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Syed Raheel Adeel IM-098(Section, B) Metrology & Gauging

Qno.1: List down the positive & negative aspects for each material used for the manufacturing ofgage blocks.

. Steel CrobloxChrome-carbide Ceramic

Tungsten-carbide(Not availablefrom Webber)

corrosion resistance poor excellent excellent fairthermal expansion excellent

6.4ppm/F good4.7ppm/F very good5.5ppm/F poor2.5ppm/Fresistance to wear fair to poor very good very good excellent

resistance toscratching fair to poor very good excellent very good

resistance to nicksand burrs fair to poor good very good good

resistance to chipping very good fair good fair to goodlong term stability fair to poor

(unpredictable) excellent(No long term data

at this time)(No long term data.Not available from

Webber)thermal conductivity

(ability to acclimate toits surroundings) very good

very good(takes 1.2 times

longer than Steel)poor

(takes 2.2 timeslonger than Steel)

fair(takes 1.5 times

longer than Steel)surface finish fair to good

(0.7in. AA) excellent(less than 0.3in. AA) very good(0.5in. AA) (Not available fromWebber)wring ability

(ability to makecombinations) fair to good excellent excellent very good

Qno.2: What are wear blocks and for which purpose they are used?

Ans: Wear block are "throw away" blocks whose purpose is to prevent wear on the other

blocks ina set. Webber Wear blocks are made from croblox

(chrome-carbide) material to provide

better wear resistance and longer life.

Wear blocks are used at both ends of combinations. The desired length of the combination

must include the length of the Wear blocks. The "wear" side should always be on the

outside of the combination. This is the side that is to take any punishment or wear during

use.

The other side of the Wear block should always be kept in as good of condition as possible.Inspect the non-wear side of the gage block before using it in a combination. The non-wearside is to be wrung to the other gage blocks and should not itself scratch any of the blocks

it is supposed to protect.

When Wear blocks are sufficiently worn and scratched, they may be discarded and replaced at

a fraction of the cost that would be necessary if regular gage blocks had to be replaced.

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Syed Raheel Adeel IM-098(Section, B) Metrology & Gauging

Qno.3: What do you understand about the grades of gage blocks. Make a table and list down allthe grades of gage blocks along with their purpose.

Ans : Gauge blocks being used to measure the height of a ball bearing and a plug gage using

interferometry. Gauge blocks are available in various grades, depending on their intended use.

The grading criterion is tightness of tolerance on their sizes; thus higher grades are made totighter tolerances and have higheraccuracy and precision.Various grading standards include:

JIS B 7506-1997 (Japan)/DIN 861-1980 (Germany), ASME (US), BS 4311: Part 1: 1993 (UK).Tolerances will vary within the same grade as the thickness of the material increases.

reference (AAA): smalltolerance (0.05 m) used to establish standards calibration (AA): (tolerance +0.10 m to 0.05m) used to calibrate inspection blocks

and very high precision gauging

inspection (A): (tolerance +0.15 m to 0.05m) used astoolroom standards for settingother gauging tools

workshop (B): large tolerance (tolerance +0.25 m to 0.15m) used as shop standardsfor precision measurement

More recent grade designations include (U.S. Federal Specification GGG-G-15C): 0.5generally equivalent to grade AAA 1generally equivalent to grade AA 2generally equivalent to grade A+ 3compromise grade between A and B

and ANSI/ASME B89.1.9M, which defines both absolute deviations from nominal dimensionsand parallelism limits as criteria for grade determination. Generally, grades are equivalent to

former U.S. Federal grades as follows:

00generally equivalent to grade 1 (most exacting flatness and accuracyrequirements)

0generally equivalent to grade 2

AS-1generally equivalent to grade 3 (reportedly stands for American Standard - 1) AS-2generally less accurate than grade 3 Kgenerally equivalent to grade 00 flatness (parallelism) with grade AS-1 accuracy

http://en.wikipedia.org/wiki/Accuracy_and_precisionhttp://en.wikipedia.org/wiki/Engineering_tolerancehttp://en.wikipedia.org/wiki/Toolroomhttp://en.wikipedia.org/wiki/Toolroomhttp://en.wikipedia.org/wiki/Toolroomhttp://en.wikipedia.org/wiki/Engineering_tolerancehttp://en.wikipedia.org/wiki/Accuracy_and_precision