VERNIER BEVEL PROTRACTOR-FITTER ONLINE NOTE

INTRODUCTION-
1- It is a precision measuring instrument.
2- It is measured by angle.
3- Its accuracy is 5'
4-All parts made by good quality alloy steel.
PARTS OF VERNIER BEVEL PROTRACTOR -
a)-STOCK, b)-DISC, c)-DIAL, d)-BLADE,  e)-LOCKING SCREW.
a)-STOCK- 
1- It is one of the contacting surface during the measurment of an angle.
2- It should be kept in contact with the surface from which the inclination is measured.
b)-DISC -   
1- The disc is an integrated parts of the stock.
2- It is circular in shape and the edge is graduated in degree.
c)-DIAL -   
1- It is pivoted to the disc and can be rotated 360 degree.
2- The vernier scale of the instrument is attached to the dial.
3- The dial is locked to the disc during reading the measurement.
d)-BLADE -
1- This is other contacting surface of the instrument that contacts the work during measurement.
2- It is fixed to the dial with the help of clamping lever.
3- Blade one end 60 degree and other end 45 degree.
e)-LOCKING SCREW - 
1- It is two lucking screw are provide.
2- One is dial to disc & other blade to the dial

GRADUATION OF VERNIER BEVEL PROTRACTOR-
1- The full circumference of the disc is graduated in degree.
2- The 360 degree are equally divided and marked in four quardrants.
3- It is graduated by 0-90 degree, 90-0 degree, 0-90 degree and 90-0 degree.
4- Every 10th division is marked longer and numbered.
5- Each division represents 1 degree.
6- The graduation on the disc are know as the main scale division.
7- The 23rd division of main scale is equal to 12 parts of the vernier scale.
8- the vernier scale each 3rd line is marked longer line and number as 0,15,30,45,60.
LEAST COUNT IS-  
12 VSD = 23 MSD
1 VSD = 23/12 OR 1 11/12 OR 1 degree 55 minute
Hence the least count is - 1 MSD - 1 VSD
1 degree - 1 degree 55 minute ( Not possible)
2 degree - 23/12 = 1/12 degree ( 1 degree= 60 minute)
60 x 1/12 = 5'or 5 minute(Accuracy).



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