Experiment No. 2 Error determination of linear / angular measuring instruments and determination of linear and angular dimensions of given part.

 

EXPERIMENT NO2

TITLE: Error  determination  of  linear  /  angular  measuring  instruments  and  determination  of  linear  and  angular dimensions of given part.

 

APPARATUS:

 Steel Rule, Vernier Caliper, Vernier Height Gauge, Micrometer, Digital Vernier Caliper, Digital Micrometer. 

 THEORY:

STEEL RULE: It is also known as scale. It is the line measuring device. It is the simplest and common measuring instrument used for inspection. It works on the basic measuring technique of company on unknown length to the one previously calibrated. It consists of a strip of hundred steel having line graduation etched engraved on internal of fraction of standard unit of length, depending upon the internal at which graduations are made. The scale can be manufactured in different sizes and styles. It may be 150 mm, 300 mm, 600 mm or 1000 mm long.

 

VERNIER CALLIPER: The principle of vernier is that when two scales or divisions slightly different in size are used, the difference between them can be utilized to enhance the accuracy of measurement. The Vernier Calliper essentially consists of two steel rules and these can slide along each other. The details are shown in fig. below

 

1.    Outside jaws: used to measure external diameter or width of an object

2.    Inside jaws: used to measure internal diameter of an object

3.    Depth probe: used to measure depths of an object or a hole

4.    Main scale: gives measurements of up to one decimal place (in cm).

5.    Main scale: gives measurements in fraction(in inch)

6.    Vernier gives measurements up to two decimal places(in cm)

1 msd = 0.1mm, total no. Vsd = 5 therefore LC = 0.02mm t

Suppose 50 vernier scale I division coincide with 49 divisions on main scale, and 1 msd=1 mm.Then 1 VSD = 49/50 of MSD = 49/50MM.and LC = 1-49/50= 0.02

mm.Alternatively, it is just as easy to read the 13 on the main scale and 42 on the hundredths scale. The correct measurement being 13.42mm.

1 cmm = 10mm

VERNIER HEIGHT GUAGE: This is also a sort of a vernier caliper equipped with a special base back and other attachments which make the instrument suitable for height measurement.

Along with the sliding jaw assembly arrangement is provided to carry a removable clamp.
The upper and the lower surface of the measuring jaw are parallel to the base so that it can be used for measurement over or under the surface. The vernier height guage is merely used to scribe lines of certain distance above surface. However, dial indicator can be attached in the clamp and many useful measurements can be exactly made as it exactly gives the indication when dial tip just touches the surfaces. For all these measurements, use of surface plates as datum surface is very essential.

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MICROMETER: The micrometer essentially consists of U shaped frame. The component to be measured is held between fixed anvil and movable spindle. The spindle can be moved with the help of thimble. There are two scales on micrometer, a main scale and a circular scale. The barrel is graduated in unit of
0.5 mm whereas thimble has got 50 divisions around its periphery. One revo- lution of thimble moves 0.5 mm which is the lead of the screw and also the pitch.

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 2.5 mm+ (46*0.01) = 2.96 mm (for Figure 3)
DIGITAL MICROMETER:
1)    It is used where high accuracy is required.
2)    It is based on electronic technology.
3)    It can be zeroed at any position, which greatly speeds the process of inspection.

V BLOCK:
The Vee-block is essentially tool steel blocks that are very precisely 100mm square. Standard Vee-blocks come as 45 degree block, i.e. the vee-sides slope 45 degree from horizontal or vertical, the included angle of the vee being of course, 90 degrees. But blocks with different angles and shapes are also available. For special purpose such as checking triangle effects or for taps and other three-fluted tools, 60 degree Vee-blocks are also available. The included angle of the vee then is 120 degrees.
The major purpose of the Vee-blocks is to hold cylindrical pieces, or move to the point, to establish precisely the centre line or axis of a cylindrical piece. In using a vee-block, it is very essential that the cylindrical piece should rest on firmly on the sides of the vee and not on the edges of the vee.

 

 

H & G Magnetic V Block
•    All sides are hardened and ground,Used for grinding, light Milling, Drilling and inspection of         round and square jobs
•    Accuracy for Flatness, squareness and parallelism within 0.005 mm upto 150 L and 0.010         mm for 200 L
•    Hardness above 60 Rc
•    Supplied in matched pair Uniform and Strong magnetic pull to all three magnetic surface              Top, Bottom and V Faces
•    Easy ON - OFF facility

 

VERNIER DEPTH GAUGE

1)    This is similar to vernier height gauge.
2)    It consists of main scale, vernier scale, jaws, and lock nut fine adjustment screw like vernier caliper as shown in fig.
3)    In vernier depth gauge, graduated scale can slide through the base and vernier scale remains fixed.
4)    The vernier scale is fixed to the main body of the depth gauge and is read in the same way as vernier caliper.
5)    In vernier depth gauge, graduated scale can slide through the base and vernier scale remains fixed.
6)    The main scale provides the datum surface from which the measurements are taken.Vernier depth gauge is used to measure depth of holes, distance from a plane surface to a projection and recess.

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SURFACE PLATE

For majority of dimension measurement and establishment of geometric accuracies, a reference datum plane and flat surface is required. The instrument and jobs are kept on this surface for measurement and also the surface is used for direct comparison and acts a master for checking of flatness and other characteristics of work surface.
This perfectly flat plane of reference is available on important methodical device known as surface plate.
Types of surface Plate:-
1) Cast Iron Surface Plate. 2) Granite Surface Plate.
3)    Glass Surface Plates.

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PROCEDURE:
For Vernier Calliper/Micrometer/Height gauge :
1.    Check the zero of main and vernier scale to be coinciding.
2.    Read the instrument for at least three random vernier positions.
3.    Measure the samples at indicated places and record as per the format

OBSERVATION TABLE:

For Vernier Calliper:

S. NO.	ACTUAL READING (mm)	MEASURED READING (mm)	ERROR (mm)
1.	20	20.09	0.09
2.	28	27.91	0.09

 For Micrometer:

S. NO.	ACTUAL READING(mm)	MEASURED READING(mm)	ERROR (mm)
1.	20	19.89	0.11
2.	28	27.29	0.71

 For Digital Height Gauge: LC : 0.001

S. NO.	ACTUAL READING	MEASURED READING	ERROR
1.	100	100.96	0.96
2.	28	27.29	0.71

 For Vernier Depth Gauge:

S. NO.	ACTUAL READING	MEASURED READING	ERROR
1.	30	30.10	0.10
2.	50	49.90	0.10

 Study of Gauge R & R and measurement analysis

CONCLUSION: Hence we have studied various measuring instruments and it's error determination.

Reference :- 

1.https://www.google.com/url?sa=i&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FFile%3AVernier_caliper.svg&psig=AOvVaw0aa0RwwdaE59K6tX0_noWk&ust=1597133684937000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCKjI2dyYkOsCFQAAAAAdAAAAABAF

2.https://www.google.com/url?sa=i&url=https%3A%2F%2Fgaugehow.com%2Fvernier-height-gauge%2F&psig=AOvVaw2au2m3bBnbzoJWh702apYK&ust=1597134305113000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNC_k4SbkOsCFQAAAAAdAAAAABAJ

3.https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.mscdirect.com%2Fbasicsof%2Foutside-micrometers&psig=AOvVaw0b51PHcI1s7uDwxnBOB8T3&ust=1597134393283000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNiO4qubkOsCFQAAAAAdAAAAABAG

4.https://www.technocart.com/pub/media/catalog/product/cache/image/540x648/beff4985b56e3afdbeabfc89641a4582/v/-/v-block-vertex-vcp-25_1.jpg

5.https://i0.wp.com/gaugehow.com/wp-content/uploads/2019/01/vernier-depth-gauge-gaugehow.png?w=980&ssl=1 

6. https://5.imimg.com/data5/VF/AY/OT/SELLER-82405780/surface-plate-500x500.jpg