measurement 20and 20inspect

7/29/2019 Measurement 20and 20inspect

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Dr. P. M. Pandey

http://paniit.iitd.ac.in/~pmpandey


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Measurement & Inspection

Measurementis a procedure in which an unknownquantity is compared to a known standard, using anaccepted and consistent system of units. Measurementprovides a numerical value of the quantity of interestwithin certain limits of accuracy and precision.

Inspection is a procedure in which a part or productcharacteristic, such as a dimension is examined todetermine whether it conforms to the designspecification.Many inspection methods rely on

measurement techniques, while others use gaugingmethod. It is faster than measurement and provides scantinformation about the actual value of the characteristic. Ininspection part passes or fails.


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Linear Measurements

Gage blocks 9 blocks with 0.0001 in. increment from 0.1001 to 0.1009

49 blocks with 0.001 in. increment from 0.101 to 0.149

19 blocks with 0.050 in. increment from 0.050 to 0.950

4 l blocks with 1 in. increment from 1 to 4

2 tungsten steel blocks, each 0.050 in. thick


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Two sizes of outside Calipers Vernier caliper

Micrometer


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Comparative Instruments: Dial Indicator


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Use of Laser in measurements

Laser Interferometer

Fringes created by the two

sources are the measure of

distance. Graphic or digital

output is taken and sensitive

up to a speed of 0.1m/s

ALHD cot


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Angular Measurements

Bevel protractorSine bar


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Surface roughness measurement

Center-line average value (Ra) Root-mean-square-average value (Rq)

Peak to valley height (Ry)


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Three Dimensional Surface Measurement

Optical interference microscopes

Atomic force microscope


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Inspection of Geometric Features

Measurement of Straightness

Autocollimator is used to detect straightness accurately in which alight beam bounces back from the object and measures small

angular deviations. Optical means like laser beams are used to

align individual machine elements in the assembly of machine

components.


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Measurement of Flatness: Interferometry

(a)Measuring flatness using an optical flat (b) Fringes on a flat inclined

surfaces (c) Fringes on a surface with two inclinations (d) Curved fringe

patters indicate curvatures on surface (e) Scratch on the surface


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Measurement of Roundness

(a) Schematic illustration of out of roundness, Measuring roundness using

(b) V-block (c) Part supported on centers and rotated and (d) circular tracing

with part being rotated on a vertical axis


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Measurements of ProfilesThread gauges, Gear

measurement, CMM

(a) Radius gages (b) Dial indicator

Profile Projector


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Limits Fits and Tolerances

Upper and Lower limits of shaft and hole

Clearance, Interference and Transition fits


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Fixed Gages

(a) Plug gage for holes, with Go Not Go on

opposite side

(b) Plug gage for holes, with Go Not Go on one

end

(c) Plain ring gages for round rods

(d) Snap gage with adjustable anvils
http://www.daneprairie.com/


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measurement 20and 20inspect

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