HOW TO MEASURE WITH A BORE DIAL GAUGE ?

NAME OF EXERCISE: MEASURING WITH MICROMETER

TOOLS REQUIRED: micrometer

MATERIALS REQUIRED: cotton waste, kerosene. Round stock.

PROCEDURE

       I.            Select a suitable range of micrometer.

     II.      FIND OUT THE LEAST COUNT OF THE MICROMETER.

1.     To find out the pitch of the micrometer, note down the linear distance moved after one complete revolution of the thimble.

2.     Note down the total number of division on the thimble scale.

3.     Calculate the least count by the equation, 

  III.            CHECKING THE ZERO ERROR OF THE MICROMETER

1.     Bring the spindle tip on to the anvil of the screw gauge.

2.     When touching, note down the zero line of the thimble scale coincided with the datum line of the main scale.

3.     If the zero line is below the datum line, the error will be positive. Note down the number of division zero line of thimble scale towards the datum line, along with a positive sign.

4.     If the zero line is above the datum line, the error will be negative. Note down the number of division zero line of thimble scale towards the datum line, along with a negative sign.

5.     Find out the value of zero error by multiplying the least count with zero error.

  IV.            MEASURE THE OUT SIDE DIAMETER OF THE ROUND STOCK

1.     Clean the surface to be measured.

2.     Place the work piece in between the anvil and spindle.

3.     Rotate the thimble scale until the spindle just touches the work surface and ensure the tightness with the ratchet stock.

4.     Take the main scale reading.

5.     Take the thimble scale reading.

6.     Find out the total reading by using the equation,

7.     For getting actual reading, use the formula

8.     Repeat the steps 2 to 7, note down the reading and take the average for final reading.

TABULAR COULUMN

SL.NO.	MAIN SCALE READING	THIMBLE SCALE READING	LEAST COUNT	TOTAL READING	ACTUAL READING	FINAL READING
1
2
3
4

All dimensions are in mm

SAMPLE CALCULATION

1.      TO FIND OUT THE LEAST COUNT OF THE MICROMETER,

   Pitch of the micrometer=________mm

    Number of divisions on the thimble scale=______mm

    Least count=(1/50)x0.5

                      =0.01mm

2.      TO FIND OUT THE ZERO ERROR OF THE MICROMETER,

Zero error value=least count x ___________=__________mm

3.      TO FIND OUT THE ACTUAL READING,

Main scale reading=__________mm

Thimble scale reading=_________mm

Total reading= main scale reading + ( thimble scale reading x least count )

                       =________________+(______________x_____________)

                      =____________mm

Actual reading= Total reading – Zero error value

                         =_______________-______________

                       =________mm

Final reading= average of total reading

=(____________+____________+__________+_________)/4

= ___________mm