instruments for angular measurement 3. sine table: 25/02/20121lec # 19 & 20

Lec # 19 & 20 1

INSTRUMENTS FOR ANGULAR MEASUREMENT3. Sine Table:

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INSTRUMENTS FOR ANGULAR MEASUREMENT

3. Sine Table: • Sine table (or sine plate) is used to measure angles of large

workpieces of greater height• A sine table is the development of sine bar & the procedure

of setting it at any angle is same as that of sine bar• It has one hinged roller & the slots to facilitate work holding • A further development of this is the compound sine table

having their axis of tilt set at right angle to each other are provided

• These two tables are mounted on a common base & the table can be set at compound angle

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Lec # 19 & 20 3


4. Sine Centre:

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4. Sine Centre:• A special type of sine bar is sine centre which is used

for conical objects having male and female parts.• It cannot measure the angle more than 45 degrees• The principle of setting of sine centre is same as that

of sine table• Rollers are clamped firmly to the body without any

play• This is very useful device for testing the conical work

centre at each end

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Lec # 19 & 20 5

INSTRUMENTS FOR ANGULAR MEASUREMENT5. Angle Gauges:

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5. Angle Gauges:• An angle gauge is a hardened steel block of varying

width & length• It has two lapped flat working faces lying at a very

precise angle to each other.• These are supplied in set, & can be wrung together

to form desired angles• In 1941 the late Dr. G.A Tomlinson, working at the

NPL, devised a series of 12 angle gauges & a square block

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INSTRUMENTS FOR ANGULAR MEASUREMENT5. Angle Gauges (Cont…):

• The gauges were made to following sizes, each accurate to within 1 second

• The angles represented by the gauges can be added together or subtracted, when used in combination, they can be wrung together

• A gauge is subtracted by wringing it in position in the reverse direction• Any one degree up to 81 degree in steps of 3 seconds of arc may be build

up . The range can be extended to 90 degree by the addition of 2nd 9 degree gauge.

• The complete range of 360 deg, can be covered if the guages are used in conjuction with the square block included in the set

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Unit Angle Gauge Series

Degree 1,3,9,27,41

Minute 1,3,9,27

Second 3,9,27

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6. Sprit Level

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6. Sprit Level• The spirit level is a simple form of mechanical

measuring device.• It is mainly used for static leveling of machinery &

other equipment.• The sensitive sprit level consists of a curved glass

tube of uniform bore, nearly filled with a liquid so that an air bubble is left. The glass tube is fitted to a metal block in such a manner that when the lower surface of the block horizental, the air bubble will centre itself at the highest point of the tube.

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6. Sprit Level (cont..)

• In order that the movement of air bubble be proportional to the angle of tilt, it is necessary that the radius of the curvature of the glass tube is made constant over its hole length

• The internal cross section of the tube should be uniform • The sensitivity of a spirit level is expressed as the angle of

tilt in seconds for which bubble will move by one division on the tube. One division is generally 2.5mm in length

• Thus, Sensitivity = angle in seconds/ one division on tube

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7. Clinometers

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7. Clinometers• An inclinometer or clinometer is an instrument for

measuring angles of slop (or tilt), elevation or depression of an object with respect to gravity.

• It is also known as a tilt meter, tilt indicator, slope alert, slope gauge, gradient meter, gradiometer, level gauge, level meter, declinometer, and pitch & roll indicator.

• Clinometers measure both inclines (positive slopes, as seen by an observer looking upwards) and declines (negative slopes, as seen by an observer looking downward).

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Lec # 19 & 20 13


7. Clinometers• There are various makes & types of clinometers

obtainable, but they are all designed on one of the two basic principles:– One involve the use of spirit level & – The Other make use of the plumb-bob (or pendulum)

principle & works from the vertical

• Clinometers are used for checking angular faces, & relief angles on large cutting tools & milling cutter inserts

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Lec # 19 & 20 14


7. Clinometers• Different types of clinometers include:

a. Vernier Clinometerb. Micrometer clinometerc. Dial Clinometerd. Pendulum clinometere. Optical Clinometers

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8. Plain Index Centre:• Fundamentally index centre were meant for use

on milling machines but they now being used for inspection work also

• This is specially suited to those problems which involve the measurement of a large number of angular dimensions about a common centre.

• The work is set b/w the centers & correct angular dimensions are set directly from indexing plate

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instruments for angular measurement 3. sine table: 25/02/20121lec # 19 & 20

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