There are various types of surface gauges
(Figure 6.17), but in the main they consist of a very
accurately machined base, an adjustable pillar
Figure 6.16 Wire gauges (metric) (Neill Tools Ltd
(Moore and Wright))
Figure 6.17 Universal surface gauges (Neill Tools
Ltd (Eclipse))
194 Repair of Vehicle Bodies
fastened to the base, and an adjustable clamp
attached to the pillar for holding the scriber. The
surface gauge is used in conjunction with a marking-
off table or surface plate to mark out very
accurate, parallel lines to a true surface. The
machined base enables it to slide over the surface
of the table while the scriber retains its accurately
set position. The scriber can be set at various
heights and angles in order to mark out different
jobs or parts of jobs with horizontal lines at a fixed
height above the surface of the marking-off table.
Scribed lines show up more readily on a work surface
that is first covered with a solution of copper
sulphate or marking compound.
Vee blocks
These blocks are made in matching pairs, and have
to be used in conjunction with a marking-off table.
They are made of cast iron with vees machined
accurately to 90 into the top of the block to hold
the work (Figure 6.18). Along each side of the
block runs a groove into which a clamp can be
fitted in order to secure round-shaped work in
place during marking off with scriber, try square or
scribing block. In order to make sure that you have
a matching pair of vee blocks, before using them
always check that each of the blocks is stamped
with the same number.
6.3.5 Engineers level
This is used for setting surfaces level and parallel
to a marking-off table. The base is machined
so that it can slide across the surface of the
work-piece, and if the surface is level then a bubble
in a tube across the top of the level lies at the
centre of its scale. The base of the level has a
concave groove along its length which allows it
to lie on curved work. Some levels are shown in
Figure 6.19.
Vernier caliper gauge
These calipers are made in a variety of types,
some being used for external measurements only
and others for both external and internal measurements.
Vernier calipers consist of a fixed
jaw attached to a main beam which is graduated,
and another jaw which slides along the main
beam. This sliding jaw is marked with the vernier
scale which coincides with the main scale when
the jaw is moved. The vernier scale is based on
the difference between measurement made on
two scales which normally have one division
difference. By careful use of this adjustment a
reading can be taken to 0.02 mm or 0.001 in
(Figure 6.20).
Figure 6.18 Vee blocks (Neill Tools Ltd (Eclipse))
Measuring and marking-out instruments 195
Micrometer
The micrometer (Figures 6.21 and 6.22) is used to
measure and record accurately to 0.01 mm, or when
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using a vernier micrometer to 0.001 mm. The size
of an object is measured by the contact principle,
which requires it to be positioned between the
anvil and the spindle head of the micrometer. The
micrometer has a C-shaped steel frame. An anvil
with a flat face is attached to one end of the frame
and the other end accommodates the spindle and
the barrel, which is graduated in linear measure.
The bore of the barrel is screw threaded and
engages the part of the spindle which is externally
cut to the same thread. The outer end of the spindle
has a ratchet stud and a thimble which is graduated
around its bevelled circumference. When this thimble
is turned it moves the spindle forward on to
the object to be measured, and in so doing moves
along the linear scale on the barrel. A locking ring
Figure 6.19 Engineers levels (Neill Tools Ltd
(Moore and Wright))
Figure 6.20 Vernier caliper gauge (Neill Tools Ltd
(Moore and Wright))
Figure 6.21 Micrometer (Neill Tools Ltd (Moore and
Wright))
Figure 6.22 External micrometers (Neill Tools Ltd
(Moore and Wright))
1 Spindle and anvil
faces
2 Spindle
3 Locknut
4 Sleeve
5 Main nut
6 Screw adjusting nut
7 Thimble adjusting
nut
8 Ratchet
9 Thimble
10 Steel frame
11 Anvil end
196 Repair of Vehicle Bodies
is usually provided in the frame at the point where
the spindle emerges from the barrel, so that the
spindle can be locked in position after a measurement
has been taken. An object to be measured
is held squarely in position between the anvil and
the spindle, then the spindle is closed on the object
by turning the ratchet stud clockwise until it starts
to slip, indicating that there is a predetermined
pressure on the object. If there is no ratchet stud
the thimble is turned just until resistance is felt
to the turning; great care must be taken to avoid
over-tightening. Next the spindle is locked in position
by turning the locking ring and the reading is
taken. The working principle of the micrometer is
based on the distance a screw moves forward for
each turn made. The screw thread has a lead of
0.5 mm while the thimble and barrel are graduated
into divisions of 0.5 mm for the barrel and 0.01 mm
for the thimble. Therefore, one revolution of the
thimble moves it along the barrel for 0.5 mm. The
thimble has 50 equal divisions and as one revolution
of the thimble is 0.5 mm, then one of the thimble
divisions will equal:
There are a number of different types of micrometers
made to serve a variety of uses in the field of
precision engineering: internal micrometer, tube
micrometer, screw-thread micrometer, adjustable
micrometer, depth-gauge micrometer, tubular inside
micrometer, bench micrometer and gear-teeth
micrometer.
Questions
1 When would a body repairer need to make
templates?
2 Describe the making of a template and the types
of materials which could be used for this purpose.
10.5
_ 0.01mm
3 Make a list of measuring and marking-out
instruments which would be used in vehicle body
work.
4 Explain the type of steel that would be suitable to
manufacture a scriber.
5 Suggest an appropriate repair situation
which would require the use of a long straight
edge.
6 Explain the difference between a try square and
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a centre square.
7 Explain the uses of a set of trammels.
8 Illustrate the two types of calipers which are used
in the workshop.
9 State the reasons why gauges are a necessary
piece of equipment in engineering.
10 Make a sketch, and state the operation of, a
micrometer.
11 Explain the term datums.Why are they used
when marking out?
12 With the aid of a sketch, illustrate the principal
parts of an engineers combination square.
13 Explain the use of the vee block when marking out.
14 What is the purpose of a marking-off table and a
surface gauge?
15 Explain the operation of a vernier caliper gauge.
16 State the effects of parallax error when
measuring with a steel rule.
17 Explain the purpose of a metre square when
marking out.
18 Describe a method by which a surface can be
checked to ensure that it is vertical.
19 With the aid of a sketch, show how to locate the
centre between two points using dividers.
20 Explain the difference between a radius gauge
and a drill gauge.
Methods of joining
7.1 Development of joining methods
In the manufacture of motor vehicles, the development
of new and more effective fastenings is
almost a branch of engineering in itself. However,
the traditional nut and bolt is still in use, and for
many applications it is difficult to imagine how it
can be replaced. Indeed, there are instances of a
return to nuts and bolts from newer methods of
fastening; some British and many continental cars
now have bolt-on wings or body panels where
previously welding was employed or the structure
was integral. The bolt has not changed much in
design since it was first developed, apart from the
use of special materials for certain applications and
also greater standardization of threads. Nuts, however,
are produced in a variety of special types; for
example, high-tensile steel bolts having greater
strength than hitherto use special shake-proof nuts
which form a very efficient fastening.
Solid rivets have also been used since the early
days of motor vehicle manufacture to form a permanent
joint, but nowadays riveted joints are being
replaced by welding.
In the field of mechanical fasteners, the modern
motor vehicle uses special types of spring-clip
fasteners in ever-increasing quantities. The most
usual form of such fastenings is the simple spring
clip made of tempered strip or wire; polythene,
nylon and other plastics fastenings have been used.
Another method is that of fastening panels together
using adhesives; this is proving to be very successful
in certain types of construction.
7.2 Solid rivets
The strength of a riveted joint depends on several
factors: the material in which the rivets and plates
to be riveted are made; whether the holes for the
rivets are punched or drilled; and the workmanship
involved in the riveting of the joint. In light sheet
metal, rivets are usually applied in the cold state so
that there is virtually no possibility of distortion.
However, in heavier metal plate riveted joints often
have to be comparable with the surrounding metal,
and so the rivets are inserted in the hot state as this
increases the strength of the joint.
Rivets used in hot riveting are made from steel
and/or iron, while for cold working rivets made
from copper, brass, aluminium and aluminium
alloys are used. In body work, steel rivets are used
on commercial chassis frames and also on fabricated
sections such as subframes and structural
load-bearing members. In addition aluminium
rivets are used on alloy frame construction in the
body building industry.
Rivets are classified according to the shape of
the head, and the diameter and the length of
the rivet. The shape of the rivet head is selected
according to the intended use of the workpiece to
be riveted. The diameter is selected according to the
required strength and thickness of the component
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to be riveted. Most important, the length of the
rivet must correspond to the total thickness of the
components to be joined. The various types of
rivets are shown in Figure 7.1, together with their
British Standard proportions.
The snap or round head rivet is used where high
strength is required. The pan head, similar to the
snap head, is also used where strength is required.
The mushroom is used in thin sheet metal which
would be weakened by the use of countersunk
rivets. Flat head rivets are used for riveting flat bar
and angle sections to thin metal sheet as the head
is fairly flush and does not obstruct. The countersunk
head rivet is used when the surface of the
component must remain smooth.
Rivet holes
Rivet holes can be punched or drilled. Punched
holes are generally slightly conical, and for an
efficient joint the work has to be arranged so that
198 Repair of Vehicle Bodies
the holes are brought together with their smaller
ends adjacent. Punched holes also have ragged
edges which must be smoothed, otherwise they
will decrease the shearing resistance of the rivets.
Drilling produces holes with smooth edges, and
has the further advantage that it can be carried
out with the plates in position so that there is no
damage due to badly aligned holes. A joint formed
with drilled holes is about 8 per cent stronger than
a joint made with punched holes. Table 7.1 gives
rivet and hole diameters.
Riveting dimensions
The diameter of a rivet is usually determined by
where D is the diameter of the rivet
and t is the thickness of the plate.
The allowance for riveting is the allowance
for the head of the rivet, and is the amount of
rivet showing above the plate before riveting. The
allowances are: snap head _ 1.5 D; countersunk
head _ 0.15 D; flat head _ 0.5 D.
The pitch of a rivet is the spacing between the
rivet centres. It can be calculated from the principle
that the part of the plate between each pair of holes
should be the same strength as one rivet. Therefore
if the pitch is less than 3 D (Figure 7.3) the plate
between the rivets will be too weak. The pitch can
then be extended to 8 D in special cases, but above
that the plate will tend to buckle.
The width of lap is the distance from the centre
of the rivet to the edge of the plate. It is generally
taken as 1.5 D, so that a single-riveted lap joint
would have an overlap of 3 D (Figure 7.2) and a
double lap joint an overlap of 5 D.
Types of riveted joint
The simplest form of riveted joint is the single lap
joint (Figure 7.2), in which the plates overlap a
short distance with a single row of rivets along the
D _ 1.2_ t,
Figure 7.1 Small rivet heads (BS 641)
Table 7.1 Rivet sizes and hole diameters for solid rivets
Rivet diameter (mm) 2.38 3.17 3.96 4.76 6.35 7.93 9.52 12.70
(in) 0.094 0.125 0.156 0.187 0.25 0.312 0.375 0.5
Hole diameter (mm) 2.43 3.25 4.03 4.85 6.52 8.02 9.80 13.10
(in) 0.096 0.128 0.159 0.191 0.257 0.316 0.386 0.516
Methods of joining 199
centre of the lap. The double-riveted lap joint has
two rows of rivets arranged either in line or staggered
alternately. The single-strap butt joint consists
of two plates butted edge to edge with a strap
covering the centre of the butt and riveted down
each side (Figure 7.3). The double-strap butt joint
is the same as the single-strap butt joint with the
addition of a second strap on the opposite side.
A single-riveted joint has an efficiency of only
about 55 per cent. In a double-riveted joint this
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is raised to about 70 per cent, whilst in a trebleriveted
joint 80 per cent or greater efficiency may
be attained.
Riveting procedure
Plates to be riveted should be clamped together
with their rivet holes in alignment. If hot rivets are
being used, they should be at forging temperature
and the operation should be completed before they
become black hot. For snap head rivets, a punch
or tool (snap) having a half-spherical cavity similar
to the rivet head is used to support the rivet head,
while the other-end of the rivet is riveted over by
holding a similar punch to the rivet end and striking
it with a hammer, thus forming a second cup head
on the other end of the rivet. The aim in riveting is
to swell the body of the rivet until it completely
fills the holes, and to complete the process as
quickly as possible while the rivet is still very hot
so that there is maximum contraction of the rivets
after riveting to pull the plates together. Pneumatic
or air operated hammers are used extensively for
closing over rivet heads. They are designed to
deliver the right weight of blow at the correct speed
to form the rivet head speedily and accurately. For
cold riveting the closure of the rivet is similar to
that of a hot rivet except that the metal is not as
plastic and greater difficulty will be encountered in
swelling the rivet shank to fill the hole. Cold riveting
plates cannot be as tight as with hot riveted
because there is no contraction of the rivets to pull
them together.
Care should be taken that the rivet head is spread
evenly in all directions and not bent over in one
direction only. This is often helped by giving the
rivet a few preliminary blows with the ball end of
the hammer, thus spreading the rivet a little before
using the riveting tool (Figure 7.4). Countersunk
rivets should be supported with a flat-headed
punch. The initial spreading is done with the ball
end of the hammer and the head is finished with
the flat end of the hammer. When riveted joints are
large it is advisable not to start at one end of the
workpiece but to rivet the extremities first and next
the centre, then the rest of the joint. This eliminates
creeping of the plates and misalignment of the
holes.
7.3 Bifurcated, tubular and semitubular
rivets
These rivets have the outstanding advantage that
there is no swelling of the solid portion of the
shank during the closure operation. They are used
extensively for the joining of soft materials such
as plastic, rubber, leather and/or brake and clutch
linings to metal. Only a small percentage is used
in the body building industry.
Figure 7.2 Single-riveted lap joint
Figure 7.3 Butt joint
200 Repair of Vehicle Bodies
7.4 Blind rivets
The blind rivet was originally developed in the
1930s for use in the aircraft industry, but since then
it has been adopted in the light engineering industries.
It is now employed as a standard sheet metal
fastener in cars, buses and all forms of commercial
vehicles. Blind rivets, as their name implies are
rivets which can be set when access is limited to
only one side of a structure. They are invaluable
both in car construction work, where many of the
panel assemblies are of the double-skinned type
so that accessibility would be impossible for conventional
riveting methods, and also in body repair
work as they eliminate any unnecessary stripping of
interiors. Blind rivets are manufactured by several
companies under brand-names, the most famous of
which is POP. POP is the registered trademark of
Tucker Fasteners Limited who were the pioneers
of blind riveting.
Blind rivet types
POP rivets
The POP rivet comprises a hollow rivet assembled
to a headed steel mandrel or stem (Figure 7.5). It is
inserted into a predrilled hole of the correct size in
the workpiece, and a special tool containing a
gripping device is applied to the mandrel or stem
of the rivet. When the tool is operated, either manually
or automatically, the mandrel head is drawn
into the hollow rivet, expanding the end of the rivet
which is on the blind side of the structure and at
the same time pulling the material together. When
and only when, a tight joint has been formed, the
mandrel breaks at a predetermined position, so that
the mandrel head is left as a plug in the bore of the
rivet (Figure 7.6). The spent portion of the mandrel
is then ejected from the tool. POP rivets are manufactured
from aluminium alloys, Monel, mild steel,
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copper and stainless steel. They are supplied with
domed or countersunk (90, 100 or 120) heads in
diameters of 2.4 mm, 3.2 mm, 4.0 mm, 4.8 mm and
6.4 mm, for riveting thicknesses up to 12.7 mm.
Shear strengths range from 400 N for 2.4 mm diameter
aluminium alloy rivets, to 5400 N for 6.4 mm
diameter Monel rivets. Owing to the high clenching
action of the rivet, tensile strengths are in excess of
these figures.
Seven types of POP blind rivet are shown in
Figure 7.7. These and other types are described as
follows:
Standard open rivet is subdivided into the breakhead
mandrel type, which leaves the mandrel head
Figure 7.4 Riveting procedure
Methods of joining 201
free to fall away from the rivet (Figure 7.6), and the
break-stem mandrel type, which retains the broken
portion of the mandrel within the set rivet, thus
sealing the rivet to a certain extent. The latter type
is intended for use in all normal blind riveting
situations where the materials to be fastened do not
present structural problems. This is a hollow rivet,
preassembled on to a headed pin or mandrel.
The mandrel is designed to fracture at a predetermined
point during the setting operation, when the
materials to be fastened have been drawn closely
together and the joint is tight. Sealed rivet consists
of a tubular rivet with a sealed end containing
a steel or stainless steel mandrel. The riveting
sequence is similar to that of a POP rivet, but this
type has the advantage that in setting the rivet it
is both compressed beyond its elastic limit and
expands radially, thus ensuring a joint which is
airtight and watertight up to 34 bar. The rivet is
available with two alternative mandrels: one, called
short break (Figures 7.8 and 7.9), fractures immediately
under the mandrel head which is retained
in the blind end of the set rivet; and the second,
known as the long break type, fractures at a point
outside the rivet and can be finished off to result in
a flush finish. The sealed rivet is a fastener of high
shear and tensile strength and vibration resistance.
Owing to its high rate of expansion in setting, it cannot
be recommended for use in very soft or brittle
materials. It is designed for use where the fastening
to be used has to be pressure or water tight.
LSR rivet This range of aluminium rivets is
designed to offer two particular advantages in joining
soft friable or brittle materials. Its controlled
setting gives outstanding reliability and it produces
a neat uniform appearance. The LSR is suited to
plastics, wood, GRP laminates and thin gauge materials.
It has an important role to play in such applications
as the assembly of caravans and trailers.
MGR rivet has been designed for use in situations
where hole sizes are inconsistent. It also
offers a multi-grip facility. The rivet is available in
aluminium 2.5 per cent magnesium alloy with a
carbon steel mandrel. MGR is valuable where
components are supplied to the user with holes
already punched or drilled, or where the sheets to
Figure 7.5 POP blind rivet: standard open type
(Tucker Fasteners Ltd)
Figure 7.6 POP blind rivet, standard open type:
setting sequence (Tucker Fasteners Ltd)
202 Repair of Vehicle Bodies
be joined are folded or curved, making it difficult
to match up two holes of the correct size.
Grooved rivet has been developed for use in thick
sections of soft or brittle materials such as hard
board, plywood, glass fibre, asbestos board, concrete
and brick. The POP grooved rivets gain their
name from the series of grooves around the shank
which engage into the workpiece on setting and set
inside the material rather than against the rear face.
Construction and setting action is similar to the
standard open type. The body is of aluminium alloy
with a carbon steel mandrel. When set, this rivet
is capable of withstanding high pullout loads (see
Figures 7.10 and 7.11).
Figure 7.7 Types of POP blind rivet (Tucker Fasteners Ltd)
Figure 7.9 POP blind rivet, sealed type: setting
sequence (Tucker Fasteners Ltd)
Figure 7.8 POP blind rivet: sealed type (Tucker
Fasteners Ltd)
Methods of joining 203
Peel rivets are specifically developed for fastening
soft or friable materials. They will secure blowmoulded
or glass-reinforced plastic, rubber and plywood
to metal panels or sections up to 13.5 mm
thick. The rivet has an aluminium alloy body and a
special carbon steel mandrel. On setting, the rivet
body is split into four petals by the action of the
mandrel head, producing a large blind-side bearing
area capable of withstanding high pullout load (see
Figures 7.12 and 7.13).
ELF rivet is an aluminium 3.5 per cent magnesium
alloy with an aluminium alloy mandrel. The body
of this rivet splits and folds on setting to form three
neat leaves which spread clamp-up load over a wide
area. It is a totally sealed rivet designed for use on
roofing but is suitable for materials like composite
board, GRP, hard rubber and laminates, and is used
in commercial vehicle construction and caravans.
Special POP rivets are shown in Figure 7.14. Earth
terminal rivets are designed to provide an effective
Figure 7.10 POP blind rivet: grooved type (Tucker
Fasteners Ltd)
Figure 7.11 POP blind rivet, grooved type: setting
sequence (Tucker Fasteners Ltd)
Figure 7.12 POP blind rivet, peel type: before setting
(Tucker Fasteners Ltd)
204 Repair of Vehicle Bodies
earth connection to pre-painted sheets without
damaging the finish. Tab rivets are designed to perform
two or more functions, such as fastening the
tops of rechargeable batteries and at the same time
providing a tab to serve as a connector. Tamperproof
rivets are set in the workpiece with a standard
tool; a stainless steel pin is then tapped into the
bore of the rivet and its domed head locates in a
recess in the rivet head, making the fastening virtually
impossible to remove without obvious traces.
T-rivets are designed for exceptional strength and
versatility; they can be reliable and vibration-proof
in holes as much as 0.8 mm oversize.
Blind rivet nut is a threaded insert system, and is
a remarkably simple fastening system for use in all
kinds of assemblies. It provides a straight, reliable
threaded insert to which other components can be
attached. It can be used as a blind rivet for permanently
fastening one or more panels or sections
together, and provides an anchorage with the holding
strength of at least six full thread turns. It can
be installed at any stage without damaging the
work-piece finish, even after painting. It can be
used in materials with thicknesses varying between
0.25 and 7.5 mm. There are a wide range of sizes
available in steel, aluminium or brass with thread
sizes from M4 to M10. (M is the metric screw
thread designation, and when followed by a number,
e.g. M4 is a metric thread of 4 mm diameter.)
Sealed or open types are available with flat or
countersunk heads. They can be used in drilled or
punched holes with normal tolerances (Figure 7.15).
Well nut This demountable blind screw anchor
is designed to provide a vibration-resistant fixing
for engineering and automotive structures. It consists
of a captive brass nut in a resilient neoprene
bush which can be installed from one side of the
workpiece using only a screw and a screwdriver
(Figure 7.16). It is suitable for materials from light
gauge metal panel, too thin for self-tapping or
set screws, to plastic sheet up to 16.5 mm thick.
The flanged ends prevent electrolytic corrosion at
metal-to-metal assembly points.
Repetition rivets
Repetition riveting systems are widely used on
vehicle body construction, especially commercial
vehicles. Some examples are as follows:
Chobert riveting system operates on an entirely
different principle from other blind riveting systems
(Figure 7.17). Instead of a break-stem type of mandrel,
there is a mandrel with a tapered hardened
Figure 7.13 POP blind rivet, peel type: after setting
(Tucker Fasteners Ltd)
Figure 7.14 Special POP rivets (Tucker Fasteners Ltd)
Methods of joining 205
steel head larger in diameter than the tapered bore
of the rivet. The mandrel is drawn through the rivet
towards the head, and is thus part of the placing
tool rather than the component. It is possible
to extend the mandrel length to accommodate a
charge of up to 100 rivets and to achieve a rate of
placing up to 2000 per hour. The Chobert rivet is
made in a wide range of materials and sizes. Head
forms currently available include snap, mushroom,
flat and countersunk, and sizes range from 2.38 mm
to 6.35 mm diameter. Materials include a wide
range of aluminium alloys and zinc-plated steel.
They are supplied in tube loaded form, each
317.5 mm long and containing up to 100 carefully
aligned rivets. The tubes can be used in special
tools which can be either manually or pneumatically
operated. If additional strength or water
tightness is required the rivets can be pinned,
giving in effect a solid rivet.
Chobert Grovit system has been developed so that
the widest range of materials (such as wood, plastic,
aluminium) may be joined. The Grovit has grooves
on its shank which bite firmly into the material when
Figure 7.15 Blind rivet nut, installation sequence
1 POP nut screwed on to tool
2 POP nut inserted into hole
3 Tool operated: mandrel retracts into tool, and
unearthed part of nut expands on blind side of
workpiece
4 Tool mandrel unscrewed
5 Assembly completed
Figure 7.16 Well nut (Tucker Fasteners Ltd)
Figure 7.17 The Chobert hollow rivet (Avdel Ltd)
206 Repair of Vehicle Bodies
the rivet is expanded (Figure 7.18). The rivets can
also be used in the high-speed Chobert system. These
types of riveting systems are ideal for mass production
and are invaluable in the body building industry
where speed and economy are essential (Figure 7.19).
Briv system is a high-speed, high-clench riveting
system for use with a wide range of assembly materials.
Briv is installed from one side of the workpiece
with the use of a mandrel loaded into the Avdel
power tool. The action of the mandrel draws through
the rivet, expanding the shank to fill the hole. The
applications range from body component assembly
to fixing electronic control panels (see Figure 7.20).
Blind riveting tools
The majority of blind riveting tools have been
designed on the assumption that the operator will
be moving around a stationary structure, as in body
building. However, some stand tools are available.
Figure 7.18 The Chobert grooved rivet (Avdel Ltd)
Figure 7.19 The Chobert and Grovit riveting systems (Avdel Ltd)
1 2 3 4
Figure 7.20 Briv placing sequence (Avdel Ltd)
1 Place Chobert rivet or Grovit in prepared hole
2 Draw steel mandrel, which has opposite taper to rivet, through from tail end of rivet, expanding rivet tail
around rear side of hole, to form shoulder. (For the Grovit, annual convolutions are forced into materials.)
3 Continue to pull the mandrel through rivet, which symmetrically expands shank to fill hole
4 The rivet has good bearing in hole and a parallel bore is left in the rivet
1 Magazine loaded rivet is
placed into hole
2 Tool draws mandrel through
rivet, compressing rivet
3 Mandrel expands shank of
rivet to fill hole and clamp
materials
4 Completed rivet. Tool
reloads automatically
Methods of joining 207
The range of tools has been designed to cater for
all riveting conditions, whether they are used on
high-speed assembly production lines or for occasional
use. The basic types of tools consist of:
1 Manually operated plier types
2 Manually operated lazy tongs
3 Portable pneumatically operated guns
4 Portable pneumatic hydraulic guns
5 Pneumatically operated stand tools.
In addition various heads are available for attaching
to either manual or power operated tools which can
gain access to restricted places. In order to change
the rivet diameter or type of rivet being used, it is
necessary merely to change the nose-piece or the
gripping jaws which hold the mandrels. It must be
remembered that certain special rivets and fasteners
can only be used by their appropriate setting tool.
Some examples of riveting tools are given in
Figures 7.217.24.
Hole size Drill sizes for each diameter of rivet are
usually specified by the manufacturers. These are
usually designed to give a clearance of 0.05 mm to
0.13 mm between the rivet and the hole, and in the
case of rivets capable of only limited radial expansion
these recommendations must be followed if
maximum efficiency is to be achieved.
Rivet length Manufacturers also specify the correct
rivet length to be used on a given thickness
of material. It is often advantageous to use rivets
which are longer than those recommended as they
will set satisfactorily on thinner materials, and the
longer length, when expanded, increases the grip
of the rivet, but the higher cost for longer rivets
should be taken into account before doing so.
Pitch of rivets In load-bearing joints the distance
between rivets in the same row should not exceed
six times the rivet diameter. Even when the joint is
not load bearing, the rivet pitch should not exceed
Figure 7.21 Hand operated riveting tool, plier
type (Tucker Fasteners Ltd)
Figure 7.22 Hand operated riveting tool, lever type
(Tucker Fasteners Ltd)
Figure 7.23 Hand operated riveting tool, lazy tongs
type (Tucker Fasteners Ltd)
Rivet selection
The following factors must be considered when
selecting the type of rivet to be used on a particular
job:
Rivet diameter In some cases this may be decided
by the size of an existing hole. When designing
new work the main factor is usually the shear or
tensile strength required from the riveted joint. In
load-bearing joints the diameter of the rivet should
be at least equal to the thickness of the thickest
sheet but should not be greater than three times the
thickness of the sheet.
208 Repair of Vehicle Bodies
twenty-four times the thickness of the thinnest
sheet in the joint.
Edge distance In lap or butt joints which are
likely to be subjected to shear or tensile loads rivet
holes should not be drilled within a distance equal
to two rivet diameters from the edge of the sheet,
but should not exceed twenty-four rivet diameters.
Rivet material The choice of rivet material will
normally be related to the strength required from
the riveted joint. Usual rivet materials are steel,
aluminium alloy, copper and Monel. Other factors
affecting the choice are weight, high temperatures
and corrosion resistance, especially electrolytic
corrosion which can occur when different metals
are joined together.
Mandrel type The break-stem mandrel is usually
chosen where the rivet is to act as a waterproof
plug, and also where it would be inconvenient to
eject the mandrel head on the blind side of the
enclosed structure. The break-head mandrel is used
where weight is a factor, and where a comparatively
clear hole is required through the rivet set.
7.5 Structural fasteners
Figure 7.25 shows a variety of structural fasteners
used on a vehicle body.
Figure 7.24 Automatic riveting system (Tucker
Fasteners Ltd)
Figure 7.25 Types of structural fastener used on a vehicle body (Avdel Ltd)
Methods of joining 209
Avdelok system
This is not a blind fastener, but has a number of
advantages over the conventional rivet or nut and
bolt which it replaces. The Avdelok is a two-piece
high-strength fastener consisting of a bolt and
collar made from carbon steel, stainless steel and
aluminium alloy (Figure 7.26). It gives a high clench
action and a positively locked nut or collar which is
proof against vibrations. It can be placed very simply
by manual or pneumatic tools. The Avdelok bolt is
placed through the prepared hole and the collar is
slipped on to the other side of the joint (Figure 7.27).
The nose of the tool is then pushed over the tail of
the bolt and the trigger is pulled. This draws the
bolt tight, clamping the sheets together. The pull
continues until the nose of the tool is drawn over the
collar, compressing the collar until it is swaged into
the grooves of the pin. The tail of the bolt breaks off
at the deep breaker groove, flush with the collar. No
finishing is needed. This system is employed in such
applications as chassis cross-bearer brackets on commercial
vehicle bodies.
plated and gold passivated to ensure good corrosion
resistance. The fastener is supplied in 6.4 mm
diameter in various lengths. It is installed from one
side of the workpiece, thus making it a blind fastener.
It is designed with a chamfer at both ends
of the stem; this facilitates easy insertion into the
placing tip of the installation equipment, and into
the hole in the workpiece. The installed fastener
breaks flush with or below the surface of the lowprofile
Hemlok head, leaving a clean finish and
appearance. Hemlok provides strength and good
clamp-up, and the well formed fastener tail
achieves this without deforming thin sheet material.
This fastener is designed to be used on thin-gauge
materials for high-strength joints suited to automotive
work (see Figures 7.28 and 7.29).
Threaded inserts
Steel threaded inserts (such as Nutsert) of high
strength (Figure 7.30) can be placed by any of three
specially designed tools. The Nutsert is placed on
the threaded drive screw of the placing tool and
inserted into a prepared hole in the workpiece.
The drive screw turns clockwise drawing the
tapered nose portion of the Nutsert back into its
outer shell and thus causing the shell to expand into
the preformed hole. The drive screw is then withdrawn,
leaving the Nutsert permanently and tightly
placed in the hole and ready to receive either a
screw or a bolt. It can be used on all types of metals
and also plastic and timber, and is made in a wide
range of thread sizes, both imperial and metric
(Figure 7.31).
Figure 7.26 The Avdelok fastener (Avdel Ltd)
1 Insert Avdelok pin through predrilled hole and slip
collar over pin tail
2 Place tool nose over pin tail and press trigger
Figure 7.27 The Avdelok system (Avdel Ltd)
3 Swage collar into locking grooves of pin
4 Tail of pin breaks flush with collar and is
ejected
Hemlok system
The Hemlok is a blind fastener which comprises
a steel stem and shell. Both components are zinc
210 Repair of Vehicle Bodies
Monobolt system
Monobolt is a precision engineered two-part component.
It is a high-performance flush-break fastener
designed to build in strength, security and
quality. It consists of a body and a stem and is
supplied as a one-piece assembly. A sealing on
the Monobolt stem provides exceptional resistance
to moisture, an essential requirement for many
applications in vehicle body work. The fasteners
are available in aluminium alloy, carbon steel
and stainless steel, in diameters of 4.8 mm and
6.35 mm. Fast and simple to install, Monobolt is a
Figure 7.28 Hemlok fastener (Avdel Ltd)
Figure 7.29 Hemlok placing sequence (Avdel Ltd)
1 Hemlok inserted into power tool and workpiece
2 Tool operated: Hemlok tail deforms over material
Figure 7.30 Standard Nutsert (Avdel Ltd)
3 Tail fully formed: fastener stem breaks off
blind fastener, ideal for original structural assembly
and to replace conventional fastening methods,
particularly when access to the workpiece is difficult.
A major feature of the Monobolt construction
is the visible locking element which allows
easy, visible inspection after placement (see
Figure 7.32).
Avtainer system
This system has been designed for the joining
of composite panels of plywood and glassreinforced
plastic to metal framing. This fastener
has the ability to join firmly, but without cracking
or pulling the bolt right through the composite. It
is a two-piece fastener consisting of a zinc-plated
carbon steel pin with a nylon seal and a collar
which is pulled tight from the other side of the
workpiece, thus causing no damage to the material
during installation. One of its main applications
is in the building of commercial vehicles
(see Figure 7.33).
Methods of joining 211
7.6 Screws and bolts
Wood screws
Joining by wood screws is an essential part of the
construction of vehicle bodies which incorporate
timber. Screws are available in steel, brass and
bronze, with a variety of alternative finishes. Sizes
range from no. 2 (1.6 mm in) to no. 8 (7.9 mm,
in), and lengths vary from 6.35 mm, in, up to
101.6 mm, 4 in and longer in special cases. The
head types include the standard countersunk (used
in most timber fixings), round head (sometimes
used when fixing metal fittings to wood), and raised
head (used when fixing mouldings where the raised
head gives a decorative effect) (Figure 7.34). A new
development is the Supadriv recess head, specially
engineered to give a cling-fit between driver and
screw; it is increasingly used in robotic assemblies.
In body shops wood screws are applied by hand or
with special power operated screwdrivers which are
either electrically or pneumatically operated.
