# linear measurements

Topics: Metalworking measuring instruments, Vernier scale, Dimensional instruments Pages: 63 (6532 words) Published: August 13, 2014
Department of MECH

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ica

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Paavai Institutions

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UNIT II

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LINEAR AND ANGULAR MEASUREMENTS

UNIT-II

2. 1

Department of MECH

CONTENTS
LINEAR MEASURING INSTRUMENTS
2.1.1

SCALES

2.1.2

CALIPERS

2.1.3

VERNIER CALIPERS

2.1.4

MICROMETERS

2.1.5

SLIP GAUGES

2.3

LIMIT GAUGES

2.4

PLUG GAUGES

2.5

TAPER PLUG GAUGE

2.6

RING GAUGES

2.7

SNAP GAUGE

2.8

TAYLOR’ S PRINCIPLE

2.9

COMPARATORS

2.9.2
2.9.3

MECHANICAL COMPARATORS

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2.9.1

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INTERFEROMETERS

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2.2

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2.1

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Paavai Institutions

ELECTRICAL COMPARATOR
ELECTRONIC COMPARATOR

SINE BAR

2.11

BEVEL PROTRACTORS

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2.10

2.11.1 VERNIER BEVEL PROTRACTOR:

2.12

AUTO- COLLIMATOR
2.12.1 WORKING OF AUTO-COLLIMATOR

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2.12.2 APPLICATIONS OF AUTO-COLLIMATOR

2.13

UNIT-II

ANGLE DEKKOR

2. 2

Department of MECH

TECHNICAL TERMS

Comparators

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Paavai Institutions

Comparators are one form of linear measurement device which is quick and more

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convenient for checking large number of identical dimensions.

Least count

The least value that can be measured by using any measuring instrument known

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as least count. Least count of a mechanical comparator is 0.0 1 mm.

Caliper

Caliper is an instrument used for measuring distance between or over surfaces

rules etc.

Interferometer

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comparing dimensions of work pieces with such standards as plug gauges, graduated

They are optical instruments used for measuring flatness and determining the length of the slip gauges by direct reference to the wavelength of light. 

Sine bar

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Sine bars are always used along with slip gauges as a device for the measurement of angles very precisely.

Auto-collimator

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Auto-collimator is an optical instrument used for the measurement of small

angular differences, changes or deflection, plane surface inspection etc.

UNIT-II

2. 3

2.1

Department of MECH

l.in

Paavai Institutions

LINEAR MEASURING INSTRUMENTS

Linear measurement applies to measurement of lengths, diameter, heights and

thickness including external and internal measurements. The line measuring instruments

have series of accurately spaced lines marked on them e.g. Scale. The dimensions to be

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measured are aligned with the graduations of the scale. Linear measuring instruments are

designed either for line measurements or end measurements. In end measuring instruments, the measurement is taken between two end surfaces as in micrometers, slip gauges etc.

The instruments used for linear measurements can be classified as:

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1. Direct measuring instruments

2. Indirect measuring instruments

The Direct measuring instruments are of two types:

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The graduated instruments include rules, vernier calipers, vernier height gauges, vernier depth gauges, micrometers, dial indicators etc.

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The non graduated instruments include calipers, trammels, telescopic

gauges, surface gauges, straight edges, wire gauges, screw pitch gauges, radius gauges, thickness gauges, slip gauges etc.
They can also be classified as

1. Non precision instruments such as steel rule, calipers etc.,

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2. Precision measuring instruments, such as vernier instruments, micrometers, dial gauges etc.

2.1.1 SCALES

The most common tool for crude measurements is the scale (also known as rules, or

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rulers).

Although plastic, wood and other materials are used for common scales, precision scales use tempered steel alloys, with graduations scribed onto the surface.

UNIT-II

2. 4

Department of MECH

l.in

Paavai Institutions

These are limited by the human eye. Basically they are used to compare two dimensions.

The metric scales use decimal divisions,...