Angular Msmt 2

7/30/2019 Angular Msmt 2

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ANGULAR MEASUREMENT-SINE

BAR

A sine bar is a tool used to measure angles

in Metalworking


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ANGULAR MEASUREMENT-SINE

BAR

Uses sine principal --

Measurement usually limited to 45degree due to loss of accuracy pt of view.

Sine bar used in conjunction with slip

gauges


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Important parameters

Made from high carbon, high chromium, corrosion

resistant steel, hardened, ground stabilized.

Two cylinders of equal diameter are attached at theends.

Axis of cylinder parallel to each other and parallel to

and at equal distance from upper surface of sine bar.


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SINE BARworking principal

Angles are measured using a sine bar with the help of gauge

blocks and a dial gauge or a spirit level. The aim of a

measurement is to make the surface on which the dial gauge

or spirit level is placed horizontal. For example, to measure

the angle of a wedge, the wedge is placed on a horizontal

table. The sine bar is placed over the inclined surface of the

wedge. At this position, the top surface of the sine bar is

inclined the same amount as the wedge. Using gauge blocks,

the top surface is made horizontal. The sine of the angle ofinclination of the wedge is the ratio of the height of the

gauge blocks used and the distance between the centers of

the cylinders.


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USE OF SINE BAR

lh

Sin

= hl

1.CHECKING OF UNKNOWN ANGLE OF WORKPIECE


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USE OF SINE BAR

2.MEASURING KNOWN ANGLES OR LOCATING ANYWORK TO A GIVEN ANGLE

Knowing , h canbe found out and

any work could be

set at that angle as

The top face of sinebar is inclined at

Angle to the

surface plate.


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USE OF SINE BAR

3.CKECKING OF UNKNOWN ANGLES OF HEAVY COMPONENT

Sine bar mounted on component .The height over the

rollers can then be measured with vernier height

gauge. Differene of two readings of height gaugedivided by centre distance of sine bar gives sine of

angle of component to measure.

component

Sine bar

h2h1


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Sine bar impractical to use above 45

degree

Physically clumsy to hold.

Slight error of sine bar causes large angular error.

Temperature variation becomes critical.

Body of sine bar obstructs gauge block stack.


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PRECAUTION

Should not be used for angle greater than 60 degree.

Compound angle should not be formed by

misalignment of work piece.

Accuracy of sine bar to be ensured.

Longer sine bar used as many error reduced by

using longer bar.


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SINE BARtypes

Sine centreA 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.

Sine table

Sine table (or sine plate) is used to measure angles of large

workpieces.

Compound sine table

It is used to measure compound angles of large workpieces. In

this case, two sine tables are mounted one over the other at

right angles. The tables can be twisted to get the required

alignment.


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AUTOCOLLIMATOR

OPTICAL INSRUMENT FOR MEASUREMENT OF SMALLANGULAR DIFFERENCE


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Principles of operation

The autocollimator projects a beam of collimated

light. An external reflector reflects all or part of the

beam back into the instrument where the beam is

focused and detected by a photodetector. Theautocollimator measures the deviation between the

emitted beam and the reflected beam. Because the

autocollimator uses light to measure angles, it never

comes into contact with the test surface.


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Like in the collimator the image of the illuminated object reticle

is projected by the objective lens to infinity. In some distance,

the collimated beam is reflected back from a mirrored surface .

If the mirror surface is tilted by an angle with respect to the

optical axis, the reflected beam will enter the objective lens withan angle 2. This leads to a shift dof the image in the image

plane which can be calculated with the objective focal lengthf

giving d= 2 x for = d/( 2f). Thus, the sample angle is

directly proportional to the measured shift in the image plane(small angles assumed). The resolution of an autocollimator

increases proportionally and the angular field of view

reciprocally with the focal length of the objective lens.


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ANGLE GAUGES

1)Direct use of angle gauges to measure the angle in die insert

2)Use of angle gauges with square plate.

Angular Msmt 2

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