1702me402 measurements and metrologyjeevamalar.weebly.com/uploads/2/8/9/8/28980229/unit_3...unit iii...
TRANSCRIPT
UNIT III
LINEAR AND ANGULAR MEASUREMENT
Lecture by
Dr. J.Jeevamalar, M.E., Ph.D.
Associate Professor/ Mechanical
E.G.S. Pillay Engineering College, Nagapattinam
1702ME402 – MEASUREMENTS
AND METROLOGY
UNIT III LINEAR AND ANGULAR MEASUREMENTS 6 Hrs
Linear Measurements:
Vernier Caliper
Vernier Height
Depth Gauges
Micrometer and depth micrometer
Slip gauge
Limit gauge and its classification
Comparator
Mechanical
Electrical types
Pneumatic
Angular Measurements:
Sine bar
Bevel protractor
Autocollimator
Angle Decker
3
© Dr. J.Jeevamalar, Mechanical/EGSPEC
LINEAR MEASURING INSTRUMENTS
- Includes the measurement of lengths, diameters, heights and
thickness.
- Comparison with standard dimensions.
• Devices used for measuring the linear measurements are,
(i) Vernier calipers
(ii) Micrometers
(iii) Slip gauge or gauge blacks
(iv) Limit gauges
(v) Comparators
1. VERNIER CALIPER
4
© Dr. J.Jeevamalar, Mechanical/EGSPEC
5
© Dr. J.Jeevamalar, Mechanical/EGSPEC
6
© Dr. J.Jeevamalar, Mechanical/EGSPEC
One small division on main scale = 1 mm
No. of divisions on Vernier scale = 50
50 Vernier scale divisions = 49 divisions on main scale (or 49
mm)
Each division on Vernier scale = (49/50) mm
Least Count = 1 MSD – 1 VSD
= 1 - (49/50) mm
= (50 - 49)/50
= (1/50) mm
Least Count of Vernier = = 0.02 mm
a. TYPE-A VERNIER CALIPER
7
© Dr. J.Jeevamalar, Mechanical/EGSPEC
b. TYPE-B VERNIER CALIPER
8
© Dr. J.Jeevamalar, Mechanical/EGSPEC
c. TYPE-C VERNIER CALIPER
9
© Dr. J.Jeevamalar, Mechanical/EGSPEC
2. VERNIER HEIGHT GAUGE
10
© Dr. J.Jeevamalar, Mechanical/EGSPEC
3. VERNIER DEPTH GAUGE
11
© Dr. J.Jeevamalar, Mechanical/EGSPEC
4. MICROMETER
12
© Dr. J.Jeevamalar, Mechanical/EGSPEC
13
© Dr. J.Jeevamalar, Mechanical/EGSPEC
TYPES OF MICROMETER
1.Outside Micrometer
2. Inside Micrometer
3.DepthMicrometer
1. OUTSIDE MICROMETER
Pitch of the Barrel = 0.5 mm
Thimble graduation = 50 mm
So LC = 0.01 mm
14
© Dr. J.Jeevamalar, Mechanical/EGSPEC
2. INSIDE MICROMETER
• Used to measure Inner Diameter
• 4 Parts – Measuring Heads, Extension Rods, Spacing Collars, Handles
• Used to measure cylinder Diameter, rings
• Ranges of IMM 25-150, 150-300, 300-450, 450-600mm
15
© Dr. J.Jeevamalar, Mechanical/EGSPEC
3. DEPTH MICROMETER
• Used to measure depth of holes, slots
• Can side up & down & perpendicular to axis of hole
• Range of depth MM is 0 – 225 mm
• Length of extension rod equal to range of micrometer
16
© Dr. J.Jeevamalar, Mechanical/EGSPEC
• Fixed Gauges are used for checking the size, shape
without a scale being used to check dimensions, and
form.
Example of fixed gauges:
1. Slip Gauges
2. Limit Gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
GAUGE BLOCKS
These are small blocks of alloy steel.
Used in the manufacturing shops as length standards.
Rectangular blocks with thickness representing the dimension
of the block.
The measuring surfaces of the gauge blocks are finished to a
very high degree of finish, flatness and accuracy.
Come in sets with different number of pieces and a typical set
consisting of 88 pieces for metric units.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
1. SLIP GAUGE (Gauge Block)
Grade II : Workshop grade for rough
checks.
Grade I : Used for setting up sine bars,
checking gap gauges and setting
dial test indicators to zero.
Grade 0 : Used in tool room and
inspection department.
Grade 00 : Kept in standard room and
used for high precision work such
as checking Grade I and Grade II
slip gauges.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
TYPES OF SLIP GAUGE
• Wringing is defined as the property of the measuring faces of slipgauges to adhere to the measuring faces of other slip gauges.
• Wringing is nothing, but removing the atmospheric air betweentwo mating surfaces of any two gauge blocks, so that the blocksstick to each other due to vacuum.
• Due to do this, hold the two blocks edge-to -edge, and gently pushone of the blocks inside so as to make it sit on the other block,completely.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
WRINGING OF SLIP GAUGE
2 LIMIT GAUGES
© Dr. J.Jeevamalar, Mechanical/EGSPEC
LIMIT GAUGES
• These are also called “GO” and “NO GO” gauges refers to
an inspection tool used to check a workpiece against its
allowed tolerances.
• To check the accuracy of a hole, a cylindrical bar with
highly finished ends of different diameters is used.
• Its name derives from its use: the gauge has two tests; the
check involves the workpiece having to pass one test (Go)
and fail the other (No Go).
• It is an integral part of the quality process that is used in
the manufacturing industry to ensure interchangeability of
parts between processes, or even between different
manufacturers.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
TYPES of LIMIT GAUGES
1. Plug gaugesa. Double ended Plug gaugesb. Progressive type of Plug gauges
2. Taper Plug Gaugea. Taper plug gauge - Plainb. Taper plug gauge – tanged
3. Ring Gaugesa. Taper ring gauge - Plainb. Taper ring gauge – tanged
4. Combined Limit Gauges
5. Position Gauges
6. Snap gauges
a. Double ended Snap gauges
b. Progressive type of Snap gauges
c. Adjustable Snap gauges
d. Plate type Double ended Snap gauges
e. Plate type single ended Snap gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
The ends are hardened and accurately finished
by grinding. One end is the GO end and the
other end is NOGO end.
Usually, the GO end will be equal to the lower
limit size of the hole and the NOGO end will be
equal to the upper limit size of the hole.
If the size of the hole is within the limits, the GO
end should go inside the hole and NOGO end
should not go.
If the GO end and does not go, the hole is under
size and also if NOGO end goes, the hole is
over size.
Hence, the components are rejected in both the
cases.© Dr. J.Jeevamalar, Mechanical/EGSPEC
1. PLUG GAUGES
1. PLUG GAUGES
© Dr. J.Jeevamalar, Mechanical/EGSPEC
a. Double ended Plug gauges
b. Progressive type of Plug gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
2. TAPER PLUG GAUGE
• It is used to check the taper. It is also used to measure the
diameter of the taper at some point.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
28
a. Taper plug gauge - Plain
b. Taper plug gauge – Tanged
© Dr. J.Jeevamalar, Mechanical/EGSPEC
3. RING GAUGES
© Dr. J.Jeevamalar, Mechanical/EGSPEC
Ring gauges are mainly used for checking the
diameter of shafts having a central hole.
The hole is accurately finished by grinding and
lapping after taking hardening process.
The periphery of the ring is knurled to give more
grips while handling the gauges.
We have to make two ring gauges separately to
check the shaft such as GO ring gauge and NOGO
ring gauge.
But the hole of GO ring gauge is made to the
upper limit size of the shaft and NOGO for the
lower limit.
While checking the shaft, the GO ring gauge
will pass through the shaft and NOGO will not pass.
To identify the NOGO ring gauges easily, a red
mark or a small groove cut on its periphery.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
a. Taper ring gauge - Plain
b. Taper Ring Gauge – Tanged
© Dr. J.Jeevamalar, Mechanical/EGSPEC
4. SNAP GAUGES
a. Double ended Snap gauges
• It is used for checking external diameters. Shafts are
mainly checked by the snap gauges.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
b. Progressive type of Snap gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
c. Adjustable Snap gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
d. Plate type single ended Snap gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
e. Plate type Double ended Snap gauges
© Dr. J.Jeevamalar, Mechanical/EGSPEC
5. COMBINED LIMIT GAUGES
In case of gauging of cylindrical holes, it is
impossible to combine both the 'Go' and 'No Go'
dimensions of plug gauge and thus a single
gauge doing the work of checking both the upper
and lower limits
© Dr. J.Jeevamalar, Mechanical/EGSPEC
6. POSITION GAUGES
© Dr. J.Jeevamalar, Mechanical/EGSPEC
It is designed for checking the
position of features in relation to
another surface.
Ex: Contour gauges, receiver
gauges, profile gauges etc.
An instrument, which provides the measurement
in terms of comparison, is called a comparator.
A comparator works on relative measurement.
Comparators are generally used for linear
measurements.
A comparator has to be set to a reference value
(usually zero setting) by employing a standard.
Once it is set to this reference value, all
subsequent readings indicate the deviation from
the standard.
The variation in the measured value may be in
terms of change in displacement, pressure, fluid
flow, temperature, and so on.
COMPARATOR
39
© Dr. J.Jeevamalar, Mechanical/EGSPEC
40
© Dr. J.Jeevamalar, Mechanical/EGSPEC
TYPES OF COMPARATOR
1. Mechanicalcomparators
2. Electrical comparators
3. Pneumaticcomparators
a. Free Flow Type/ Velocity Type Pneumaticcomparators
b. Back Pressure Pneumaticcomparators
i. Solex AirGauge
ii. DifferentialComparator
MECHANICAL COMPARATOR
DIAL INDICATOR
41
© Dr. J.Jeevamalar, Mechanical/EGSPEC
•It is primarily used to compare workpieces against a master.
•It consists of a body with a circular graduated dial, a contact point
connected to a gear train and an indicating hand, which directly
indicates the linear displacement of the contact point.
APPLICATIONS
42
© Dr. J.Jeevamalar, Mechanical/EGSPEC
42
2. ELECTRICAL COMPARATORS
© Dr. J.Jeevamalar, Mechanical/EGSPEC
© Dr. J.Jeevamalar, Mechanical/EGSPEC
Electrical comparators generally depend on a Wheatstone bridge circuit for
measurement.
The plunger is the sensing element, the movement of which displaces an
armature inside a pair of coils. Movement of the armature causes change in
inductance in the two coils, resulting in a net change in inductance.
This change causes imbalance in the bridge circuit, resulting in an output.
Least count of the electrical comparator is 0.001mm
Ex: Linear Variable Differential Transformer (LVDT)
Advantages
1.Very less number of moving parts
2.High magnification
3.Pointer is very light and not sensitive to vibrations
Disadvantages
1.It is more expensive than the mechanical comparator
2.Heating of coils in the measuring unit may cause zero drift and alter thecalibration
43
3. PNEUMATIC COMPARATORS (Pneumatic Gauge)
1. FLOW / VELOCITY TYPE
45
© Dr. J.Jeevamalar, Mechanical/EGSPEC
2. PRESSURE TYPEa. SOLEX AIR GAUGE
46
© Dr. J.Jeevamalar, Mechanical/EGSPEC
2. PRESSURE TYPEb. DIFFERENTIAL COMPARATOR
47
© Dr. J.Jeevamalar, Mechanical/EGSPEC
48
© Dr. J.Jeevamalar, Mechanical/EGSPEC
Advantages
1. The operation is very simple and low price
2. Indicating & measuring is done at two different places
3. The gauging members are direct contact with the work
Disadvantages
1.These comparators are very sensitive are temperature and
humidity.
2.For different job, it requires different gauging heads
ADVANTAGES AND DISADVANTAGES OF
PNEUMATIC COMPARATORS
• Angle is defined as the opening between the two lines meet
at a point.
49
© Dr. J.Jeevamalar, Mechanical/EGSPEC
ANGLE MEASUREMENT - INTRODUCTION
1. Sine Bar
2. Universal Bevel Protractor
3. Auto Collimator
4. Angle Dekkor
© Dr. J.Jeevamalar, Mechanical/EGSPEC
50
INSTRUMENTS USED FOR ANGULAR MEASUREMENT
• It is a precision measuring instrument and is an excellent example
of combination of linear measurement and angular measurement
when used in conjunction with gauge blocks (slip gauges).
• Sine bar is made of high carbon, high chromium corrosion
resistant steel, suitably hardened, precision ground and stabilized.
• It consists of a bar carrying a suitable pair of rollers set a known
centre distance.
• Relief holes are provided for easy handling of sine bar and for
reducing the weight of the sine bar.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
51
SINE BAR
• The principle of operation of sine bar is relay upon the application of
trigonometry.
• The sine bar is placed on the surface plate with the slip gauges of the
required length (H) under one roller and opposite to the angle as
shown in figure.
WORKING PRINCIPLE OF SINE BAR
The angle is given by, Taper Angle, Sin = h / L in Degrees
h = Height of the Slip Gauge in mm. L = Length between two rollers in mm
© Dr. J.Jeevamalar, Mechanical/EGSPEC
52
1. Checking unknown angles of small components:
When an angle of component to be compared is unknown, it is necessarily first
find out the approximate taper angle with the help of bevel protector.
If the angle is θ, then the sine bar is set at an angle θ with the help of slip gauges
and clamped to an angle plate as shown in figure.
A dial indicator is set at a one end of the work and moved to the other end and
the deviation is note down.
Again slip gauges are so adjusted (according to the deviation) such that dial
indicator reads zero as it move from one end to other end of the work piece.
If the deviation is noted down by the dial indicator .
© Dr. J.Jeevamalar, Mechanical/EGSPEC
53
USE OF SINE BAR
2. For locating any work to a given angle
For this, assume surface plate is perfectly flat, so that its surface is
perfectly horizontal.
One roller of the sine bar is placed on the surface plate and the other is
placed on the slip gauge rack of height H.
Let the sine bar is set to an angle θ. Sine θ = h/L
where L is the distance between the center.
Thus knowing θ, H can be found and any work can be set out at this angle
as the top face of the sine bar is inclined at angle θ to the surface plate.
For better result both rollers must placed on slip gauge of height h1
and h2 respectively.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
54
© Dr. J.Jeevamalar, Mechanical/EGSPEC
55
3. Checking of unknown angles of heavy component:
When components are heavy and cannot be mounted on the sine bar, the sine bar
is mounted on the component as shown in figure.
The height over the rollers can be measured by a Vernier height gauge using a
dial gauge mounted on the anvil of it.
The difference in the two readings of height gauge divided by the centre distance
of sine bar gives the sine angle of the component to be measured.
ADVANTAGES AND DISADVANTAGES OF SINE BARS
• Advantages of sine bar
1. It is precise and accurate angle measuring device.
2. It is simple in design and construction.
3. It is easily available
• Disadvantages
1. It is not fairly reliable at angles less than 15 but become
increasingly inaccurate as the angle increases. It is
impractical to use sine bar for angle above 45 .
2. It is difficult to handle and position the slip gauges.
3. The sine bar is physically clumsy to hold in position.
4. The application is limited for a fixed center distance
between two rollers.
5. Slight errors of the sine bar cause larger angular errors.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
56
• Bevel protractors is a type of protractor which is used as an
angular measuring instruments.
• Types of bevel protractors:
1. Vernier Bevel Protractor or Universal Protractor
2. Optical Protractor
2. BEVEL PROTRACTOR
© Dr. J.Jeevamalar, Mechanical/EGSPEC
57
It has a base plate or stock whose
surface has a high degree of flatness
and surface finish and it is placed on
the workpiece whose angle is to be
measured.
An adjustable blade attached to a
circular dial is made to coincide with
the angular surface.
It can be swiveled to the required
angle and locked into position to
facilitate accurate reading of the
circular scale that is mounted on the
dial.
The main scale on the dial is
graduated in degrees and rotates with
the rotation of the adjustable blade.
1. Vernier or Universal Bevel Protractor
© Dr. J.Jeevamalar, Mechanical/EGSPEC
A stationary vernier scale mounted close to the dial, enables measurements to
a least count of 5’ or less.
An acute angle attachment is provided for the measurement of acute angles. 58
LC of Universal Bevel Protractor
• The main scale on the dial is divided into four quadrants, each measuring
90°. Each division on this scale reads 1°.
• The Vernier scale has 12 Divisions each side of the centre zero.
• The 12 divisions are denoted as 60 min on the vernier scale (Like this 15,
30, 45, 60). That means 12 division = 60 minutes.
• One division= 60/12 = 5 minutes
© Dr. J.Jeevamalar, Mechanical/EGSPEC
59
• The total reading =the main scale reading + the number of
the division at which it exactly coincides with any division
on the main scale × least count of the vernier scale.
• In the above case, The main scale reading = 10°
• Vernier scale reading (the number of the division at which it
exactly coincides with any division on the main scale) = 3rd
division
• Least count of the vernier Bevel protractor = 5 Minutes
• The total reading = 10°+15 minutes = 10°
2. Optical Bevel Protractor
• A recent development of
Vernier bevel protector is
optical bevel protector.
• In this instrument, a circular
glass plate is divided at 10
minutes intervals throughout
the whole 360º are fitted inside
the main body.
• A small microscope is fitted
through which the circular
graduations can be viewed.
• The readings are taken against
a Vernier scale with the help of
a microscope.
• With the help of microscope it
is possible to read about 2
minutes.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
61
3. AUTOCOLLIMATOR
© Dr. J.Jeevamalar, Mechanical/EGSPEC
62
Auto-collimator is an optical instrument used for the measurement of
small angular differences, changes or deflection, plane surface
inspection etc.
For small angular measurements, autocollimator provides a very
sensitive and accurate approach.
If a light source is placed in the flows of a collimating lens, it is
rejected as a parallel beam of light.
If this beam is made to strike a plane reflector, kept normal to the
optical axis, it is reflected back along its own path and is brought to
the same focus.
If the reflector is tilted through a small angle ‘’. Then the parallel
beam is deflected twice the angle and is brought to focus in the same
plane as the light source.
The distance of focus from the object is given by, x = 2.fWhere, f = Focul length of the lens
= Tilted angle of reflecting mirror/plane
WORKING OF AUTOCOLLIMATOR
© Dr. J.Jeevamalar, Mechanical/EGSPEC
APPLICATIONS OF AUTOCOLLIMATOR
1) Measuring the difference in height of length standards.
2) Checking the flatness and straightness of surfaces.
3) Checking squareness of two surfaces.
4) Checking alignment or parallelism.
5) Comparative measurement using master angles.
6) For machine tool adjustment testing.
© Dr. J.Jeevamalar, Mechanical/EGSPEC
4. ANGLE DEKKOR
© Dr. J.Jeevamalar, Mechanical/EGSPEC
65
ANGLE DEKKOR
© Dr. J.Jeevamalar, Mechanical/EGSPEC
• This is also a type of auto-collimator.
• This instrument is essentially used as a comparator and measures the
change in angular position of the reflector in two planes.
• It has an illuminated scale, which receives light directed through a
prism.
• The light beam carrying the image of the illuminated scale passes
through the collimating lens and falls onto the reflecting surface of the
workpiece.
• After getting reflected from the workpiece, it is refocused by the lens in
field view of the eyepiece.
• While doing so, the image of the illuminated scale would have undergone
a rotation of 90° with respect to the optical axis.
• Now, the light beam will pass through the datum scale fixed across the
path of the light beam.
• When viewed through the eyepiece, the reading on the illuminated scale
measures angular deviations from one axis at 90° to the optical axis, and
the reading on the fixed datum scale measures the deviation about an axis
mutually perpendicular to this.
APPLICATIONS OF ANGLE DEKKOR
1. Measurement of sloping angle of V-blocks
2. Calibration of taper gauges
3. Measurement of angles of conical parts
4. Measurement of angles of work part surfaces, which are
simultaneously inclined in two planes
5. Determination of a precise angular setting for machining
operations, for example, milling a slot at some precise angle to a
previously machined datum surface.
© Dr. J.Jeevamalar, Mechanical/EGSPEC