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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