Lab manual Metrology

8/19/2019 Lab manual Metrology

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Experiment # 1

To measure the diameters of pins using vernier calipers

Apparatus:-

Vernier calipers, set of pins

Vernier caliper

The vernier is a convenient tool to use when measuring the length ofan object, the outer diameter (OD) of a round or cylindrical object, the

inner diameter (ID) of a pipe, and the depth of a hole.

Parts of a vernier caliper:

1. Outside jaws: used to measure external lengths

2. Inside jaws: used to measure internal lengths3. Depth probe: used to measure depths4. Main scale (cm)

5. Main scale (inch)6. Vernier (cm)

7. Vernier (inch)

8. Retainer: used to block movable part to allow the easytransferring a measurement


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Least count:- It can be defined as min. reading on

main scale divided by total no. of divisions on vernier scale.It is actually the min. measurement that an instrument can

take place.

L.C = Minimum division which can be measured from main scaleNo. of division on the vernier scale

=1/10=0.1mm

How the vernier works:The vernier consists of a main scale engraved on a fixed ruler and an

auxiliary vernier scale engraved on a movable. The movable auxiliaryscale is free to slide along the length of the fixed ruler. This vernier's

main scale is calibrated in centimeters with the smallest division inmillimeters. The auxiliary scale has 10 divisions that cover the same

distance as 9 divisions on the main scale. Therefore, the length of theauxiliary scale is 9.0 mm.

Principle of working:


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PROCEDURE1 The whole movable jaw assembly is adjusted so that the two

measuring tip just touch2 the parts to be measured. 3 Final adjustment depending upon the sense of correct feel is

made by the adjusting 4 noted down the reading.

5 The measuring tip is so designed as to measure inside as well as

outside dimension.

Observations and calculations:

Sr. No. Main scalereading

Vernierscale

division

No. ofdiv.*L.C

Diametersof pins

1

2

3

4

5

Comments:a. Vernier caliper is a precision measuring toolb. Capable to read within .001 inch.

c. Used for inside, outside and depth measurements.

d. At a time we can take both inches and metricsmeasurements

References:• http--itdc_lbcc_edu-cps-machineTool-precisionTools-

precisionToolsALT-images-universal2_jpg.htm• http://www.amazon.co.uk/Silverline-677256-Digital-Vernier-

Calliper/dp/B000OIG00C • http://www.tradekey.com/ks-vernier-calliper/


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Experiment # 2

Objective:

To develop dimensions with the help of slip gaugeson gauge blocks.

Apparatus:Box of slip gauges, Spirit, Soft cloth, Petroleum jell.

Gauge blocks

A gauge block (also known as a gage block, Johansson gauge, slip

gauge, or Jo block) is a precision ground and lapped measuring

standard. It is used as a reference for the setting of measuringequipment such as micrometers, sine bars, dial indicators (when usedin an inspection role).

Gage blocks are used for:

• calibration and inspection of precision instruments• to set comparators/indicators• setting of sine bars

• precision layout•

machine setups

General Care

• Protect gauge blocks from dirt, dust, and moisture by keepingthem enclosed in their case.

• While in their case, steel gauge blocks should not become

magnetized. Otherwise, they will attract dust.

Preparation before use

• If a protective coating was applied to the blocks afterprevious usage, a solvent (isopropyl or methyl alcohol)

shouldbe used in removing the product.

• Measuring faces should be cleaned every time a block is used

with chamois leather or a soft linen cloth.

• Keep in mind a thin film of grease should remain on the blocks.


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Care in Use• Gloved hands should handle the blocks so as to prevent

finger prints

•

It is important that the blocks do not take up the heat of thehand. Before using them for testing purposes, allow theblocks to adjust themselves to room temperature.

• When the highest accuracy is required, the test room should

be 20˚ C. For ordinary purposes, the block and workpiece (ifthey are the same material), may assume the temperature

of the room.

Damaged gauges• The edges undergo the most damage. They can easily be

fixed by drawing an Arkansas type stone across the damagededge away from the measuring face of the standard.

• Thoroughly clean the edge afterward.

• A standard with a damaged measuring face should be

returned to the manufacturer for restoration.

Care after use• Each block should be wiped clean after use and placed back

into its appropriate case.

• Remove any fingerprints from the measuring surfaces.

• A corrosion preventive substance should be applied to the

blocks before putting them away, if they are usedinfrequently.

• A preparation should be applied to the measuring surfaceswith a clean linen cloth as opposed to a brush. The brush

may aerate the preparation, creating bubbles which in turnwill result in rusting.


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Wringing

It is the process of sliding the two blocks together so that their faceslightly bond. When combined with a very light film of oil, this actionexcludes any air from the gap between the two blocks. The alignment

of the ultra-smooth surfaces in this manner permits molecularattraction to occur between the blocks, and forms a very strong bond

between the blocks along with no discernible alteration to the stack'soverall dimensions.

Grades Gauge blocks:They are available in various grades depending on their

intended use.

• reference (AAA) — small tolerance (± 0.00005 mm or 0.000002in) used to establish standards

• calibration (AA) — (tolerance +0.00010 mm to -0.00005 mm)used to calibrate inspection blocks and very high precision

gauging

• inspection (A) — (tolerance +0.00015 mm to -0.00005 mm)used as toolroom standards for setting other gauging tools

• workshop (B) — large tolerance (tolerance +0.00025 mm to -0.00015 mm) used as shop standards for precision

measurement

More recent grade designations include (U.S. FederalSpecification GGG-G-15C):

• 0.5 — generally equivalent to grade AAA

• 1 — generally equivalent to grade AA

• 2 — generally equivalent to grade A+

• 3 — compromise grade between A and B

Grades are equivalent to former U.S. Federal grades as follows:

• 00 — generally equivalent to grade 1 (most exacting flatness

and accuracy requirements)

• 0 — generally equivalent to grade 2

• AS-1 — generally equivalent to grade 3 (reportedly stands for

American Standard - 1)

• AS-2 — generally less accurate than grade 3


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• K — generally equivalent to grade 00 flatness (parallelism) withgrade AS-1 accuracy

Procedure:To develop any dimension, (mm or inch) the principle is tostart from first digit on the extreme right hand side of the dimensionand then successively moves towards the left.

For example:To make 3.189 file we shall take the following slip gauges

1.0091.08

1.1sum=3.189 mm

Gauge block 1 Gauge block 2 Gauge block 3 Gauge block 4Requireddimension

Comments:

• Blocks are wrung together to form a stack of the required

dimension, with the minimum number of blocks.• They are made of material resistant to wear steel, tungsten

carbide or ceramics.

References:• http--itdc_lbcc_edu-cps-machineTool-precisionTools-

precisionToolsALT-images-universal2_jpg.htm


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Experiment no: 3

Objective:To measure the angle of wedge-shaped block with the

of a sine-bar.

Apparatus:Wedge shaped blocks, Sine-bar (10%), Set of slip gauges, Surface plates, Dial

indications.

Sine barSine bar is used for checking angles, typically used with gage blocks.Precise angles are measured using the sine bar.

The sine bar is a precision bar that has been hardened and thenground and lapped to very precise dimensions. It is also used for

machine setups.

SINE PRINCIPLE:-

The sine principle uses the ratio of two sides at right angle triangle isDeriving a given angle .It may be noted that devices operating on sineprinciple are capable of self generation. The measurements are usuallylimited to 45 from loss of accuracy point of view. Sine bars used in

conjunction with gauges constitute a very good device for the precisemeasurement of angles .Sine bars are used to measure angles veryaccurately or for locating any work to a given angle within much closedlimit.


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Material for sine bar

Sine bars made from• High carbon steel• High chromium steel• Corrosion resistant steel

CHECKING OF UNKNOWN ANGLES:-Many a times, angle of component to be checked is unknown .In sucha case it is necessary to first find the angle approximately with the helpof a bevel protractor. Then the sine bar is set at an angle and clampedto an angle plate .Next the work is placed on sine bar and clamped toAngle ,Slip-gauges are so arranged (according to deviation) that thesprit level is at centre ( the air bubble).

Procedure:-The figure below shows a sine bar from the side,


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A simple example is - set up a sine bar with an angle of 24°-57', if the

sine bar has 5" centres.

The sine bar shown above will only allow a single angle to be set, but

in some cases we want to set two angles, for this a compound sineplate is used.

Sine Bar Limitations

• When using a sine bar, the height setting is limited by the gaugeblock divisions available (often 0.0001"). This results in an error

that may be negligible, or in some cases quite significant.

• A simple example to illustrate this effect is given below for two

extreme cases. In the first case the sine bar is near horizontal, inthe second case it is near vertical.


No. of

observations

L(in) H(in) Sin ө = h/l Ө(Degrees)

1

2

3

45


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Comments:-• A compound angle should not be formed by miss-dignity of w/p

with the sine bar.• This can be avoided by attaching the sine brand work against anangle plate.

• Accuracy of sine bar should be ensured.• As far as possible longer sine bar should be used since4 many

errors are reduced by using longer sine bars

Preferences:• http--claymore_engineer_gvsu_edu-eod-manufact-manufact-212_gif.htm

• http://www.eod.gvsu.edu/eod/manufact/manufact-130.html


12/21

Experiment#4

Objective:To measure a taper bore with balls and depth gauge.

Apparatus:Given piece with taper bore, Spherical ball, Taper bore apparatus, Depth

gauge.

DEPTH GAUGE

The depth gauge micrometer is a precision measuring instrument, used by engineers to

measure depths.

Types:-

• Dial depth gauge• Digital depth gauge• Dial calipers• Dept micrometer• Digital depth micrometer

Application of depth gauge:Depth gauge can be used to

• Determine the capacity at the fill point.• Determine the distance between the surfaces.• For the inspection of the depth of hole.• Inspect the depth of slots.• In tool and dial industrial applications.


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Precautions:• Ball should not drop into the taper but they should give gently roll.

• The wedging effects of the balls and the consequent elastic deformation

both of the balls and the gauges can cause appreciable .


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Observations and calculations:h = height of gauge blocks=50mm

h2 = height of smaller ballh2 = height of bigger ball

r1 = radius of smaller ball

r2 = radius of bigger ball

LM = center to center distance between balls

Ө = taper angle

LM = h2-h1-r1+r2

Sin ө/2 = (r2-r1)/LM

Sr. no. R 1 R 2 H1 H2 LM Sin ө/2 ө/2

1

2

3

Comments:• Small ball does not touch the bottom surfaces

• Centre of the large ball is inside the component

• lines joining the centers to the tangents are parallel


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Experiment : 5

Objective:

To find out the angle of the given flat plates with the help of

bevel protector.

Apparatus:

Given flat plates, Bevel protector.

BEVEL PROTRACTOR

It is used to lay out, measure, or check angles.

The universal bevel protractor is capable of measuring obtuse angles as well as acuteangles when accompanied with the correct attachments. Look at below to give you an idea

as to the uses of the universal bevel protractor.

Main Components:-

The main component of the bevel protractor is the main scale The main scale is

graduated into four 90-degree components. The main scale is numbered to read from 0 to

0 degrees and then back from 90 degrees to 0.As with other vernier measuring devices, the

vernier scale of the bevel protractor allows the tool to divide each degree into smallerincrements. The vernier scale is divided into 24 spaces, 12 spaces on either side of the

zero.

Least count:-

Each space on the vernier scale is, therefore, one-twelfth of a degree.One-twelfth of a degree is equal to 5 minutes.


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Main Components:-The main component of the bevel protractor is the main scale The

main scale is graduated into four 90-degree components. The mainscale is numbered to read from 0 to 0 degrees and then back from 90degrees to 0.As with other vernier measuring devices, the vernier scaleof the bevel protractor allows the tool to divide each degree intosmaller increments. The vernier scale is divided into 24 spaces, 12spaces on either side of the zero.

Least count:-

Each space on the vernier scale is, therefore, one-twelfth of a degree.One-twelfth of a degree is equal to 5 minutes.

Procedure:-To read the protractor, note where the zero on the vernier cale lines upwith the degrees on the dial in Figure 10. The degrees are read directlyfrom the main scale. The zero on the vernier scale is just pass the 85degree mark. Now, adding in the same direction (counter- clockwise),count, by five, from zero on the ernier scale to the lines that match upon the dial. Add this number of minutes to the number of whole


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degrees. The total number of degrees and minutes in figure wouldequal 85 degrees and 30 minutes.

Types of bevel protractor:-

•

A

•

B

•

C

• D In types A, B the vernier is graduated to read 5min arcs whereas incase C the scale is graduated to read in degrees and the bevelprotractor is without vernier or fine adjustment. the difference betweentype A and B is that a is provided with fine adjustment devices or acuteangle attachment whereas type is not the scale of all types are

graduated either as a full circle marked 0-90-0-90 with one vernieras semi circle marked 0-90-0 with two vernier 180 apart .Type D isgraduated in degrees and is not provided with either vernier or fineadjustment devices or acute angle attachment.


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Comments:-•

When reading from 90 degrees, make sure to note the positionswhere the angle and the supplement are from.

• Working surfaces should be plane.

• It should not use for precise measurements


angle 0f plates Angle found out

Refrences:-• http://process-equipment.globalspec.com/Industrial-

Directory/bevel_protractor • http://material-

handling.globalspec.com/LearnMore/Manufacturing_Proc

ess_Equipment/Inspection_Tools_Instruments/Protractors_Angle_Gages

• http://www.manufacturers.com.tw/office/Bevel-Protractor.html


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Experiment # 6

Objective:To draw the histogram based on the data obtained in

experiment no. 1.

HistogramPurpose Of A Histogram A histogram is used to graphically summarize and display the distribution of aprocess data set.

Mathematical definition

In a more general mathematical sense, a histogram is a mapping mi that counts the number of observations that fall into various disjoint

categories (known as bins), whereas the graph of a histogram ismerely one way to represent a histogram. Thus, if we let n be the total

number of observations and k be the total number of bins, the

histogram mi meets the following conditions:


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Cumulative histogram:

A cumulative histogram is a mapping that counts the cumulativenumber of observations in all of the bins up to the specified bin. That

is, the cumulative histogram M i of a histogram mi is defined as:

Class limit:The class limits are defined as the numbers or the values of the

variables which describe the classes. The smaller no. is the lower class limit

and the larger no. is the upper class limit. There should be no overlappingbetween the classes.

Class boundaries:These are the precise numbers which separate the two classes.

They form the boundary between the two. This particular number is commonfor both classes.

Class width or interval:It is equal to the difference between the two successive lower

class limits.


No ofobservations Measurements

1 5.7

2 5.6

3 5.8

4 5.6

5 5.7

6 5.6

7 5.5

8 5.4

9 5.5


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10 5.4

5.7

5.6

5.8

5.6

5.7

5.6

5.5

5.4

5.5

5.4

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

1

Series1

Series2

Series3

Series4

Series5

Series6

Series7

Series8

Series9

Series10

Preferences:• http--itdc_lbcc_edu-cps-machineTool-precisionTools-

precisionToolsALT-images-universal2_jpg.htm

• http://www.amazon.co.uk/Silverline-677256-Digital-Vernier-Calliper/dp/B000OIG00C

• http://www.tradekey.com/ks-vernier-calliper/

Documents

Lab manual Metrology