sine bar

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Angular Measurements – Sine Bar

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A sine bar is a tool used to measure angles in metalworking. Sine bars are made from high carbon, high chromium, corrosion resistant steel which can be hardened, ground & stabilized. Angular Measurements – Sine Bar

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It consists of a hardened, precision ground body with two precision ground cylinders fixed at the ends . Two cylinders of equal diameters are attached at the ends as shown in fig. The distance between the centers of the cylinders is precisely controlled The distance between the axes can be 100, 200 & 300 mm. Angular Measurements – Sine Bar

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1. Slip Gauge Height (H) = 68.6 mm 2. centre distance (L) =200 mm 3. Φ =sin-1(H/L)= 20.097 4. Angle of specimen=20.1 degrees Angular Measurements – Sine Bar

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For checking unknown angles of a component, a dial indicator is moved along the surface of work and any deviation is noted. The slip gauges are then adjusted such that the dial reads zero as it moves from one end to the other. Angular Measurements – Sine Bar

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Limitations of Sine bars: The accuracy of sine bars is limited by measurement of center distance between the two precision rollers & hence it cannot be used as a primary standard for angle measurements. Sine principle is fairly reliable at angles less than 15deg , but becomes inaccurate as the angle increases. For angles exceeding 45 deg, sine bars are not suitable for the following reasons: 1. The sine bar is physically clumsy to hold in position. 2. The body of the sine bar obstructs the gauge block stack, even if relieved. 3. Slight errors of the sine bar cause large angular errors. Angular Measurements – Sine Bar

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Sine centers are used for mounting conical work pieces which cannot be held on a conventional sine bar. Sine center consists of a self-contained sine bar hinged at one roller and mounted on its own datum surface & the top surface of the bar is provided with clamps & centers to hold the work. For the dial gauge to read zero, the accurate semi cone angle a=q=sin-1(H/L). Angular Measurements – Sine Centre