382783006-M6-M7-Module.pdf

Preparation for basic skills
P66 A/B M6/M7 BS E
EASA Part-66 Cat. A / B1 / B2
M6 Materials and Hardware
M7 Maintenance Practices
Fundamentals

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M6 MATERIALS AND HARDWARE
M7 MAINTENANCE PRACTICES
PREPARATION FOR BASIC SKILLS
SAFETY PRECAUTIONS
Part-66
HAM US/F-5 KrC Dec 2005 1
SAFETY PRECAUTION
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SAFETY PRECAUTIONS
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HAM US/F-5 KrC Dec 2005
INTRODUCTION
This module is concerned with fire and safety precautions around workshops
and hangars, it is up to all of us who work in this environment to ensure the
safety of people and equipment. Bear in mind that most accidents are the re-
sult of over-confidence or the action of inexperienced people. Therefore, to
avoid injury to expensive equipment or personnel a sensible approach to your
workplace should be adopted.
We will also be looking at the storage and handling of aircraft, and will cover
general aspects of these tasks; for specific applications, the manufacturers
manuals must be consulted.
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Types of Accident Agent of Accident
25%
Falling
or jumping
24%Stepping on,
striking against,
or struck by
objects
3%
5%
28%
Over-exertion
and strain
10%
Other
Exposure or contact
with extreme temperatures,
electric current,
hazardous chemicals
or radiation
Struck by
falling oblects
Caught in objects
5%
16%
Means of tranport
and lifting
equipment
6%
Machines
19%
Equipment
9%
Other
8% Crates and
other containers
22%
Working
enviroment
20%
Materials, chemicals
and radiation
Page 3
Figure 1 Industrial Injuries

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FIRE PRECAUTIONS
You will already be aware of the potential fire hazards of working in an environ-
ment containing vast amounts of highly flammable fuel such as that contained
in aircraft. Because fire is a most dangerous threat which will always be with
us the following precautions must be observed:
S Smoke only in designated areas set aside for that purpose.
S Observe and obey ’No Smoking’ signs on flight lines.
S Do not carry non-safety matches and do not wear steel tips on shoes as
they can create sparks.
S When operating petrol engined ground equipment have a foam fire extin-
guisher handy.
S Flammable liquids like paints and dope should be kept in an approved store
outside the hangar or workshop.
S If using heat torches in a workshop such as blow lamps, the flame should
be directed towards fire bricks when not in immediate use.
S You should find out where fire extinguishers and fire buckets are located in
your place of work.
S When refuelling or defuelling an aircraft no electrical system should be
switched on or off. Ensure the aircraft is bonded before starting work.
S When fuel tanks have been completely emptied, the fire risk is still present
due to the fumes, always use flameproof torches when entering tanks.
The above is a list of some of the general precautions that you must observe.
Fire instruction notices should be found in your place of work, it is in your inter-
est to read and understand them, they are there for your protection.
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Close door to confine fire
Sound alarm
Notify fire brigade
If safe to do so, fight fire
If fire cannot be controlled, evacuate
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Figure 2 Fighting Fires

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SAFETY IN THE WORKSHOP AND HANGAR
Safety in and around your place of work is vital to ensure that accidents to
people and equipment are prevented. it is essential that all notices and warn-
ings placed near machines are strictly obeyed.
Precautions should be taken to protect your skin by the application of barrier
cream prior to practical work, especially if handling oils and greases which can
cause irritation, after completion of work ensure all traces are removed by
washing.
All accidents no matter how small should be reported to your supervisor, the
nature of the accident and the treatment received should be entered in a book
to record the accident should any other action be required.
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UNSAFE WORKING ENVIRONMENT
SAFE WORKING ENVIRONMENT
KEEP WORKPLACE
SAFE, EFFICIENT
AND TIDE
Close- fitting
high- buttoned
overalls
Ear protection
Head protection
Tidy hair style
Close-
fitting
cuffs
No rings
or watch
Cuffless
trousers
Insulated
soles
Reinforced
footwear
Eye
protection
Page 7
Figure 3 Workshop and Hangar Safety

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ELECTRICAL EQUIPMENT
General
When using electrical equipment you must ensure the following conditions are
met:
S A three pin plug must be fitted incorporating an earth wire.
S Switch the current OFF before disconnecting or plugging in to the mains
supply.
S Stand on a dry floor, if not stand on a wooden platform or move to a dry
position.
Electric Shock -
- First Aid
If personnel are subject to an electric shock you should proceed as follows:
S Switch off current or remove the victim from the supply by the use of insu-
lated material, e.g., rubber gloves or a broom.
S Treat for shock, keep the victim warm.
S Get medical assistance immediately.
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WILL CAUSE
DEATH
MAY CAUSE
MUSCULAR
CONTRACTION
MAY CAUSE
SOME
SENSATION
240 VOLTS
PATH OF
CURRENT
EARTH (0 VOLTS)
ELECTRIC SHOCK
0.1AMP
to
0.2AMP
0.012AMP
to
0.02AMP
0.001AMP
to
0.008AMP
REACTION OF BODY TO 100 VOLTS
TAKE PRECAUTIONS WHEN
WORKING ON LIVE EQUIPMENT
Insulated
soles
Work with
one hand
in pocket
Insulated
mat
Page 9
Figure 4 Working with Electricity

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MACHINE TOOLS
In all cases, machine tools should be operated only by trained personnel. The
following safety precautions must be taken when using grinding and drilling ma-
chines:
Grinding Machines
S Always wear goggles.
S Ensure tool rest is as near to the wheel as possible.
S Do not use the side of the wheel.
S Do not exert excessive pressure on the wheel.
Drilling Machines
S Ensure all guards and covers are secure and correctly fitted.
S Make sure the work is clamped.
S Don’t allow loose clothing to become entangled with moving parts.
S Don’t use excessive pressure on the drill.
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HAIR AND EYE UNPROTECTED
UNSAFE WORKING
NO SAFETY
GOGGLES
NO WHEEL GUARD
GAP TOO LARGE
BADLY ADJUSTED
WORK REST
AVOID UNSAFE PRACTICES
AND CONDITUONS
WEAR WELL-FITTING
SAFETY GOGGLES
CLOSE-FITTING
OVERALLS BUTTONED
TO NECK
HANDS
KEPT
CLEAR
SAFETY
BOOTS
SUPPORT YOURSELF
COMFORTABLY ON
BOTH FEET KEEP AREA CLEAR
DEVELOP AN AWARENESS
FOR SAFETY
POSITION YOURSELF
TO ENABLE THE
REQUIRED PRESSURE
TO BE APPLIED
Page 11
Figure 5 Working with Power Tools

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PRECAUTIONS TO BE OBSERVED WHEN WORKING IN AND
AROUND AIRCRAFT
Below are listed some general precautions you must obey when working in and
around aircraft:
S Before operating any system be aware of the implications, the operation of
one system could influence another.
S Before moving flight controls ensure the area around the control surface is
clear of ground equipment and personnel.
S When items are being hoisted by crane, do not walk under suspended
loads, and don’t leave loads unattended.
S Take care with oxygen equipment, ensure no oil or grease comes in contact
with pipeline threads. You should wear clean overalls and have grease free
hands when replenishing oxygen systems.
S Any bonding wire disturbed during maintenance must be replaced to avoid
the build up of static electricity. A bonding test must then be carried out.
S Grommets and seals particularly in fire zones must be in a serviceable
condition.
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BARRIERS INDICATE
RESTRICTED SITUATIONS
TAKE NOTICE OF SIGNS CLEAN UP RUBBIISH
CLEAN UP OIL AND FLUIDS
Page 13
Figure 6 Precautions around the Aircraft

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INTEGITY AWARENESS
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INTEGRITY AWARENESS
INTRODUCTION
Airplane structural integrity depends upon the diligent performance of all avi-
ation industry personnel. The responsibility for safety cannot be delegated to a
single participant. The following information is presented to become more
aware of the possibility that minor structural problems could lead to a decrease
of structural integrity. Extreme cases could result in the loss of an airplane.
Aircraft safety is one goal that cannot be compromised and requires diligent
performance by the manufacturers, regulatory agencies, airlines and mainte-
nance organisations.
CAUTION: MODERN AIRCRAFT ARE MADE OF LIGHTWEIGHT,
HIGHLY REFINED METALS WHICH ARE REACTIVE TO
CONTAMINANTS IN THE ATMOSPHERE AND CAN EASILY
BE DAMAGED WHILE ON THE GROUND.
EXPERIENCE HAS SHOWN THAT EARLY SINGS OF
STRUCTURAL DAMAGE HAVE OFTEN BEEN FOUND BY
ALERT PERSONNEL WHILE PERFORMING TASKS ON THE
AIRPLANE WHICH WERE UNRELATED TO THE JOB AT
HAND.
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HAM US/F-5 KrC Dec 2005 Page 15
Figure 7 Awareness

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AIRCRAFT SAFETY
Improper safety precautions can cause thousands of pounds worth of damage
and extensive unscheduled downtime.
Structural integrity is everyone’s job. Extensive damage to the airframe will re-
quire many hours of repair time by skilled maintenance personnel to restore
structural integrity - mechanics, painters, engineers, planners, inspectors, etc.
Doing a good job is everyone’s responsibility.
Awareness should be everyone’s responsibility and reporting anything noted is
crucial. This awareness includes being conscious of surroundings and looking
for that which is out of the ordinary.
Modern aircraft are made of lightweight, highly refined metals which are reac-
tive to contaminants in the atmosphere and can easily be damaged while on
the ground. Experience has shown that early signs of structural damage have
often been found by alert personnel while performing tasks on the airplane
which were unrelated to the job at hand.
CAUTION: AIRCRAFT SAFETY IS ONE GOAL THAT CANNOT BE COM-
PROMISED AND REQUIRES DILIGENT PERFORMANCE BY
THE MANUFACTRER, REGULATORY AGENCY AND THE
OPERATOR.
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OPERATOR
MANUFACTURER
NEED FOR SAFETY
REGULATORY
AGENCY
Page 17
Figure 8 Aircraft Safety

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CARELESSNESS
Damage to airplane structure can occur in many ways, some of these are by
accident, collision with ground equipment, mid-air collision, lightning strike or
hail.
Careless handling of the airplane at the ramp can result in a costly time-con-
suming repair to replace the damaged skins and restore structural integrity.
CAUTION: REINFORCING THE NEED TO REPORT
AWARENESS SHOULD BE EVERYONE’S RESPONSIBILITY
AND REPORTING ANYTHING NOTED IS CRUCIAL. THIS
AWARENESS INCLUDES BEING CONSCIOUS OF SUR-
ROUNDINGS AND LOOKING FOR THAT WHICH IS OUT OF
THE ORDINARY.
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THE NEED TO REPORT ANYTHING „NOT NORMAL“
Page 19
Figure 9 Carelessness

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GENERAL MAINTENANCE PRACTICES
It is essential that proper procedures as well as correct parts and tools be
employed. Poor practices during maintenance operations, repairs, servicing or
loading and unloading can create structural damage. Any incorrect repair can
cause premature cracks in primary structural parts.
Poor Housekeeping
Poor housekeeping, leaving behind garbage, tools, batteries, flashlights, dirt,
chips, etc., can result in the disruption of drain paths, plugged drain valves,
contamination and encourage corrosion to form.
Incorrect Use of Tools
Using tools and equipment incorrectly can result in rough finishes, gouges or
scratches on metal and composite assemblies. All will require premature main-
tenance action to restore structural integrity.
Stepping on Structure
Stepping on or using tubing, wiring, cables or light structural parts as hand-
holds can cause damage to or completely run essential systems.
CAUTION: WALKING / STEPPING ON STRUCTURE
STEPPING ON OR USING TUBING, WIRING, CABLES OR
LIGHT STRUCTURAL PARTS AS HAND-HOLDS CAN
CAUSE DAMAGE TO OR COMPLETELY RUIN ESSENTIAL
SYSTEMS.
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Figure 10 Stepping on Structure

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MATERIALS
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MATERIALS
GENERAL
Abbreviations
AA Aluminum Association of America
AISI American Institute of Steel and Iron
AL Aluminum
ALF3 Aluminum Fluoride
Al2O3 Aluminum Oxide
ALCOA Aluminum Corporation of America
CAF2 Fluorspar
Clad Cladding
CO2 Carbon Dioxide
CR Chromium
CRES Corrosion Resistant Steel
CU Copper
DC Direct Chill
F As fabricated
H Strain hardened
H2O Water
NA3ALF3 Cryolite
NI Nickel
MG Magnesium
MN Manganese
MO Molybdenum
O Annealed
PSI Pounds per Square Inch
SAE Society of Automotive Engineers
SI Silicon
T Heat treated
VA Vanadium
ZN Zinc
Conversions
Fahrenheit to Centigrade Conversion
S °C = (°F - 32) x 0.555
Centigrade to Fahrenheit Conversion
S °F = °C x 1.8 + 32
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THIS PAGE INTENTIONALLY LEFT BLANK
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Strength of Materials
Strength of materials deals with the relations between external forces applied
to an elastic body and the deformations and internal stresses resulting from
these applied forces. The use of the principles of strength of materials to meet
functional requirements. Certain of the formulas that are used in strength of
materials calculations are based solely on mathematical analysis; others, em-
pirical formulas, are the result of experiment, test and observation. Whether of
the former or the latter type most of these formulas make use of certain con-
cepts and experimentally determined physical properties of materials such as
tensile strength, modulus of elasticity etc. The meaning of some of these terms
is explained in the following paragraphs.
Elasticity
A body is said to be periectly elastic if, after it has been deformed by external
forces, it returns completely to its original shape when the forces are removed.
Although there are no perfectly elastic materials, steel and some other structu-
ral materials may be so considered in certain ranges of loading and deforma-
tion (see elastic limit). Partially elastic materials are those that do not com-
pletely resume their original shape when the external forces are released,
some of the energy of deformation having been lost in the form of heat.
Unit Stress
If a load (force) is uniformly distributed over a certain area, the force per unit of
area, usually expressed in pounds per square inch, is called the unit stress or
simply the stress. If the stress is the result of forces tending to stretch or
lengthen the material it is called a tensile stress; if to compress or shorten the
material a compressive stress; and if to shear the material, a shearing stress.
Tensile and compressive stresses always act at right angles to (normal to) the
area being considered; shearing stresses are always in the plane of the area
(at right angles to compressive or tensile stresses).
Combined Stress
When the stress on a given area is a combination of tensile and shearing
stresses, or, compressive and shearing stresses, the resulting stress on the
area is called a combined stress.
Simple stress
Simple Stress: When a tensile, a compressive, or a shearing stress alone is
considered to act, a body is said to be subject to a simple stress.
Unit Strain
Unit Strain: The amount of deformation of a dimension of a body resulting from
the application of a load divided by the original dimension of the body.
Poisson‘s Ratio
Poisson’s Ratio: The ratio of lateral strain to Iongitudinal unit strain for a given
material subjected to uniform longitudinal stress within the proportional limit.
For steel, it equals 0.30; for wrought iron, 0.28; for cast iron 0.27; for brass,
0.34.
Elastic Limit
Elastic Limit: The maximum stress to which a material may be subjected and
still return to its original shape upon release of the load. The elastic limit for
steel is for all purposes the same as its proportional limit.
Proportional Limit
Proportional Limit: That stress beyond which stress is no longer proportional to
the strain.
Yield Strength
Yield Strength: The maximum stress that can be applied to a material without
permanent deformation of the material.
Ultimate Strength
Ultimate Strength: The stress at which a material in tension, compression or
shear will rupture.
Modules of Elasticity
Modulus of Elasticity: The ratio of stress to strain within the proportional limit of
a material in tension or compression.
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MATERIALS
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PROPERTIES OF MATERIALS
Hardness
The property of a material that enables it to resist penetration, wear, or cutting
action.
Strength
The ability of a material to withstand forces which tend to deform the metal in
any direction, or the ability of a material to resist stress without breaking.
Elasticity
The capability of an object or material to be stretched and to recover its size
and shape after its deformation.
Plasticity
The property of a metal which allows it to be reshaped.
Ductility
The property which allows metal to be drawn into thinner sections without
breaking.
Malleability
That characteristic of material that allows it to be stretched or shaped by beat-
ing with the hammer or passing through rollers without breaking.
Toughness
The property of a metal which allows it to be deformed without breaking.
Brittleness
The property of a metal to break when, deformed, or hammered. It is the
resistance to change in the relative position of the molecules within the
material.
The characteristic of a material which makes it possible for it to transmit heat or
electrical conduction.
Durability
The property of metal that enables it to withstand force over a period of time.
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MATERIALS OVERVIEW
Metallic materials
Having the nature of metal or containing metal.
Non -
- metallic materials
Having the nature to containing no metal.
Ferrous materials
Iron, or any alloy containing iron.
Non ferrous materials
A metal which contains no iron.
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Figure 11 Overview: Metallic and Non- Metallic Materials

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MEASUREMENT
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MEASUREMENT
GENERAL
Introduction
In order to arrive at values of distance, weight, speed, volume, temperature,
pressure etc., it is necessary that we get familiar with the accepted methods tor
measuring these values and the units used to express them.
Through the ages human beings have devised many methods for measuring
however, it would be impossible to cover even a small part of the information
accumulated for these several thousands of years. Now we shall concern our-
selves principally with the English system and the SI metric system, both of
which are used extensively throughout the world.
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Figure 12 Measurement Exampels

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Measurement of Dimensions
Measuring of material and machined subjects involves the use of measuring
tools to determine sizes of length, width, thickness, diameters etc.
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WIDTH
THICKNESS
LENGTH
DIAMETER
Page 31
Figure 13 Measurement Of Dimensions

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Di
MEASUREMENT UNIT SYSTEM
Metric System
The International System of Units, which is now called SI, had its origin when
the meter was selected as the unit of length and the kilogram as the unit of
mass. These unitS were created by the National Academy of Science and
adopted by the National Assembly of France in 1795.
The United States Congress legalized the use of the metric system throughout
the United States on July 28, 1866, but it was not until December 23, 1975,
that the metric Bill was signed into law in the United States to convert alt of our
measurements into the metric system. It is becoming more and more important
for us to be familiar with this system.
One of the great advantages of the metric system is the fact that it is built on
decimal units. Each basic unit may be multiplied or divided by ten as many
times as it is necessary to get a convenient size. Each of these multiples has a
definite prefix, symbol, and name.
English System
The majority of people in English-- speaking countries are familiar to the Eng-
lish unit system. Its units of length, time, and weight are inch, second, and
pound. So the complete documentation of Boeing aircrafts are made in the
English unit system.
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Figure 14 Number Prefix Table

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Temperature Unit
The temperature is the degree of heat or cold measurable in a body. The mea-
surement is accomplished with a thermometer, and the value is expressed in
degree Fahrenheit or Celsius.
Fahrenheit Unit
In the English / American unit system all temperatures are given in degrees
Fahrenheit.
Water boils 2120F
Ice melts 320F
Absolute zero --4600F
Celsius unit
In the metric system the temperatures are given in degrees Celsius.
Water boils 1000C
Ice melts 00C
Absolute zero --2730C
Fahrenheit / Celsius Conversion
To convert one type of scale to the other we use the following formula:
0F =9/5 0C + 32
0C = 5/9 (0F -- 32)
Conversion Examples
1. ?0C = 630F
5/9 (63--32) = 630F
5/9 * 31 = 630F
17.20C = 630F
2. ?0F = 270C
27 * 9/5 + 32 = 270C
80.60F = 270C
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English Length System
Originally the units inch, foot, yard, and mile were not exact multiples or factors
of one another, but for the sake of convenience the foot was made equal to 12
in, the yard was made 3 ft, and the mile was made 5,280 ft or 1,760 yd. It is
said that the inch was the width of a finger, the foot was the length of a human
foot, and the yard was the distance from the tip of the nose to the tip of the
thumb when the arm was extended to the side with the thumb pointing forward
and the head faced forward. The mile was originated by the Romans and rep-
resented 1,000 paces, each pace being two steps, or 5 ft. This distance was
later changed to 5 280 ft, which is the present statute mile in the United States.
The nautic mile, used internationally for navigation, is based on one--sixtieth of
one degree of the earth’s circumference at the equator. It is approximately
6,080 ft, or 1,853.2 m. Many other units of length measurement have been
used in various countries some being the rod, elI, fathom, and league. All these
units were established to meet particular needs in different areas. Because of
the increase in travel, international commerce, and scientific exchanges, there
is a need for standardization of measurements. This is taking place through the
use of the metric system.
Boeing Dimensioning System
All linear dimensions on Boeing drawings are in inches and decimal fractions
enable the guys to clearly specifv the degree of accuracy required for a given
dimension. Boeing system of dimensioning, the decimal system, is in units of
ten, hundreds, thousands, ten thousands (1’s, 10’s, 100’s, 1,000’s, 10,000’s),
and so on. Each unit, when multiplied by ten falls into the category of the next
larger unit or, when divided by ten, into the next lower unit. Decimal fractions
may seem rather difficult at first, but in reality they are much simpler than com-
mon fractions. Decimal fractions work in units of ten the same as whole num-
bers; however, decimal fractions are always on the right side of the decimal
point. When ever numbers follow the decimal point, they represent measure-
ments smaller than one inch.
The first number after the decimal point is in tenth of an inch. There are ten
tenth of an inch.
The second number after the decimal point is in hundredth of an inch. Since
the second number in 0.12 falls into the hundredths category, the entire dimen-
sion must be read in hundredths, that is, twelve onehundredths of an inch. A
dimension is read in terms of the smallest unit shown; therefore 0.0015 is read
as fifteen tenthousandths of an inch, or one and one--halfthousandths.
Page 36

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1 INCH
Page 37
Figure 15 English Length System

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Metric Length System
The basic unit of measurement in the metric system is the meter. The length of
a meter is based on a distance equal to one ten-- millionth of the distance from
the equator to the poles measured along a meridian, the meridian being the
shortest distance along the earth’s surface and at right angles to the equator.
This distance is equal to 1,650,763.73 wavelength of the orange--red light of
excited krypton of mass number 86. Thus we see that the meter is based on a
sound reference that will always be approximately the same. In order to provide
an exact reference meter for scientific purposes, a bar of platinumiridium was
inscribed with two lines exactly 1 m apart at the freezing point of water. This is
320Fahrenheit (F) or 0_ Celsius (C). The International Meter bar is kept at the
Bureau of Weights and Measures near Paris. Copies of this bar have been
made and are kept in depositories in all the principal nations In the metric sys-
tem all the measurements of length are either multiples or subdivisions of the
meter based on multiples of 10. The following table shows how the units of
length are related:
10 millimeters = 1 centimeter
10 centimeters = 1 decimeter
10 decimeters = 1 meter
10 hectometers = 1 kilometer
One meter is equal to 39.37 in, which is a little longer than the U.S. yard. Thus
1 decimeter (dm) is equal to 3.937 in. In practice the units of length most com-
monly used are the millimeter, the centimeter, the meter, and the kilometer.
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Figure 16 Metric System

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Unit Conversion
P!ease keep in your mind:
1 in = 25.4 mm
So for sheet metal work it is an absolutely must to know the conversion of me-
ter and inch because all hole sizes, material gages, all dimensions etc. are
given in inch and must be often conversioned to the metric system.
Conversion Examples
1/2 in = 25.4 : 2= 12.7 mm
1/4 in = 25.4 : 4 = 6.35 mm
1/8 in =25,4:8 =3.i8--mm
3/16 in = 25.4 : 16 * 3 = 4.76 mm
5/16 in = 7,935 mm
3/8 in = 9,525 mm
5/32 in = 3,968 mm
0.312 in = 25.4 * 0.312 = 7.92 mm
1.15 in = 25.4 * 1.15 = 29.21 mm
0.159 in = 25,4 * 0.159 = 4,038 mm
0.190 in = =4,826 mm
Page 40

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Inches
Decimal Millimeter
Equivalent
Equivalent
DECIMAL AND METRIC EQUIVALENT OF INCHES
1/64
3/64
5/64
7/64
9/64
11/64
13/64
1/32
3/32
5/32
7/32
1/16
1/8
3/16
0.0156
0.0313
0.0469
0.0625
0.0781
0.0938
0.1094
0.1250
0.1406
0.1563
0.1719
0.1875
0.2031
0.2188
0.379
0.794
1.191
1.588
1.985
2.381
2.778
3.175
3.572
3.969
4.366
4.762
5.159
5.556
Page 41
Figure 17 Decimal And Metric Equivalent Of Inches

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RULES AND SCALES
General
Steel scales or steel rules are found in almost all tool chests in both 6 inch and
12 inch lengths. They are used for sheet metal layout and for making measure-
ments where the accuracy of a vernier or a micrometer is not needed.
Theses scales are made of either tempered carbon steel or of satin--finished
stainless steel. They may be graduated in either the fraction or the decimal
system of English or in metric measurements, with some scales having gradua-
tions in both systems. Fractionally graduated scales usually have one scale
divided in increments of 1/32 inch and other in 1/64 inch increments. Decimal
scales have one scale in tenth or fiftieth of an inch and the other scale in incre-
ments of 1/1,000 inch. Metric graduations are in centimeters and millimeters.
Scales are available in both the flexible form about 0.015 inch thick, and the
rigid form with a thickness of about 0.040 inch.
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12 INCH FLEXIBLE SCALE (CHESTERMAN)
6 INCH FLEXIBLE SCALE
Page 43
Figure 18 Flexible Scales

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Scale Handling
When taking measurements with a scale it should be so held that the gradua-
tion lines are as close as possible to the faces. The eye which is observing the
reading should be as near as possible opposite to the mark being read.
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Figure 19 Scale Handling

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Flexible Steel Tape (Yo-
-Yo)
The flexible steel tape is a very useful instrument for taking measurements up
to several feet. The steel tape is equipped with a hook on one end so that it will
hold to a corner or ledge, thus making it possible for the rule to be used by one
individual. Most of the steel tapes are graduated in English and metric mea-
surements.
Page 46

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Figure 20 Flexible Steel Tape

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MICROMETER
General
When a part has to be measured to the second place of decimals in the metric
system, or the third place in the English, we need a more accurate method of
measurement than can be obtained with a vernier calliper, and the micrometer
is commonly used.
Description
A micrometer consists of a semi--circular frame having a cylindrical extension
(the barrel) at its right end, and hardened anvils inside, at the left end. The bore
of the barrel is screwed 1/2 mm pitch and the spindle, to which is attached the
thimble, screws through. Adjustment is provided for the longitudinal position of
the spindle, and for tightness of the screw head. The barrel is graduated in mm
and 1/2 mm for a length of 25 mm and the rim of the thimble is divided into 50
equal divisions. The measurement is taken between the face of the anvil and
the end of the spindle, and the range of the micrometer is 25 mm, so that if we
wish to measure up to 150 mm we must have six micrometers; 0 to 25, 25 to
50, 50 to 75, and so on with 125 to 150 mm as the largest size.
Page 48

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11 1 2 3
10 4 9 5 6 7 8
Index to parts
1. Anvils
2. Spindle
3. Locknut
4. Sleeve
5. Main nut
6. Adjusting nut for main nut
7. Thimble adjusting nut
8. ratchet stop
9. Thimble
10. Frame
Page 49
Figure 21 Micrometer

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Micrometer Readings
The screw in this micrometer has a pitch of 1/2 mm, so that the jaws open 1/2
mm for each turn of the thimble. The rim of the thimble is divided into 50 parts,
which gives a reading of 1/2: 50 = 1/100 mm. The barrel is marked in millime-
ters and 1/2 mm divisions, so that to take a reading we add the number of hun-
dredths indicated on the thimble to the millimeters and 1/2 mm uncovered on
the barrel.
Reading Examples
The thimble has moved Out 13 complete turns or
13 * 0.50 = 6.50 mm. Plus
15 * 0.01 = 0.15 mm.
Reading is 6.65 mm.
In one revolution the thimble moves out 0.50 mm. There are 50 marks on the
thimble with each mark representing a thimble movement of 0.01 mm.
Each mark on the numbered line on the sleeve is 1.0 mm.
Each mark on the unnumbered line on the sleeve is 0.50 mm.
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Division on Micrometer
(Reading 11,34 mm)
Barrel Graduated
In mm And 1/2 mm
Thimble -
50 Divisions
Reading Example
Page 51
Figure 22 Reading Exampels

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20 Complete Turns
20 x 0.50 = 10.00 mm Plus
50 x 0.01 = 0.50 mm
Reading is 10.5 mm
26 x 0.50 = 13.00 mm Plus
1 x 0.01 = 0.01 mm
Reading is 13.01 mm
..... x 0.50 = .......... mm Plus
..... x 0.01 = ......... mm
Reading is .......... mm
Page 52
Figure 23 Reading Eampels (Continued)

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Page 53

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Micrometer handling
1. Set the micrometer to a oversize dimension
2. Set the frame anvil straight to the work
3. Clamp the spindle against the subject using the ratchet stop
NOTE: USE ONLY THE RATCHET STOP. OTHERWISE THE MEASURE-
MENT FAILS.
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Handling on hard to get locations
or one hand handling
Micrometer mounted on a stand (use when
you have to measure a lot of subjects)
Page 55
Figure 24 Micrometer Handling

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VERNIER CALLIPER
General
Vernier callipers / sliding gages are used to make accurate inside or outside as
well as depths measurements faster than can be made with a micrometer, and
for measurements that exceed the practical range of a micrometer.
Description
The vernier calliper consists of the bar and the two measuring jaws. One jaw is
fixed to bar, the other one slides on the bar. The bar of a metric vernier calliper
is equipped with a graved--in scale, graduated in mm the so called main scale.
Opposite to this scale there is the so called vernier scale (in German the so
called nonius) on the slide. These scale is divided in 10, 20, or 50 equal spac-
ings, the so called 1/10, 1/~0 or 1 50 vernier (nonius).
Page 56

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Figure 25 Vernier Calliper

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1/10 vernier
The distance from 0 to 1 on the main scale is 10 mm and it will be seen that 10
divisions on the sliding vernier scale are equal to 9 mm on the top main scale.
The length of the bottom division is 9 mm: 10 = 0.9 mm, and since the top divi-
sion is 1 mm the difference is 1 mm -- 0.9 mm = 0.1 mm. This difference repre-
sents the accuracy to which readings may be taken.
1/20 Vernier
The most often used vernier calliper is the calliper with the 1/20 vernier and a
accuracy reading of 0.05 mm.
1/50 Vernier
The accuracy reading is 0.02 mm
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1/10 Vernier
1/20 Vernier
1/50 Vernier
Page 59
Figure 26 Vernier

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Figure 27 Vernier Table

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Page 61

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Vernier Calliper Readings
The reading will be done as follows:
Count the total length indicated on the main scale and note the mark on the
vernier scale which is level with a mark on the main scale. This latter amount
will represent the number of dimensions which must be added to the first read-
ing.
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Reading is 30.00 mm
(1/10 Vernier)
Reading is 73.65 mm
(1/20 Vernier)
Reading is 68.32 mm
(1/50 Vernier)
Page 63
Figure 28 Vernier Reading

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Figure 29 Vernier Reading Exampels

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Reading
is:...............mm
Reading
is:...............mm
Reading
is:...............mm
Reading
is:...............mm
Page 65
Figure 30 Reading Exercises

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Reading
is:...............mm
Reading
is:...............mm
Reading
is:...............mm
Reading
is:...............mm
Page 66
Figure 31 Reading Exercises

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Page 67

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Vernier Calliper Handling
The vernier calliper is made in various sizes from 150 mm upwards, a good
size being one capable of working up to 300 mm.
When it is used for a bore or any other inside measurement set the cross jaws
to an undersize dimension and slide it to the final position.
Outside Measurement
Set the fixed leg against the work and slide the movable leg in the final posi-
tion.
Starting position with vernier calliper in oversize dimension until the final posi-
tion
Depth measurement
Ensure that the recess in the depth gauge is in the corner area.
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Figure 32 Vernier Calliper Handling

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DIAL INDICATOR
General
The dial indicator is high precise measurement tool with an accuracy of 0.01
mm. It is especially used in the mechanical engineering section to measure
alignments of shafts or to check smoothness of surfaces. A special type of the
dial indicator is an excellent tool to measure for example the removed material
after corrosion -- or lightning strike clean up
Description
One revolution of the large hand corresponds to 1 mm. The second smaller
hand of the rotation tachometer counts the revolutions of the large hand. Mea-
suring range is normally 10 mm Set to zero by revolving the rotary scale
Page 70

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Tolerance
marks
Rotation tachometer
(mm)
Climb shaft
Spindle
Pin
Page 71
Figure 33 Dial Indicator

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Work sequence
1. Clean up damaged area
2. Put the dial indicator with the measuring stand on a straight surface and
rotate the rotary scale mark to zero
3. Put the dial gage on the inspection are as shown
4. Do the inspection at different points in the inspection area until you find the
maximum depth of clean up.
NOTE: THIS PROCEDURE MEASURES THE DEPTH OF THE REMOVED
MATERIAL. THE THICKNESS OF THE MATERIAL WHICH RE-
MAINS MUST BE FOUND OUT BY CALCULATION.
Page 72

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Dail gage
Measuring
stand
Skin
Base flat
on skin
Area where you must
remove the paint
Page 73
Figure 34 Dail Indicator Work Sequence

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SQUARES AND GAGES
Square
The square is the most common tool for testing squareness. When using the
square care should be taken to ensure that its blade is held perpendicular to
the surface being tested or errors may occur.
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Inside Squareness
Measurement
Outside Squareness
Measurement
Page 75
Figure 35 Square

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Radius gage
Radius gages are used to measure either inside or outside radii. Find a biade
that fits the surface being checked.
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Radii of the work are
too small
Radii of the work are
too large
Radii found okay
Outside radius
Inside radius
Page 77
Figure 36 Radius Gage

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Protractor
The IProtractor consists of an adjustable blade with a dial that is graduated
from 0 to 180 degrees. To use a Protractor, set the blade to the angle being
checked and lock the nut. The angle is indicated on the Protractor head. The
Protractor is generally used in assembly areas to check part flanges or to verify
jig--located angles, clips, etc.
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Figure 37 Protractor

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Thickness (feeler) Gage
The feeler gage is made up of a number of thin steel leaves that fold into a
handle like the blades of a pocket knife. The thickness in thousandths of an
inch or in hundreds of a millimeter is marked on each leaf. The marked leaves
are inserted into a gap until the closest fitting leaf is found. The thickness of
that leaf represents the size of the gap. The gage is generally used in assem-
bly areas to check interface gaps or gaps under bolt heads or nuts.
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Figure 38 Feeler Gage

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Blend Out Measurement Sequence With A Feeler Gage (Ref. NDT A3 10)
1. Put the straight edge on to the inspection area.
2. Measure the gap between the straight edge and the structure with the
leaves of the feeler gage. Make sure that the gage touches the straight
edge and the structure
3. Write down the measurement by adding the respective feeler gage dimen-
sions
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AREA WHERE YOU MUST
REMOVE THE PAINT
SECTION
A-A
CORRECT USE OF THE FEELER GAGE
STRAIGHT EDGE
FEELER GAGE
SKIN
STRAIGHT EDGE
FLAT ON SKIN
SKIN
GAP
FEELER GAGE
STRAIGHT EDGE
Page 83
Figure 39 Blend Out Measurtement Sequence

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MARKING OUT AND TOOLS
General
Marking out means marking on the material all the lines and points we need to
provide work from it. In general this will be done by a dimensioned drawing, this
is a drawing showing the exact shape with all dimensions indicated. So we take
a piece of material and accurately copy the given dimensions of the work from
the drawing. Last step is to cut out the piece of material with the work marked
out on it.
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Figure 40 Marking Out Sequence

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Marking Out Rules
S Never use a lead pencil on titanium.
S When using a scriber or pencil with a straightedge hold it at a slight angle so
that the line will be parallel to and as close as possible to the straightedge.
S For marking of aluminium use only a soft lead pencil.
S Mark only thin lines.
S Mark lines only once.
Rule
For setting out length, a rule or a steel tape is used.
Try square
For squaring and for lines at right angles a try square is used
Dividers
Dividers are used for scribing arcs and circles, for measuring between points,
and for transferring dimensions taken from a steel rule. The contacts are the
sharp points of the straight legs, and measurement is by visual comparison.
Dividers are difficult to use accurately when the legs are widely extended and
the points steeply inclined to the work surface. Dividers or compasses should
not be used when marks or reference lines are draw~ on metal skin surfaces,
since the metal points will cause permanent damage. Instead, pencil are com-
monly used to lay out skins.
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Rule Try Square Dividers
Page 87
Figure 41 Marking Out Tools

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Scriber
The scriber is used to mark tines on metal surfaces.
NOTE: A SCRIBER IS USED ONLY WHEN THE MATERIAL WITHIN THE
SCRIBBED LINE IS TO BE CUT OUT AND THE SCRIBBLE MARK
IS REMOVED AS PART OF THE SCRAP.
Pencil
When working with aluminium, a soft lead pencil may be used for layout work
or for marking reference lines in areas that will not be removed.
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Scriber Pencil
Page 89
Figure 42 Marking Out Tools

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SAWING
Part-66
SAWING
GENERAL
Introduction
Sawing is mostly used for seperating material but also for producing groove
and notches.
A saw blade has many teeth. Their cutting edges are shaped like a chisel.
When sawing, at any time more than one tooth must be in contact with the
work piece. The teeth are removing small chips of the material.
The teeth must point in cutting direction.
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wing nut
adapter guide frame
handle
saw blade
cutting
direction
blade adapters
Page 91
Figure 43 Saw

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SAW BLADE
Pitch
The pitch is the space from one tooth to the next.
Saw blades are rated as follows regarding to the number of teeth on one inch
of blade lengtgh:
S Coarse: for soft materials
S Medium: for normal materials
S Fine: for hard materials
Clearance
To prevent the saw blade from binding when it proceeds into the material, the
slot which the saw generates must be wider then the blade is thick.
Therefore the saw blade must cut the required clearance. This is accomplished
in either of the following:
S The teeth are set.
S The blade is waved.
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Waved blade
Teeth are set
coarse
medium
fine
22 teeth
32 teeth
14 teeth
25
(1 inch)
(1 inch)
(1 inch)
25
25
clearance
clearance
bottom
view
bottom
view
Page 93
Figure 44 Saw blade

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SAWING
Guiding the hack saw
Sawin is mostly accomplished by moving the arms. appropriate motions of the
body assist the process.
To produce a good cut, startthe cut by holding the saw at an angle.
S Forward stroke under pressure.
S Ruturn stroke without pressure.
Use up as much of the blade length as possible.
Near the end of the cut, just before the material separates, reduce the
pressure on the saw.
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chips
tooth gap
cutting direction
angle
return stroke
without pressure
cutting stroke
with pressure
Page 95
Figure 45 Sawing

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FILING
Part-66
HAM US/F-5 KrC Dec 2005 A
FILING
GENERAL
Introduction
Filing is a process which removes chips from a material.
Filing can be :
S A roughing process to alter the size and shape of a part by removing con-
siderable material.
S A finishing process to smooth a surface without removing much material.
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tip
blade
tang
handle
Page 97
Figure 46 File

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FILE SHAPES
General
The selection of the file with regarard to the shape depends on the size and
shape of the surface to be worked.
Flat files
Flat files are used for flat or convex surfaces.
Triangular files
Triangular files have across-section that is an equilateral triangle, these files
are limeted to a internal angles greater than 60˚.
Squre files
Square files are used for filing keyways and for enlarging square and rectengu-
lar holes.
Ruond files
Ruond files are used to file small radius.
Half round files
Half round files are used to file medium and large radius.
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FLAT
SQUARE
TRIANGULAR
ROUND
HALF ROUND
Page 99
Figure 47 Files shape

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CUT OF FILES
General
The cut of files is divided, with reference to the character of the teeth, into
single-cut, double-cut, rasp-cut, and curved-tooth.
Single-cut files:
single cut files are generelly used to produce a smooth surface or to file a
keenedge.
Also for use on soft metals like lead, zinc or aluminum.
Double-cut files:
Double-cut files are used for fast metal removal and where a rought finish is
permissible.
Rasp-cut:
A rasp-cut file produce a extremly rought cut and is used on very soft materials
such as wood and leather.
Curved-tooth:
A curved-tooth file is used to produce a very smooth finish on soft metals such
as aluminum.
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single cut double cut rasp cut curved cut
Page 101
Figure 48 Cut of files

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PROPPER WORKING POSITION
Bench vise
The adjustment of the bench vise is important to have a proper working posi-
tion.
The bench vise should be 5--8 cm / 2--3 inch below your elbow (see picture).
To hold the file
Hold the handle with your right hand so that the end of the handle presses
against the palm.
With the palm of your left hand press down on the file tip.
Left handed persons hold the handle in left hand and press on the file blade
with the right hand.
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5--8 cm
2--3 inch
Page 103
Figure 49 Working position

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FILE TECHNIQUE
General
Guiding the file by moving your body evenly:
Move the file in the direction of its longditudinal axis in oder to avoid burrs in
the work surface.
Pressing on the file
With your right hand push the file in longditudinal axis and press it down, and
with your left hand press it down only. Left handed persons vice versa.
Apply pressure on the forward stroke. Return the file without pressure.
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HAM US/F-5 KrC Dec 2005 A Page 105
Figure 50 File Technique

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FILING OF RADII
Filing of convex radii
In oder to obtain a radius flat surface are filed until they approximately from a
radius.
The file is moved in longditunial direction and up and down at the same time.
The position of the work in the vise has to be changed frequently in oder to pro-
ducean accurate radius.
Filing of concave radii
The radius of the file must be smaller than the radius to be filed.
Guide the file straight as if a flat surface is to filed but turn the fileabout its lon-
gitudinal axis at the same time.
To produce an even radius it is necessary to adveance the file sideways. Do
not feed sideways in order to avoid burrs.
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flat
surface
up and down motion
Page 107
Figure 51 Filing of radii

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DRAW FILING
General
As a final finish you can use the draw filing process. This process is often used
on parts that are long relative to ther width for example aluminum sheets
edges.
This procedure is used to get a fine surface on the edges to prevent crack
growth.
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1
start of stroke
finish of stroke
cut on
forward stroke
only
Page 109
Figure 52 Draw filing

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CLEANING DIRTY FILES
General
Files need to be cleaned frequently. A dirty file cannot produce a good finish
and a dirty file acts like a dull file.
You can clean a file with a file brush by brushing across the file in a direction
parallel to the teeth.
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File brush
Cleaning with file brush
Page 111
Figure 53 Cleaning dirty files

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DRILLING
GENERAL
Introduction
The technicians are often faced with the necessity of boring / drilling accurately
sized round holes in order to make attachments and to join parts in an assem-
bly. The tool usually used for drilling such holes is the spiral, or twist, or drill.
The steel drill usually consists of a cylinder into which has been cut spiral
grooves or flutes. One end is pointed, and the other is shaped to fit a particular
drilling press such as a hand--drill motor.
Drills are made of both carbon steel and high speed steel (HSS). The carbon
steel drills cost less, but they will overheat and lose their hardness when they
are used to drill very hard or though material. For this reason HSS drills are by
far the most economical for use in aviation work. There are several types of
drills available so in generally we have to use for different materials different
drills, drill speeds, cutting agents, and pressure.
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Figure 54 Drill

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TWIST DRILL NOMENCLATURE
Shank
The shank of a drill is the part designed to fit into the drilling machine. It may be
a plain cylinder in shape, which is the design for use in a drill chuck on a drill
motor, drill press, or hand drill. The drill shank may also be tapered or pyramid--
shaped. The tapered drill shank is usually used in drill presses. The pyramid--
shaped shank is also called a bit shank and is designed to fit a hand brace
such as that used for wood bits.
Body
The body of a drill is the part between the point and the shank. It includes the
spiral flutes, the lands, and the margin. The body is slightly larger in diameter
at the tip than at the shank, thus causing it to bore a hole with clearance to pre-
vent the drill from binding.
Cutting edge
The point of a drill includes the entire cone-- shaped cutting end of the drill. The
point includes the cutting edges or lips, which are sharpened when the drill is
ground. The web is the portion of the drill at the center along the axis. It be-
comes thicker near the shank. The web may also be defined as the material
remaining at the center of the drill after the flutes have been cut out. The web
forms the dead--center tip at the point of the drill. The dead--center is in the ex-
act center of the tip and is on the line forming the axis of the drill.
Land
The land is the peripheral portion of the body between adjacent flutes.
Flutes
Helical grooves cut or formed in the body of the drill to provide cutting lips, to
permit removal of chips, and to allow cutting fluid to reach the cutting lips.
Margin
The cylindrical portions of the land which is not cut away to provide clearance.
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Body
Flute
Lip or Cutting Edge
Margin
Land
Shank
Page 115
Figure 55 Twist Drill Nomenclature

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TYPE OF DRILLS
Jobbers drills
The jobbers drill is the most often used twist drill in sheet metal work. It is a
pointed tool that is rotated to cut holes in material.
It is made of a cylindrical hardened steel bar having spiral flutes (grooves) run-
ning the length 0 the body, and a conical point with cutting edges formed by the
ends of the flutes.
Twist drills have from one to four spiral flutes. Drills with two flutes are used for
most drilling; Those with three or four flutes are used principally to follow
smaller drills or to enlarge holes.
The principal parts of a twist drill are the shank, the body, and the point. The
drill shank is the end that fits into the chuck of a hand or power drill. The
straight shank generally is used in hand, breast, and portable electric drills.
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Figure 56 Jobbers Drill

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Taper shank drills
Tapered shank drills have a tape called the Morse taper. The size of taper in-
corporated on any particular drill depend on the drill diameter. At the end of the
taper shank of a drill is a tongue called the tang, and when the taper shank is
fitted into the socket or machine spindle, this tang engages in a slot. If the ta-
per itself is in good condition the frictional grip between this and the surface of
the taper hole should be almost, if not entirely, sufficient to drive the drill, but if
the taper becomes damaged, more load will be thrown on the tang in driving
the drill, and if the drill sizes in the hole the tang may be twisted off. For this
reason, taper shanks should be given every consideration in use and always
extracted with the proper taper drift.
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Figure 57 Taper Shank Drill

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Machine Spindle
The number of the Morse taper hole in a machine spindle will depend on the
size of the machine, varying from No. 1 in small machines to No. 4 or No. 5 in
large ones, and when a drill has to be accommodated in a spindle with a larger
taper than its shank, taper sockets must be used. These should also be cared
for, as if they become damaged the drill fitted into them will no longer run true.
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MASHINE
SPINDLE
TANG ON
DRILL
DRIFT
BLOW
Page 121
Figure 58 Machine Spindle

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Extension drill
The extension drill has a long shank for reaching limited--access areas. The
drill should not be used unless absolutely necessary. Use a drill guard (a plastic
tube
slipped over the drill to protect adjacent structure from drill whip, and to make it
possible to guide the drill by hand). Hold the drill guard as near the drill point as
possible.
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123
Figure 59 Extension Drill

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DRILLING WORK SEQUENCE
GENERAL
Using the drill
4. Hold drill motor as shown. Notice that the thumb and forefinger of one hand
are used to steady the motor. This method can be used only with a short
drill; short drills are always preferred.
5. Put drill point on spot to be drilled.
6. Keep the drill perpendicular to the surface being drilled. If necessary use a
drill guide.
7. When drilling thick material (two or three times drill diameter or more) with-
draw the drill from the hole periodically to prevent chips from packing in the
drill flutes. Tightly packed chips can cause an oversize scarred hole.
8. Use just enough pressure to allow the drill to cuts its way through the
metal. Never force the drill; this can cause drill breakage, separation of
parts, or oversize or out--of--round holes.
9. Ease the pressure just as the drill point breaks through the material. Drill
through material no more than 1/4 inch.
10.Use a stop drill to prevent the drill from going through the part farther than
necessary (Adjust stop). If a drill stop is not used, the part may be marred
by the drill chuck, and the under--structure may be damaged by the drill
point.
11.Keep drill motor running while withdraw drill from hole.
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125
PRESSURE ON
CENTERLINE
OF DRILL
RIGHT
WRONG
DRILL STOP
SET SREW
SET DRILL STOP
TO MATERIAL
THICKNESS; PLUS
.10 INCH
Page 125
Figure 60 Using The Drill

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DEBURRING
General
When holes are drilled trough two sheets of material, small burrs are formed
around the edges of the holes, and chips were pressed between the two
sheets. So it is absolutely necessary to remove the burrs and the chips. It usu-
ally done by hand with a larger drill larger than the hole, a countersink, or a
specially deburring tool. Removal of burrs from drilled holes may be accom-
plished with a manufactured deburring tool, a countersink using a very light cut,
or other tool which will clear the edges of a drilled hole. Care must be taken to
remove only the rough edges and chips from the hole. When two or more
sheets where drilled at the same time, it is necessary to remove chips from
between the sheets. The picture next show the results of leaving material be-
tween drilled sheets.
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Figure 61 Deburring

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Special deburring tool
These tool is designed to debur holes on the exit side which you could not
reach with standard deburring tools (limit access area). This tool is chucked in
a drill motor for rapid work. The retractable blade is held in place by spring
pressure. To use, push the tool through the hole and remove burrs from the exit
side. Then draw the tool back through the hole and remove burrs from the
entry side. This burring tool comes in common hole sizes from 5/32 to 3/8 inch
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Figure 62 Special Deburring Tool

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COMMON DRILLING ASPECTS
Drilling Problems
Indication
Outer corners of drill break off
Parts of the cutting edges break off
Cracks in drill cutting edges
Drill breaks
Drill splits up its center
Drill will not feed into material
Hole wall rough
Hole oversize
Probable Cause
1. Excessive cutting speed.
2. Hard spots in the material.
3. Flutes clogged with swarf.
1. Excessive feed rate.
2. Excessive drill cutting edge clearance.
1. Drill overheated or cooled to quickly whilst sharpening or drilling.
1. Drill point improperly ground.
3. Drill not sharp.
4. Flutes clogged with swarf.
1. Insufficient drill cutting edge clearance
1. Drill not sharp.
2. 2. Insufficient drill cutting edge clearance
3. 3. Drill too large (i. e. pilot hole required).
1. Drill point improperly ground is not sharp.
2. 2. Insufficient or incorrect lubricant.
3. 3. Excessive feed rate.
4. Material not rigid.
1. Unequal angle and / or length of cutting edges.
2. Loose spindle.
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131
Drilling hints
1. For soft metals use a drill having a quick twist to its flutes, and vice versa
for hard metals. For chilled iron a flat drill gives best results.
2. Cut with soluble oil for steel and malleable iron, kerosene or turpentine for
very hard steel. Cast--iron or brass should be drilled dry, or with jet of com-
pressed air.
3. If the corners wear away rapidly, the speed is too high.
4. If cutting edges chip1 reduce feed or grind with less clearance.
5. If drill will not start drilling there is no clearance on lips.
6. Examine relative sizes of turnings issuing from each flute. They should be
approximately the same, and if not, the drill is wrongly ground with one lip
doing more cutting than the other.
7. Drill breakage may be caused by point wrongly ground; feed too great; not
easing drill at ”break through”; binding in hole due to lands being worn
away; drill choked in a long hole.
8. The blueing of a high--speed steel drill is not detrimental but it is fatal to a
carbon steel drill.
9. A hard spot encountered may be removed by reducing speed and using
turpentine
10.For holes larger than 4.8 mm it is necessary to drill at first a pilot hole and
enlarge it to the required hole size.
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132
WORK CLAMPING
General
Unless work is so large and heavy that there is no danger of its moving, or be-
ing rotated with the drill, it should always be clamped or held by some method,
and too much attention cannot be given to clamping because unclamped or
insecurely clamped work is not only a danger to the operator, but also a cause
of inaccurate work and broken drills. The chief danger in drilling occurs just as
the drill point breaks through at the underside of the part being drilled. Whilst
the point is being resisted by solid metal, the feeding pressure causes some
spring to take place in the machine and the work, putting them into a similar
condition to a strong spring which is compressed slightly under a load. As soon
as the drill point breaks through, most of the resistance against it suddenly va-
nishes and the stress in the machine releases itself by imparting a sudden
downward push to the drill, just as a sudden relieving of the load from a spring
would allow the end of it to jump up. The sudden downward push on the drill
generally causes one or both of the lips to dig in, often with disastrous results.
When feeding the drill by hand the pressure should be eased off when the point
is felt to be breaking through, and for this reason small drills should always be
fed by hand. Special care is necessary when drilling thin plate as the drill point
often breaks through before the drill is cutting its full diameter.
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Page 133

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Drill press clamping
To secure work by using the drill press the vise, clamps and dogs are often
used.
1.Vise
The most works will be secured by the vise. The main use of the vise is to hold
the work during drilling, reaming etc. in a correct position. Care should be taken
to ensure that when the drill passes through the work it does not drill into the
bottom of the vise.
2.Clamps and dogs
The tables of most drill presses are provide either with Tee slots to accommo-
date bolt heads, or with long slots running through whichever be the case the
slots enable bolts and clamps / dogs to be used.
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Figure 63 Drill Press Clamping

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Hand drill clamping
When using a hand drill motor, the work to be drilled must be properly secured
so it cannot move. It should never be held by hand, because in the event of a
broken drill, the broken end may pierce the hand or a finger and can cause
painful injury. Angle vices, pin vices, hand vices etc. are to be used to hold the
work to be drilled in position.
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Figure 64 Hand Drill Clambing

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DRILLING AIDS
ADDITIONAL TOOLS FOR DRILLING
Stop drilling of cracks (Ref. SRM Hole preparation and stop drilling of
cracks)
Propagation of a crack may be stopped by drilling a hole at the end of the crack
as follows:
1. Drill or counterbore a 0.25--inch diameter crack stop hole through a struc-
ture at each end of a crack. Locate each stop hole so that the center of the
hole is 0.10 inch beyond the visible end of the crack.
2. Make an Eddy Current Method inspection of each stop drilled hole to con-
firm that there is no further cracking on the side of the hole opposite the
crack
S If the crack has not continued to the other side of the hole, enlarge the hole
to 0.312--inch diameter to ensure removal of fatigued material.
S If the crack has continued to the other side of the hole, enlarge the hole by
additional l/16~inch diametral increments until the crack indication is re-
moved. Enlarge the hole an additional 1/16 inch in diameter to remove any
fatigue damaged material.
NOTE: THE TOTAL AMOUNT THAT THE STOP DRILL HOLE MAY BE EN-
LARGED MUST BE DETERMINED FOR EACH SPECIFIC CASE
DEPENDENT UPON THE LOAD PATTERN AND STRESS LEVEL
IN THAT AREA.
3. Install a 2017--T3 flush plug rivet in the stop drill hole, if required.
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Page 139

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Drill stop
The drill stop regulates the hole depth, cushions the break through, eliminates
surfaces marks, and reduces drill breakage. The drill stop locks onto the drill
with a set screw.
Drill guide
The hand held drill guide keeps the drills 900 to the skin surfaces. The guide
assembly consists of a clear plastic housing and special screw in type hard-
ened steel bushing. The bushing can be interchanged.
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Figure 65 Drill Stop and Drill Guide

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Nut plate drill jig
The nut plate drill jig is designed for accurate drilling of rivet holes for nut pla-
tes. It is manufactured with a flexible handle to provide hand clearance when jig
is in use. There are a lot of different drill jigs available.
Drill jig handling
1. Align pilot with pilot hole when drilling the first hole.
2. Align pilot with pilot hole and pilot pin with hole drilled in the first operation
and than drill the second hole.
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Figure 66 Drill Jig

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Hole finder
When replacing an old skin with a new one, if there are no pilot holes drilled in
the new skin, it is quite difficult to locate precisely the holes in the structure. For
this procedure, a hole finder may be used. The finder resembles a clamp that
slips over the new skin, and on its underside is a pin that exactly fits through
the hole in the structure. A hole in the top side guides the drill in making a hole
in the new skin that will align with the one in the structure.
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Figure 67 Hole Finder

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Drill gage
The size of a drill is stamped on its shank. If the size cannot be read, it can be
determined by using the proper drill gage. Drill gages are available for all three
series of drill sizes; fractional, letter, and number. Fractional drills are furnished
in sizes from 1/16 to 1 inch in diameter, graduated in sixty--fourth of an inch.
Letter drills range iii size from A (the smallest) to Z (the largest). Number drills
range from I (the largest) to 80 (the smallest).
To gage a drill, insert the point into a hole in the drill gage. If the drill slips easily
into the hole, insert it into the next smaller hole. When the correct size has
been determined, the drill will rub lightly in the hole.
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Figure 68 Drill Gage

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DRILL AGENTS
General
Drilling agents are recommended (unless prohibited by the engineering draw-
ing) to improve tool life, hole tolerance, and hole finish. Recommended cutting
agents for drilling, reaming, and countersinking are shown in the following ta-
ble. Cutting agents are mandatory only when so specified.
Boelube
Boelube is used an agent for drilling aluminium, magnesium, steel, as well as
titanium.
Boelube consists of cetyl alcohol, a non-- toxic lubricant from the fatty alcohol
chemical family. It is suitable for many production operations and manufactured
in solid, paste, and liquid forms. It is approved for use with aluminum, steel, or
titanium materials. Also it is sealant and paint compatible, and is non--corro-
sive. Disassembly for cleaning is not required in sealant or paint areas.
Boelube lubricants have the following characteristics:
-- non--toxic, non--polluting, and non-irritating under normal conditions
-- excellent lubricating properties under extreme pressure
-- removed by solvent wiping or washing with warm water and mild deter-
gent
-- compatible with most lubricant application systems
Remaining Boelube residue must be removed within 48 hours after use.
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Figure 69 Drill, Reamer and Countersink Cutting Agents

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DRILLING SIZES
General
Twist drills used in aircraft sheet metal are usually of the number drill sizes be-
tween one and sixty; however, for larger sized holes, either fraction drills or let-
ter drills may be used. Following pages show a twist-- drill--size chart that lists
sizes from No. 80, the smallest normally in use, up through 1/2 inch. There are,
of course, drill sizes smaller and larger than those listed, but they fall outside of
the general use of the aircraft mechanic. You will notice that the smallest drills
have the largest numbers; for example. A No. 80 drill is much smaller than the
No. 1 drill. In addition to the number drills, there are letter drills from A through
Z, with A being the smallest. The fraction drills are interspersed among the
number and letter drills, and only at one place do we find a fraction and a num-
ber or letter drill of the same size; both the quarter--inch drill and the E drill are
0.250 inch.
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Figure 70 Drill Size Chart

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DRILL SPEEDS
GENERAL
Introduction
The drill speeds are an important factor in getting good results. Drill speed de-
termines the rate at which the outer cutting edge of the drill is moving across
the material being out.
The proper speed for aluminium alloy will not produce the best results with
stainless steel or titanium. When harder materials are drilled, slower speeds
are required.
The following drill speed tables are recommended for drilling. Material / revolu-
tions per minute (RPM) values and speeds and feeds for most materials com-
monly used are given. These speeds and feeds are a guide for selecting the
proper portable and stationary drilling units to improve tool life, hole tolerance,
and hole finish. In some portable drilling applications, speeds and feeds may
have to be reduced to be compatible with motor power and other limitations.
However, the speeds and feeds shown in the tables should never be exceeded.
Material / RPM tables
Table IV--1 Material / RPM:
Drilling ferrous metals
Drilling high Temperature alloys (Inconel, titanium)
Drilling nonferrous metals (aluminium alloys, magnesium)
Table IV--4 Material / RPM:Drilling nonferrous metals (fiberglass laminates,
nylon Teflon, graphite, epoxy, kevlar epoxy)
Drilling composite with metal (graphite or kevlar epoxy and aluminium stack,
and graphite or kevlar and titanium stack)
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Figure 71 RPM Table IV - 1

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Figure 72 RPM Table IV - 1 (Continued)

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Figure 77 Table IV - 2

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Figure 78 Table IV - 2 (Continued)

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