measuring instruments for tool

8/10/2019 Measuring Instruments for tool

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METAL CUTTING &

METEROLOGYCOURSE CODE : MEL201

110/29/2014


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Classification of Measuring Instruments Based on determination of measured Value

Direct measurement like micrometer, Vernier calipers etc

Indirect measurement like sine bar, divider

On the basis of deviation of Measured dimensions Absolutelike steel rules, vernier etc

Comparativelike dial indicators, optimeters etc.

Based on type of contact

Contactlesslike microscope, projection comparator etc.

Contact like dial indicators, calipers

According to functions

Linear Measuring instruments like steel rule, vernier calipers etc

Angular Measuring Instruments like Protactor,sine bar etc.

Depending upon accuracy

According to metrological properties

Rangewhich is the size values between which an instrument can measure.

Scale division is the measured value corresponding to one division of

instrument scale.

Sensitivityis the ratio of scale spacing to the scale division value.


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Sensitivity

It is the ratio of scale spacing to the scale

division value.

If on the indicator, the scale spacing is 1.5 mm

and the scale division value is 0.01 mm, then

the sensitivity of the instrument is 150.

Sensitivity is also called amplification factor or

gearing ratio.


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Tool Makers Microscope


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Tool Makers Microscope

It measures by optical means with nopressure being involved.

It is used for measurements on the small &

delicate parts. Measurements on parts of complex form like

profile for external threads, measuring center

to center distance of holes in any plane.


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Tool Makers microscope

(Working)

A ray of light from a light source is reflected by aplanemirror through 90 degrees.

It thenpassesthrough a transparent glass plate.

A shadow image of the outline of workpiece passes through

theobjective of optical head, and isprojectedby a system ofthree prisms to a ground glass screen.

Observations are made through an eyepiece.

Measurements are made through the means of cross line

engraved on the ground-glass screen. The screen can be rotated through an angle of 360o,the

angle of rotation is read through an auxiliary eyepiece.


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Auto Collimator


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Auto-Collimator

The instrument is used to measure small

angular inclinations, straightness, flatness &

alignment.

It is a tube for projecting parallel rays of light.

It consist simply of a light source and a

collimating lens.


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Auto-Collimator

(Principle of working)

Basic principle of working of this instrument is the principle of

reflection of light.

Let a point source of light be placed at the principle focus of

converging lens.

After passing through the lens, the beam of light becomes

parallel. If the beam of light falls on flat reflecting surface

which is perpendicular to the optical axis, it will be reflected

back along its original path & refocused at the same point.

Now, if the mirror is tilted by an angle , the beam of light

will be reflected back but deflected through an angle 2


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OPTIMETERS Optimeters are known as optical comparators because

measurements are made by the comparative method.

In this instrument the principle of reflection is utilized i.e. if a

beam of light strikes a flat reflecting surface which is

perpendicular to the direction of ray, it is reflected back along

its original path.

If the mirror is tilted through a small angle, the reflected ray

will get deflected at twice the angle of tilt of the mirror.


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OPTIMETERS(Construction)

It consist of a vertical tube, vertical columnmounted rigidly in a wide base.

The tube is of right angular design is held in

bracket which can move up and down the

column and can be clamped at any position

along the column.

There is an optimeter table on which the

parts to be checked will be placed, is under

the measuring tip of the tube and is well

suppported on the base.


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Optimeter (Working)

The Optimeter tube consists of eyepiecethrough which the scale deviations are

observed, the scale is engraved on a flat

circular disc in front of eyepiece. From the light source, a beam of light is

directed by a hinged mirror at the side of the

tube to the scale of the disc.

The reflected beam of light passes through the

triangular prism, where it is reflected at an

angle of 90o.


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Optimeter (Working)

Then through the objectiveto the tilting

mirror.

The reflected image of the scale is visible in

the eyepiece .

The first step in measurement is that the

measuring tip of the instrument is set to the

required dimensionsin relation to the table

with the help of gauge blocks.

The scale of eyepiece rests at zero.


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Optimeter (Working)

Now the mirror becomes inclined to the direction of

the beam and the beam will be reflected at certain

angle and returned to the eyepiece. The reflected

image of the scale will be slightly dispaced on glassdisc in reference to index line.

The spindle displacement will be the proportional to

the tilt of the mirror.

The feeler point resting against the work may be

raisedby the means of small lever which place &

remove the work.


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Optimeter (Working)

The pressure exerted by the feeler point onthe work is very small and is kept uniform by

the action of small springs.

The vertical Optimeter is designed for externalmeasurement of shafts & plates. The range of

measurement varies from 0 to 180 mm.


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Clinometer


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Vernier Bevel Gauge


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Sine Bar


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Dial Indicator


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measuring instruments for tool

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