1. AIM: Measurement of an angle of an angle gauge plate by Sine-Bar method.
2. INSTRUMENT REQUIRED: Two sets of Dial gauges ,
Sine Bar, Slip gauges, Bevel Protractor
3.SPECIMEN REQUIRED: Angle Plate gauge.
4.THEORY: The sine principle uses the ratio of the length of two sides of a right triangle in deriving a given angle. Sine bar is made from high carbon, high chromium corrosion resistant steel. Two cylinders of equal diameter are attached at the ends which are parallel to each other.
For taking measurement with the sine bar, surface plate, gauge block, dial indicator set and clamps are required. Dial gauge is used to check the parallelism of the job surface with the surface plate.
Universal Bevel protractor is widely used to measure angles directly by semi-circular graduated protractor in degree along the periphery.
Any angle can be formed with the help of slip gauge pile and Sine Bar as
shown below. Sine Bar with two rollers is placed with one end on surface plate and
other end on slip gauge.
Angle gauge plate (job) is placed on the inclined surface of sine Bar.
Let q 1=Angle made by slip gauge and sine-bar with surface plate.
q =Angle of the gauge plate.
L =Length of the sine-bar (i.e. the distance between the rollers, which is constant for a particular sine bar)
H =Height of the slip gauge.
Then Sinq 1=H/L
q 1 =Sin-1(H/L)
Now, a dial indicator is placed on gauge plate at two different positions (A & B).
If d q =Angle formed between the true horizontal and AB.
L1=Distance between the points A & B on the angle plate.
Then d q =Sin-1(d h/L1)
where d h=Difference between dial gauge readings at A & B.
Let hA &
If hA >hB ,then q 1< q
hA <hB ,then q 1>q
Therefore the actual angle q = q 1 ± d q = Sin-1(H/L) ± Sin-1(d h/L1).
5.1 Measure the angle of angle plate by the use of Bevel protractor.
5.2 Find out height of the slip gauge pile by using the formula (Sinq 1=H/L).
5.3 Maintain the height of slip gauge pile and arrange the sine-bar on the surface plate.
5.4 Place the angle plate on the sine-bar.
5.5 Set the dial indicators on specified marked lines on the plate and measure hA & hB.