ENGG. METROLOGY for MECHATRONICS (GTI/MCT/07/01)

1.0) Engg. Measurements1.0) Engg. Measurements

By By SREERAJSREERAJ

ENGG. METROLOGY for MECHATRONICS (GTI/MCT/07/01)

1.0) Engg. Measurements1.0) Engg. Measurements

By By SREERAJSREERAJ

OBJECT OF MEASUREMENTOBJECT OF MEASUREMENT

MEASUREMENT :

Help to timely detect inaccurately machined parts and to avoid rejects and defects.

HOW TO MEASURE?1)MEASURING INSTRUMENT :

Any device that may be used to obtain a dimensional or surface measurement.2)GAUGES

Intended for quickly checking the parts in production, that is to determine whether or not a dimension is within its specified limits. It only compares.

STANDARDS OF MEASUREMENT

1) International standard Metre. In 1960 11th general conference on weights and

measures adopted the International System of Units(SI).2) Imperial Standard Yard.

LINE AND END STANDARDS In line standard line standard unit of length is defined as the

distance between the centres of engraved lines as in a steel as in a steel rulerule. In the end standards end standards it is the distance between the end faces of the standard as in a micrometer. as in a micrometer.

DDue to the practical convenience, end standard scores over the line standard.

CLASSIFICATION OF MEASURING INSTRUMENTSCLASSIFICATION OF MEASURING INSTRUMENTSCLASSIFICATION OF MEASURING INSTRUMENTSCLASSIFICATION OF MEASURING INSTRUMENTS

ACCURACY

PRECISION INSTRUMENTSEg : Micrometre,Vernier caliper etc.PRECISION INSTRUMENTSEg : Micrometre,Vernier caliper etc.

NON-PRECISION INSTRUMENTSEg : Graduated rule,Scale etc.NON-PRECISION INSTRUMENTSEg : Graduated rule,Scale etc.

MODE

DIRECT READING : Used to determine the actual dimension and size.DIRECT READING : Used to determine the actual dimension and size.

IN DIRECT or TRANSFER TYPE : It transfer the measurement from the work to a direct measuring instrument and a comparison is made.

IN DIRECT or TRANSFER TYPE : It transfer the measurement from the work to a direct measuring instrument and a comparison is made.

TYPELINE MEASURING DEVICESLINE MEASURING DEVICES

END MEASURING DEVICESEND MEASURING DEVICES

Most measuring instruments have specific and limited uses, although some can be used for more than one purpose. Some are measuring linear dimensions , some are for angular or geometric dimensions and some are devoted for measuring surface finish. Some are for reference purposes as standards of comparison.

PRINCIPAL MEASURING INSTRUMENTSPRINCIPAL MEASURING INSTRUMENTS

1.LINEAR1.LINEAR

A.NON PRECISION(a) Steel Rule(b) Calipers(c) Dividers(d) Telescopic Gauge(e) Depth Gauge

B.PRECISION(a) Micrometers(b) Vernier Calipers(c) Height Gauges(d) Slip Gauges

C.COMPARATORS

D.MEASURING MACHINES

2.ANGULAR2.ANGULAR

A.NON PRECISION(a) Protractors(b) Adj.Bevel(c) Engineers Square(d) Combination set

B.PRECISION(a) Bevel Protractors(b) Dividing Head(c) Sine bar(d) Angle Gauges(e) Spirit Levels(f) Clinometers(g) Autocollimators

3.TAPER3.TAPER

4.SURFACE4.SURFACE(a) Straight edge(b) Surface Table(c) Surface Gauge(d) Optical Flat(e) Profilometer(f) Use of Laser

LINEAR MEASUREMENT – NON PRECISIONLINEAR MEASUREMENT – NON PRECISION

Includes the measurement of length,diameter,height,thicknessetc.Basic principle of linear measurement is that of comparison with standard dimensions on suitably engraved instrument or device.

STEEL RULE

It is one of the most useful tool in the shop for taking linear dimensions of blanks and articles to an accuracy of from 1.0 to 0.5 mm. This hardened steel strip rules are available in different lengths 150,300,500 and 1000mm.Usually marked in both mm and inches.

CALIPERCALIPERSS

A caliper is used to transfer and compare a dimension from one object to another or from a part to a scale or micrometer where the measurement cannot be made directly. There are 4 types mainly.

OUTSIDE CALIPEROUTSIDE CALIPER It is a two legged steel instrument with its legs bent inwards. It is used for measuring or comparing thickness, diameters, and other outside dimensions. A steel rule must be used in conjunction with them if a direct reading is desired. The size of a caliper is specified by the greatest distance it can be opened at the tip of the legs.

INSIDE CALIPERINSIDE CALIPER

An inside caliper is exactly similar to an outside caliper in appearance with its legs bent outward. This is used for comparing or measuring hole diameters, distances between shoulders or other parallel surfaces of any inside dimension.

SPRING CALIPERSPRING CALIPERSPRING CALIPERSPRING CALIPER

For finer work the use of spring caliper both outside and inside advocated. A loop spring on top of the joint between the two legs applies force tending to separate the legs at the bottom. An adjusting nut and screw keep the legs in position. When a spring caliper is applied to an object , it must make sure contact but not to be forced. A sense of “feel” or “touch” is necessary to use a caliper successfully.

HERMAPHRODITE CALIPERHERMAPHRODITE CALIPERHERMAPHRODITE CALIPERHERMAPHRODITE CALIPER

This is sometimes called odd-leg caliper. It has one pointed leg like a divider and one bent leg as shown in fig. The caliper is extremely useful for scribing lines parallel to the edge of the work and for finding the centre of a cylindrical work.

TRANSFER TRANSFER CALIPERCALIPERTRANSFER TRANSFER CALIPERCALIPER

This is convenient for measuring recessed work where ordinary calipers cannot be with drawn. The nut is first locked and the caliper opened or closed against the work. The nut is then loosened and the leg swung clear of the obstruction leaving the auxiliary arm in position. The leg can now be moved back against the stop, where it will show the previous size.

DIVIDERDIVIDERSS

DIVIDERDIVIDERSS

A divider is similar in construction to a caliper except that both legs are straight with sharp hardened points at the end. This is used for transferring dimensions , scribing circles, and doing general lay out works. A large circle or an arc having a large radius may be made with a tool called TRAMMEL or BEAM COMPASS.

TELESCOPIC TELESCOPIC GAUGEGAUGETELESCOPIC TELESCOPIC GAUGEGAUGE This is used for measuring the inside size

of slots or holes. The gauge consist of a handle and two plungers, one telescopic in to the other and both under spring tension. The plungers can be locked in position by turning a knurled screw at the end of the handle. The measurement is made by first compressing plungers and locked in position and after inserting to the slot it is allowed to expand to touch the edges and locked in place. After taking out of the slot measurement can be made with the help of an outside micrometer like instruments.

DEPTH GAUGEDEPTH GAUGEDEPTH GAUGEDEPTH GAUGE

This is used for measuring the depth of blind holes, slots, grooves, the height of shoulders in holes etc. this is essentially a narrow steel rule to which a sliding head is clamped at right angles to the rule. The head forms a convenient marker in places where the rule must be held at a distance from the point being measured.

LINEAR MEASUREMENT - LINEAR MEASUREMENT - PRECISIONPRECISION

LINEAR MEASUREMENT - LINEAR MEASUREMENT - PRECISIONPRECISION

VERNIER VERNIER CALIPERCALIPERVERNIER VERNIER CALIPERCALIPER

Primarily intended for measuring both inside and outside diameters of shaft, thickness of parts etc. to an accuracy of 0.02mm by a vernier scale attached to the caliper.

A vernier scale is the name given to any scale making use of the difference between two scales which are nearly, but not quite alike, for obtaining small differences.

INTERNAL JAW

LOCKING NUT

MAIN SCALE

VERNIER SCALE

FIXED JAW

MOVABLE JAW

49 MMMAIN SCALE

VERNIER SCALEVERNIER SCALEVERNIER SCALEVERNIER SCALE

READING : On the main scale,1cm is divided in to 10 parts, each being 1mm. The vernier scale has 50 divisions. Every 5th division is numbered. The length of 50 divisions on the vernier is equal to the length of 49 divisions (49mm) in the main scale.Therefore, each vernier division = 49/50 = 0.98mmDifference b/w one division on the main scale and one division on the vernier is equal to 1-0.98 = 0.02mm

To read the vernier first note the centimetres, millimeters, that the zero of the vernier has moved from the zero of the main scale. Then count the number of divisions on the vernier scale from zero line to the line which coincides with a line on the main scale.

Example :

1) 2 MAIN DIVISIONS

2) 1 SUB DIVISION 3) COINCIDING LINE 15TH

1) 2 Main Divisions = 2x10mm = 20mm2) 1 Sub-Division = 1x1mm = 1mm3) 15 Vernier Divisions = 15x 0.02mm = 0.30mm total = 21.30mm

Assignment 1Assignment 1

1) Main divisions = 2) Sub divisions = 3) Vernier divisions =

3 = 3 x10mm = 30mm5 = 5 x 1mm = 5mm37 = 37 x 0.02 = 0.74mm

Total = 35.74mm

ASSIGNMENT ASSIGNMENT 2 :2 :ASSIGNMENT ASSIGNMENT 2 :2 :

READING : 9.16mm

ASSIGNMENT ASSIGNMENT 3 :3 :

ASSIGNMENT ASSIGNMENT 3 :3 :

READING : 17.16mm

ENGLISH VERNIER CALIPER.ENGLISH VERNIER CALIPER.ENGLISH VERNIER CALIPER.ENGLISH VERNIER CALIPER.

An English vernier has an accuracy of 0.001 in.

On the main scale, 1 Inch is divided in to 10 equal parts and each 1/10th is divided in to 4 giving ¼ of 1/10th = 1/40 in = 0.025 in. The vernier scale has 25 divisions, which are numbered from 0 to 25. every 5th division is numbered. The length of 25 division on the vernier is equal to the 24 divisions on the main scale. 24 divisions being equal to 24x0.025= 0.6 in.

One division on the vernier equals 1/25 of 0.600 or 0.024 in. The difference, therefore, b/w one division on the main scale and one division on the vernier is 0.025 – 0.024 = 0.001 in.= 1/1000 in.

MICROMETERMICROMETERMICROMETERMICROMETER

This instrument, invented by William Gascoigne in the 17th century, is often used to measure diameters of wires and spheres , thickness of parts, parallelism of faces etc. To improve accuracy (as with all measurements) we would take several readings and find their average. Thus we could not only ensure accuracy but, by taking readings at different positions along the length, we could test for a consistent diameter along a piece of work.

There are different kinds of micrometers available. a) EXTERNAL b) INTERNAL or INSIDE c) DEPTH d) SCREW THREAD etc.

EXTERNAL MICROMETER.EXTERNAL MICROMETER.

It is primarily used to measure external dimensions like diameters, thickness. Usually these will be having a least count or accuracy of 0.01 mm. The essential parts of micrometer are,1)FRAME : This is made of steel, cast steel, malleable cast iron or light alloy.2)HARDENED ANVIL : Usually made of a hardened steel and the face will be given with a highly accurate lapped surface. The anvil shall protrude from the frame for a distance of at least 3mm for the easiness of measure as well as to ensure a proper measuring area contact.

3) SCREWED SPINDLE : Extremely hard and stable one-piece spindle (the heart of our accuracy). This spindle does the actual measuring and possesses thread of 0.5mm pitch.4) GRADUATED SLEEVE or BARREL : It has datum or fiducial line and fixed graduations.5) THIMBLE : This is tubular cover fastened with the spindle and moves with the spindle. The beveled edge of the thimble is divided in to 50 equal parts, every fifth being numbered. 6) RATCHET or FRICTION STOP : This is a small extension to the thimble. The ratchet slips when the pressure on the screw exceeds a certain amount. This produces uniform reading and prevents any damage or distortion of the instrument.7) SPINDLE CLAMP or CLAMP RING : This is used to lock the instrument at any desired setting.

EXTERNAL MICROMETER - PARTS

EXTERNAL MICROMETER - PARTS

READING READING ::Before using the micrometer it is important to ensure that the

faces of the anvil and spindle are clean and to check that the instrument reads zero when they are closed. The thimble is on a screw thread of pitch 0.5mm, so that the gap between anvil and spindle will change by 0.5mm when the thimble is moved through one revolution. The graduations on the sleeve are each of 0.5mm to reflect this.The thimble has a scale of 50 equal divisions, each division is 0.01mm (each individual thimble mark is therefore 1/50th of 0.5mm = 0.01mm).To take a measurement using the micrometer, place the object to be measured between the anvil and spindle. Grip the ratchet and turn until the object is lightly gripped. DO NOT OVERTIGHTEN.

Each revolution of the ratchet moves the spindle face 0.5mm towards the anvil face. The object to be measured is placed between the anvil face and the spindle face. The ratchet is turned clockwise until the object is ‘trapped’ between these two surfaces and the ratchet makes a ‘clicking’ noise. This means that the ratchet cannot be tightened any more and the measurement can be read.

Example 1: 1. Read the scale on the sleeve. The example clearly shows12 mm divisions.2. Still reading the scale on the sleeve, a further ½ mm (0.5) measurement can be seen on the bottom half of the scale. The measurement now reads 12.5mm.3. Finally, the thimble scale shows 16 full divisions (these are hundredths of a mm).The final measurement is 12.5mm + 0.16mm = 12.66

Example 1 :

Sleeve reads full mm = 12.00Sleeve reads 0.5 mm = 0.50Thimble reads = 0.16

Total measurement = 12.66mm

Sleeve reads full mm = 12.00Sleeve reads 0.5 mm = 0.50Thimble reads = 0.16

Total measurement = 12.66mm

Example 2 :

Sleeve reads full mm = 16.00Sleeve reads 0.5 mm = 0.00Thimble reads = 0.36

Total measurement = 16.36mm

Sleeve reads full mm = 16.00Sleeve reads 0.5 mm = 0.00Thimble reads = 0.36

Total measurement = 16.36mm

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Example 3:

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Example 4 :

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Sleeve reads full mm =Sleeve reads 0.5 mm =Thimble reads =Total measurement =

Example 5 :

Micrometer Correction : A micrometer is said to be having an error when the the zero on the thimble and the zero line on the index line is not collinear while it is in the closed condition. When the zero on the thimble is below the index line, then the zero error must be deducted from the reading and vice versa.

ERROR ON MICROMETERERROR ON MICROMETER

Example : When the micrometer is closed let the reading on the thimble be 47. Let the micro meter reading of the object be 15.58mm. Find the actual reading.

Zero error = ( 50-47=3 ; 3x0.01=0.03)Since the zero of the thimble is above the index line zero error is negative.Therefore zero error is -0.03. which implies it should be added with the micrometer reading. Thus the actual reading is 15.58 + 0.03 = 15.61mm.

DEPTH MICROMETER.DEPTH MICROMETER.DEPTH MICROMETER.DEPTH MICROMETER.

It is an instrument used to measure the depth of pockets to an accuracy of 0.01mm. Depth micrometer can only be used in places where there is a satisfactory seating for the instrument head, and the bottom of the hole being measured is parallel with the seating.

The principle of measurement is similar to that of an external micrometer. Each one is supplied with three interchangeable spindles and thus has the measuring ranges 0 to 25mm, 25-50mm, 50-75mm, 75-100mm.

INSIDE MICROMETERINSIDE MICROMETER This is intended for the measurement of internal features like bore dia, pocket sizes etc. In principle, it is similar to an external micrometer and is used for measuring holes with a dia over 50mm. Instrument consist of a measuring unit, extension rod with or with out spacing collar, and a handle. The first range can be vary from 50 to 63mm. Further measurement is possible by fitting the extension rods available in sizes 13, 25, 50, 100, 150, 200 and 600mm. Normally the least count will be 0.01mm.

INSIDE MICROMETER

MEASURING WITH AN INTERNAL MICROMETERMEASURING WITH AN INTERNAL MICROMETER

SLIP GAUGESSLIP GAUGES Slip gauges or precision gauges blocks, as they are sometimes called, are used for precise measurement of parts and for verifying measuring tools such as micrometer, comparators, and various limit gauges. Slip gauges often called johannsen gauges after their originator, are rectangular blocks made of alloy steel having a cross-section of about 32mm by 9mm which, before being finished to size, are hardened and finished to a high degree of accuracy. They are also carefully matured so that they are independent of any variation in shape or size. The distance between two opposite faces determines the size of the gauges.

SLIP GAUGES or GAUGE BLOCKSSLIP GAUGES or GAUGE BLOCKSSLIP GAUGES or GAUGE BLOCKSSLIP GAUGES or GAUGE BLOCKS

SLIP GAUGE BOXSLIP GAUGE BOXSLIP GAUGE BOXSLIP GAUGE BOX

Slip gauges are made in five grades of accuracy: Grade 1,Grade II, Grade 0, Grade 00 and calibration grade. The grade most commonly used in the production of components, tools, and gauges is Grade 1, for rough work Grade II and for checking other gauges and standards Grades 00 and calibration grade. Slip gauges are supplied in sets, the sizes of which varies from a set of about 112 pieces down to one containing 32 pieces. The grade and size of set desirable depend on the class of work for which they are required and the number of combinations that they should be available.

During the use the slip gauges are “wrung” together to form the required dimension taking extreme care in handling. The cleanliness of the surface of the slip gauges and a standard temperature of 20°C during measurement is essential for accurate and reliable inspection. A number of slip gauge holders also will be sold together with each box.

WRINGING EFFECT : Since the measuring faces of gauges are lapped and made to a high degree of surface finish, when rub with each other these will cling together. This is so called wringing effect of slip gauges.

1)What is a measuring instrument?2)What is a gauge?3)Explain different standards of measurement.4)Differentiate line standard and end standard with

eg.5)Brief- Classification of measuring instrument.6)With a neat sketch explain briefly A) steel rule B) Calipers i) out side ii) Inside iii) Spring iv) Hermaphrodite

v) Transfer vi) Dividers7) Explain about telescopic gauges- construction &

applications.

QUESTIONS- ASSIGNMENTQUESTIONS- ASSIGNMENT

8) Write a short note on depth gauge.9) What is a “ Vernier scale ”?10) Explain about vernier caliper& its parts.11) With a neat sketch explain about micrometer & its parts.12) What is meant by error on micrometer? How to consider it

while measuring?13) With a sketch explain about Depth, Internal micrometers.14) Give a small note on slip gauges & its applications.15) What are the cares to be taken while dealing with slip

gauges?16) What is meant by “wringing of gauges” ?

QUESTIONS- ASSIGNMENT (Cont.)QUESTIONS- ASSIGNMENT (Cont.)