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. Aissa Dr. Walid A. Aissa Associate Professor, Mech. Engg. Dept. Faculty of Engineering at Rabigh, KAU, KSA Chapter #2 September XX, 2012
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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.
c) Dial Caliper:
Dial Caliper used for measurement of external
dimension of workpiece.
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.
2- Electronic Caliper for depth measurement:
Electronic Caliper for depth measurement.
3- Dial Caliper for depth measurement:
Dial 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:
2.4.3. Types of Micrometers:
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.
5) Do not expose the micrometer to cooling water
and lubricating oil.
Sheet #2
20
Problem 2–1: A =?, B = ?, C = ?, D = ?.
30 40 50
B B C D
Problem 2–2: What are the values of accuracy and measurement of VernierCaliper?
Problem 2–3: What are the values of accuracy and measurement of VernierCaliper?
Problem 2–4: What are the values of accuracy and measurement of VernierCaliper?