fall 1433h (2012g) saturday, monday & wednesday...

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

[email protected]

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.

Chapter 2DIMENSIONAL METROLOGY

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.

-Small steel rulers with holder for measurement of small

dimensions.

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:

b) Internal

Measurements:

c) Depth Measurements:c) Depth 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.

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 2–5: What are the values of

accuracy and measurement of Vernier Caliper?

Problem 2–6: What is the Micrometer reading?

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