Measurements tools

Unit 2: Measurements
Dr. Abdullah Dhaiban
Unit_2: Measurements Mechatronics Engineering Dep. (2017/2018) Dr. Abdullah Dhaiban

Introduction
 Measurement is the comparison of an unknown
dimension to a known standard.
 Good measuring instruments are a key to high volume
production. Without them, parts could not be built
accurately enough to be interchangeable. Each
assembly had to be hand fitted together.
 Today, measuring tools are essential for most machining
operations from initial part layout to final inspection.
Unit_2: Measurements Mechatronics Engineering Dep. (2017/2018) Dr. Abdullah Dhaiban 2

Classification of Measuring
Instruments
 Direct measuring Instruments
 Determine the actual dimension and size of a work
piece
 Indirect measuring Instruments (comparison
instruments)
 Transfer the measurement from the work piece to
the direct measuring instrument, then comparison
is made.

Engineering Measurements
 Engineering Measurements Include the following
1. Lengths
2. Angles
3. Coordinates (Location)
4. Surfaces
5. Roughness
6. Volumes
7. Force, weight, ….etc.

Principal Measuring Instruments
 Linear Measurements
 Steel rule
 Calipers
 Vernier caliper
 Micrometers
 Angular Measurements
 Protractors
 Bevel protractor
 Sine bar
5Unit_2: Measurements Mechatronics Engineering Dep. (2017/2018) Dr. Abdullah Dhaiban

Principal Measuring Instruments
 Surface Measurement
 Straight edge
 Surface plate
 Surface gauge
 Optical gauge
 Profilometer

1. Vernier Caliper
 The vernier is a convenient tool to use when
measuring the length of an object, the outer diameter
(OD) of a round or cylindrical object, the inner
diameter (ID) of a pipe, and the depth of a hole
 A vernier caliper (or vernier) is a common tool used in
laboratories and industries to accurately determine
the fraction part of the least count division.
 .

1. Vernier Caliper

1. Vernier Caliper
 A vernier consist of two scales: one moving and one
fixed.
 The fixed scale is graduated in millimetres, every 10
divisions equalling 10 mm, and is numbered 0, 1, 2,
3, 4 up to the capacity of the instrument.
 The moving or vernier scale is divided into 50 equal
parts which occupy the same length as 49 divisions
or 49 mm on the fixed scale

85
Fixed
scales Vernier
scales
Locking
screws
A B
C
Beam
Fixed
jaw
Sliding jaw
Adjusting
nut
Vernier caliper adjustment

Vernier scale readings
 This means that the distance
between each graduation on the vernier
scale is 49⁄50 mm= 0.98 mm, or 0.02 mm
less than each division on the fixed
scale (see(a)).
 If the two scales initially have their
zeros in line and the vernier scale is
then moved so that its first graduation
is lined up with a graduation on the
fixed scale, the zero on the vernier scale
will have moved 0.02 mm ((b)).
Vernier scale reading

If the second graduation is lined up, the
zero on the vernier scale will have moved
0.04 mm ((c)) and so on.
If graduation 50 is lined up, the zero will
have moved 50 × 0.02 = 1 mm. Since each
division on the vernier scale represents
0.02 mm, five divisions represent 5 × 0.02 =
0.1 mm.
Every fifth division on this scale is marked 1
representing 0.1 mm, 2 representing
0.2 mm and so on Vernier scale readings
Vernier scale readings

How to read a vernier scale
This reads 3.3

In the readingThe eleventh line coincides with a line on the fixed scale, therefore
11 × 0.02 = 0.22 mm is added to the reading on the fixed scale, giving a total
reading of 40.22 mm shown in Fig. (a) the vernier scale has moved 40 mm to the
right..
Similarly, in Fig. (b) the vernier scale has moved 120 mm to the right plus 3 mm
and the sixth line coincides, therefore, 6 × 0.02 = 0.12 mm is added to 123 mm,
giving a total of 123.12 mm.

Fixed
scales Vernier
scales
Locking
screws
A B
C
Beam
Fixed
jaw
Sliding
jaw
Adjusting
nut
To take a measurement, loosen both locking screws A and B in the (Fig.).
Move the sliding jaw along the beam until it contacts the surface of the
work being measured. Tighten locking screw B.
Adjust the nut C until the correct ‘feel’ is obtained, then tighten locking
screw A. Re-check ‘feel ’ to ensure that nothing has moved. When you are
satisfied, take the reading on the instrument. Jaws may be carbide tipped
for greater wear resistance

85
External Internal Depth
External, internal and depth measurement

Dial calipers
Are a form of vernier caliper
where readings of 1 mm steps are
taken from the vernier beam and
subdivisions of this are read direct
on a dial graduated in 0.02 mm
divisions.
Figure Dial caliper

Digital caliper

Caliper special jaws
a) Point jaw type – for uneven surface measurement.
b) Offset jaw type – for stepped feature measurement.
(a) uneven surface
(b) stepped feature

Caliper special jaws
c) Neck type – for outside
diameter measurement such
as behind a shrouded recess.
d) Tube thickness type – for
tube or pipewall thickness
measurement
(c) shoulder recess
(d) tube thickness

How to use vernier calliper ?
1. Before use, clean the jaws of the measuring surfaces.
Ensure the instrument reads zero before taking a
measurement.
2. Wipe (clean) sliding surfaces before use.
3. Look straight at the vernier graduations when making
a reading. If viewed from an angle, an error of reading
can be made due to parallax effect

4. Ensure the surface to be measured is clean
5. Do not use excessive force when taking a
measurement.
6. Do not measure a workpiece at a position near the
outer end of the jaws. Move the workpiece as close to
the beam as possible to ensure greatest accuracy of
measurement
7. Keep jaws square/parallel with surface being measure
ensure greatest accuracy.

8. For internal measurement, ensure the inside jaws are
inserted as deeply as possible before taking a
measurement.
9. Be careful not to drop or bang the caliper such as
would cause damage to the instrument.
10. Caliper jaws are very sharp so handle with care to
avoid personal injury.
11. Always store the instrument in a clean place
12. Do not leave the caliper jaws clamped together when
not in use. Always leave a gap between the
measuring faces.

Vernier height gauge
 The beam, carrying the fixed scale, is
attached to a heavy base. The vernier
scale carries a jaw upon which
various attachments can be clamped.
It is most widely used with a chisel-
pointed scribing blade for accurate
marking out, as well as for checking
the height of steps in components.
Vernier height guage

87
Digital height gauge
Vernier depth gauge

2. Calipers
 A caliper is used to transfer and compare a dimension
from one object to another.
 Spring-loaded calipers do not have calibrations. You
obtain measurement by placing the measuring arms
against a rule (stainless steel ruler with English and
Metric scales shown). As you can see the accuracy of
this tool and method does not compare with the
accuracy of the Vernier or electronic caliper.

2.1 Outside caliper

2.1 Outside caliper
 Spring-loaded OD Calipers are an inexpensive
alternative to vernier calipers.
 They do have limitations - primarily in accuracy and
versatility.
 Advantages other than cost may be in the increased
measuring capacity or range, and heat tolerance
when making rough measurement. Horizontal
threaded rod contains a thumbwheel for adjusting the
width of the two measuring arms.

2.1 Outside caliper

2.2 Inside Caliper
 Spring-loaded ID Calipers have the same features
and limitations of the OD Calipers. The difference is in
the shape/orientation of the measuring arms allowing
access to the inside of the object.

2.2 Inside Caliper

3. Angular Measurement
 Circles are divided into 360 equal parts, each being a
degree.
 Each of these degrees can be evenly divided into 60
equal parts. These parts are called minutes.
 These minutes can be evenly divided into 60 equal
parts. These parts are called minutes.

 1 Circle = 360 Degrees ( 360° )
 1 Degree ( 1° ) = 1/360th of a Circle
 1 Degree ( 1°) = 60 Minutes ( 60' )
 1 Minute ( 1' ) = 1/60th of a Degree
 1 Minute ( 1') = 60 Seconds ( 60" )
 1 Second ( 1" ) = 1/60th of a Minute

 The unit of degree can also be divided into either
decimal or fractional parts and is referred to as decimal
degrees or fractional degrees respectively.
 1½ Degree = 1.5 Degree ( 1.5°)
 87¼ Degrees = 87.25 Degrees ( 87.25° )

 Minutes and seconds can each be expressed as
decimal or fractional degrees.
 1 Minute ( 1' ) = 1/60th of a Degree = 0.01667°
 1 Second ( 1" ) = 1/60th of a Minute = 0.01667'

 Change 5°25' to decimal degrees
 Divide the minutes by 60
 Add 0.4167 to 5 = 5.4167°
 5°25' = 5.4167°
 25 divided by 60 = 0.4167

Angular Measure
Tools

 Most common tools
1. Simple Protractor
2. Vernier bevel protractor
3. Sine bar

3.1 Simple Protractor

3.1 Simple Protractor
Whole degree increments

3.2 Vernier bevel protractor
 As well as linear measurement, vernier scales can
equally well be used to determine angular
measurement.
 The vernier bevel protractor uses the principle of two
scales, one moving and one fixed.

3.2 Vernier bevel protractor
 Used to measure obtuse angle (90º-180º)
 Acute-angle attachment
Fastened to protractor to measure
angles less than 90º
 Main scale divided into
two arcs of 180º
 Scale divided into 12
spaces on each side of 0
 If zero on vernier scale
coincides with line on
main: reading in degrees

How to Read a Vernier Protractor?
 Note number of whole degrees between zero on main
scale and zero on vernier scale
 Proceeding in same direction, note which vernier line
coincides with main scale line
 Multiply number by 5' and add to degrees on protractor
dial
 50º
 4 x 5'= 20'
 Reading = 50º 20'
Fourth

3.3 Sine Bars
 Used when accuracy of angle must be checked to
less than 5 minutes
 Consists of steel bar with two cylinders of equal
diameter fastened near ends
 Centers of cylinders exactly 90º to edge
 Distance between centers usually 5 or 10 inches
and 100 or 200 millimeters.
 Made of stabilized tool hardened steel

3.3 Sine Bars

3.3 Sine Bars
 Used on surface plates and any
angle by raising one end of bar
with gage blocks
 Made 5 inch or in multiples of 5 or
100 millimeters or multiple of 100
 Distance between lapped
cylinders.
 Face accurate to within .00005 in.
in 5 inches or 0.001 mm in 100
mm.

3.3 Sine Bars

4. Micrometers
 The micrometer relies for its measuring
accuracy on the accuracy of the spindle screw
thread. The spindle is rotated in a fixed nut by
means of the thimble, which opens and closes
the distance between the ends of the spindle and
anvil. For one revolution, the spindle and the
thimble attached to it will move a longitudinal
distance of 0.5 mm.

Anvil Locknut Ratchet stop
4.1 External micrometer

4. Reading micrometers
1 mm
0.5 mm

4.1 External Micrometer
 External micrometers with fixed anvils are available
with capacities ranging from 0–13 mm to 575–600
mm.
 External micrometers with interchangeable anvils
(provide an extended range from two to six times
greater than the fixed-anvil types.
 To ensure accurate setting of the interchangeable
anvils, setting gauges are supplied with each
instrument.

4.1 External Micrometer
External
micrometer
with
interchangeab
le anvils

4.2 Internal micrometer
 It is designed for inside measurement and consists of
a micrometer measuring head to which may be added
external rods to cover a wide range of measurements
and a spacing collar to make up for the limited range
of the micrometer head.
 Micrometers of less than 300 mm are supplied with a
handle to reach into deep holes.
 Each extension rod is marked with the respective
capacity of the micrometer when that particular rod is
used.

4.2 Internal micrometer
Digital inside micrometer 59Unit_2: Measurements Mechatronics Engineering Dep. (2017/2018) Dr. Abdullah Dhaiban

4.3 Depth Micrometer
Depth micrometer

5. Dial indicators
 Dial indicators magnify small movements of a plunger
or lever and show this magnified movement by means
of a pointer on a graduated dial.
 Dial indicators are used to check the dimensional
accuracy of workpieces in conjunction with other
equipment such as gauge blocks, to check
straightness and alignments of machines and
equipment, to set workpieces in machines to ensure
parallelism and concentricity and for a host of other
uses too numerous to list completely.

5. Dial indicators
Dial test indicator and standPlunger-type dial indicator

6. Modern measuring
techniques
 Laser scan micrometer
The laser scan micrometer is a high-precision
laser measuring system that performs non-
contact dimensional measurement using a high-
speed scanning laser beam.
Measure workpieces that are (hot workpieces,
brittle or elastic workpieces, workpieces that
must be kept free from contamination, and soft
workpieces which would be affected by
measuring forces.)

6. Modern measuring
techniques
 Basic principle:
A laser beam is directed across the workpiece. The
part of the beam not obstructed by the workpiece
reaches a receiver which sends a signal for processing
and the dimension is displayed digitally on the
connected display unit.
Data software is available which allows import of
measurement data from one or more display units
to a PC for statistical and quality control purposes.

6. Modern measuring
techniques
Laser scan micrometer

6. Modern measuring
techniques
CNC co-ordinate measuring machine
66Unit_2: Measurements Mechatronics Engineering Dep.

Questions
1. What are the relation between good measuring
instruments and production?
2. How are the measuring instruments classified?
3. What is the accuracy of vernier caliper?
4. What are the types of Vernier caliper?
5. What is the measuring accuracy of a micrometer
without a vernier scale?

Questions
6. Describe the basic principle of the vernier scale.
7. What is the difference between the graduations of an
external micrometer and a depth micrometer?
8. State the types of measurement which can be carried
out using a vernier caliper.
9. What is the measuring accuracy of vernier bevel
protractor?
10.What is the basic principle of a laser scan micrometer?

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