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Metrology & Quality Control
Fall 1433H (2012G)
Saturday, Monday & Wednesday 11:00am -
11:50am and Saturday 13:00am - 14:50pm
MENG 436 Class FA
Dr. Walid A. AissaDr. Walid A. Aissa
Associate Professor, Mech. Engg. Dept.
Faculty of Engineering at Rabigh, KAU, KSA
Chapter #2
September XX, 2012
Announcements:
Dr. Walid’s e-mail and Office Hours
walid_aniss@yahoo.com
Office hours for Metrology & Quality Control will be
every Sunday and Tuesday from 11:00 – 13:00 am in Dr.
Walid’s office (Room 5-109).
Text book:Text book:
1-Metrology for Engineers, J.F.W. Galyer & C. R.
Shotbolt, 4th Edition, Cassell Ltd., London, ISBN-0-
304 30612 6, 1980.
2-Essentials of Quality With Cases and
Experimental Exercises, Victor E. Sower, John Wiley
& Sons Inc., London, ISBN-978-0-470-50959-3, 2011.
Objectives of CH2: To
• Recognize concepts of
-Dimensional Metrology,
- Dimensions Measurement Using Steel Ruler, Vernier Caliper and Micrometer.
2. Dimensional Metrology
2.1. Definition:
Chapter 2
• Dimensional metrology is that branch of Metrology
which deals with measurement of “dimensions“ of a
part or workpiece (lengths, angles, etc.)part or workpiece (lengths, angles, etc.)
• Dimensional measurements at the required level of
accuracy are the essential link between the
designers’ intent and a delivered product.
Although the huge technological advance in the field of
measurements, which enabled the use of precise ,
complicated and electronic instruments for
measurement of dimensions, however simple
mechanical devices still considered basic tools for
measurement of dimensions in workshops and labs.
The most important simple mechanical devices are:The most important simple mechanical devices are:
1) Steel ruler 2) Vernier Caliper 3) Micrometer
2.2. Dimensions Measurement Using Steel Ruler:
Steel ruler is the most common tool for measurement
of dimensions in workshop. Usually, it is made of
Steel Which is not affected by variations of
temperature, humidity and vibrations in workshop.
Steel ruler often has two scales; one (in mm) on one
side and one (in inch) on the other side.side and one (in inch) on the other side.
Conversion rule between the two systems of units is:
1 inch = 25.4 mm
The accuracy of some steel rulers is 1 mm. The
accuracy of other steel rulers is 0.5 mm.
Steel rulers; graded based on British units, are graded
in parts of inch:
1/128, 1/64, 1/32, 1/16, 1/8, ¼, ½, 5/8, ¾, 7/8.
2.2.1. Types of Steel Rulers: Steel rulers used in
workshop have different lengths; 6 in, 12 in and 18
in.
-Steel rulers may have special end to be fixed on one end
of workpiece to increase the accuracy of measurement.
-Narrow Steel rulers used for measurement of depth of
holes.
2.2.2. Utilizing steel rulers for dimensions measurement:.
EXAMPLE 2–1: A =?, B = ?, C = ?, D = ?.
Examples of dimensions measurement on steel ruler
A = 12 mm. B = 22 mm. C = 31.5 mm. D = 40.5 mm.
A B
2.3. Dimensions Measurement Using Vernier Calipers:
-During cutting operations of workpiece, operator verifies
that the dimensions of workpiece coincides with those
specified in process sheets in terms of shape,
dimensions and surface finish.
-When required quality of workpeice exceeds the
accuracy of steel ruler, Vernier Calipers or micrometers accuracy of steel ruler, Vernier Calipers or micrometers
should be used for dimensions measurement.
-In addition, Vernier Calipers and micrometers should be
used for mounting (or maintenance) of machines and
cutting tools.
-The importance of Vernier Calipers in workshops and
machining centers is due to both high capabilities of
dimensions measurement and ease of operation.
2.3.1. Uses of Vernier Calipers:
a) External Measurements:
2.3.2. Parts of Vernier Caliper:
-Vernier Caliper consists of two main parts:
a) Fixed part: consists of fixed Jaw connected to main
scale (usually main scale is graded in “mm” from one
side and in “inch” in the other side). Integer numbers
are read on main scale.
b) Movable part: It slides relative to fixed part. It consists
of movable Jaw and vernier scale . Vernier scale is
graded in “fraction of mm” representing the accuracy
of the instrument.
Vernier scale enables the reading of fractions on main
scale with high accuracy. This accuracy is usually in
c) Stem for depth measurement.
scale with high accuracy. This accuracy is usually in
0.1 mm (= 1/10 mm) or 0.05 mm (= 1/20 mm) or 0.02
mm (= 1/50 mm).
Measurement is done by putting the part to be
measured between the movable jaw and fixed jaw
without pressing by force.
2.3.3. Method of Dimension Measurement Using VernierCaliper:
Measurement of dimension using Vernier Caliper is
done on two basic steps:
a) Look at Vernier scale; and precisely, at zero position,
read the number left to it on the main scale in integer
“mm”; “A”.
Main scale
ruler
Vernier
scale
Do not read from edge of
Vernier scale
Reading of main scale on left
of vernier scale zero
Measurement reading at best
coincidence of vernier scale
zero and main scale.
b) Look at Vernier scale; and precisely, at zero position,
read the number left to it on the main scale in integer
“mm”. Multiply this number by “Accuracy of Vernier”.
The resulting number is called: Vernier reading; “B”.
c) The sum of “A” and “B” is “Vernier Caliper reading of
the measured dimension”.
d) “Accuracy of Vernier” is obtained from specification d) “Accuracy of Vernier” is obtained from specification
list of the instrument. Usually, it is registered on the
“Vernier Caliper”.
e) If “for any reason”, You could not obtain the
“Accuracy of Vernier” from instrument specification list
of the instrument or You could not read it on the
“Vernier Caliper”; You can simply specify it as follows;
Keeping in mind that the “Total Vernier scale = 1 mm”,
“Number of divisions of Vernier scale = N”. Hence,
“Accuracy of Vernier = 1/N ”. e.g., if “N =10”. Hence,
“Accuracy of Vernier = 1/10 = 0.1 mm” , if “N = 20”.
Hence, “Accuracy of Vernier = 1/20 = 0.05 mm”& if
“N = 50”. Hence, “Accuracy of Vernier = 1/50 = 0.02
mm”.
EXAMPLE 2–2: What is the Caliper reading?
Solution:
A = 3.6 cm = 36 mm.
Solution:
N = 20, Accuracy = 1/N = 1/20 = 0.05 mm.
B = 13× 0.05 mm = 0.65 mm . Hence, Vernier Caliper reading of the measured
dimension = 36 mm + 0.65 mm = 36.65 mm= 3.665 cm.
EXAMPLE
2–3: What is the Caliper reading?
Solution:
A = 2.4 cm = 24 mm.
Solution:
N = 50, Accuracy = 1/N = 1/50 = 0.02 mm.
B = 31× 0.02 mm = 0.62 mm .
Hence, Vernier Caliper reading of the measured
dimension = 24 mm + 0.62 mm = 24.62 mm= 2.462 cm.
2.3.4. Types of Calipers:
a) Vernier Caliper:
Vernier Caliper used for measurement of external
diameter of a cylinder
b) Digital Caliper:
Digital Caliper used for measurement of external
diameter of cylinder; Reading is 36.34 mm.
d) Depth Caliper: used for measurement of depth of
longitudinal grooves and length of holes and grooves.
There are three types of depth calipers; namely:
1- Vernier Caliper for depth measurement:
Vernier Caliper for depth measurement.
e) Height Caliper: This caliper is used for measurement
of workpiece height and for making marks on it.
Height Caliper
2.4. Dimensions Measurement Using Micromters:
Micrometer is one of the most precise dimension
measuring instruments in the workshops and labs. Its
accuracy might reach 0.01 mm. In some instruments,
it might reach 0.001 mm. Micrometers are
characterized by simplicity and ease of operation.
Knowledge of correct method of use of micrometer is Knowledge of correct method of use of micrometer is
essential for any technician or engineer supervising
the machining or inspection of workpieces.
2.4.1. Parts of Micrometer:
External micrometer contains of two main parts:
a) Fixed part: consists of frame; U shape, for holding
remaining parts ;fixed and movable. The frame holds
the anvil and spindle (measuring rod), which are used
to fix the workpiece to be measured.
The frame also holds the sleeve with main scale. The
sleeve is graded in mm upward and in 0.5 mm
downward.
b) Movable part: The main movable part is the sleeve ;
which when turned using Ratchet Knob, the spindle
(measuring rod) advances to hold the part to be
measured.
Usually, the perimeter of the sleeve is divided into 50
divisions. When the sleeve is turned one complete
turn, the measuring rod advances by 0.5 mm. Hence,
it could be concluded that the accuracy of the device
is 0.5 mm/50 = 0.01 mm.
2.4.2. Correct Method of Reading of Micrometer Measurement:
Micrometer is very sensitive. So, it is used for accurate measurement .
Specifying Micrometer reading goes through the following steps:
1) Main Micrometer reading: 1) Main Micrometer reading:
-Look at the edge of Sleeve with main scale. Read the value marked on cylindrical main scale. Register it; call it A.
-Look whether there is 0.5 grade (or not) at the edge of cylindrical main scale after the value of A. In the case of existing of this grade, add B = 0.5 mm to the measure. In the case of non existence of this grade, add B = 0.0 mm to the measure.
-Define the coincidence of sleeve scale and main line on
2) Reading of the measure on sleeve:
-Define the coincidence of sleeve scale and main line on cylindrical main scale. Multiply, the value registered on sleeve by the value of the accuracy of the device. Call the result of multiplication; C.
-Hence, Micrometer Reading of Measured Dimension = A + B + C.
3) Specifying Micrometer Reading of Measured Dimension:
EXAMPLE 2–4: What is the Micrometer reading?
A = 7.0 mm, B = 0.0 mm, C = 38××××0000....01010101mm=mm=mm=mm=0.38 mm, Hence, Micrometer Reading of Measured Dimension = A + B + C = 7.0 mm+ 0.0 mm+ 0.38 mm = 7.38 mm
Solution:
EXAMPLE 2–5: What is the Micrometer reading?
Solution:
A = 7.0 mm, B = 0.5 mm, C = 22××××0000....01010101mm=mm=mm=mm=0.22 mm, Hence, Micrometer Reading of Measured Dimension = A + B + C = 7.0 mm+ 0.5 mm+ 0.22 mm = 7.72 mm
Solution:
1) Outside Micrometer:
Outside micrometer is used to measure outside
diameters (or surfaces’ dimensions) of machined
parts. There are different ranges of outside
micrometers used in measurements in workshops.
Their sizes vary from zero to 1000 mm. Sizes often
used are 0-25 mm, 25-50 mm, 50-75 mm, 75-100
mm. mm.
2) Inside Micrometer:
This type is used to measure the internal diameters of
holes and grooves in workpieces. This type is
provided with extensions which allow increasing the
range of the micrometer. Reading is taken as the
same manner followed in outside micrometer.
However, the base length of the micrometer and
extension length should be added to the reading to
give the measured value.
3) Depth Micrometer:
This type is used for measuring of depth
of holes and grooves. Depth
micrometer consists of fixed part, micrometer consists of fixed part,
movable part (As in the case of outside
micrometer) and holding base for fixing
the device on the workpiece to be
measured.
2.4.4. Protection and Care of Micrometers:
Micrometer is very sensitive instrument. Its accuracy
may reach to 0.001 mm. Hence, to prevent its
damage and to keep this accuracy, care must be
taken when dealing with it. The following
precautions must be followed:
1) Do not allow the micrometer to fall down.1) Do not allow the micrometer to fall down.
2) Put it in clean and safe place.
3) While measurement, use ratchet knob and lock in
order to prevent excessive pressing on
measuring rod.
4) Do not put the micrometer on the chip resulting
from machining process.
Recommended