Learn how working sheet metal in automotive maintenance technology works.

1. Mohd. Hafizin Jamil Bin Rashidi
Muhammad Irfan Bin Mohd Noor

2.  Automotive Sheet Metal
 Types of Body Damage
 Classifying Body Damage
 Understanding Metal
 Metal Straightening Technique
 Metal Shrinking, Stress Relieving
 Working Aluminum Panel
 Paintless Dent Removal

3. GETTING TO KNOW ABOUT METAL.

4.  Sheet metal is metal formed by an industrial process
into thin, flat pieces.
 It is one of the fundamental forms used in
metalworking and it can be cut and bent into a variety
of shapes.
 Extremely thin thicknesses are considered as foil or
leaf, and pieces thicker than 6mm(0.25 in) are
considered as plates.

5.  The most common sheet metal used in automotive to
make bodies is steel. It is reasonably cheap and easy to
press into shape to make body parts.
 The next best is aluminum. It is lighter but harder to
bend into tight shapes without cracking. It is also
harder to weld in mass production.

6.  There are three types of steel used in the automotive
body and only two are commonly used.
 The first type which is used by Volvo™ is boron steel
which is stronger than the other two types of steel.
 The two types commonly used are:
 Mild and low-carbon steel
 Higher carbon steel

7.  Boron steel is developed using boron as an alloying
element in developing Ultra High-Strength
Steel(UHSS).
 Once bent, it can’t be straightened and it requires
replacement if damaged.
 Boron steel are also sensitive to heat and it weakens
when it’s heated rapidly.
 Because of its sensitivity to heat, it can’t be galvanized.
Therefore, corrosion protection is crucial and essential
after welding.

8.  Also called plain-carbon steel, is the most common
form of steel because of its price is low while it
provides material properties that are acceptable for
many applications, more so than iron.
 Contains approximately 0.05-0.3% carbon making it
malleable and ductile.
 Mild steel has a relatively low tensile strength, but its
cheap and malleable; surface hardness can be
increased by carburizing.
Note:
Carburizing is a heat treatment process in which iron or steel absorbs carbon
liberated when the metal is heated in the presence of carbon bearing material,
such as charcoal or carbon monoxide with the intent of making the metal
harder.

9.  Carbon steels which can successfully undergo heat
treatment have a content in the range of 0.3-1.7% by
weight.
 Medium carbon steel: approximately 0.3-0.59% carbon
content. (Balances ductility and strength and has good
wear resistance)
 High-carbon steel: 0.6-0.99% carbon content. (Very
strong)
 Ultra-high-carbon steel: 1.0-2.0% carbon content.
(Steels that can be tempered to great hardness)

10.  6111 aluminum and 2008 aluminum alloy are
extensively used for external automotive body panels,
with 5083 and 5754 used for inner body panels.
 Hoods have been manufactured from 2036, 6016, and
6111 alloys.
 Truck and trailer body panels have used 5456
aluminum.
 Automobile frames often use 5182 aluminum or 5754
aluminum formed sheets, 6061 or 6063 extrusions.

11.  2000 series(2008,2036) – alloyed with copper, can be
precipitation hardened to strengths, comparable to
steel. Formerly referred as duralumin, they were once
the most common aerospace alloys, but were
susceptible to stress corrosion cracking and are
increasingly replaced by 7000 series in new designs.
 5000 series(5083,5754,5456,5182) – alloyed with
magnesium.
 6000 series(6111,6016,6061,6063) – alloyed with
magnesium and silicon, are easy to machine, and can
be precipitation hardened, but not to the high
strengths that 2000 and 7000 can reach.

12. KNOWING BODY DAMAGE

13.  When determining the kind of repair procedures, we must
determine the construction of the damaged panel; angle of
impact; speed of the impact object; and size, rigidity and
weight of the impact object.
 You must be able to visualize how the metal folded during
impact.
 Body damage can be separated into five types:
 Simple bends
 Displaced areas
 Rolled buckles
 Stretches
 Upsets

14.  Simple bends are bends in the metal such as minor dings
and bumps, and damage in which high stress is not a factor.
 Displaced areas are metal sections that have been moved
but not otherwise damaged.
 Rolled buckles or S-shaped bends, are pronounced
displaced areas with the metal folded or tucked under
itself.
 Stretches are caused by tension rather than compression.
 Upsets happen when opposing forces push against an area,
causing it to yield. Caused by compression rather than
tension, this is sometimes called accordion pleat.

15. HOW TO CLASSIFY BODY DAMAGE

16.  There are three conditions where metal is damaged by
impact:
 Direct damage – a tear, gouge or scratch
 Indirect damage – buckle (a fold or hinge in metal due
to damage or tension) or pressures(unwanted force due
to impact damage.
 Work hardening – normal and impact created.

17.  Direct damage is a simple, visible damage and easy to
find; i.e gouge, tear, scratch.
 It is the damaged portion of the panel that came in
direct contact with the object that caused the impact.
 The damage is usually about 20% of the total damage
and the repair at the point of impact is limited.
 Usually requires some body filler or, on rare occasions,
lead, after all indirect damages have been handled.
 Direct damages varies from job to job.

18.  Indirect damages are caused by the shock of collision
forces travelling through the body and inertial forces
acting on the rest of the unibody.
 It is hard to completely identify and analyze.
 It is also can be found anywhere on the vehicle.
 Indirect damage represents on the average of 10-20%
of the overall damages.

19.  Work hardening occurs when plastic deformation
has caused the metal to become very hard in the bent
area.
 As the metal is worked to its limit, it becomes harder
and harder.
 With this increase in hardness, there is an increase in
strength and stiffness as a result of work hardening.

20. WHAT YOU SHOULD KNOW ABOUT METAL

21.  There are three properties of sheet metal that is
needed to be familiarize with to do quality bodywork:
 Plasticity
 Work hardening
 Elasticity

22.  Plasticity is the property that allows metal to be
reshaped when enough force is applied to it. This is
the same property that allowed it to be stamped into a
fender, hood or door.
 Work hardening or cold working occurs when metal
is bent, stretched, shaped or moved. How much a
piece of metal can be cold-worked has a limit, after
which, it will break.
 Elasticity is the property of metal that allows it to
regain it’s original shape after being deflected.

23. TECHNIQUES TO STRAIGHTEN METAL THAT NEEDS TO BE
MASTERED

24.  There are a few techniques that we can learn theoretically.
However, learning by methodically is most preferred since
the techniques would be much better off by doing it.
 The techniques available to straighten metal are:
 Using body hammer
 Hammer-on-dolly
 Hammer-off-dolly
 Picking dents
 Straightening with spoon
 Using rubber air bladders
 Straightening with suction cups
 Straightening with studs

25.  The body hammer is often used to remove small dents in
sheet metal parts.
 It is designed to strike the sheet metal and rebound of the
surface.
 Minor low and high spots in
sheet metal can often be fixed
with a body hammer.
 The secret of metal straightening
is to hit the right spot at the right
time, with the right amount of
force.

26.  A method to exert a powerful but concentrated
smoothing force to a small area on a damaged panel.
 The dolly is held against the back of the damage and
the hammer hits the metal right over the top of the
dolly.
 This exerts a pinching force on the metal between the
dolly and the hammer head.

27.  Is used to raise low spots and lower high spots
simultaneously.
 The hammer hits the panel slightly to one side of
where the dolly is being held.
 It is often used to rough out or shape large areas of
damage during initial straightening.

28.  Often involves final straightening of very small areas of
damage with the pointed end of a body hammer or
with long rod that has a curved, pointed tip.
 A pointed head or pick on a hammer is often used to
mower small high spots during final straightening of a
panel.
 All high spots must be lowered to be even or slightly
below the original contour to allow application of body
filler.

29.  Spoons can be used in a number of ways to straighten
sheet metal.
 They can be used to pry out dents and certain kinds
can be struck with a hammer to drive out dents.
 In hard-to-reach areas, a spoon can be used as a dolly,
some are even designed to be used in place of a
hammer.
 Spoons are handy when a dolly
cannot be held on the back of a
panel.

30.  Are designed to push out larger sized dents from the
back of panels.
 The air bladder can be installed inside doors, quarter
panels, and other unibody areas to push out large
dents.

31.  A suction cup can be used to straighten shallow dents.
 Wet the area and install the cup. If handheld, pull
straight out on the cup’s handle. If mounted on a slide
hammer, use a quick blow to pop the dent out.
 A vacuum suction cup uses a remote power
source(separate vacuum pump or air compressor air
flow) to produce negative pressure(vacuum) in the
cup.
 This increases the pulling power because the cup will
be forced against the panel tightly. Larger, deeper
dents can be straightened with a vacuum suction cup.

32.  A stud spot welder joins “pull rods” on the surface of a
panel so that drilling holes are not needed.
 It is one way to straighten dents.
 Straightening with spot-welded studs avoids drilling or
punching through the metal and undercoating, which
can lead to corrosion.

33.  Don Taylor and Larry Hofer. Paint & Body Handbook.
Penguin. 1994. Print.
 James E. Duffy and Robert Scharff. Automotive Body
Repair Technology. 4th ed. Cengage Learning. 2003.
Print.
 James E. Duffy. I-Car Professional Automotive
Collision Repair. Cengage Learning. 2000. Print.