10 Outside Micrometer

8/2/2019 10 Outside Micrometer

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Lesson No.10

Week No.06

Lesson Name

Outside Micrometer


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OUTSIDE MICROMETER

Principle :- The Micrometer works on the principle of

screw and nut. The linear movement of the spindle during

one rotation is equal to the pitch of screw.

Uses :- Precision Outside linear measurement.

Range :- (Metric) :-

0-25mm, 25-

50mm 50-75mm, 75-

100mm (British) :-0-1, 1-2, 2-

3...... up to 12.

12-16, 16-20, 20-

24.


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Construction of Outside Micrometer

1. Frame :- The frame is made of

Cast iron on which the whole

assembly is attached.

12 2. Barrel/Sleeve:- Main scale is

graduated on it with 0.5 mm

distance.

3

3. Thimble:- Divisions are markedon this cylindrical portion.

Knurling is made on it for better

gripping.


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Construction of Outside Micrometer

4 4. Spindle:- Spindle is one of thecontacting surface during

measurement. It moves to and

fro as thimble rotated.

5

5. Anvil:- It is the another

contacting surface which is

fixed in Frame.

6

6. Lock nut:- This nut is used to lock the movement of the

spindle.

7

7. Ratchet:- Ratchet is used to apply uniform pressure during

measurement.


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Graduation of Outside Micrometer

In metric micrometer the pitch

of the spindle thread is 0.5 mm.

Thereby in one rotation of thethimble, the spindle advances

by 0.5 mm. On the barrel a 25

mm long datum line is marked.

This line is further graduated tomillimeters and half

millimeters. The graduations are

numbered as 0, 5, 10, 15, 20 and

25 mm.

Barrel

graduation


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Graduation of Outside Micrometer

The circumference of the bevel

edge of the thimble is graduated

into 50 divisions and marked 0-

5-10-15...45-50 in a clockwisedirection. The distance moved

by the spindle during one

rotation of the thimble is 0.5

mm.

Thimble

graduation


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Reading of Outside Micrometer

First note the minimum range of the outside micrometer.

While measuring with a 50 to 75 mm micrometer, note it as

50 mm.

Least Count:- The least count of a Metric Micrometer is 0.01mm. It is the ratio of value of 1 main scale division and total

graduations on thimble. i.e. 0.5/50

Then read the barrel graduations. Read the value of the

visible lines on the left of the thimble edge.


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Reading of Outside Micrometer

Then read the thimble graduations. Multiply these

graduations with least count.

Add all above reading together. The sum of these reading is

the actual reading of the object.


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Example of Reading - 1

In given figure first readthe barrel graduation.

Which is 13. i.e. 13 mm.

Half millimeter is alsovisible.

Thus 13.00 mm

+

00.50 mm

13.50 mm


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Next read the thimblegraduation, which is 13.

Multiply it by L.C. which is

0.01mm. = 13 x 0.01 mm

=0.13mm.

Summation of all above

readings,13.50mm

+0.13mm

13.63mm


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In given figure first read the barrelgraduation. Which is 7. i.e. 7 mm.

Half millimeter is not visible.

Next read the thimble graduation,

which is 31. Multiply it by L.C. which is

0.01mm. = 31 x 0.01 mm

= 0.31mm.Summation of all above readings,

07.00

+00.31

07.31 mm


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QUESTIONS

What are the parts of Micrometer ?

Which material is used in Out side micrometer ? What is the use of Out side micrometer ?

What is the principal of Out side micrometer ?


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CONCLUSIONThus, we learnt about Out side micrometer

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10 Outside Micrometer