Read off directly from the main scale the number of whole degrees between 0 on this scale and the 0 of the vernier scale. Thus, the difference between the space occupied by two degrees on a main scale and the space of the vernier scale is equal to one twenty fourth of two degrees or one twelfth of one degree (or five minutes). Twenty four spaces on the vernier scale equal in extreme length twenty three double degrees. Each space on the vernier scale is 5 minutes less than two spaces on the main scale. The bevel protractor vernier scale indicates every five minutes or 1/20 of a degree. Reading the bevel protractor Vernier scale: Picture below illustrates a variety of uses of the bevel protractor. The readings can be taken either to the right or to the left, according to the direction in which the zero on the main scale is moved. Since the spaces, both on the main scale and the vernier scale, are numbered both to the right and to the left from zero, any angle can be measured. This is because, the dial is graduated from opposite zero marks to 90 degrees each way. But remember this: To obtain the measurement of the angle between the beam and the blade of over 90 degrees subtract the number of degrees as indicated on the dial from 180 degrees. When the edges of the beam and blade are parallel, a small line on the swivel plate coincides with the zero line on the graduated dial, and when any measurement of an angle between the beam and the blade of 90 degrees or under is desired, the reading may be obtained direct from the position of the line on the swivel plate with regard to the graduation numbers on the dial. The bevel protractor consists of a beam, graduated dial and blade which is connected to swivel plate (with Vernier scale) by thumb nut and clamp. For calculation a degree is divided into 60 parts called minutes and a minute is sub-divided into 60 parts called seconds. A circle can be divided into 360 equal angles.
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