i want you to translate this text to persiasn i send you ( this text is for maintnance and dont translate professional words or phrases) "Metal Inert Gas Welding (MIG}
in this semi-automatic welding process the heat source is also an electric arc, but the electrode
is a bare wire, which is consumable and is supplied, from a reel, to the welding gun, by a wire
feed unit, A shielding gas is employed; in place of a flux material, to protect the weld pool. The
type of shielding gas, used, will vary with the application. Some of the gases and gas mixtures
used are;
Argon
Cartoon dioxide
Argon/cartoon dioxide
Argon/oxygen
Argon/nitrogen
Helium.
Note: I hrs process may also be referred to according to the type ot shielding gas (or mixture of
gases) which is being used and whether those gases are inert or active. The two types ol this
process are:
Metal Inert Gas (MIG) welding; where the shielding is provided by a shroud ot inert gas.
Metal Active Gas (MAG) welding: where the shielding is provided by a shroud of active,
or non-inert, gas or mixture of gases.
Tensile
Where the two surfaces are pulled directly apart,

Shear
Where the two surfaces tend to slide across
each other.

Cleavage
Where two edges are pulled apart.

Peel
Where one surface is stripped back from the other

Bonding
Adhesive bonding has been used on an ever-increasing scale and particularly in the aerospace
industry. Adhesives are used for constructional tasks varying from aircraft fuselages, flight
control surfaces, to propellers and helicopter rotor blades.

The Mechanics of Bonding
The actual adhesive bond may be achieved in two ways;
Mechanical: - here the adhesive penetrates into the surface and forms a mechanical lock,
by keying into the surface. It also forms re-entrants, where the adhesive penetrates
behind parfs of the structure, and becomes an integral part of the component to be joined.
Chemical (Specific): - in this method of bonding, the adhesive is spread over the surfaces
to be joined and forms a chemical bond with the surface
In practice, most adhesives use both ways of bonding to form a joint.

Stresses on a Bonded Joint
Adhesive joints are liable to experience four main types of stress
Joint stress is at a maximum when the adhesive is in shear (refer to figure 1 5-14). Adhesives
should not be used if significant stresses will be carried in tension or peel. Lap joints are the
types more, generally favoured, as the strength of the adhesive bond is proportional to the area
bonded.
Soldering
Soldering differs from welding in that it is done at considerably lower temperatures so that the
parent metals do not melt and fuse together.
Instead, a fusible and, usually, non-ferrous alloy (with a lower melting point) is applied between
the heated metals of the joint, such that the fusible alloy lorms a metallic bond with the parent
metals and, on cooling, creates a solid joint.
The word ‘solder’ does, in fact, come from the same stem as the word 'solid' (as does the
American term, which is pronounced 'sodder', for the same process).

Methods of Soldering
Soldering can be divided into two baste methods, one of which uses higher temperature ranges
than the other, but both of which are conducted at temperatures below the melting points of the
parent metals of the intended joint.
The iwo basic methods of soldering are:
Hard Soldering: done at temperatures in excess of 500'C and which include the
processes of Brazing and Silver Soldering
Soft Soldering; done at temperatures within the range of 180*0 to 3300, which,
consequently, create joints of lower strength (but less expense) than those achieved by
the hard soldering methods.
Note: The hard soldering processes are, normally, beyond the remit of the aircraft servicing
technician, so only brief consideration is given to them here, with more attention being given to
the soft soldering method

Hard Soldering (Brazing and Silver Soldering)
Brazing, as the name implies, uses a Cupper/Ziric (Brass) alloy, as Lite filler metal (spelter)
between the parent metals of the joint. The degree of alloying will dictate the temperature at
which the process is done but the melting point o! the brazing alloys can be as high as 880

O.
Brazing is a process of loinmg in which, during, or after heating, the molten filler metal is drawn
into, or retained in, the space between closely adjacent surfaces of the parts to be joined, by
capillary attraction.
In general applications, workshops and small factories, a flame, directed onto the joint area, is
the source of heat. However, in the mom sophistical cd applications, used in industry, heating
for hard soldering may be provided by a:
Gas, oil or electrically heated, closed furnace
High-frequency (HF) induction coif.
Bucking Bars
Bucking bars are tools used to form shop
heads on solid-shank rivets during
installation. Bucking bars are available in
many sizes, shapes and weights. An
assortment of bucking bars is illustrated in
figure 8,14. When installing rivets, it is
important to remember that ihe bucking
bar weighl should correspond to the
diameter of the rivet being driven (figure
8.15).
The face of the bucking bar is smooth and
must be protected from any nicks or scars
which can affect the proper shaping of the
driven head. Damaged bucking bar faces
can be filed and then smoothed using oil
and crocus cloth.
Rivet Faults
Before commencing any type of riveting job, the operator should whenever possible, make a
“dummy run” by forming rivets in some spare piece ol metal of corresponding thickness.
The main causes ol faulty rivaling are as follows:
a) Excessive or insufficient shank allowance.
b) Rivel holes nol drilled straight or drilled to wrong size,
c) Aivet holes out of line on separate plates,
d) Surface of metal not drawn up together, possibly due to burrs around the drill holes.
e) Wrong size of dolly or snap used, thus damaging the metal surface or forming a bad
nvet head.
f) Rives not filling rivet holes correctly because initial hammer blows on the tail of the
nvet have not swollen the shank.
Riveted Joints
Introduction
In considering a typical joint it should be understood that the plate resists shear, bearing and
tensile loads while the rivet resists shear and bearing loads only.
At no time should the rivets be in tension as this tends to burst them apart with a load they are
not designed to withstand.
Strength of Joints
The factors that govern the strength of a joint are:
a) Plate specification. This will be of such a material and gauge as to successfully
withstand tensile and bearing loads.
b) Rivet specification. This will be selected to withstand shear loads, in cases where the
specification of the rivet is not given, use a rivet of the same material as the plate, with a
diameter of 3 x T where T is the thickness ot one of the sheets.
c) Rivet pitch. This is Important as too great a pitch will result in Insufficient rivets to take
the shear loads and too small pitch will result in lowering the resistance of the plate to
tensile loads.
Types of Rivet Spacing
a) Single Chain - used chiefly on attachment and lightly stressed joints .
Cherry- Max Rivet
Introduction
The Cherry-max rivet is a high strength structural fastener available with a dome or countersunk
head. The rivet when broached fractures (lush with the head, the mandrel remaining in the rivet
is positively locked in position with the locking collar contained in the rivet assembly. The driving
anvil eliminates wear on the installation tool and additionally allows one pulling head to install
1/8 in., 5/32 in. and 3/16 in. nominal and oversize diameter rivets.
Identification of the Cherry-Max Rivet
The diameter of this rivet is graduated in 1/32 in. The maximum grip length is graduated in 1/16
in The following is an example of an identification number-
identification Number CR 3242-6 04
CR - Cherry-max rivet
3242 - Rivet type and material.
6 - Rivet diameter in 1/32 in.
= 6/32 in. = 3/16 in.
04 - Maximum grip length in 1/16 in.
= 4/16 in. = 1/4in.
Gold mandrel signifies normal diameter.
Silver mandrel signifies oversize diameter.
Multiple Chain - used on watertight joints and in places of high stress, where thick
gauge plate is used.
Staggered Riveting - used as an alternative to Multiple Cham in watertight joints,
circular patches, etc.
Hi-Shear Fasteners
Introduction
Hi-Shear pins are used to eltect a saving in weight while retaining the lull shear strength of an
equivalent size bolt. When setting Hi-Shear pins there is also a considerable reduction in time
as opposed to fining split pinned bolts. Access is required for bolh sides of the structure.
Collars
In production, the collars are impregnated with a special lubricant to ensure satisfactory closing.
Collars are available in only one length for each diameter ol pin, any excess length being
trimmed automatically during riveting by the Hi-Shear Set
Pins
The pins are available with flat or countersunk heads and in a range of diameters and lengths.
Pm lengths for rivets of 3/16 in. diameter and above are supplied in 1/1

6m, increments and for

diameters below 3/1 bin in 1/32 in. increments.

Imex Rivets
Introduction
The Imex blind rivet is similar to the conventional pop rivet but has a permanently sealed end
which completely encloses the mandrel head. When the rivet is set, the rapid radial expansion
of the formed head ensures a joint which is pressure tight up to 34 bar (500 Ibf/in

2 ).

Description
Imex rivets are supplied with domed or countersunk heads. The countersunk heads are
normality 120°, but 100

G heads are manufactured for a limited range of rivet sizes. Mandrels are
supplied as short break or long break types and mandrel heads remain permanently captured
when formed. When the long break mandrel fractures, it does so outside the rivet and the
protruding portion must be cropped off and sanded to achieve a flush finish.
Not all materials are suitable for use with Imex rivets as the rapid expansion of the formed head
is unsatisfactory in very soft or very brittle materials. For this reason the appropriate air
publication must be consulted.
Imex rivets are manufactured from 5 per cent magnesium aluminium alloy to BS L58.
Identification
The node sequence used for Imex rivets is as follows:
Material (A for aluminium alloy).
Type of Head (D for domed-head r K tor countersunk-head).
Rivet Diameter (in 1/32 in increments).
Rivet grip length (in 1/32 in increments).
As the pin lengths are graduated in 1/16 in. or 1/32 in. increments, depending on diameter, the
material thickness can vary 1/16 in. or 1/32 in., respectively without changing pin lengths.
Adjustment for variations of material thickness in between the pin lengths is made automatically
by trimming the collar to the required length while the rivet is driven as shown.
In this Minimum Grip
example, the collar edge
extends slightly beyond
the trimming edge of the
pin

Jn mis Maximum Grip
example, the collar edge is
well beyond the trimming
edge of the pin

W

Figure 6.44; Hi-Shear pin gnp variations

Variations in Material Thickness
In addition to flat or countersunk-headed pins Hi-Shear dowel pins are manufactured for
application to sloping surfaces. Where the face of the metal on both sides of the joint is out
normal to the centre line of the pin, the collars adapt themselves to the surfaces as the pins are
set.

Hi-Shear dowel pin used
for two sloping surfaces

Normal Hi-Shear pin used
lor one sloping surface

Figure s.45; Hi-Shear collars on sloping surfaces

6-42
TTS integrated Tracing System
©Copyright am I

Module 7.8 Riveting

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Jo-Bolts
Introduction
Jo-Boits is the trade name for a fastener which is used where a nut and bolt would normally bo
fitted but where access is available from one side only with the additional advantages of being
self-locking at a pre-determined torque and is less weight than a nut and boll. The Jo-Bo Its are
available with a hexagonal or countersunk headed nut.

SLEEVE

BOLT WAISTED BREAKER GROOVE

FLATS

SLEEVE

HEXAGON-HEADED
NUT

COUNTERSUNK- HEADED NUT

Figure 8,50: Jo-Bolt parts

Driving Tool
Hand ratchet tools are supplied for fitment of Jo- Bolts. One for the 3/ 16 in. and 1/4 in. both and
one for the 5/16 in, bolts.

8-47
TTS Integrated Training System
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Module 7.6 Riveting

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Hi-Lok Fasteners
Introduction
The Hi-lok / Hitique fastener combines the best features of a rivet and a bolt. The three main
advantages include:
• A controlled pre-load or clamp up which is consis tent Io within a 10% error.
• Minimum size and weight.
• Simple, quiet and rapid installation, carried out by one man from one side of
the work.

Threaded collar

HMok/Hi-tiguc pin

Figure 8.55: Hi-Lok / Hi-Tigue Pin and Threaded Collar

Description.
The pin is available with a countersunk or protruding head, threaded like a bolt with a hexagonal
recess in the threaded end. The collar is threaded and has a shear-off hexagonal nut connected
to it by a thin wall. A hexagonal wrench engages the recess preventing rotation of the pin whilst
the collar is being secured with a ring spanner. As the collar is tightened, the plates are drawn
together and at a pre-determrned torque, the hexagonal nut shears off.

8-52
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Module 7.8 Riveting

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Cherrylock Rivets
Introduction
Cherry-lock rivets are similar to the conventional tucker pop rivet except that the rivet itself Is
fully sealed and easily recognised in situ by the code number embossed on the head. These
fasleners are locked-spindle and flush-fracluring structural blind rivets and available in two
types; a Cherrylock and bulbed Cherrylock ,

locking collar

plain
cherryiock

tessfisssfiss!

SSSSSSSSSSSit

bulbed
cherrylock

Figure a.69: Cherrylock rivets

Description
The Chenylock rivets are available with a variety of protruding and countersunk-heads each
having special applications as follows:
Universal. For protruding head application in Cherrylock and bulbed Cherrylock rivets.
1000 Countersunk. Two types of countersunk rivets are used:
MS20426 - For normal sheet thickness in Chenylock and bulbed Cherrylock.
NAS 1097 - For this top sheet machine countersunk application in Cherrylock only.
Unisink. A combination countersunk and protruding head for use in very thin top sheets.
Strength equal to double-dimpling. Bulbed Cherrylock only.
1 Countersunk. A large diameter, shallow counte rsunk head providing a wide bearing
area for honeycomb application.

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Huck Blind Rivets
Introduction
Huck rivets are very similar to Cherry

lock rivets in that they have mandrels which are also
mechanically locked in position with collars when the rivets are broached.
Description
The Huck nvet composes three separate items, a sleeve having a pre-formed head, a
mechanical lock collar and a spindle on which the sleeve and lock collar are mounted.
The sleeves are normally supplied in either 1000 countersunk or protruding (snap) head types.
Annular grooves on the spindle shank provide a secure grip for the puller tool during setting,
As the rivet is set the spindle is drawn into the sleeve forming the blind head of the rivet. During
the final stages of setting, the mechanical lock collar is pressed into the lock groove in the
spindle, thereby securing the spindle in position. Continued tension on the spindle causes it to
fracture flush with the nvet head

locking
COllJf

INSTALLED RIVET

Figure 8.75: Huck blind rivets

Identification of Huck Rivets
The maximum grip length number is stamped on lhe head of each Huck rivet and its grip range
extends to 1/16 in from the length represented by that number. A typical part number is as
follows:
Identification number: MLS - P - M5 - 6C
ML - Mechanically locked mandrel
S - Self plugging
P - Protruding (domed) head
M - Monel metal
5 - Rivet diameter in increments of 1/32 in. = 5/32 in.
6 - Maximum grip length in increments of 1/16 tn. = 3/8 in.
C - Cadmium plated finish

Module 7.8 Riveting R-71

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Huckbolts
Introduction
Huckbolt fasteners are designed for use in high strength structural joints where access is
available from both sides of the structure. A Huckbolt is not a bolt in the accepted sense as it is
not threaded; it is really a form of shear pin which is secured by the cold swaging of a metal
collar into annular locking grooves on the stud.
Description
Two types of Huckbolt fasteners are used, a pin type using a long serrated pin for use where a
puller tool can be used, and a stump type having a short serrated pin for use with a swaging set
where operating space is limited. Both types are basically the same except for the length of the
pins and each use the same metal collar. The pin is manufactured of cadmium plated steel or
anodised aluminium alloy with a variety of head styles including pan, countersunk and crown
head.
Collars are produced in anodised aluminium alloy orcadmium-plated mild steel. The recessed
end of the collar is applied to the face of the work. All collars are supplied lubricated to assist
the swaging process.
A Huckbolt can, when required, be applied to work with an interference fit; this makes it
unnecessary for holes to be reamed subsequent to drilling, and ensures fuel and water- tight
joints.
Identification
Huckbolt fasteners, both pin and stump type are manufactured in a range of shank diameters
and grip lengths and can be identified as follows. The basic part number denotes the type i.e.
1446 for pin type and 1426 for sump type, the dash number indicates the grip length is 1/16 in
(0.0625 in) increments. N after the basic number denotes Nickel-cadmium plating. M after the
basic number denotes a sealant escape groove. For the diameters and grip ranges, the relevant
tables should be consulted.

8’72
TTS Integrated I raining System
©Copyright 201 1

Module 7 8 Riveting

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The riveting tools are available in different sizes depending on diameter or rivet being used and
the shape of head.
Cleco Clamps and Pliers
Cleco clamps are used to align parts prior to being re-riveted to an aircraft. The clamps are in-
stalled with Cleco pliers (figure 8.10). The color of the Cleco clamp indicates the diameter of the
rivet it is to be used with. Four commonly used sizes are 3/32 of an inch (silver), 1/8 of an inch
(copper), 5/32 of an meh (black), and 3/16 of an inch (brass, gold).

inch (copper), 5/32 of inch

(copper), b/32 of an inch (black), and 3/16 of an inch (brass, gold)..

■

POWER CLECO
WEDGELOCK

WINGNUT
CLECO

CLECO
CLAMP

PIN TYPE
CLECO

CLECO
PLIERS

RIVET DRILL
3/33 #4D
ia #30
M2 #21
3/16 #11

CLECO COLOR
SILVER
COPPER
BLACK
GOLD

Fig 8.10 Metal Cleco clamps

8-11
ITS integrated Training System
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Maduie 7.8 Riveting

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Figure 11.4: Loose fit damage

Bri

nulling — True and False
Brinelling marks on a bearing raceway resemble the indentations that result from a Brinell
Hardness Test. They are described as being cither True Brinell or False Brinell marks.

Brinefling is caused when a load is applied to a ball bearing that exceeds the elastic limits of the
steel and the raceways are permanently deformed. Brinelling creates measurable dents at each
ball location similar to the deformation caused by a Brinell Hardness Tester, This type of
damage can occur quite easily if proper care is not taken. High energy rmpacts (from hammers
and smash -ups), improper bearing handling and incorrect spindle assembly can all damage
bearings. Remember that we are talking about bearings with raceways with roundness
measured in millionths of an inch. You might not even realize the damage has occurred except
for increases in vibration and non-repetitive run-out.
False brinefling is not related to excessive loads. False brinelling is caused by ambient vibration.
Even a brand new bearing, sealed in a box on a shelf, is subject to false brinelling if it is
exposed to environmental vibrations for an extended period. When a bearing is not operating it
is subject to false brinelling in the box or in the machine. When a bearing is operating, there is
an oil film between the rolling elements and the raceways. This is called elasto-hydro-dynamic
(EHD) film. Most people can relate to hydroplaning. When you reach a certain speed on a wet
road your tyres actually lift off the road (not good). But when a bearing operates with the proper
lubrication and at the right speed the balls or rollers lift off the raceway slightly (this is good).
This extremely thin film protects and lubricates the bearing while it is running. When the bearing
is stopped there is no EHD Film and there IS metal to metal contact. That is when false brinelling
can quietly attack your bearings. The combination of metal to metal contact and vibration create
a wear and corrosion pattern that mimics brinelling.
The prevention is to rotate spindles routinely if they are not in use to reposition the rolling

11-16 Module 7.11 Gearings

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Flaking or Spalling
Fatigue is the result of shear stresses cyclically appearing immediately below the load carrying
surface. After a time these stresses cause cracks which gradually extend up to the surface. As
the rolling elements pass over the cracks fragments of material break away and this is known as
flaking nr spalling The flaking progressively increases in extent (figure 1 1 8) and eventually
makes the bearing unserviceable.
The life of a rolling bearing is defined as the number of revolutions the bearing can perform
before incipient llaking occurs. This does not mean to say that the bearing cannot be used after
then. Flaking is a relatively long, drawn-out process and makes its presence known by
increasing noise and vibration levels in the bearing. Therefore, as a rule, there is plenty of time
to prepare for a change of bearing.

Figure 11.8: Stages in flaking (spalling)

Electric Current Damage
When an electric current passes through a bearing, i.e. proceeds from one ring to the other via
the rolling elements, damage will occur. At the contact surfaces the process is similar to electric
arc welding.
Such electric currents can be of a low level but last for considerable lengths of time (such as
voltage leakage from a motor or generator) or be very high level for a short duration (such as
that caused by a lightning strike of the aircraft). Equal amounts of damage can occur from both
situations.
The appeaiance of the damage is dtukbruwri or greyish black fluting (corrugation) or cialeisin
raceways and rollers. Balls have dark discolouration only. Sometimes zigzag bums in ball
bearings raceways. Also, localised burns in raceways and on rolling elements.
Thc material is heated to temperatures ranging from tempering to melting levels. This leads to
the appearance of discoloured areas, varying in size, where the material has boon tempered,
re-hardened or melted. Small craters also form where the metal has melted.
The passage of electric current frequently leads to the formation of fluting (corrugation) in
bearing raceways. Rollers are also subject to fluting, while there is only dark discolouration of
balls.
It can be difficult to distinguish between electric current damage and vibration damage. A
feature of the fluting caused by electric current is the dark bottom of the corrugations, as

1

Module 7.11 Bearings 1-19

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Module 7.12 - Transmissions

Gears
Transmission is lhe geared assembly that transfers power from the engine to the propeller
(reduction gear unit) or main rotor/tail rotor (main or tail rotor gear box) in the case of
helicopters. The primary purpose of the transmission unit is Io allow the engine to operate at its
optimum RPM while allowing the propeller or rotor to operate at its optimum RPM (usually much
lower than the engine). This may be achieved by using various gear arrangements, e.g. ring
and pinion gear or epicyclic gears.
The primary purpose of a gear is the transmission of force through motion; therefore, stress and
wear occur continually. For that reason, it is important to visually examine all gears for cracked
or chipped teeth and the presence of pitting or excessive wear. Deep pit marks or excessive
wear on gear teeth are reasons for rejecting and replacing a gear, Minor scratches and
abrasions on a gear's bearing surfaces can normally be dressed out with a fine abrasive cloth,
however, deep scratches or scoring is unacceptable. Correct gear backlash must be checked
and maintained to ensure proper gear mesh with the aid of DTI and special fixture for the
particular gear box.
Lash and Pattern
The lash and pattern of a gear is determined by how the teeth of one gear mate with the teeth of
another gear. If the teeth of one geai are set too lightly into the teeth of another, there will be no
lash and the gears will not be properly lubricated because a film of oil must be prese-nl between
the leeth of lhe gears as they mesh. If the gears are meshed too high in relation to lhe teeth, the
load will be transmitted to the smallest portion of the tooth, breaking the teeth because of the
load area. The ideal placement of the teeth is in the middle area. At this position the teeth will
receive proper lubrication and loading. At this point a measurable amount of lash may some-
times be felt by holding one gear and trying lo move the other gear. In most instances this is a
minute amount of lash and will be measured with a backlash flag and a dial indicator. A typical
gear may have 0.003 (o 0.004 lash. In all instances lhe amount of lash will be given in the main-
tenance manual and must be followed.

12-5

TTS Integrated T

raming System
©Copyright 2011

Mockjle 7. 12 Transmissions

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Module 7.13 - Control Cables

Swaging of End Fittings
The majority of aircraft control cables have swaged end fittings. Splicing is seldom used on
modem aircraft.
Swaging is an operation in which a metal end fitting is secured to the end of the cable by plastic
deformation of the hollow shank of the fitting.
The end of the cable is inserted into the hollow shank of the end fitting, and the shank is then
squeezes in a swaging machine, so that it grips the cable. This is the most satisfactory method
attaching an end fitting to a cable, and it can be expected to provide a cable assembly at least
as strong as the cable itself.
Most transport aircraft and a large number of light aircraft, use control cables manufactured in
this way.
Manufacturers of cable assemblies normally swage with rotary machines. In these machines the
shank of the end fitting is placed between suitable dies and is subjected to a series of forming
blows, which reduce the shank diameter and lock the fitting to the cable.
Swaging may also be carried out on a portable swaging machine, which squeezes the shank of
the end fitting between dies.
A range of swaged end fittings is covered by BS specifications, but some older lypes of aircraft
may be fitted with cable assemblies containing components complying with S BAG AS
specifical ions which are not obsolete. When it is necessary to make up control cables for these
aircraft, approval may be granted for the use of equivalent BS parts, but the complete cable
control run may have to be changed. BS specifications provide a range of fittings which prevent
incorrect assembly of control cables. Turn-barrels and tension rods are designed to connect to
screwed end and tapped end swaged fittings respectively. For each size of cabie two alternative
sizes of end fittings are available and each size is provided with either a left or right hand
thread. Swaged fittings can thus be arranged to ensure that a control run cannot be incorrectly
assembled.

13-5
TTS inlegratad T rainng Syslem
■0 Cup iight 201 1

Module 7.1 3 Control Cables

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Fairleads
To prevent chafing of the cables, fairleads are fitled to the aircraft siructure where the cables
pass through, e.g. bulkheads and frames. They are made of Tufnol. Micarta or Nylon, and are
normally of two halves bolted together. The cable runs through a hole in the fairlead.
Fairleads must not be lubricated as they wil collect dust and dirt.

< nylon iiirietds
torltid
<Errnj pl<3tE J

Figure 13.10: A typical fairlead

13-16
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Module 7.13 Control Cables

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Turnbuckles
Turnbuckles are the usual device for tensioning a cable system. A turnbuckle assembly consists
of a left hand threaded fitting swaged on to one cable end, and a right hand threaded fitting
swaged to the other cable end P and a barrel, tapped left and right hand between them.

CABLE EN0 FITTINGS

LH TH FAO
ICENTIFYING
npnovc x

Figure 13.12: Components of a turnbuckle

Turnbuckles are in safety when:
British types - A hardened steel pin will not pass through the safety inspection hole.
American types - All of the fitting thread is engaged in the barrel.
It is common practice for the left hand threaded end of the barrel to be identified with a grooved
machined on the outer surface.

INSPECTION
(SAFETY | HOLE

INSPECTION
(E.AFETY1 HOLE

TPNtlOH ROD

CONNECTER

LOCKNUT LGCKMUT
Figure 13.13: Turnbuckle assembly

Turnbuckle locking
Most turnbuckles currently are locked using spring clips which are passed down grooves cut in
the threads of the fittings and the barrel, The clip is positively located when the locking tongue is
located under the lip of the barrel centre hole.
When use of a clip is not possible, or wire locking 1$ specified, this should be done in
accordance with the aircraft manufacturer's requirements, usually to the FAA or CAA standards
as appropriate.

13-18
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Square (or sharp) angles, in aluminium alloys, arc only formed by adhesive, casting,
extrusion or welding methods. Whether it be the bending bars or the bending brake method,
which is used to bend aluminium alloy sheet, the bend will always be formed around a radius,
as it is not possible to creaie square angles by bending without cracking the metal.
Bend Allowance and Setback
When making a bend ar fofd in a sheet of metal, the bend allowance must be calculated. Bend
allowance is the length of material required for the bend This amount of metal must be added
to the overall length of the layout pattern to assure adequate metal for the bend.
REND ALLOWANCE NEUTRAL LINE

RADIUS |
OF REND

t
RADIUS "R'*!

Bend altowance - Wdegree be nd

R +*rT
J ____»

Figure 14,1: Bend Allowance (BA) for a 90° bend
Bonding a strip compresses the material on the inside of the curve and stretches the material on
the outside of the curve. However, at some distance between these Iwo extremes lies a space
that is not affected by either force, This is known as the neutral line or neutral axis and occurs at
a distance approximately 0.445 times the metal thickness (0.455 x T) from the inside of the
radius of the bend.
When bending metal to exact dimensions, the length of the neutral line must be determined so
that sufficient material can be allowed for the bend. To save time in calculation of the bend
allowance, formulas and charts for various angles, radii of bends, material thicknesses, and
other factors have been established,
By expenmentation with actual bends in metals, aircraft engineers have found that accurate
bending results could be obtained by using the following formula for any degree of bend from 1
degree to 180 degrees:

Module 7.1A Material Handling 14’9

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Bend allowance = (0.01743 xR + 0.0076 * T) x N where;
R = The desired bend radius,
T = Thickness of the material, and
N = Number of degrees of bend.
This formula may be used in the absence of a bend allowance chart. To determine bend
allowance for any degree of bend by use of the bend allowance chart find the allowance per
degree tor the number of degrees in the bend,
Radius of bend is given as a decimal fraction on the top line of the chart. Bend allowance is
given directly below the radius figures. The top number in each case is the bend allowance for a
00 degree angle, whereas the lower placed number is for a 1 degree angle. Material thickness
is given in the lelt column of the chart.
To find the bend allowance when the sheet Ihickness is 0.051", the radius of bend is 1/4

u
(0-250”), and ths bend is to ba 90 degrees. Reading across the top of the bend allowance chart,
find the column for a radius of bend of 0.250" Now find the block in this column that is opposite
the gauge of 0.051 in the column al left. The upper number in the block is 0.428, the correct
bend allowance in inches for a 90-degrea bend (0.428

1' bend allowance).
If the bend is to be other than 90 degrees, use the lower number in the block (the bend
allowance for 1 degree) and compute the bond allowance. The lower number in this case is
0.004756. Therefore, if the bend is to be 120 degrees, the total bend allowance in inches will be
120 x 0.004756, which equals 0.5707 inches.
When bending a piece of sheet stock, it is necessary to know the starting and ending points of
the bend so that the length of the “flat" of the stock can be determined. Two factors are
important in determining this, the radius of bend and the thickness of the material.
Note that setback is the distance from the bend tangent line to the mold point. The mold point is
the point of intersection oi the lines extending from the outside surfaces, whereas the bend
tangent lines are the starting and end points of the henrt Also note that setback is the same for
the vertical flat and the horizontal flat.

14-10 Module 7.14 Malerial Handling

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Scriber
A scriber (refer to figure 3.3) is used for marking lines on the surface of metats. Scribers are
made from high-carbon steel and are classified by their length. One end of the scriber is usually
bent at right angles to enable lines to be scribed in difficult places such as through a hole.
Due to the nature of metal, and the accuracy generally sought after when machining it a thick
pencil or ink line would either be impossible to lay down accurately ar prone to erasure during
the machining operation. The crisp, bright mark exposed by the scratch of a scriber is semi-
permanent and thin. The process of using the scriber is referred to as marking-out and may
require the addition of other hand tools and equipment.

Figure 3.3: Various forms of scnber
Usually a layout stain of some form is used to increase the contrast between the scribed line
and the background surface and is washed off with solvent on completion.
All scribed lines on soft materials must only be cutting (boundary} lines, and none must be left
on the surface of the metal on completion, as they can cause cracks. Other lines, including
bend lines and lines for the position of rivets must be marked with a sharp pencil.
Scriber points must be kept sharp and fine by careful 'stoning', with an oil stone, rather than an
abrasive wheel (grindstone). Using a wheel is likely to generate too much heat, which will result
in the temper being drawn from the steel and the point of the scriber becoming soft and useless.
When not in use (and as with other tools with sharp points), placing pieces of cork, plastic or
similar material over their points will protect them

3-9
ITS Integrated Tinning System
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Hammers
Hammers (refer to figure 3.25) are classified by their weight and type of head. Steel heads are
forged and manufactured from high -carbon steel. Most shafts are made from straight-grained
Ash or Hickory and are secured to the head by wedging.

Pah P&in Cross Pein Straight Pein Copper or Lead Hide Faced

Figure 3.25: Common types of hammer

As can be seen from figure 3.25, the mam types of engineering hammers are the:
• Ball Pein: The flat surface is used for most general-purpose work whilst the ball pein is
used primarily for riveting-type operations
• Straight Pein Used for general work, the narrow, straight pein being particularly suitable
for use where access to the work is limited
• Cross Pein: As for the straight pein, but the axis of the pein is at 90’to that of the shaft
■ HidefCopper Face: The rawhide facing enables heavy blows to be delivered without
damaging the surface of the work, while the copper face may be used for heavier types
of work than hide faced hammers.

Figure 3.26. Plastic face
hammer

Rubber Head and Plastic Face: More
modern versions of lhe Hide Face hammer.
Can often have one of each type of face on
each end of the head

Figure 3.27: Claw hammer

• Claw Hammer More commonly used for
woodworking. The face is used for hammering
nails whilst the claw is used for removing nails

3-22
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P Iannis hing Hammen Little used in aircraft work, as they
are primarily used to remove dents and blemishes from
sheet metal, They are also known as body hammers.
The weight of hammer required can be found with experience.
Before use. it must be ensured that the head is secure on the shaft.
The shaft should be gripped close to the end opposite the head, as
proper control is not possible if it is held close to the head.
Figure 3.28: Piannishing
hammer

Punches
Although punches are not pounding tools', they du allow the force from a hammer blow to be
concentrated in the immediate area of the punch tip. This in turn means that the pressure at the
end of the punch is increased compared to a hammer blow without a punch.
Over a period of time, the hammered shank end of a punch, tends to deform into the shape of a
mushroom. To reduce the chance of a metal chip flying off and causing injury, during punching
operations, the deformation should be removed and the shank end returned to its original shape
by the use of a bench grinder.
Eye or face protection should always be used when using punches of any type.
The types of punches, more commonly found in an engineer's toolkit, include:
• Centre Punches
• Pin Punches
• Hollow Punches
• Drifts
The first three punches are, usually, constructed from hexagonal (or knurled, round} rods of
tempered, cast steel with a length of approximately 127 mm (5 in), a gripping diameter of
approximately 3.175 mm (0.125 in} and a smaller, driving end of the appropnate size.
Centre Punches are relatively sharp-pointed
tools, used to make an indentation in metal
The indentation aids in locating the centre of a
hole and for starting a drill bit when drilling the
hole. The points may be ground at angles
between 60° to 90° depending on the hardness
of the metal on which the punch is being used.
The softer the metal, then the larger will be the
angle of the punch's point.

Figure 3.29: Centre Punch

3-23
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Sheet Metal Shears and Snips
Shears are another type of cutting tool used on aircraft sheet metal. Long, straight cuts, across
a piece of sheet metal, are made on a guillotine, which may also be referred to as 'squaring
shears'.
The fabrication of smaller parts requires hand cutting, followed with further trimming to the final
dimensions. This can be achieved with different types of shears, known as Tinman's Shears or
Aviation Snips. They can vary in length from 175 mm (7 in) up to 300 mm (12 in) and can be
straight or curved cutting.

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Figure 3.51 : Straight shears and curbed shears

Straight shears (or snips) are primarily for cutting straight or wide radius curves whilst the
curved shears are dedicated solely to cutting curves.
Curved shears can be found in symmetrical form, which can be used to cut curves in either
direction, or they can be asymmetrical and dedicated to cutting curves in one direction only. The
handles of asymmetrically curved shears are usually colour-coded (red and green), to indicate
the intended cutting direction. 'Left-cutting' shears are coloured red while Tight-cutting' shears
are coloured green).
Unlike hacksaws (and files), shears simply part the metal without removing any material. This
can, however, cause tiny fractures to occur along the severed lines and so, for this reason, cuts
should be made approximately 0.8 mm (0.03 in) from the marking out line and the metal then
filed down to the line.

3-37
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O Copyright 201 1

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Special Files
Diamond files
Instead of having teeth cut into the file's
working surface, diamond files (pictured to the
right) have small partides of industrial
diamonds embedded in their surface (or into a
softer material that is bonded to the underlying
surface ot the tile). I he use ct diamonds in this
manner allows the file to be used effectively
against extremely hard materials, such as
stone, glass or very hard metals such as
hardened steel or carbide against which a
standard steel filo is ineffective.

Figure 3.62: A selection of diamond files

Needle files
Ths image Io the left Rhnws A selection nf
needle files in an assortment of cross sectional
shapes.
Needle files are usually sold in sets of 6 or 12
(or more) different shapes, packaged in a soft
pouch, both for ease of handling and protection
of the files’ teeth. They are small files that are
used in applications where the surface finish
takes priority over metal removal rates but they
are most suited for smaller work pieces.
They are often used as pictured, however like all files, they are safest when used with a handle
The handle is often designed around the collet principle which allows the files and handle to be
interchanged quickly.

Figure 3.63; A selection of needle files

Riffler Files
Riffler files, as pictured to the right, are small to
medium sized files in an assortment of cross
sectional shapes and profiles. The varying
profiles and shapes enable them to be used in
hard to reach, or unu&ually shaped areas. They
are often used as an intermediate step in die
making where the surface finish of a cavity die
may need to be improved. - e.g.; plastic
injection moulding or die casting

Figure 3.64: A selection of Riffler files

3-44
TTS Integrated Trainng System
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Machine files
A selection of machine files
The files pictured on the left are designed for
use in a filing machine.
A filing machine is similar in appearance to a
scroll saw or band saw in that the file is
mounted vertically in the middle of a table.
When in operation the file reciprocates
vertically while the workpiece is presented to
the file's face and manipulated around lhe
table/file as the shape requires.

Figure 3.66: A selection of machine files
The cone point of lhe pictured, lop two files allows the files to centre themselves firmly in the
bottom file holder. The pictured, lower two files are required to be inserted into lhe bottom file
holder and physically restrained with set screws, an identical process as for the tap holder.
Filing machines are useful tools as they reduce fatigue and improve product accuracy, and
although not usually seen in modern production environments, they may be found in alder
toolrooms or die-making shops as an aid in the manufacture of specialist tooling

3-45
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Screwdrivers
Despite the many shapes and sizes which may be met, it can be stated that screwdrivers may
hs* divided into two main groups, which, basically, are:

Blade S crowdn vers
• Cross-Point Screwdrivers.
Blade (or Common) screwdrivers consist of a high carbon or an alloy steel blade, mounted into
a wooden or composite handle. The end of the blade is ground to engage the diagonal slot in
the head of the screw. If the blade is of high carbon steel, it will be hardened and tempered.
Screwdrivers in this category are classified by type and by lhe length of blade, which can be
from approximately 35 mm (1 .5 in) to 300 mm (12 in) long, although special screwdrivers can be
obtained with blade lengths of 500 mm (20 in).
Some variations may incorporate a reversible ratchet device in the handle while others may also
have an Archimedes' drive (as in a 'Pump’ screwdriver)).
All of these features would form part of the classification of the screwdriver
The correct engagement of the screwdriver blade in the slotted head of the screw or bolt is most
important (refer to figure 3.85). The most common faults can be seen in the illustration The end
of the blade should never be ground to a sharp chisel edge and a blade of the correct thickness
and width should always be chosen.
Scrowdrivers of the wrong size can cause serious damage to fasteners, surrounding aircraft
structure and to the persons using them.
Blade loo Small Blade Correct Blade too Large
Figure 3 85" Screwdriver blade sizes.

3-67
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Sockets
Sockels are tools that typically have a square hole in one end for a drive handle, and another
end with a six- or twelve- point opening designed to fit different sized nuts. Sockets are available
in both standard and metric sizes and can be used with a wide variety of handles and
extensions.
Socket sets are available in a wide variety of drive sizes. However, in aviation maintenance the
1/4 inch square drive and the 3/fl inch square drive are the most popular. Additional drives th al
are available include the 1/2 inch, 3/4 meh, and 1 meh square drives, in tact, tor extremely large
work., socket wrenches are available in square drives as large as 2 1/2 inches.
Standard Sockets
Standard sockets are available in all of the popular drive sizes and
with either four-, six-, eight-, or twelve-point openings. These
sockets are also deep enough to fit over a bolt head or a nut if too
much shank does not protrude. The six- and twelve-point sockets
are used in aviation., whereas the four- and eight-point sockets are
available to turn square head pipe plugs.

Figure 3 106: Standard Socket

Deep Sockets
There are several applications where a bolt extends through a
nut too far for a standard socket to grip the nut. In these cases
deep sockets are available to allow the socket to grip the nut
and still allow room for the bolt end.

Figure 3.107: Deep Socket

Flex Sockets
When additional clearance is needed between the socket drive
and the socket, a flex socket is used. Flex sockets have a pivot
point between the drive handle end of the socket and the nut
end. These sockets are made with both six- and twelve-point
openings and are available in the drive sizes most used tn
aviation maintenance

Figure 3.108 Flex Socket

Crowsfoot Sockets
Nuts are sometimes placed in locations on aircraft where neither
a box-end., nor open-end wrench, or standard socket wrench can
be used. The. crowsfoot socket is designed to reach these nuts
and is available with open, box, and flare-nut ends. Furthermore,
crowsfoot sockets are available in several drive stzes including
1/4 and 3/8 inch.

Figure 3.109: Crowsfoot Socket

3-78
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Go/No-Go Gauges
Where a single dimension has to be repeatedly measured, a comparator-type of gauge is used
which checks, simply, whether a component is within a pair of dimensions, usually referred to as
maximum and minimum dimensions. These gauges are referred to as GO/NO-GO

7 gauges (Fig
42} and, providing the item being checked passes through one jaw of the gauge, (the 'GO'
dimension), and fails to pass through the other jaw, (the ‘NO-GO

1 dimension), it is considered to

be Satisfactory.

O
O
O
%

GO NOGO

Plug Type Gauge

Calliper or Snap Gauge

Figure 3 164: Calliper- and Plug -Type Go/No-Go Gauges

Straight Edges
Straight Edges can be found in a variety of types, from a precis ion -ground rule, to heavy-duty,
cast iron straight edges, (e g. the 'camel back’ straight edge). The tighter straight edges arc
used to either visually check the flatness of a surface (by holding it up to a light), or to use feeler
gauges. Heavy-duty straight edges will, probably, be used, to check other items for
straightness, by a similar bluing method to that used on surface tables"