worktable not being part of the measuring system, can be or substantial construction, so the

weight of the part is not a limitation on measuring capacity many large parts (cylinder blocks) of



30

asymmetrical shape, with the centre of the bore or surface to be measured off set from the centre of gravity long shafts and crankshaft can also be accommodated.

Turntable type Since the pick up is not associated with the spindle this type of instrument is more easily

adapted for roundness measurements, such as concentricity and alignment. It is more easy in positioning the pick up to reach into slots or to underside of shoulders without having to use long or cranked stylus arms.

The weight of the turntable and the part being tested has to be supported by the spindle bearing, this limits the weight of parts that can be measured. It also limits the off set of the part that can be accommodated.

V–Block Method

This method is simplest and useful in determining the circularity errors and number of lobes. When

a rounded port held in chuck is compressed at the point of contact. Even when the part is turned or

ground to perfect round on the machining, after it is removed from the chuck, the stress on the metal

gets relived, course the lobes. The number of lobes can be varied from two to hundreds about the

circumference of the cross section. Two, three, five, seven and nine lobes are common result of

machining processes.

The specimen in fist cleaned and marked 12 points @ 30° each on the face of the specimen.

A V-block is placed on the surface plate and the specimen is placed upon it.

A dial indicator with a stand is rest against the surface of the job.

The dial indicator is set just above the specimen so that it touches the work piece at the axis

of the specimen.

Specimen is then rotated and dial reading are taken at each marking.

For plotting the polar graph, a suitable scale is chosen depending upon the maximum value

of the dial indicator.

A draw a circle of dia nearly 4 times the max reading of the dial indicator. Inside this circle,

draw another circle nearly half of the max value of outer circle. Now divide this circle into

12 points to indicate the actual shape of the work piece.

Now the values are plotted in radial (clockwise) direction taking the smaller circle as the

reference circle in order that both the positive & negative readings are plotted

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