METROLOGY LABORATORY

NAME: Swarup Ghosh

CLASS : B.M.E. – III; B2

ROLL : 000611201094

EXPERIMENT NO. – 3

DATE : 22-04-09

TITLE : MEASUREMENT OF INTERNAL RADIUS BY SLIPGAUGE, VERNIER CALLIPER & ROLLER

1. A. Sketch the radius gauge and state its use.

B. A portion of solid sphere is available. Deduce an expression for measuring its radius of curvature with the help of fixed roller type micrometer depth gauge

Ans :>

A.

USE :These are frequently used to measure clearances between components. A familiar example is the use of these gauges for adjusting the spark gap between the distributor points of an automobile.

B.

In this above figure a micrometer type of instrument by means of which the radii of both convex an of concave are can be determined. From this figure the distance ‘a’ from the arc to the line joining the roller. Centre is measured by means of the micrometers. From these dimensions together with the centre distance of the roller and then diameters the radius is calculated.

The instrument is first placed on a true straight edge and a reading of the micrometer is taken with spindle in contact with the straight line. It is then placed on the arc and a reading taken

on this. The difference between the two readings is the height of the arc above tangent to the rollers (h).

Then, a = h – d/2And, (R + d/2)2 = (c/2)2 + (R - a)2

or, (R + d/2)2= (c/2)2 + (R – h + d/2)2

or, 2Rh = c2/4 – h(d - h)

or, R = c2/8h - (d - h)/2

To provide the error micrometer reading must be taken very carefully.

2. With neat sketch and deduction of necessary formulae, show how to determine accurately the different diameters of a cylindrical shell under the following situations when a part of the shell is available:

i. Concave side diameter of the job is extra large in size.ii. Convex side diameter of the job when the job can be held

conveniently on the surface plate.iii. Both convex and concave side diameters of the job are very

small in size.Ans :>

For measurement using rollers, using Pythagoras’ theorem,

When the job is very small in size the it is fastened on a table room microscope and the Cartesian coordinates of three points on the arc is determined moving the microscope to bring the required point

under the cross hairs of the microscope. The coordinates of the microscope can be measured by the scale attached to it. The coordinates are then put in the equation of a circle:

It becomes simpler when the coordinates of the origin of the system is one point one the arc, The equations yield:

: SAMPLE CALCULATION:

With small diameter rollers;

h = 25.70 mm. d = 10.80 mm.

Length of the slip gauge s = 43.01 mm.

R = [ (s + d)2/4 + h(h - d) ] / [ 2(h - d)]

= 37.14 mm.

With large diameter rollers;

h = 25.70 mm. d = 15.90 mm.

Length of the slip gauge s = 27.45 mm.

R = [ (s + d)2/4 + h(h - d) ] / [ 2(h - d)]

= 36.81 mm.

Mean internal radius Rmean = (37.14 + 27.45)/2

= 36.97 mm.