Experiment No. 3 MEASUREMENT OF TAPER ANGLE USING SINE BAR

Transcription

1 Experiment No. 3 MEASUREMENT OF TAPER ANGLE USING SINE BAR Aim:- To determine unknown angle using sine bar. Apparatus:- Sine bar, surface plate, dial indicator, slip gauges. Introduction:- Sine bar is used in conjunction with slip gauges for precise angular measurement. Sine bar is used either to measure angle very accurately or face locating any work to a given angle. Sine bars are made from high chromium, corrosion resistant steel, hardened, ground and stabilized. Figure: Sine Bar Two cylinders of equal dia. are attached at ends. The axes of these two cylinders are mutually parallel to each other and also parallel to and at equal distance from the upper surfaces of the sine bar. Accuracy up to 0.01mm /m length of sine bar can be obtain. -1-

2 Application of sine bar :- A] Checking of unknown angles of small workpiece. L h Figure. Checking of unknown angles of small workpiece. B] Checking of unknown angles of heavy component. L H1 H2 Figure. Checking of unknown angles of heavy component. -2-

3 Slip Gauges:- Introduction:- Slip gauges are rectangular blocks of steel having a cross-section of about 30 by 10mm. These gauges are used to provide end standard of specific length by temporarily combining a number of individual gauge by wringing, each representing a dimension (standard) into a single gauge bar. Here the basic requirements are formation of a bar in reasonable cohesion between individual element and its dimension truly within specific limits representing the desired nominal dimensions. Accuracy:- Accuracy up to 10 millionth of an inch for flatness and parallelism can be obtained in slip gauges. Grading:- Grading according to accuracy and application. AA - for master slip gauges. A - for reference purpose. B - for working slip gauges. Grade 2 - Workshop grade Grade 1 - Tool-room grade (More precise work) Grade 0 - Inspection grade Grade 00 - Standard-room grade Calibration grade - Special grade (Prepared on chart) Slip Gauge Table:- Sr. No. Slip gauge value or range Step (mm) Nos to to to to Total = 76-3-

4 Precaution in use of sine bar :- 1) The sine bar should not be used for angle greater than 60 o. 2) A compound angle should not be formed by mis-aligning the component with sine bar. 3) Accuracy of sine bar should be ensured. 4) As far as possible longer sine bar should be used since many errors are reduced by using longer sine bars. Wringing:- Figure. wringing The term wringing refers to condition of intimate and complete contact and of permanent adhesion between measuring faces. Wringing is done by hand though sliding and twisting motions. One gauge is placed perpendicular to other using standard gauging pressure and rotary motion is then applied until the blocks are lined up. In this way air is expelled from between the gauge faces causing the blocks to adhere. This adherence is caused partly by molecular attraction and partly by atmospheric pressure. Similarly, for separating two wring slip gauges, combined sliding and twisting motion should be used. -4-

5 Procedure:- 1) Surface plate is placed on a horizontal surface. 2) Build up slip gauges of a proper height by wringing. 3) Place one of the cylinders of sine bar on surface plate and other on slip gauges. 4) Dial indicator is set at one end of the component and moved to the other end. 5) Note the deviation in dial reading. 6) Again slip gauges are so adjusted that dial indicator reads zero deviation across the work surface if deviation is δh over length l 1, change slip gauge height by (δh x L / l 1 ) Where L is standard sine bar length 7) Again take dial indicator reading to assure zero deviation. 8) Read slip gauge height and perform calculation Reading:- A] h= L= B] h1= h2= L= Calculations:- A] Sin θ = h/l θ = Sin -1 ( h/l ) θ = B] Sin θ = h1-h2 / L θ = Sin -1 ( h1-h2 / L) θ = Results:- The unknown angle of component is -5-