Assignment No. 1 Introduction to Metrology (Marks 10) · 2. Scientific metrology: i) Concerns the...

Year : SYME Sub: Engineering Metrology (2019-20) Sub. Code: 22342

Prof. N. B. Devi (Head of Dept. Mech. Engg.) K. B. P. Polytechnic, Satara 1

Assignment No. 1

Introduction to Metrology (Marks 10)

Sr.

No.

Question Marks

1 Define metrology. State objectives of metrology.

Answer:

Definition:

“It is a science of measurement which deals with the ensuring

instruments, measuring technique and measuring standards”

Objectives

1. To ensure that the product is as per quality standard.

2. To enhance total customer satisfaction.

3. To reduce rework and rejections.

4. To increase profitability of organization.

5. It helps in manufacture of interchangeable parts.

6. Overcome the short coming in the production process.

4

2 List down different categories of metrology. State specific

use of each of them.

Answer:

Categories of metrology and their specific uses:

1. Legal metrology:

i) Control of measuring instruments;

ii) Testing of prototypes/models of measuring instruments;

iii) Examination of a measuring instrument to verify its

conformity to the statutory requirements etc. 2. Scientific metrology:

i) Concerns the establishment of measurement units, unit

systems, the development of new measurement methods,

realization of measurement standards.

ii) The transfer of traceability from these standards to users in

society.

3. Deterministic metrology

i) Deterministic metrology is a new philosophy in which part

measurement is replaced by process measurement. The new

techniques such as 3D error compensation by CNC

(Computer Numerical Control) systems and expert systems

are applied, leading to fully adaptive control. This technology

is used for very high precision manufacturing machinery and

control systems to achieve micro technology and

nanotechnology accuracies.

4. Industrial metrology:

i) Concerns the application of measurement science to

manufacturing and other processes and their use in society,

ensuring the suitability of measurement instruments, their

calibration and quality control of measurements.

4



3 State the various needs of the inspection.

Answer:

Needs of inspection

1) To ensure that the part, material or a component confirms to the established standard. 2) To meet the interchangeability of manufacturer. 3) To maintain the customer relation by ensuring that no faulty product reaches the customer. 4) Provide the means of finding out shortcomings in manufacture. 5) It helps to purchase good quality of raw material, tools, equipment which governs the quality of the finished product. 6) It helps to coordinate the functions of quality control, production, purchasing and other departments of the organization. 7) To take decision on the defective parts.

4

4 Explain the terms calibration and traceability.

Answer: Calibration:- The instruments, gauges to be used for measurement

should be of known accuracy in order that the results obtained are

meaningful. In order to identify the errors and rectification of

errors the instruments are compared with masters or standards. This act of comparison is known as calibration. Traceability: - Traceability is the property of the results of a

measurement, not of an instrument or calibration report or laboratory. Traceability means the result of measurement can be

related to a reference through series of calibration reports.

4

5 Distinguish between accuracy and precision with suitable

sketch.

Answer:

Accuracy Precision

1. The closeness to the

measured value with true

value is called accuracy.

1. Repeatability of

measuring process is called

precision.

2.Costlier to achieve great

accuracy

2.Easier and cheaper to

achieve precision

3.It is related to true value 3.It is related to average

value.

4.Example 4. Example

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6 Define sensitivity

Answer:

Sensitivity refers to the ability of a measuring device to detect

small differences in a quantity being measured.

2

7 Define reproducibility

Answer:

Reproducibility of measurement is the quantitative measure

of the closeness of agreement between the results of

measurements of the same measured, carried out by changing

the method of measurement, observer, measuring instrument,

location, condition of use, time etc

2

8 Define readability

Answer:

Readability: Readability is the ease with which the reading

of a measuring instrument can be read.

2

9 Explain least count for vernier calliper

Answer:

LC = Smallest division on main scale

Total number of divisions on vernier scale =

1

50 = 0.02 mm

4

10 Explain least count for micrometer.

Answer:

LC = Smallest division on main scale

Total number of divisions on circular scale =

0.5

50 = 0.01 mm

4

11 Explain the various sources of errors in measurements.

Answer

Various Sources of errors in Measurement: 1. Defect in measuring Instrument. 2. Adjustment of an Instrument. 3. Imperfection in instrument design. 4. Method of location of instrument. 5. Environmental Effects. 6 Error because of properties of object. a. Error due to surface finish of object. b. Error due to change in size of object. c. Observation error d. Error caused by measuring forces of instrument

4

12 Define any four factors affecting accuracy of measurements.

Answer:

1) Measuring Instrument:- The accuracy of the

measurement depends upon the various static and

dynamic characteristics of the measuring instruments.(like

range, readability, sensitivity, repeatability

ect.)

2) Environmental Conditions: Factors like temperature,

pressure and humidity greatly affects on the accuracy of the

measurement.

As per the international practices temperature in the test

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laboratories should be maintained at 200c

It is recommended to maintain positive air pressure (10-20

N/m2).

3) Calibration of instruments: It is important that any

measuring system should be calibrated periodically to get

meaningful results

4) Handling of instruments: measuring instruments must be

handled carefully to avoid the errors in measurement and also

to save the life of instrument.

13 State criteria for selection of instruments.

Answer:

Criteria for selection of instruments

1 Range of measurement

2 Scale spacing

3 Sensitivity of instrument

4 Least count

5 Accuracy of instrument

6 Error generated during measurement

7 Effect of environmental conditions on the instrument

8 Parallax error during reading an instrument

9 Repeatability of instrument

10 Cost of the instrument

4

14 Explain parallax error with neat sketch.

Answer:

Parallax error mainly happens when the object is viewed

from an angle due to the wrong positioning of eye. The first

way to curb this error is to orient your eyes in a straight line.

Your eyes should be in a straight line directly above the

marking on your device, be it a scale or a Vernier caliper etc

4



15 Define least count of an instruments

Answer:

The smallest value that can be measured by the measuring

instrument is called its least count.

2

16 Explain the need and standard procedure for calibration

Answer:

Need of calibration

1. Standard of accuracy

2. Wearing of measuring faces

3. Stability of instrument over the period of time

4. Remove the errors ( deviation from standard)

5. For consumer and employee safety

Procedure for calibration

Apply the low range value (LRV) to the instrument

and note the reading.

Rotate the Zero adjustment if there is any irregularity

in the reading, adjust until the instrument register

accurately at this point.

Now after setting the LRV, apply the upper range

value (URV) to the instrument and note the reading.

Rotate the span adjustment until the instrument shows

the correct URV reading if there is any malfunction in

the readings.

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17 Differentiate between systematic errors and random errors.

Answer:

4

18 State the advantages of interchangeability. (at least two)

Answer:

Advantages of Interchangeability:-

i) Assembly time is reduced, as the operator is not

required to waste his/her skill in fitting the mating

components by trial and error.

ii) There is an increased output with reduced

production cost.

iii) Improve quality and reduce the time for operation.

iv) The replacement and worn-out or defective parts

and repairs becomes very easy.

v) The cost of maintenance and shutdown period is

also reduced to minimum.

2

19 Explain

(i) Environmental error

(ii) Calibration error

Answer:

Environmental errors:

The measuring instruments are assembled and calibrated in

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certain environmental conditions and are designed to be used

in within certain restricted conditions, but when they are used

in different conditions, there are errors in measurement,

which are considered to be the environmental errors.

Most of the instruments are designed to be used within

certain limits of temperature, pressure, humidity, altitude etc

and when the limits are extended there are errors in the

measuring instruments.

Here are some precautions to be taken to reduce the

environmental errors in the instruments:

Use in the instruments within the specified limits of

temperature, pressure and humidity for which the instrument

has been designed. These limits are mentioned in the

instruments manual.

If you have to use the instrument beyond the specified

limits of environmental conditions, then apply suitable

corrections to the recorded measurement.

One can also calibrate the instrument newly in the new

conditions.

There are some devices that enable applying the

compensation automatically.

Calibration error:

The difference between values indicated by an instrument and

those that are actual. Normally, a correction card is placed

next to the instrument indicating the instrument error. Also

called calibration error.

Calibration in measurement technology and metrology is the

comparison of measurement values delivered by a device

under test with those of a calibration standard of known

accuracy. Such a standard could be another measurement

device of known accuracy, a device generating the quantity to

be measured such as a voltage, sound tone, or a meter ruler.

Any deviation from standard, engraving scales, is considered

as calibration error.

20 State the term selective assembly.

Answer:

In selective assembly, the parts are classified into several groups as per size and mating parts are also classified in same number of groups. Assemblies are made as per the sizes from corresponding groups with little or no further machining. Selective assemblies results in reduced cost of production without affecting the quality of the product.

2



Assignment No. 2

Standards and Comparators (Marks 10)

Sr.

No.

Question Marks

1 List different measuring standard

Answer:

Different measuring standard

1) Primary standard

2) Secondary standard

3) Tertiary standard

4) Working standard

5) Line standard

6) End standard

7) Meter standard

8) Yard standard

9) Wavelength standard

2

2 Draw the labeled diagram of Sigma comparator and explain

its working

Answer:

Construction and working of Sigma comparator

1. The Plunger will hold the contact with the workpiece,

and it is positioned in place with the help of slit

diaphragms.

2. The plunger will have a notch at its centre as shown in

the figure.

3. A knife Edge is attached to the plunger to magnify the

linear movement of the plunger. and which is

connected to the Cross strip with the help of moving

the block.

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4. The Y-shaped metallic arm is connected to the cross

strip to Driving drum. This arm rotated and make the

drum to rotate and hence the pointer will move on the

scale.

5. The first step of magnification take place at the knife

edge and cross strip and the second step of

magnification is done at the drum diameter and the

pointer length.

3 Define- Line Standard

Answer:

Line standard is the standard in which distance is measured

between two parallel lines

Application: Steel rule, measuring tape

2

4 State the Term NABL Certification.

Answer:

NABL stands for National Accreditation Board for

Laboratories. It consists of the calibration laboratories, which

are accredited and supervised according to the contractual

basis established by Department of Science and Technology.

This means the official recognition of the NABL calibration

certificates in nearly all important countries in the world.

2

5 Differentiate between mechanical and Pneumatic Comparator

Answer:

Mechanical Comparator Pneumatic Comparator

Consists of mechanical parts

like gear, pinion, springs,

levers etc.

Consist of pneumatic parts

compressor, filter,

manometer, gauging head

etc.

No need of electric supply Need of electric supply

Portable equipment. Bulky and heavy

equipment.

Less accurate More accurate

Wear and tear of parts No wear and tear of parts

Low magnification High magnification

Not suitable for internal

dimensions.

Suitable for internal

dimensions.

Low cost More cost.

Suitable for job production Suitable for mass

production only.

4



6 Draw a labeled diagram showing the working mechanism of

dial indicator.

Answer:

4

7 Explain with neat sketch construction and working of

pneumatic comparator.

Answer:

Principle: A pneumatic comparator or air gauge utilize a

pneumatic circuit to measure linear dimensions of

component.

Construction:-

1) It consist of FRL (filter regulation and lubrication unit)

2) A vehicle tank is filled with water a dip tube immersed

into the tank up to depth corresponding to the back air

pressure it required a calibrated manipulated tube is

connected between water tank and control orifice as shown in

figure.

Working:-

1) A compressed air from it source is given to the input

through FRL unit. Its pressure is then reduced and maintained

at constant value by dip tube into water chamber.

2) Air will bubble out from the bottom of dip tube and air

moving through a control value will be at

a constant pressure.

3) The air at constant pressure then passes through a control

orifice and escaped through the

measuring jet.

4) When there is no restriction to the escape of air this level

of water in manometer tube will

consider with that in the tank.

5) Due to this back pressure will be created in pneumatic

circuit and level of water in monometer fall

4



down.

8 Define the term ‘comparator’

Answer: Definition: Comparator is a device which. 1) Pick-up small variation in dimension. 2) Magnified it. 3) Display it by using indicating device so that comparison can be

made with same standard value.

2

9 State the essential characteristics of the good comparator (any

eight) Answer: Characteristics of a good comparator:- 1) It should be compact. 2) It should be easy to handle. 3) It should give quick result or quick response. 4) It should be reliable while used. 5) It’s weight must be less. 6) It must be portable. 7) It must be easily available in market. 8) It should be sensitive as per requirement. 9) It should be robust in design. 10) It should have less maintenance. 11) It should be linear in scale, so that easy to read and get uniform

response. 12) It should have hard point of contact with longer life.

4

10 State the need and uses of the comparators.

Answer:

Need of comparators:- in mass production identical

components , parts are produced on a very large scale. To

achieve interchangeability these parts should be produced to a

close dimensional tolerances. As a result, inspection is often

more concerned with the dimensional variation from the

standard or basic dimension of the part. To this extent

inspection becomes a process of comparing manufactured

part to the master part imagined by the designer.

Uses of Comparators:-

1) Comparators are used as laboratory standards.

2) Used as working gauges to prevent work spoilage and to

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maintain required tolerance at all important stages of

manufacture.

3) Used as final inspection gauges.

4) Used as a receiving inspection gauges for checking parts

received from outside sources.

5) For checking newly purchase gauges.

11 State any four advantages of optical comparator

Answer:

Advantages of optical comparator

Maximum magnification can be obtained,

No need of electric supply It is a non contact types of measurement hence no wear and tear. Instruments are more accurate

4

12 Define wavelength standard. State advantages and

disadvantages.

Answer:

Wavelength standard :

Using wavelength of monochromatic light which is natural

and invariable unit of length, the working standard is no more

dependent upon the physical standard. Rather the definition

of a standard of length relative to the metre is expressed in

terms of the wavelength of the red radiation of cadmium.

Thus for all practical purposes the use of phenomenon of the

interference of light waves to provide working standard may

be accepted. It was decided that Kr 86 is used in a hot-

cathode discharge lamp maintained at 68 °K temperature

generates orange radiation can be used as ultimate

wavelength standard.

Advantages: 1) It is not a material standard and hence it is not influenced by effects of variation of environmental conditions like temperature,

pressure and humidity.

2) It need not be preserved or stored under security and thus there is no fear of being destroyed as in case of meter and yard.

3) It is not subjected to destruction by wear and tear.

4) This standard is easily available to all standardizing laboratories

and industries. 5) There is no problem of transferring standard to other standards

meter and yard.

6) It gives a unit of length which can be produced consistently at all the times in all the circumstances.

7) It can be used for making comparative measurements of very

high accuracy

Disadvantages:

Maintenance cost is high.

Requires accurate wavelengths of spectral radiations.

4



Assignment No. 3

Limits, Fits, Tolerances and Gauges (Marks 12)

Sr.

No.

Question Marks

1 Explain with representation of features of geometrical

tolerance in simple engineering part.

Answer:

Geometric Dimensioning and Tolerance (GD&T) is a system

for defining and communicating engineering tolerances. It

uses a symbolic language on engineering drawings and

computer-generated three-dimensional solid models that

explicitly describes nominal geometry and its allowable

variation.

4

2 List Different types of “Fit”

Answer:

Different types of “Fit” a) Clearance fit b) Transition fit c) Interference fit.

2

3 List the uses of Snap Gauges

Answer:

Uses of snap gauge

1) Used for gauge shaft

2) Used for cylindrical and non-cylindrical parts.

3) Used to quickly verify whether an outside dimension of a

part matches a preset dimension or falls within predefined

tolerances.

4) Snap gages facilitate making interchangeable parts.

2

4 Explain Hole basis System? Why it is Preferred

Answer:

In hole basis system the hole dimensions are kept constant

and shaft dimensions are varied to get the different clearances

4



and interferences with a single hole whose lower deviation is

zero.

- Basic size of the hole is taken as the lower limit of hole.

- The system is denoted by symbol ‘H’.

Hole basis system is preferred over the shaft basis system

because holes are machined by standard drills or reamers

having fixed dimensions, while the shafts can be turned or

ground to any given dimension. Hence it is convenient to

produce various sizes of shafts than holes of various sizes

5 A shaft of +/- 0.004 mm is to be checked by means of GO

and NOGO gauge. Design the dimension of gauge required.

Answer: Upper limit of shaft= Basic Size + 0.004 mm Lower limit of shaft= Basic Size - 0.004 mm Work tolerance= Upper limit of shaft -Lower limit of shaft =0.008 mm Gauge maker Tolerance=10% of work tolerance = 10/100 X 0.008 = 0.0008 mm Wear allowance = 10% of gauge tolerance = 10/100 X 0.008 =0.0008 mm Size of Go gauge= Upper limit of shaft + Wear allowance = Basic Size + 0.004 + 0.0008 Size of NO-GO gauge = Lower limit of shaft = Basic Size - 0.004 mm Design of plug gauge= Upper Limits for Go gauge= Basic Size + 0.004 + 0.0008 + 0.0008 Lower Limits for Go gauge= Basic Size + 0.004 + 0.0008 - 0.0008 Upper Limits for NO-Go gauge = Basic Size - 0.004 + 0.0008 Lower Limits for NO-Go gauge = Basic Size - 0.004 - 0.0008

4



6 Define limits and state their types.

Answer:

Limits of size are two extreme permissible sizes between

which the actual size is contained.

Types of limits

1 Upper (Maximum) limit

2 Lower (Minimum) limit

4

7 Define fit

Answer:

The degree of tightness or looseness between two mating

parts is called fit.

2

8 Design a a general type plug gauge for checking a hole

dimension 30−0.03+.0.05consider both wear allowance and gauge

tolerance as 10% of work tolerance.

Answer:

6



9 Draw the conventional diagram of limits and fits and define

the terms 1) Basic size 2) Fundamental deviation

Answer:

Fundamental

Deviation Zero line

Basic size

Datum line

4



Basic size:- It is the standard size of a part, with reference to which all the

limits of variations of size are determined. 1 mark Fundamental Deviation:- The algebraic difference between size and corresponding basic size is known as deviation.

10 What is the meaning of 35 H8f7? State meaning of each term

35 - 35 indicates Basic size is 35 mm.

Answer:

H – H indicates Basic hole is designated H. For the basic hole

fundamental deviation (lower deviation) is zero

8 – 8 indicates Hole with tolerance grade IT8

f – f indicates shaft

7 – 7 indicates shaft with tolerance grade IT7

4

11 Differentiate between Hole basis system and Shaft basis

system. (atleast four points)

Answer:

Sr.

No.

Hole Basis System Shaft Basis System

01 Lower deviation of

hole is zero

Upper deviation of shaft is

zero

02 Limits of hole is kept

constant and those on

shaft are varied to

obtained desired type

of fit

Limit on shaft is kept

constant and those on hole

are varied to obtain

desired type of fit

03 It is preferred for mass

production

It is not suitable for mass

Production

04 It is easy to

manufacturing

It is difficult to

manufacturing

05 It required less amount

of capital and storage

needed produced shaft

of different sizes

It needs large amount of

capital and space for tool

storage.

4

12 Define maximum clearance and minimum interference. Draw

suitable sketch.

Answer:

Maximum clearance: The maximum clearance of a fit is the

difference between the upper limit of the hole diameter and

the lower limit of the shaft diameter.

4



Minimum interference: The minimum interference of a fit is

the difference between the lower limit of the shaft diameter

and the upper limit of the hole diameter.

13 A shaft of 25 ± 0.004 mm is to be checked by means of GO

and NOGO gauge. Design the dimensions of a gauge

required.

Answer:

Maximum size of shaft = 25.004 mm

Minimum size of shaft = 24.996 mm

Go gauge (Maximum material condition) = 25.004 mm

No Go gauge (Minimum material condition ) = 24.996 mm

4

14 Write the examples of use of following types of fits :

(i) Push fit

(ii) Press fit

(iii) Running fit

(iv) Wringing fit

Answer:

4



i) Push fit Requires a moderate pressure. e.g. gear slip bushing, PVC pipe push fit with solvent ii) Press fit Interference required to maintain this fit e.g. bushing, bearing pins, gears, pulleys, shaft collar iii) Running fit Permits free rotation or movement e.g. nut bolt assembly, running shaft in bearing. iv) Wringing fit Provides either zero interference or clearance e.g. gears of machine tools

15 Explain with neat sketch hole basis system.

Answer: In hole basis system the hole is kept as the constant and the shaft upper and lower deviation values determine the type of fit. In hole basis system the Lower deviation of the hole will be Zero. - In this system lower deviation of the hole is Zero i.e the lower limit of hole is the same as basic size. - The higher limit of hole and the two limits of size for the shaft are then varied to give the desired type of fit. - - The system is denoted by symbol ‘H’.

Hole basis system is preferred over the shaft basis system because holes are machined by standard drills or reamers having fixed dimensions, while the shafts can be turned or ground to any given dimension. Hence it is convenient to produce various sizes of shafts than holes of various sizes

4



16 Differentiate between ‘Tolerance’ and ‘Allowance’.

Answer:

4

17 Describe ‘Taylor’s principle’ for design of limit gauges.

Answer:

It states that GO gauge should be designed to check the maximum material limit, while the NO-GO gauge should be designed to check the minimum material limit. Plug gauges are used to check the hole, therefore the size of the GO plug gauge should correspond to the low limit of hole, while that of NO-GO plug gauge corresponds to the high limit of hole. Similarly, the GO snap gauge on the other hand corresponds to the high limit of shaft while NO-GO snap gauge corresponds to the low limit of shaft. GO gauges should check all the related dimensions (roundness, size, location ect). Simultaneously whereas NO-GO gauge should check only one element of the dimension at a time. For example the bush to be inspected has a curved axis and a short GO plug gauge is used to check it. The short plug gauge will pass through all the curves of the bent bushing. This will lead to wrong result that the workpiece (hole) is within the prescribed limits. Actually such a bushing with curved hole will not mate properly with its mating parts and thus defective. A Go plug gauge with adequate length will not pass through a curved bushing and the error will be detected. A long plug gauge will thus check the cylindrical surface not in one direction but in a number of sections simultaneously.

4



Assignment No. 4

Screw Thread Measurement (Marks 06)

Sr.

No.

Question Marks

1 Calculate the diameter of best wire size for M20 x 1.5

Answer:

Best wire size d

d = p

2 sec

2

p = 1.5 mm

For metric thread = 600

d = 1.5

2 sec 30

d = 1.5

2 X 1.155 = 0.866 mm

4

2 Suggest a suitable method of inspection for the profile of screw

thread with sketches.

Answer:

Screw threads can be easily measured using profiler projector

and the thread profile is amplified and parameters are measured

by moment and comparison methods chart gauges are used for

comparison purpose so depending upon the type of screw thread

whether it is Whitworth thread or metric thread or acme method

we should select appropriate chart gauges. The chart gauge

should be mounted on the viewing screen, so this is a chart

gauge so which will have 2 contour lines and then we should

obtain the image of the contour of the work piece if the image

lays between the 2 lines on the chart gauge then the is this image

obtained so if it lies within these 2 lines corresponding with

maximum size and is corresponding to the minimum size so

there is a tolerance band in the image contour is well within the

tolerance band.

4



3 Draw a neat labelled sketch of screw thread micrometer. State

its principle of working

Answer:

Screw thread micrometer is similar to the simple outside

micrometer. The difference is instead of flat anvils, thread

profile anvils are used in screw thread micro meter . The anvils

are removable. Anvils are selected depending on angle of thread

and pitch of thread. Screw thread micrometer is used to measure

effective diameter of threads. The method of finding total

reading is same as that of the simple micrometer

4

4 List the different errors in threads.

Answer:

Different types of errors in threads

1. Drunken thread.

2



2. Progressive pitch error.

3. Periodic pitch error.

4. Irregular error.

5 State principle of three wire method. Where it is used?

Answer:

The three-wire method is the accurate method. In this method

three wires of equal and precise diameter are placed in the

groves at opposite sides of the screw. In this one wire on one

side and two on the other side are used. The wires either may

held in hand or hung from a stand. This method ensures the

alignment of micrometer anvil faces parallel to the thread

axis.

The three wire method is used in the direct measurement of

threaded gages and components. It has been found to be the

most satisfactory procedure for measuring the pitch diameter

of straight threads.

4

6 What is ‘best size of wire'? State the expression for the same,

indicating meaning of each term.

Answer: This wire is of such diameter that it makes contact with the flanks

of the thread on the effective diameter or pitch line. Actually effective diameter can be measured with any diameter wire which

makes contact on the true flank of the thread, but the values so

obtained will differ from those obtained with ‘best size’ wires if

there is any error in angle or form of thread. It is recommended that for measuring the effective diameter,

always the best size wire should be used and for this condition the

wire touches the flank at mean diameter line within ± 1/5 of flank length. With best size wire, any error on the measured value of

simple effective diameter due to error in thread form or angle is

minimized

4



Best wire size d

d = p

2 sec

2

Where, d= best wire diameter P= pitch of thread = thread angle

7 Explain the two wire method of effective diameter

measurement with neat sketch.

Answer: In this method the effective diameter of screw thread is measured

by placing two wires or rod of identical diameters between the

flanks of the thread as shown in fig. and measuring the distance

over the outside of these wires. - in two wire method wires of suitable size are placed between the standard and the micrometer

anvils and first micrometer reading is taken. – Let the micrometer reading over standard and wires=R1. The standard is then replaced by the screw thread to be measured

and the micrometer reading is taken. – Let the micrometer reading over screw thread and wires = R2 The diameter of the standard = S The diameter under the wires = T The effective diameter of the screw = E Thus E = T+ P Where, T = S – (R1 – R2) And P is a constant calculated for different threads, it depends upon the diameter of wire and pitch of the thread

4



8 How major diameter is measured using floating carriage

micrometer?

Answer:

Principle:- It works on the principle of nut and bolt or screw thread. Construction:- 1) A fig. shows floating carriage used for Measurement of major diameter 2) It consist of two centres maintained the piller of the based. 3) The centres are used for fixing the job which is shown in fig. 4) The floating body is kept on the based which has two pillers on it. 5) One piller consist of fudical indicator which sense the pressure applied on the anvil end. Working:- 1) As drum of micrometre rotates by one revolution it will move forward by one pitch of internal thread. 2) The movement will be measured using number of division on drum and main scale.

Dmajor = Ds + ( Rt – Rc )

Ds = Diameter of Setting Cylinder in mm

Rt = Reading on threaded object in mm

Rs = Reading on Setting Cylinder in mm

4

9 State and explain the various pitch errors in the screw

threads.

Answer: Pitch Errors in Screw Thread: Following are the Pitch errors

in screw thread

1. Progressive pitch error

2. Periodic pitch error

3. Irregular error

1. Progressive pitch error:- As the length of thread increases

,the cumulative pitch error increases this is called as

progressive pitch error. This error occurs when the tool work

velocity ratio is incorrect.

4



2. Periodic pitch error:-Error is getting repeated itself at a

regular intervals along the thread is known as periodic pitch

error. In this case, successive portions of the thread are either

longer mean. This type of error occurs when the tool work

velocity ratio is not constant.

3. Irregular error:- These type of errors are not having

specific causes and correspondingly no specified

characteristics also. These errors include erratic pitch error.

10 Explain the working principle of floating carriage dial

micrometer enlist its application.

Answer

Floating Carriage Micrometer:

-The floating carriage micrometer consists of a three units a)

A casting base carries a pair of centers, on which the treaded

work piece is mounted. b) Another carriage mounted at

exactly 900 to the above, which is capable to move parallel to

thread axis. c) Another carriage mounted on the above, which

is capable to move at 900 to the thread axis. - on one end of

the upper carriage, there is a fixed anvil and a fiducial

indicator which ensures that all the measurements are made at

same pressure.

Floating Carriage Micrometer is supplied with the set of

master cylinders and wires, which are used to measure

effective diameter of threads. Limitation of floating carriage

micrometer is , it can be used for measurement of external

threads only. Least count of this instrument is 0.002 mm

4



Applications :-

1) Measurement of Major diameter of screw thread

1) Measurement of Minor diameter of screw thread

1) Measurement of Effective diameter of screw thread

11 Explain terminology of screw thread.

Answer:

Terminology of screw thread

1) Major diameter: It is the diameter of an imaginary co-axial

cylinder which touches

the crests of an external thread and the root of an internal

thread.

2) Minor diameter: It is the diameter of an imaginary co-axial

cylinder which touches

the roots of external threads.

3) Pitch: It is the distance measured parallel to the screw

threads axis between the corresponding points on two

adjacent threads in the same axial plane.

4) Effective diameter: It is the diameter at which the thread

space and width are equal to half of the screw thread.

5) Angle of the thread: It is the angle between the flanks or

slope of the thread measured in an axial plane.

6) Lead: The axial distance advanced by the screw in one

revolution is the lead.

4



Assignment No. 5

Gear Measurement (Marks 06)

Sr.

No.

Question Marks

1 List different methods of measuring Tooth Thickness

Answer:

a) Measurement of tooth thickness by Gear tooth Vernier

Caliper

b) Measurement of tooth thickness by Constant Chord

method

c) Measurement of tooth thickness by base tangent

comparator method

2

2 Describe the procedure of measurement of tooth thickness using

constant chord method with neat sketch

Answer:

Constant chord of a gear is measured were the tooth flanks touch the flank of the basic rack. The teeth of the rack are straight and inclined to their centre lines at the pressure angle as Shown in fig. The gear tooth and rack space are in contact in the symmetrical position at the point of contact of the flanks. The chord is constant at this position irrespective of the gear of the system in mesh with the rack. This is the property utilized in the constant chord method of the gear measurement. The measurement of tooth thickness at constant chord simplified the problem for all number of teeth. Line AB is known as constant chord. The value of C and its depth from the tip d where it occurs can be calculated mathematically and then verified by an instrument.

4



d = m (1 -

4 cos sin )

c = AB = Constant chord c =

2 m . cos2

3 Draw the spur gear showing its terminology.

Answer:

Spur gear terminology

6

4 Define- Pitch diameter

Answer:

It is a diameter of a circle which by pure rolling action would

produce the same motion as the toothed gears.

2

5 List different types of errors in gear.

Answer: 1. Profile 2. Pitch 3. Cyclic 4. Gear tooth thickness 5. Backlash 6. Run out 7. Lead

2



6 Explain the principle of working of ‘Parkinson’s Gear tester”

with neat sketch.

Answer:

Use:- By using this instrument instead of measuring individual error

composite error are checked. Principle:- The gear to be tested is rolled in meshed with master gear and error

will indicated by dial gauge. Construction:- 1) The fixed spindle and other movable spindle is mounted on flat

plate. 2) The movable spindle moves with the base by rolling axle on main base plate. 3) The master gear is mounted on fixed spindle where the gear to

be tested is to mounted on movable spindle. 4) The dial gauge is to set to note the error which shown in fig. Working: 1) Master gear rotated slowly a gear to be tested will also get

rotation because of meshing. 2) The error in the manufacturing gear (tested gear) caused to gear

to moved away center line of spindle. 3) When gear is moves, the floating body is also moves by same displacement. 4) The vibrations in the reading can be observed and plotted in

graphical format.

4



7 Draw a neat labeled sketch of gear tooth vernier and name its

different parts.

4

8 Explain various errors in gears.

Answer: 1. Profile error : these errors can be traced out during inspection on optical profile projector. Many times tool marks, pits etc are

observed on the profile of the gear. 2. Pitch error : It is defined as the actual length between corresponding flanks of teeth not adjacent to each other. 3. Cyclic error : it is a error occurring during each rotation of

element under consideration. 4 Tooth thickness error: It is the difference between actual tooth

thickness and the required tooth thickness which is chordal tooth

thickness. This can be found with gear tooth calliper. 5 Backlash error : Backlash is the play between the mating tooth surfaces i.e the distance through which a gear can be rotated to

bring its non working flank in contact to the teeth of the mating

gear. 6 Run out error : It is the total range of the readings of a fixed

indicator with contact point applied to a surface rotated , without

axial movement about a fixed axis . Run out error is related to

concentricity of gear outer diameter with mounting hole. This error is find out using Parkinson gear tester 7 Lead error: Lead is the axial advance of a helix gear tooth

during one complete turn (360°), that is, the Lead is the axial

travel (length along the axle) for one single complete helical

revolution about the pitch diameter of the gear.

4

9 Define – Run out w.r.t. gear.

Answer:

Run out error: It is the total range of the readings of a fixed

indicator with contact point applied to a surface rotated,

2



without axial movement about a fixed axis. Run out error is

related to concentricity of gear outer diameter with mounting

hole.

10 Describe the procedure of measurement of tooth thickness using

‘Base Tangent Method’ with neat sketch

Answer:

Base tangent method

In this method, the span of a convenient number of teeth is

measured with the help of the tangent comparator.

Consider a straight edge ABC being rolled back and forth

along a base circle as shown in fig. Its ends thus sweep out

opposed involutes A2AA1 and C2CC1 respectively. Thus the

measurements made across these opposite involutes by span

gauging will be constant

Length of arc BD = distance between two opposite involutes = Nm cosφ[ tanφ – φ – π/2N + πS/N]

6



11 Explain the principle of measurement of gear tooth thickness

using a gear tooth vernier.

Answer:

Gear tooth vernier caliper is an instrument similar to the

ordinary vernier caliper but having a second beam at right

angles to the main beam. This additional beam carries a

tongue sliding between the jaws, which can be set on the

vernier scale so that, when it rests on the top of a tooth, the

tips of the jaws are at the correct distance from the tooth

flanks for the required measurements.

For measuring the chordal thickness, the tongue of the gear

tooth vernier is set so that the jaws will touch the flank at the

pitch circle. The thickness of the tooth is then measured on

the main scale of the instrument.

4



Assignment No. 6

Linear Measurement (Marks 06)

Sr.

No.

Question Marks

1 What are uses of surface plate?

Answer:

Surface plate is used as a measuring base or a datum surface

for testing of flatness of surfaces. Surface plate forms the

basis of the measurement. Surface plates are widely used in

where the inspection is carried out.

2

2 Give applications of V block

Answer:

1) V-Blocks are used to hold cylindrical jobs or pipes for

performing drilling or milling operations.

2) They are also used to hold the cylindrical objects for

marking the centres for further lathe machining.

2

3 What are types of callipers? Sketch any one.

Answer:

Types of calipers

1 Inside caliper

2 Outside caliper

3 Divider caliper

4 Oddleg caliper

5 Vernier caliper

6 Dial caliper

7 Digital caliper

8 Micrometer caliper

4

https://en.wikipedia.org/wiki/Calipers#Oddleg_caliper



4 Explain vernier caliper with neat skech.

Answer:

A vernier caliper is a precision measuring tool. It can be used

for three types of measurements, outside distance (such as the

length of an object) , inside distance such as the width of a

groove or the diameter of a large hole, and depth, such as the

depth of a hole or the height of a step.

4

5 Explain micrometer with neat sketch.

Answer:

A micrometer is a precision measuring instrument, used to

obtain very fine measurements and available in metric and

imperial versions. Metric micrometers typically measure in

0.01mm increments. They are widely used in mechanical

engineering for precisely measuring components.

Micrometers have two scales: a primary scale, on the barrel

or sleeve, and a secondary scale, on the thimble. Values are

taken from each of these scales and combined to make the

total measurement.

4



6 State uses of vernier height gauge.

Answer:

1) A height gauge is used for measuring the height of objects.

2) It can be also used for marking of jobs.

4

7 What are uses of combination set.

Answer:

1) Combination set is used non-precision instrument to be

used in layout and inspection work

2) The squaring head also contains a spirit level which is used

to test the surfaces for parallelism.

3) The squaring head and scale can be used for height and

depth measurements, inside and outside squaring operations.

4) The centre head attachment is used with the scale to locate

the centre of bar stock.

4

8 Explain vernier depth gauge with neat sketch.:

Answer:

A Vernier depth gauge is a useful measurement device

equipped with two scales, one fixed and one that slides. It is

used to measure the depth of a slot, hole or recess.

4

9 Explain micrometer depth gauge with neat sketch.

Answer:



The depth gauge micrometer is a precision measuring

instrument, used by engineers to measure depths. Each

revolution of the ratchet moves the spindle face 0.5 mm

towards the bottom of the blind hole. The diagram shows

how the depth gauge is used. The ratchet is turned clockwise

until the spindle face touches the bottom of the blind hole.

The scales are read in exactly the same way as the scales of a

normal micrometer

10 List the minimum no. of slip gauges to be wrung together to

produce an overall dimension of 73.975 mm using a set of 87

pieces.

Answer:

4



73.975 = 70 + 2.5 + 1.47 + 1.005

11 Explain the wringing of slip gauges with neat sketch.

Answer:

The slip gauges are joined by a sliding process called

wringing, which causes their ultra-flat surfaces to cling

together. A small number of gauge blocks can be used to

create accurate lengths within a wide range.

Wringing is nothing, but removing the atmospheric air

between two mating surfaces of any two gauge blocks, so that

the blocks stick to each other due to vaccum.

4

12 A cylinder of 80mm diameter was placed between the

micrometer anvils due to inaccurate placement, the angle

between the micrometer and cylinder axis was found to be 1

minute .calculate the amount of error in the measured diameter,

take anvil diameter 6mm.

4



Answer:

D’ = D sec + 2 (d

2 tan )

= D sec + d tan

Error = D’ – D = D (sec – 1) + d tan

D = 80 mm

= 1’ = 1

60

0

d = 6 mm

Error = 80 (sec 1

60– 1) + 6 tan

1

60

= 80 (1 – 1) + 6 (0.000291) = 0.001745 mm

14 Measure a distance of 6.905 mm with the help of slip gauges

using 112 set of slip gauges. Show the arrangement with neat

sketch.

4

18 Prepare stack of slip gauges for height 58.975 mm using set

M112.

4



21 Draw the diagram indicates a reading of 4.32 mm on vernier

scale.

Answer:

4



Assignment No. 7

Angular Measurement (Marks 06)

Sr.

No.

Question Marks

1. An angle of 49° 29' 18" is to be developed by using standard

angle gauge set of 13 pieces. Calculate the gauges required and

sketch the arrangement.

Answer:

06



2. The angle of Taper plug gauge is to be checked using sine

centre and slip gauges ,Sketch the set up and describe the

procedure.

Answer:

a) Clean the universal bevel protractor and workpiece.

b) Measure the approximate angle using universal bevel

protractor in degree (decimal form)

c) Calculate height of slip gauges h required.

sin = h

L

h = L sin mm

L = Length of sine bar = 300 mm

d) Select slip gauges from M87 set to make size h

e) Keep workpiece on sine bar and support one roller with

slip gauges selected of height h

f) Ckeck top surface of workpiece is parallel with datum

surface using dial indicator or vernier height gauge.

g) Deviation Angle calculated from formula

tan = h

l

l = length of workpiece

h = difference in height at two ends of workpiece

Calculate Unknown angle ’ = ±

g) By trial and error increase or decrease height of slip

gauge to make top surface parallel to datum

surface and new height of slip gauges is noted as h’

h) Calculate accurate angle ’ as below

sin’ = h′

L

’ = sin -1 h′

L

06



3. Explain the construction of Bevel Protractor with neat sketch

Answer:

It is probably the simplest instrument for measuring the angle

between two faces of component. It consists of a base plate

attached to the main body, and an adjustable blade which

is attached to a circular plate containing vernier scale. The

adjustable blade is capable of rotating freely about the centre

of the main scale engraved on the body of the instrument and

can be locked in any position

06

4. State the limitation of sine Bar

Answer:

Limitation of sine Bar

1) Sine bar operating on the sine principle are fairly reliable

at angles less than 15°, but

become increasingly inaccurate as the angle increases.. 2) The sine bar inherently become increasingly impracticable

and inaccurate as the angle exceeds 450

3) The sine bar is physically clumsy to hold in position.

4) The body of the sine bar obstructs the gauge block stack,

even if relieved.

5) Slight errors of the sine bar cause large angular errors.

6) Long gauge stacks are not nearly as accurate as shorter

gauge blocks.

7) Temperature variation becomes more critical.

8) A difference in deformation occurs at the point of roller

contact to the support surface and to the gauge blocks,

because at higher angles, the weight load is shifted more

toward the fulcrum roller.

9) The size of gauges, instruments or parts that a sine bar can

inspect is limited, since it is not designed to support large or

heavy objects.

02



5. List different angular measuring devices.

Answer: angular measuring devices

1) Universal Bevel Protractor

2) Sine bar

3) Spirit level

4) Clinometer

5) Angle gauges

6) Autocollimator

7) Angle dekker

02

6. List different sets of angle gauges available in Metrology lab

with their values.

Answer:

Set of angle gauges

1°, 3°, 9°, 27°, 41° - 5 pieces

1’, 3’, 9’, 27’ - 4 pieces

3”, 6”, 18”, 30” - 4 pieces

Total - 13 pieces

& 1 square block

04

7. Explain with neat sketch principle of working of clinometers

Answer:

Circular Scale Housing Spirit level Rotary member

Base Clinometer is one type of application of spirit level. It consists of

one spirit level mounted on rotary member carried in housing. The bottom face of housing forms base of the instrument, for the

measurement purpose clinometers is first kept on one side of the

inclined surface and reading is taken when vapour bubble is at centre position ,similarly it is kept on another side and reading in

terms of angle is taken which is shown in fig.

04



8. Differentiate between angle gauges and slip gauges

Answer:

Angle gauge Slip gauge 1. Angle gauges enables angle to be set to the nearest 3"

1. Slip gauges are universally accepted end standard of

length in industry.

2. It has triangular in cross section

2. It has rectangular in cross section

3. The angle gauges are

marked with engraved V

which indicates the direction of the inclined angle which

affects on addition and

subtraction of angles.

3. The direction of slip gauges

is not affected in addition and

subtraction of dimension.

4. Angle gauges are available

in 12 and 13 pieces set.

4. Slip gauges are available in

M-45, M-87, M-112 and M-

33/2.

5. Any angle can built by

adding and subtraction of

angle gauges in combination

with square block.

5. Any linear dimension can

built by adding the

combination of slip gauges.

6 Slip gauge

6 Angle gauge

04

9. An angle of 490 29’ 18’’ is to be developed by using standard

angle gauge set of 13 pieces. Calculate the gauges required

and sketch the arrangement.

Answer:

Angle gauge set of 13 pieces

[ 10 30 90 270 410 ] [ 1’ 3’ 9’ 27’ ][3” 6” 18” 30”]

490 = 410 + 90 - 10

29’ = 27’ + 3’ - 1’

18” = 18” total 7 pieces required to build the given

dimension.

4



Arrangement of angle gauges

10. Explain why size bar is not used for angle greater than 45° if

accuracy in angle measurement is required.

Answer:

Sine bar is not used for measurement of angle greater than

450 :

We know that angle is measured by using sine bar is based on

sine principle,

sin θ = h / l

Where, h = Required slip gauge combination

l = center distance of rollers.

The relationship between the angular setting accuracy (dθ)

and any error which may be present in the slip gauge

combination (dh) or the center distance between roller (dl)

can be determined by differentiating the equation sin θ = h / l

Or h = l sin θ

The effect of error in spacing of roller centers ( dl ) or error in

combination of slip gauges dh on angular setting accuracy can

be obtained by partial differentiation of the above equation.



From above it is clear that error is the function of tan θ. Below 450

errors is smaller which increases rapidly above 450, as tan 450 is

equal to one. Thus in general it is preferable not to use the sine bar for measuring angles greater than 450

if high accuracy is required



11. Explain with neat sketch principle of working of angle

dekkor

Answer:

Explanation: O is a point source of light placed at the principal focus of a collimating lens. The rays of the light from O incident on the lens will now travel as a parallel beam of light. If this beam now strikes a plane reflector which is normal to the optical axis, it will be reflected back along its own path and focused at the same point O. If the plane reflector be now tilted through a small angle θ, then parallel beam will be

deflected through twice this angle , and will be brought to focus

at O’ in the same plane at a distance X from O. Obviously, X=

2θ. f, where f is the focal length of the lens.

04

12. If length of sine bar is 100 mm, find the length of slip gauges

required to build an angle of 14° by using M87 slip gauge set.

Answer:

L = 100 mm

= 140

sin = h / L

h = L . sin

= 100 sin 14

= 24.18 mm

04



Assignment No. 8

Surface Finish Measurement (Marks 06)

Sr.

No.

Question Marks

1 Define “Lay”

Answer:

Lay is the direction of the predominant surface pattern,

ordinarily determined by the production method used.

2

2 In the measurement of surface roughness, heights of 10

successive peaks and valleys were measured from a datum as

Peaks- 45, 42,40,30,35 microns

Valleys 30,25,25,24,18 microns

Determine the Ra Value

Answer:

Ra = 45+42+40+⋯…+35

10 =

314

10

Ra = 31.4 microns

6

3 State the principle of Surface roughness Tester

Answer: Principle of Surface roughness Tester

i) A skid or shoe which is drawn slowly over the surface

either by hand or by motor drive. The skid when moved over

the surface, follows its general contours and provides a datum

for the measurements.

ii) A stylus or probe which moves over the surface with the

skid.

iii) An amplifying device for magnifying the stylus

movement and an indicator.

iv) A recording device to produce a trace or record of the

surface profile

2

4 List the causes of surface roughness

Answer:

Causes of surface roughness

Due to direct action of cutting tool, friction, wear, corrosion,

tool feed rate

Due to disturbance in set up, misalignment of centres, lack of

straightness of guide ways, non linear feed motion, vibrations

2

5 Define the following terminologies as per IS 3073-1967 for

surface finish for a machine tool. i) Primary texture

ii) Secondary Texture iii) Lay iv) Sample length v) Flaw

Answer:

i) Primary Texture:- the surface irregularities of small

wavelength are called primary texture or roughness.

ii) Secondary Texture:- The surface irregularities of

considerable wavelength of periodic character are called

secondary texture or waviness.

4



iii) Lay : Lay is the direction of predominant surface pattern, decided by the manufacturing process adopted or lay is decided

depending on manufacturing process adopted iv)Sampling Length:- It is the length of the profile necessary

for the evaluation of the irregularities to be taken into

account. It is also known as cut off length.

v) Flaws are irregularities which occur at one place or at

relatively infrequent or widely varying intervals in surface

(like scratches, cracks, random blemishes, etc.)

6 In the measurement of surface roughness, heights of 20

successive peaks and valleys measured from a datum are

as follows :

45, 25, 35, 40, 25, 16, 40, 22, 25, 34,

25, 40, 20, 36, 28, 18, 20, 25, 30, 38.

If the measurements were made over a length of 20 mm,

determine the CLA and RMS values of the surface.

Answer:

1) CLA Value= 45+25+35+⋯…+38

20

CLA Value = 29.35unit

2) RMS Value = √452+252+352+..….+382

20

RMS Value = √930.95 RMS Value = 30.51unit

4

7 Explain the principle and working of Taylor Hobsan Talysurf

with block diagram.

Answer:

The Talysurf is an electronic instrument working on carrier

modulating principle. This instrument gives the information much

more rapidly and accurately. The measuring head of this instrument consists of a diamond stylus

of about 0.002mm tip radius and skid or shoe which is drawn

across the surface by means of a motorized driving unit (gearbox), which provides three motorized speeds giving respectively X 20

and X 100 horizontal magnification and a speed suitable for

4



average reading. A neutral position in which the pick-up can be traversed manually

is also provided. the arm carrying the stylus forms an armature

which pivots about the center piece of E-shaped stamping as shown

in fig. on two legs of (outer pole pieces) the E – shaped stamping there are coils carrying an a. c. current. These two coils with other

two resistances form an oscillator. As the armature is pivoted about

the central leg, any movement of the stylus causes the air gap to vary and thus the amplitude of the original A. C. current flowing in

the coils is modulated. The out-put of the bridge thus consists of modulation only as

shown in fig. This is further demodulated so that the current now is directly proportional to the vertical displacement of the stylus only. The demodulated output is caused to operate a pen recorder to

produce a permanent record and a meter to give a numerical assessment directly. In recorder of this statement the marking

medium is an electric discharge through a specially treated paper

which blackens at the point of the stylus, so this has no distortion due to drag and the record strictly rectilinear one.

8 Distinguish between ‘Primary texture’ and ‘Secondary

texture’.

Answer:

Primary Texture Secondary Texture It is the roughness of surface. It also called micro-

geometrical error. It is

irregularity of small wavelength

It is also the roughness of surfaces. It is also called as

macro-geometrical error.

It is irregularities of larger wavelength.

These irregularities of third

order and fourth order i.e. of

feed marks of cutting tool and rupture of material due to

separation of chips.

These irregularities are caused due to direct action of cutting

element on material

This irregularity of first and

second order .i.e. of due to

lack of straightness of guide ways of tool, weight of

material itself and due to

vibration and chatter marks.

4

9 Define the terms a) CLA b) Ra c) RMS d) Rz

Answer:

i) CLA : Centre line average ( CLA ) is the value of height of

the undulation of the surface . This practice is adapted for

obtaining the numerical evaluation of the surface texture is to

use a parameter base on the cross sectional profile of the

surface under examination.

4



ii)Ra: Arithmetic mean deviation from the mean line of

profile is the average value of the ordinates from the mean

line Ra (Roughness average)

iii) RMS value : It is defined as the square root of the

arithmetic means of values of the squares of ordinates of

surface from mean line.

iv) Rz : The average difference between the five highest peaks

and five deepest valleys within the sampling length measured

form a line , parallel to the mean line and not crossing the

profile are taken which are defined as



10 State the methods of evaluation of surface roughness. Explain

any one in detail.

Answer:

Methods of Evaluation of surface roughness 1. Root mean square value method ( RMS Value ):

It is defined as the square root of the arithmetic means of

values of the squares of ordinates of surface from mean line.

2. Centre line average method ( CLA Value )

3. Ten point average method ( Rz Value ): The average difference between the five highest peaks and

five deepest valleys within the sampling length measured

form a line , parallel to the mean line and not crossing the

profile are taken which are defined as

4



11 Define – RMS value.

Answer:

R.M.S. value is defined as the square root of the arithmetic means of the values of the squares of the ordinates of the surface measured from a mean line.

2

12 Define sampling length.

Answer:

It is the length of profile necessary for the evaluation of the irregularities to be taken into account. It is measured in a direction parallel to the general direction of the profile. The sampling length is usually defined as the cut-off length (λc) of the filter used to separate roughness and waviness.

2

13 Explain the principle of stylus probe type direct instrument

measurement of surface finish.

Answer:

Principle of Stylus Probe type direct measuring instruments used for surface finish: In this instrument a skid or shoe is drawn slowly over the surface by hand or by motor drive. This skid which is moved over the surface, follows its general contours and provides a datum for the measurement. In some cases where directly probe is used, this probe traces the actual profile of the work piece i.e. crest and valleys on the work piece as it passes over the sampling length. Then with the help of some mechanical arrangements or microprocessor based arrangements this profiles are magnified and by doing calculations the surface finish is measured.

4



Assignment No. 9

Machine Tool Testing (Marks 08)

Sr.

No.

Question Marks

1 Draw the alignment test of squareness of spindle axis of radial

drilling machine.

Answer:

Squareness testing of drilling machine spindle

The test is performed by placing the straight edge in positions A A’ and BB’ . The work table is arranged in the middle of its vertical travel. The dial guage is mounted in the tapered hole of the spindle and its feeler is made to tough the straight edge first at A and readings are taken . Then the spindle is rotated by 1800 so that the feeler touches at point A ‘ and again the reading is taken. The difference of these two readings is the error in squareness of spindle axis with table. Similar reading is taken by placing the straight edge in position BB’. Permissible errors are 0.08 / 300 mm with lower end of spindle inclined towards column only for set up AA’ and 0.05 / 300 mm for set up BB’.

4

2 Describe the principle of “Interference “ with sketch.

Answer:

Interference is the process in which two or more light, sound,

or electromagnetic waves of the same frequency combine to

reinforce or cancel each other, the amplitude of the resulting

wave being equal to the sum of the amplitudes of the

combining waves.

4



3 Explain how the straightness of lathe bed may be checked by

using spirit level.

Answer:

4

4 State the function of CMM

Answer:

A coordinate measuring machine (CMM) is a device that

measures the geometry of physical objects by sensing discrete

points on the surface of the object with a probe.

2

5 What is alignment test of a machine tool. State the

instruments/ equipments needed for it.

Answer:

Various geometrical checks are carried out in static condition, called as alignment test.

Instruments/ equipments needed

• Dial gauge

• Dial gauge stand

• Magnetic Dial gauge stand

• Engineering Square

• Spirit level

• Test Mandrel

• Straight edge

• Slip gauges set

• Optical Flat

• Autocollimator

• Beam Comparator

4

6 Describe with neat sketch alignment testing of a lathe

machine as per IS standard procedure.

Answer:

Levelling of the Machine.

4



True Running of Locating Cylinder of Main Spindle.

Axial Slip of Main Spindle and True Running of Shoulder

Face of Spindle Nose.

True Running of Headstock Centre.



Parallelism of the Main Spindle to Saddle Movement.

7 State the procedure for straightness measurement of a lathe

bed guides.

Answer:

In case of measurement by auto-collimator, the instrument is

placed at a distance of 0.5 to 0.75 metre from the surface to

be tested on any rigid support which is independent of the

surface to be tested. The parallel beam from the instrument is

projected along the length of the surface to be tested. A block

fixed on two feet and fitted with a plane vertical reflector is

placed on the surface and the reflector face is facing the

instrument. The reflector and the instrument are set such that

the image of the cross wires of the collimator appears nearer

the centre of the field and for the complete movement of

reflector along the surface straight line, the image of cross-

wires will appear in the field of eyepiece. The reflector is

then moved to the other end of the surface in steps equal to

the centre distance between the feet and the tilt of

the reflector is noted down in second from the eyepiece.

4



8 Distinguish between ‘Alignment test’ and ‘performance test’

of machine tool.

Answer:

Sr.

No.

Alignment test Performance test

1 Various geometrical checks are carried out, called as alignment test.

Actual performance of job on machine tool is called performance test.

2 These tests are carried out at static condition.

These tests are carried out at working conditions.

3 In this test positions of components and displacement relative to one another are checked.

In this test the jobs manufactured on machine And its tolerance limits as per design are checked.

4 e.g alignment of axis of lathe spindle to saddle movement.

e.g. manufacturing of job on lathe

4

9 Explain how the parallelism between two planes and

parallelism between two axes is checked with neat sketch.

Answer:

Parallelism between two planes

Two planes are said to be parallel, when their distance

from each other is measured anywhere on the surface and at

least in two directions, and the maximum error (the difference

between the maximum and the minimum dimensions

obtained when measuring) over a specified length does not

exceed an agreed value. The test for parallelism of two planes

is carried out in two directions (generally

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perpendicular to each other). The dial indicator, which is held

on a support with a flat base, is moved in one plane over a

given length, and the feeler is made to rest against the second

plane and the deviations noted down.

ii) Parallelism between two axes.

This test is made in two planes, first plane being the one

passing through one of the two axes and as near as

possible to the second axis, and the other plane is

perpendicular to the first one. In this test, the dial indicator is

held on a support with a base of suitable shape, so that it

slides along a cylinder representing one of the two axes; and

the dial indicator is adjusted so that its feeler slides

along the cylinder representing the second axis. The

maximum deviation between the axes at any point may

be determined be gently rocking the dial indicator in a

direction perpendicular to the axes. In the same way

the parallelism may be tested in the perpendicular

plane.

10 Explain procedure to determine whether the given surface is

concave or convex by using optical flat.

Answer:

Concave surface:

If the optical flat is placed on some spherically concave

surface. And the contact is made at the central high point and

in centre a bright circle will be visible. Around it, there will

be concentric dark and bright circular fringes. As the distance

from the centre increases, the separation between optical flat

and surface keeps on increasing and the fringes become

narrow and more closely spaced as shown in fig.

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Fringe pattern as observed through optical flat.

Convex surface:

To distinguish between the two conditions of convex and

concave surfaces one edge of the optical flat is lightly

pressed. In case of convex surface, by light pressure the

optical flat will rock on a new high spot and the centre of the

fringe pattern will move as shown in Fig. Also the outer

fringes will move closer together. In case of spherically

concave surface, the flat is resting on a line passing around

the surface and on lightly pressing the edge of the optical flat,

the edge line does not move as the pressure is varied. Rather,

light pressure at the centre will cause the optical flat to be

deflected and will become more nearly parallel to the

concave surface, thus reducing the number of fringes

observed. Thus if by light pressure, the centre of fringes is

displaced and the fringes are brought closer, it is convex

surface and the level at that place must be lowered down to

form a flat surface. If by light pressure the number of fringes

is reduced and the fringes move apart, it is concave surface.



Test for convex surface.



11 Sketch and interpret the meaning of various interference

fringes patterns observed using optical flat.

Answer:

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12 Draw the following alignment test of Lathe Machine :

(i) Parallelism of tail stock

(ii) Run out of spindle

Answer:

(i) Parallelism of tail stock

(ii) Run out of spindle

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13 Define straightness.

Answer:

In metrology a line is said to be straight over a given length if its deviations w. r. t. to the ideal reference line are within specified tolerance limit. Or if the variations of the distances of its points from two planes perpendicular to each other and parallel to the general direction of the line remain within specified tolerance limit.

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14 Draw the following alignment test of Lathe machine.

1) Levelling of Lathe machine

2) Parallelism of main spindle to saddle movement.

Answer 1) Levelling of Lathe machine

2) Parallelism of main spindle to saddle movement

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15 Describe the flatness testing done by using optical flats.

Answer:

Answer:

Principle: The wave length of sodium yellow light is 1/160th

of a cm and with this as reference it is possible to examine

the flatness of a surface to high degree. The flatness to this

degree is said to be optically flat

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Working : The optical flat consists of a special glass disc of

about 12 to 20 mm thick and diameter ranging from 38 to 75

mm with their surface finished flat. For testing purpose a

sodium discharge lamp is used. The surface to be tested must

be sufficiently polished to reflect light. The optical flat is

placed on the surface to be tested. Sodium yellow light is the

directed on to the flat surface through optical flat. The

reflection observed is termed as „Fringes‟. The nature of

surfaces viewed through optical flat are given below

Assignment No. 1 Introduction to Metrology (Marks 10) · 2. Scientific metrology: i) Concerns the...

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Transcript of Assignment No. 1 Introduction to Metrology (Marks 10) · 2. Scientific metrology: i) Concerns the...