Auto body building & finishing

6/19/2021
Prepared By
Engr. Talha Akbar
Auto Body Building
& Finishing
C T T I Islamabad

Auto & Diesel 1
Auto Body Building & Finishing
Table of Contents
BUCKLES & THEIR TYPES ...............................................................................................................8
Collapsed hinge buckles ....................................................................................................................8
Collapsed rolled buckles....................................................................................................................8
Frame Types: .........................................................................................................................................9
2. Types of Car Frame are: ................................................................................................................9
3. Under Body:...................................................................................................................................9
4. Frame Member Cross Section and their characteristics:..............................................................10
Box Construction:........................................................................................................................10
I Beam Construction:...................................................................................................................10
5. Channel:.......................................................................................................................................10
6. Round Channel: ...........................................................................................................................10
7. Types Of Frame Damage:............................................................................................................10
Sag: ..............................................................................................................................................10
Sway:............................................................................................................................................10
8. Frame Gauges: .............................................................................................................................11
Procedure: ....................................................................................................................................11
9. Checking of Frame Alignment with Plumb bob:.........................................................................11
10. Traming:.....................................................................................................................................11
11. Repairing Frame Damages:........................................................................................................11
12. Channel Shade: ..........................................................................................................................11
13. Procedure of correction of length, width, and height are as Under: .........................................11
14. Correction of sag Damage: ........................................................................................................12
15. Correction Of Sway Damage:....................................................................................................12
16. Correcting Twist damage:..........................................................................................................12
SHRINKING METAL WITH HEAT..................................................................................................13
Safety Precautions:.......................................................................................................................13
Equipment required......................................................................................................................13
Procedure: ....................................................................................................................................13
Cautions .......................................................................................................................................13
Note..............................................................................................................................................13
Procedure .....................................................................................................................................14
Metal finishing.....................................................................................................................................14
Cross filing or Check filing:-.......................................................................................................14
Line filing;-..................................................................................................................................14

Auto & Diesel 2
Shrinking Sheet Metal;-...............................................................................................................14
Shrinking Method;-......................................................................................................................14
Cutting slits;-................................................................................................................................14
Metal Finishing............................................................................................................................15
Procedure:-...................................................................................................................................15
Using Pull Rod:- ..........................................................................................................................15
Safety of Grinder:-.......................................................................................................................15
Hammering bumping;-.................................................................................................................16
1.Power Tools ..............................................................................................................................16
2. Power Tools .............................................................................................................................16
3. Grinder.....................................................................................................................................16
4. Cone Mandrill:-........................................................................................................................16
5. Molded Disk Pads:-..................................................................................................................16
6. Wire Cup Brush:-.....................................................................................................................17
7. Care & maintenance:- ..............................................................................................................17
8.Safety:-......................................................................................................................................17
9.Sanders:- ...................................................................................................................................17
10.Pneumatic Orbital Sander:-.....................................................................................................17
11. Orbital Disk Sander:-.............................................................................................................17
12. Polisher-.................................................................................................................................17
14. Pneumatic impact tool:-.........................................................................................................17
15. Pneumatic Wrenches:- ...........................................................................................................17
16. Riveters:-................................................................................................................................18
17.Metal Shears:-.........................................................................................................................18
18. Bench Grinder:- .....................................................................................................................18
19.Heat Guns:-.............................................................................................................................18
Surface preparation ..............................................................................................................................18
2. Types of coated adhesives ...........................................................................................................18
3. Coarseness and fineness of adhesive dish....................................................................................18
4. Use of grit ....................................................................................................................................18
6. Sanding operations.......................................................................................................................18
8. Sanding methods..........................................................................................................................19
A. Dry sanding ...........................................................................................................................19
B. Wet sanding...........................................................................................................................19
C...................................................................................................................................................19

Auto & Diesel 3
D...................................................................................................................................................19
E...................................................................................................................................................19
9. Stripper.........................................................................................................................................19
10. Stripping a painted surface: .......................................................................................................19
11. Safety precautions......................................................................................................................20
12. Mashing or Tapping...................................................................................................................20
13.Mashing materials.......................................................................................................................20
14. Masking procedure.....................................................................................................................20
Fractured Panels...............................................................................................................................21
Procedure: ....................................................................................................................................21
Worker Hand tools...............................................................................................................................21
Hammer............................................................................................................................................21
Roughing hammer........................................................................................................................21
Bumping and finishing hammer...................................................................................................21
Combination or pick hammer ......................................................................................................22
Magnetic trim hammer.................................................................................................................22
Mallet...........................................................................................................................................22
Shrinking hammer........................................................................................................................22
Dolly blocks.....................................................................................................................................22
Spoons:.............................................................................................................................................22
Pick tools..........................................................................................................................................22
Files and file holders........................................................................................................................23
Solder and solder paddle..................................................................................................................23
Pliers ................................................................................................................................................23
Pry bar..............................................................................................................................................24
Pop rivet...........................................................................................................................................24
Metal shears/snipes ..........................................................................................................................24
Screw driver.....................................................................................................................................24
Wrenches/sockets.............................................................................................................................24
Clips.................................................................................................................................................24
Finishing Material................................................................................................................................25
5. Types of Paint ..............................................................................................................................25
6. Acrylic Enamel ............................................................................................................................25
7. Acrylic enamel dries in two stages ..............................................................................................25
8. Urethan Enamel. ..........................................................................................................................25

Auto & Diesel 4
9. Synthetic Enamel. ........................................................................................................................26
10. Acrylic paint...............................................................................................................................26
11. Polishing Compound..................................................................................................................26
12. Enamel Refinishing....................................................................................................................26
13. Acrylic Enamel on the based metal surface...............................................................................26
11. Mashing on wheels. ...................................................................................................................26
Safety Precautions........................................................................................................................26
Equipment required......................................................................................................................27
Procedure .....................................................................................................................................27
Shrinking Metal with Heat...................................................................................................................28
1. Equipment’s Required .................................................................................................................28
Procedure .....................................................................................................................................28
2. Caution.........................................................................................................................................28
3. Shrinking metal without Heat ......................................................................................................28
For example .................................................................................................................................28
Procedure .....................................................................................................................................29
4. Cutting slits..................................................................................................................................29
5. By use of heat...............................................................................................................................29
6. Metal finishing.............................................................................................................................29
7. Point of the initial impact.............................................................................................................29
Procedure .....................................................................................................................................29
8. Using pull rods.............................................................................................................................30
9. Removing paint and undercoat ....................................................................................................30
11. Hammering / Bumping ..............................................................................................................30
12. Direct hammering ......................................................................................................................30
13. Indirect hammering....................................................................................................................30
14. Pick hammer used for picking ...................................................................................................30
Plastic body components......................................................................................................................31
Types of plastic................................................................................................................................31
Thermo plastics............................................................................................................................31
2. UNSATURATED POLYESTER ................................................................................................31
3. Repairing Minor Tears or Cracks in Thermoplastic ....................................................................31
4. Repairing a thermoset polyurethane component when the material has been torn away ............32
Analyses of Metal Damage..................................................................................................................32
2. BODY OVER FRAME................................................................................................................32

Auto & Diesel 5
3. UNIBODY...................................................................................................................................32
4. MONOCOQUE............................................................................................................................32
5. Properties of Sheet Metals. ..........................................................................................................32
6. Physical Structure of steel Metals................................................................................................32
7. Effect of Impact Forces................................................................................................................32
8. Load & Deformation Diagram.....................................................................................................32
Glass & Doors......................................................................................................................................34
2, Types of glass. .............................................................................................................................34
3. Installation....................................................................................................................................34
Type of glass........................................................................................................................................34
2. Laminated safety glass.................................................................................................................34
3. Tempered glass ............................................................................................................................35
4. Wind shield and rear window installation ...................................................................................35
5. Removing of glass in rubber channel...........................................................................................35
6. Installation....................................................................................................................................35
FIBER GLASS.....................................................................................................................................37
1.Composition..................................................................................................................................37
Characteristics..............................................................................................................................37
Precautions...................................................................................................................................37
2. Tools/Materials ............................................................................................................................37
3. Scratches repair............................................................................................................................38
Cares ............................................................................................................................................38
4. Pits, small holes, surface cracks...................................................................................................38
5. Cracked body panels....................................................................................................................38
Spraying Techniques :..........................................................................................................................39
Viscosity: .....................................................................................................................................39
Mixing :........................................................................................................................................39
Seating Controls :.........................................................................................................................39
Air Cap:........................................................................................................................................39
Fluid volume control :..................................................................................................................39
Spray pattern with spray control :................................................................................................39
Write Action : ..............................................................................................................................39
Tilting :.........................................................................................................................................39
Triggering : ..................................................................................................................................39
Alternate strokes : ........................................................................................................................39

Auto & Diesel 6
Charge peel : ................................................................................................................................40
Sagging: .......................................................................................................................................40
Running :......................................................................................................................................40
Over Spray: ..................................................................................................................................40
Film thickness:.............................................................................................................................40
Hand portable equipment.............................................................................................................40
Korek Straightening system:........................................................................................................40
Mitek system of damage Repair: .................................................................................................41
Spray Paint Equipment ........................................................................................................................44
Types of spray gun:..........................................................................................................................44
Parts of a Spray gun:-.......................................................................................................................45
A) Air Nozzle:..............................................................................................................................45
B) Fluid Nozzle:...........................................................................................................................45
C) Needle Assembly:...................................................................................................................45
D) Side Port Control: ...................................................................................................................45
E. Fluid control assembly : ..........................................................................................................45
F. Spray gun body handle : ..........................................................................................................45
G. Air inlet:..................................................................................................................................45
H. Trigger :...................................................................................................................................45
I. Air valve: ..................................................................................................................................45
J. Fluid inlet: ................................................................................................................................45
12. Siphon cup seal ..........................................................................................................................46
Bleeder Gun: ....................................................................................................................................47
AUTO BODY PAINTS.......................................................................................................................47
1. Understanding the 5 Types of Exterior Car Paint: A Comparison Guide....................................47
Prep or Undercoat Finishes –.......................................................................................................48
2. Base Coat Paints....................................................................................................................48
3. Acrylic Lacquers – ................................................................................................................48
Clear Coat Finishes......................................................................................................................48
5. Specialty Paints .....................................................................................................................48
2. The Pros and Cons of Acrylic Car Paint.....................................................................................48
3. The Main Benefits of Acrylic Paint............................................................................................49
4.Disadvantages ...............................................................................................................................49
5. Choosing the Right Color ............................................................................................................49
6. Acrylic Car Paint Techniques for a Professional Coat ................................................................49

Auto & Diesel 7
7. Urethane Car Paint: Understanding the Pros and Cons ...............................................................50
8. Show Car Paint: Understanding What Type of Paint?.................................................................51
9. Tips ..............................................................................................................................................52
10. Is there a Difference Between Enamel Car Paint and Acrylic Car Paint?.................................52

Auto & Diesel 8
BUCKLES & THEIR TYPES
1. Collision damage impact Bulge
Stretching of metal in which thickness is reduced, more space is occupied.
2. Impact and its effects on vehicle
The effects of impact are different in nature for different types
of bodies. Following is important
• Sizes of accidental vehicles
• Angle and direction
• Numbers and position of passengers
3. Direct damage
Damage, which occurs directly at the point of contact. It is generally 10-15% of overall damage.
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4.Indirect damage
Damage which occurs away from the point of contact is due to direct damage and is 80-90% of total
damage.
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5. Buckles
A sheet is bent more than its elastic limit, a curve or a ridge is formed.
Simple hinge buckle
In this case, the surface is pulled, stretched, and work-hardened, the lower surface has compressed,
shrunk, and work hardened. There is a space in the center where the granular structure is still
undamaged represented by double arrows, if straightened properly, the sheet may gain its original
shape.
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Collapsed hinge buckles
These are formed whenever a simple hinge buckle extends and crosses over a stamped re-
enforced flange, bead, or ridge on a flat or reverse curved(concave) surface of an autobody. As the
hinged buckle passes through a ridge or a bead, the overall length of the panel is shortened. In the
case of hinge buckle, the severe over tension causes elongation to the upper surface, while the severe
over-compression, causes shortening to the surface.
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Collapsed rolled buckles
These are formed when a hinged buckle extends or crossover into a crown surface of a panel
causing the metal to collapse and shrink severely and the overall metallic sheet shortens. Simple

Auto & Diesel 9
hinge buckles are pushed upward buckles, while collapse rolled buckles are pulled inward deep into
the metallic sheet-like A B C, Collapsed rolled buckles out turn sheet, increases the length, shrink the
metal, form a narrow deep design on the crown of the panel. Collapsed rolled buckles move away
from the point of impact.
6.Pressure forces
Pushed-up areas are pressure areas. Pushed-down areas are tension areas. The tension area
damaged area is below the normal line of a metallic sheet.
1. Uhss Ultrahigh strength steel
2. Ahss Advance high strength steel
3. Hsla High strength low alloy
Frame Types:
Passenger Car Frame
Truck Frame
Integral Frame or Unitized Construction
The truck Frame is constructed flat. Its center section is flat, as it is not meant for riding but cargo
lifting. It is meant for strength and space only.
2. Types of Car Frame are:
Ladder Frame
Offset Frame
Off set with Cross Member
Perimeter Frame
3. Under Body:
Unitized body looks like conventional body and frame combination; however, there is the difference
among them. The biggest difference is that there is “re-enforced lower construction” which is called
body Construction.
In a unitized body, every member is connected with the other member; there for all the
components become load-bearing members. All the members rely on strength and hardness with one
another. All the members are made of steel metal and are welded or bolted in such a way that they
form a single unit.
It is the lower portion of a vehicle body. Several components are bolted and are re-enforced due
to heavy gauge metal Thus heavy re-enforcement provides the base or mounting for the rest of the
vehicle body, transmission, and also for suspension.
In under body floor panel, rocker panel and rails is spot-welded.
Rails are manufactured of heavy gauge metals. These provide the base or mounting for drive train
and suspension.
In fig. 2.9 sheet metal panels and rails are shown jointed.

Auto & Diesel 10
In fig 2.13 under body, construction is shown, in which the under body has consisted of two
components when bolted together forms a frame.
Fig 2.10 shown a sub frame along with a unitized body construction sub frame is fitted at the front
of the vehicle. It is consisted of cross members and is extended up to the front floor pan.
4. Frame Member Cross Section and their characteristics:
Box Construction:
U channels are welded together to form a box-type construction. Quiet hard and strong.
I Beam Construction:
Used in convert able top and hard top cars.
In the perimeter integral frame, closed box construction is used. In closed box construction, a
plat is mounted on a u channel in such a manner, that its ends overlap by ½” and then its end is
welded together.
5. Channel:
It is a folded sheet. It is folded on both ends and angles are made. Angle is also called edge.
6. Round Channel:
It is just like a pipe.
7. Types Of Frame Damage:
Side Collision /Damage
Front End or Rear End Damage
Rolling of Vehicle
Sag:
Front or rear collision results in frame sag. In this case, the vehicle frame squeezes in the center e.g it
squeezes in the way a child cradle is rounded and squeezed.
Sway:
The vehicle collides from the sides, the frame turns inside. it is called sway. Sway is caused by
sidewise accident.
The bottom view of the unitized body swayed in front damage will usually extend into the floor area.
Bottom view of frame swayed in front hang gauges at front and rear of passenger area and front cross
member.
Sometimes chains get bend, during front or rear-end collision and get upward or downward bend.
When it collides obliquely, its shape becomes like a diamond.

Auto & Diesel 11
8. Frame Gauges:
Several gauges are available which can identify Twisted, Saged, swayed, or diamond shed.
Then gauges are planted at various points on oil points in frame holes.
These gauges are either inside mounting or outside mounting or mounted in holes. There is a straight
pin in the center of the gauge.
Procedure:
A gauge is planted at the point where misalignment is expected another one at the front end a second
one at the rear. If one straight pin is lower than the other one there is sag at that point.
In the case of a twisted frame, no pin will be in aligned form.
In the case of diamond shape twisted damage, the radial measurements of the frame are done through
trim gauges. it is done to find out the tracking of front and rear wheels and it is done by measuring
wheel bases of vehicles.
9. Checking of Frame Alignment with Plumb bob:
Keeping plumb bob on those places whose from sway damages, sag and diamond twisted damage are
measured .we can calculate the length of these points up to the level of surface and can find the
nature of the damage.
10. Traming:
Diagonal or radial measurements are done through a tram gauge so that the exact straight-line
distance is calculated between two reference points.
11. Repairing Frame Damages:
Check the vehicle frame and cross member construction before look-up.
Six types of construction are found in different frames. Centerline is variable height. Fig (2.16).
12. Channel Shade:
The book has explained in words the construction of various types of channels on page 35 fig 2.11A.
Rail is open from one side
Open-box construction is like a channel but fitted/welded with an angled re-enforcement from each
side.
Beam Construction is like an I beam
Doubled box channels are like two channels, which are welded together and form a unit.
Closed boxes are open box rail, which is further welded with a heavy platform at its open end.
Tubular Rail is like a pipe.
13. Procedure of correction of length, width, and height are as Under:
Inspect the under the structure of vehicle for damage, unevenness

Auto & Diesel 12
Check the underbody dimensions using tram gauges.
If the problem is in rear suspension regarding adjustments, correct the condition. This adjustment can
be done for the replacement of spring, Torsion bars, and suspension bars.
After adjustment road test the vehicle
If the pull is required, adopt a proper procedure for sag or sway.
14. Correction of sag Damage:
Ascertain the direction and extent of the damage.
Examine the parts, if the damaged parts are removed, you can access the attachment points.
Park the vehicle at a safety stand. Use self-centering and tram gauges at the respective frame points.
Calculate the datum line distance from the frame.
Place the frame machine beneath the damaged area. Hook the frame sag area at front and rear using
double hook hold the frame sag area Red hot the pull areas and correct the frame rails with the frame
machine. Sufficient force is required and a bend/damage frame is pulled little more than the visible
limit, when it is then released it will resume its actual limits. Pull every side rail, straighten it up to
its length, and examine with a self-centering gauge. Frame rails are having holes. Hook and pull
through these holes. Then Under Coat/fill
Observe precautions of safety.
15. Correction Of Sway Damage:
Examine the parts, if these are replaced, you can access the damaged area
Park the vehicle at a safety stand
Check the front sway, rear sway, Center sway, through the tram gauge.
Place the frame machine under the damaged area
Hook both sides of the vehicle
Red hot the damaged area with a welding torch, and correct the frame rails with a frame machine
Stay away from the area where pulling is done.
Get measurements of the frame. Check that all points are in a single line.
All gauges bars should be at the datum line and should be parallel to one another
Check frame as per manual specification
Under Coat with required parts.
16. Correcting Twist damage:
Examine the parts, if these are replaced, you can access the attachment points.
Park the vehicle at a safety stand
Ascertain the damage through self-centering tram gauges
Place the frame machine beneath the damaged area.
Anchor the vehicle’s front. Support the frame rail center. Downward pull the rear of the frame rail in
a suitable direction. Another method is that anchor the vehicle using chains and blocks, apply jacks,
and pull upward the vehicle.

Auto & Diesel 13
SHRINKING METAL WITH HEAT
Shrinking of metals is done, when the car body colloids and results in an elongated shape. The said
elongated parts are not fit for use in the auto body. Thus the same elongation is removed either by
cold treatment of the auto panel or by treating the panels with the heat of the oxyacetylene flame.
Thus the following precautions are adopted.
Safety Precautions:
1. Do not pull the chain through sharp corners.
2. Do not heat chain with a welding torch.
3. Do not fasten with bolts.
4. Cover the chain with a tarpaulin.
5. Ensure the safety of chain anchoring points in the system.
6. Anchoring of rim, nut, and attachments point should be in one direction and straight line.
7. Use double grip hooks for hook-less chains or use double grip hooks for removing slackness
of chain.
8. Use a strip of the angle where the chain is wound around from an auto body section.
Shrinking Metal with Heat
Equipment required.
1. Oxygen acetylene flame.
2. Bumping hammer with the dolly.
3. Shrinking dolly (Flat or low crown dolly)
4. Water and Foam.
Procedure:
Following procedure is adopted for heat treatment of auto body panels.
1. Wear goggles.
2. Select a discarded panel or a stretched panel or hammer the panel for identification.
3. Use a bumping hammer and crowned dolly to straighten the damaged area.
4. Grind off paint from the working area. Remove red oxide coat.
5. Over stretched area is the originally distorted area. It should be identified and examined
carefully for treatment.
6. Switch on the flame and adjust the flame appropriately.
7. Heat 1/2” area on the highest point up to read hot. Do not overheat otherwise metal will
become red-hot and starts melting and flowing. Thus resultantly the panel will be become out of
order.
8. Place shrinking dolly beneath the spot and hammer the hand spot and then successive
hammering in continued till the panel becomes appropriate in size.
Cautions
• Use Gloves for holding the dolly.
• Quench the hot spots after it becomes green-black.
• Repeat the same for other spots.
Note
If the filling of metals is required for lower and shrunken areas, then it is done carefully.
• Always repair major damage area before shrinking, low spots left in panels creates problems.

Auto & Diesel 14
• 1/8’’ dia spot is heated for the lesser area, however, the heated spot should not be more than
1’’.
• Do not shrink the metal rapidly.
• Avoid over shrining.
• It is difficult to correct damage after over shrinking.
• Do not quench the red hot heated spot.
• Do not overwork the heated spot
Shrinking hammers have cross groves on their face used for the small stretched area without
heating. A shrinking hammer is used for slightly stretched metal with dollys. Without heating several
areas are shrunk with several tools e.g.
1. Dolly block with proper contours.
2. Shrinking hammer with the cross grooved face.
3. Body panel with the minor stretched area.
Procedure
• Remove under coating from the repaired area.
• Place suitable contour dolly.
• Use a cross grooved shrinking hammer and apply the appropriate number of strokes. Do not
overwork
• If shrinking hammer over works or contracts more than standard flat face hammer is used.
Metal finishing
Following steps are necessary:-
o Paint removing and under coating.
o Smooth surface before filing.
o Metal filing.
o Metal finishing.
Cross filing or Check filing:-
It is checked whether the metal is leveled from over ride. Filing is done at 45 degrees.
Line filing;-
It is done in a specific direction. Fig 7.3 shows the procedure for feeling surface irregularities
and also file cut patterns and damage areas at low spots and little large spots.
Shrinking Sheet Metal;-
Sheet metal stretches due to accidents and enlarge and occupies more space, it needs to be
shrunk to occupy its original space, distortion in sheets metal when it is bent.
Shrinking Method;-
1. Use of special shrinking hammer.
2. To cut slits in bulged areas.
3. By use of heat.
Cutting slits;-
Slits are cut in sheet metal surface sits edges are overlapped, then these overlapped surface
are welded among themselves .then these slits and welded slits are counter shrieked and then grinded
or filed and then smoothed. Good, a Metal shrinking method is heat treatment. Heat treatment of auto

Auto & Diesel 15
body panels results in losing the springing effect of sheet metals. If required minor parts are heated
and sheet metal should not be heated for a larger time. Too much heating results in buckle formation.
Metal Finishing
1. Simplified metal finishing
Study the impact of the accident carefully and do not start hammering bulge area, rather
find the area initially damaged and then finally damaged.
2. Start the job
Analyze the job. Remove the last ridge earlier and start work in reverse order. The metal
only flexed will spring back its, original position.
3. Point of initial impact Is the one, where the point was being removed in-depth as it is the
point where the damage gets started.
4. Simple Dent A direct hit of a vehicle over another vehicle panel. It shows the dent
and ridge points. Point A is always from B, but A is removed first, then E, Then C, and then
D.
Procedure:-
1. Remove dust, under coating.
2. Using dolly at spot A, hammer the spot.
3. Do the same action C-D and E points.
4. Now feel with palm.
5. Now file with workers file.
6. Down areas will be again hammer with the use of a dolly.
7. Use a pick hammer for dimple removal.
8. Use a pick hammer from one side and another hammer from the opposite side.
9. A most complicated form of dents and wrinkles and dents and wrinkles series is formed.
Simple damage, where metal has pushed increased however no Chanel formed. It has pushed
inward within the elastic limit and will come back to its original shape after releasing the stress.
Metal has bent up to a sharp angle it is now a complete V channel if ends are caught and straightened
it will form two other bent.
Using Pull Rod:-
The exterior trim of a door or digging in which metal braces and other structure frames are
fitted causes difficulties in the use of hammers and dolly. Then pull rods are used. 9/16’’ holes are
done in the deeper part of the craze at a distance of 1/4’’’. The hooked end of pull rods is used
endorsed in those holes and pull rods are pulled. 2X pull rod at one end and 2X on the other end.
Holes are filled with solder later on.
Removing paint and under coat:-
Disk grinder of 7’’ and 9’’ are used for removing paint and under coating
Apply grinder at a suitable angle neither large nor flat
Safety of Grinder:-
1. Keep away from clothes.
2. Transparent goggles
3. Remain in a balanced position
4. Ensure Earth of grinder

Auto & Diesel 16
5. Do not use in moister
6. Do wrap around the electric wire from the grinder
7. Always-on/off the grinder near the job.
8. Ensure socket of grinder is in off position before plugging in
9. Do not grind near the car molding and the bumper
10. Do not use broken disk
11. Ensure grinder plug is removed from socket during disk change
Hammering bumping;-
A;- Direct Hammering on the dolly
B;- Indirect Hammering off the dolly
1.Power Tools
a. Grinders
b. Cone Mandrels
c. Molded Disk Pads
d. Wire cup Brushes
e. Sanders
f. Pneumatic Orbital Sanders
g. Feather Edging
h. Orbital Disk Sanders
i. Polishers
j. Portable Power Drill
k. Pneumatic Impact Tools Pneumatic Wrenches
l. Riveters
m. Metal Shears
n. Bench Grinders
o. Heat Guns
2. Power Tools
Tools operated by electric or hydraulic force.
3. Grinder
A Heavy-duty Rotary machine through which paint can be removed welded parts can be shafted
sheets metals can be cut. It is called a disk grinder. If operated by air then it would be called a
pneumatic Disk grinder. Disk size is 7’’ to 9’’ speed 4000 rpm for 9’’ and 5500 for 7’’
If the grinder speed is more it will overheat too much heat then it may break into pieces.
The firm grip of grinder assy. Better hand control, appropriate pressure and working angle of 5
degrees, and appropriate engagement area are imp factors for better efficiency.
4. Cone Mandrill:-
Fig 5.5
5. Molded Disk Pads:-
Fig 5.5 A
These are used where narrow circular areas are grinded. Deep gauges deep threads are not formed.
the adhesive disk is used for adhesion

Auto & Diesel 17
6. Wire Cup Brush:-
Fig 5.6
Remove paint & Corrosion
7. Care & maintenance:-
1. Avoid application of body load.
2. Little extra load on the pneumatic grinder.
3. Strictly avoid placing of running grinder on floors.
4. Use of appropriate lubricant to the pneumatic grinder.
5. Avoid humid air in the air line.
6. Appropriate wire size in an electric grinder.
8.Safety:-
a) Transparent goggles.
b) Respirators
c) Start & off procedure.
d) Removal or attachment of pads be strictly avoided when the electric line is on.
e) No operation of grinder near inflammable
f) Wire in good condition.
g) No operation of electric grinder on the wet surface.
h) Grinder in a good balance position.
i) Earthling of the grinder.
j) Calm operation.
k) Grip firmly.
9.Sanders:-
Finish work, pneumatic safer
10.Pneumatic Orbital Sander:-
Operated at 70 psi firmly griped, used for too &fro motion, and removed of feather edging
A pneumatic speed sander is also called a power file.
11. Orbital Disk Sander:-
Runs off-centered or acentric more irregularly and cleans the paint. Rpm can be controlled through a
manipulating valve.
12. Polisher-
Used for removal of lacquer paint. Its Rpm is less, weight is less, moved to and fro used for feather
edging, looks like Disk Grinder.
13.Portable Power Drill:-fig 5.16
Bit size 1/16’’ to ½’’ stored in drills index. Used for grinding cleaning od uneven surfaces.
14. Pneumatic impact tool:-
Fig 5.18 pg. 103
Sheets Metal cutter, punches, chisels, special-purpose tools
15. Pneumatic Wrenches:-
Pg. 105 fig 5.19
Quick loosening and tightening of nuts, operated with compressed air.

Auto & Diesel 18
16. Riveters:-
Used for adjoining more sheets through rivets like grills, exterior trims fig 5.21
17.Metal Shears:-
Electric or pneumatic tools are used for cutting sheet metals.
18. Bench Grinder:-
Used for sharpening chisels, screw drivers, drill bits, etc.
19.Heat Guns:-
Glass installations, vinyl top work, up hole story work, removing rear view mirrors, for heating
adhesives up to 350 F
Surface preparation
Adhesives like sand paper grinding disks are used to remove paint corrosion and wax from
the auto body. The following materials are used in grinding dishes and sand paper.
a. Emery
b. Flient
c. Garnet
d. Silicon carbide
e. Aluminum oxide
Garnet emery and flint are selectively soft materials and sometimes used in auto body wheels,
but used in home and household repair. silicon carbide and aluminum oxide are tough and can be
used in auto body shops. Adhesives are either pasted attached oused on cloth as on paper.
2. Types of coated adhesives
a) Open coated dish Here granules are pasted at large spaces i.e. thinly
b) Closed coated dish Here granules are pasted thickly (fig 15.1 pg. 459)
3. Coarseness and fineness of adhesive dish
a. There are three ways to determine the coarseness of adhesives
b. Symbol
c. Mack number or mash number
d. Combining symbol and mash number
e.g. 3/0
Mash number 240-300-400
For fine sanding, fine mash number # 320 # 400 for coarse sanding, coarse mash number #60 #80#40
coarse papers are called production adhesives.
Higher the mash number fine will be the level.
4. Use of grit
Pg. no 460 Little dispute regarding the use of grit sizes.
5. Use of sanders
Pg. no 461 Shows the use of sanders for various types of sand removers.
6. Sanding operations
Before painting surface is thoroughly cleaned. Corrosion and metal arts are removed, so that
no unwanted dust, etc trap b/w the surface and coat.
7. Types of sanding

Auto & Diesel 19
a. Hand sanding Uneven cuts of hand sanders results in appearance. it is due to too much space
b/w the fingers. It can also be solved by keeping some bleek behind the sand paper. For concave and
convex surfaces use a flexible pad or hase as per the curvature of contour. Flexible has (rubber pipe)
can also be used as sanding paper patching. During hand sanding, there should be an alignment of
the hand. Do not apply more pressure, adhesive surfaces will be peeled off. A small scratch should
not be scratched more otherwise a deep scratch forms it also results in imperfection in the topcoat.
b. Power sandingDo not detect concentric sander, these will leave concentric signs, select flat
jittering sanders or orbital disk sanders. These sanders are off-centered and leave no scars. Orbital
disk sanders are kept flat against the surface and are moved continuously and are not stopped or
concentrated at a significant point.
c. Use of grinder over the surface
Grinder should be on the surface of the auto body as flat as possible and not at the angle. Use of old
disk as less diameter disk. Use of goggles and respirators.
8. Sanding methods
A. Dry sanding
The surface of the adhesive disk lift during powdery dust, however, (zinc stearate) abrasive gives
good results and gives no dogging.
B. Wet sanding
Waterproof materials are used faster cutting is possible, as water cleans the surface. A huge water
container along with a sponge is used for pouring over the surface. Electric sanders are not used for
wet sanding air pores sanders are used. Reflect light is used for surface condition knowing and
assuming.
C. Feather edgingIt means tapering of body filler surface edges or corners. There should be no
grain in the final tap. It means you have to wash on a large area around the crack or around the actual
paint line. If a power sander is selected, use orbital sanders but do not use disk sanders or grinders.
After feather edging fills the depressions with putty and use primer.
D. Back sanding Sanding extra are then the one being feather edged.
E. Cleaning
a. Use good detergent for cleaning
b. Through chemical cleaning
c. Use hosiery cloth for dipping into chemicals so that enough chemicals are used.
d. Do not use surface primer on tires
9. Stripper
Grinding or use of chemicals over the old ferrous surface only, but not on fiber glass or
plastic surface.
10. Stripping a painted surface:
a. Wash the vel with detergent and water.
b. Remove moldings, trim, etc
c. Clean the area with grease and wax removers.
d. Mash the unresolved moldings
e. Apply steel brush on 1 ft 2 area.
f. Remove the softened paint from the area.
g. Wash with water to remove let spots.

Auto & Diesel 20
h. Sanding the surface oscillating sander. Hand sanding around moldings.
i. Lacquers remover is used for the removal of paint from the spot or panel.
j. Cautions for removing lacquer
11. Safety precautions
a. Dress, goggles
b. Water
c. Aerated place
d. Respirators
e. Ear Plugs
12. Mashing or Tapping
It is an art to increase the speed of wash.
13.Mashing materials
Masking tape is available in 1/8 in, ¼ in, ½ in, ¾ in, 1 in, 1/1/2 in 2 in Width
14. Masking procedure
Correct application of tap over-molding over the upper ridge and the lower ridge.
a. Killing To pull the tap b/w the thumb and finger. The procedure is used to reduce the sticking
quality of the tap.
b. Glass areas mashing Removal of paint with layer blade. Use of touch-up brushes. For the
application of tapping mashing paper on a straight surface
c. Application of taping paper on angular area Paper is folded as per angles of angular
area. There will be under a spray due to in correct painting. Tapping mashing irregular surfaces.
Tapping mashing on curved surfaces. Correct plated surface. Antenna Tapping A single. Covering
large body opening from dust. Door frame mashing. Removing over spray from pashes. Mashing the
tire. Wheel masking. Removal of mashing materials. Remove the unwanted paints thinner/remover
immediately.
1. Inaccessible under side Repair
Clean the area.
Repair the rough area through a hack saw.
Grind the area for paint removing up to 3’’ sides.
Make a V groove.
Make the area surrounding the area.
Cut an appropriate slice of both. It should overlap the damaged area up to 2’’.
Mix epoxy resin and dip the cut fiber glass in the epoxy resin and apply on the damaged area,
getting the requisite shape.
To smooth the grinded area use mixed epoxy resin and apply.
Sand grinded the area to get the desired shape. use no 400 grit sand paper for further
smoothness.
Repeat steps 4 to 8 if desired again. Note if deficiency is observed use leaner.
2. Major fiber glass Repair

Auto & Diesel 21
Fractured Panels.
Fractured damage comes due to sharp edges of a small hole is fractured, it should be changed
to avoid benching.
Procedure:
1. Following necessary precautions make sharp edges.
2. Sand up or grind up paint up to 3’’ around the fractured area.
3. Working from the outside of the panel make edges of the fractured area at 45-degree bevel
shaped so that a V shape is formed after the joint is filled.
4. Cut member of fiber glass strips. These should cover 2’’ both sides of the fractured area.
5. Cut 1 piece each of card board and plastic film such that it can overlap the repair area up to
2’’.
6. Keep ‘card board’ on the outer side of the repair area cut 7/64’’ in the card board.
7. Mix Epoxy resin and hardness for repair.
8. Place Plastic on the card board.
9. Dip fiber glass in epoxy resin mixture in the under side of repair area though brush, Place
card board plastic film and fiber glass on the repair area plastic film and fiber glass on the repair area
such that fiber glass should face the damage.
10. Apply epoxy resin mixture in the underside of the repair area through the brush.
11. Remove screws card board plastic film of loose wire of fiber glass is visible remove with no
36-grit disk.
12. Fill the holes like the procedure for ‘cracked panel’,
13. Refinishing is done in the manner of scratches on painted surfaces.
Worker Hand tools
Hammer
Various types of the hammer are used in auto body works, these are as below.
Roughing hammer
Used for rough work, where heavy hammering is needed. It is seldom used on cars,
mostly used on trucks and buses.
Bumping and finishing hammer
Finishing hammer has several names and designs e.g light dinging hammer, offset
dinging hammer, pick hammer, bumping hammer, and finishing hammer. They’ve little
difference in design but are different in size and weight. The bumping hammer is heavy.
A finishing hammer is used for finish work. After finishing metal should look in its
original shape. A finishing hammer is used with a metal file.

Auto & Diesel 22
Combination or pick hammer
When one side is circular or square, and the other face is the cone. It has a different length
of cone sides. It is used where little spot requires hammering. Bumping hammers and
dolly are used for the straightening of sheet metal.
Magnetic trim hammer
It is used for upholstery work. It is used for seat covers and different attachment points.
Mallet
Its head is manufactured of wood, plastic, brass, etc. it is used where spotless work of hammering is
required.
Shrinking hammer
Its face is cross grooved and it is used on high crown areas of panels or where the less stretched area
is hammered.
Dolly blocks
These are of various types, these are used for removing dents with a hammer.
1. Heel dolly It has about 2 ½ pound weight. It is round on one side and flat on the other.
2. Toe dolly It is also called a low crown dolly. It is long, a little narrow, and thick. It is
used in narrow places. Its face is long. It is used for fenders and rear quarter panels flange repair.
3. Roughing dolly It is called a universal dolly. It is functioning to rough out the damaged
area. It is easy to handle due to its shape. It is used for shrinking, low spot repair, and roughing out
operations.
4. Wedge dolly These are used on the low crown and narrow places
Spoons:
These are multi-purpose tools. These are used for the repair of areas where human hands
can’t access them.
A dent in a door or deck lid can be removed by putting a spoon from back
Spoons are placed on damaged areas or ridges and hammered.
Sometimes spoon is used for very minor dents for slapping only.
Pick tools
These are used for the pickup of low areas, these are used for very small dents, repairs of
doors, deckled, etc. These are manufactured of hardened steel.
1. Short curved pick Its blade is 23-inch long. It is having a pointed tool. It repairs the
internal side of a panel. Its handle is pulled and thus dent is pried.
2. Long curved pick Its access is quite long and can access for longer pick up of low areas.
3. Chisel bit pick It has a chisel at its end.
4. Deep throated pick It can access internally up to the center of the outer door panel.
5. Short pick tools Short pick tools can erase only low spots, especially outer edges.

Auto & Diesel 23
6. Curved finishing punch Its tip is a little round. This tool can reach up to unapproachable
places and can be applied for raising small low spots.
7. Hooked finishing punch Curve starts at a longer range from the tip. It is used where the
dent is quite away and is not reachable by the common punches.
8. Piercing punch It can be used for making holes in the metal sheet.
Files and file holders
Files are classified for the finish of materials. They are general purpose and specific to some
task.
1. Adjustable file holders Various blades can be used for various contours. Low and high
spots can be repaired.
2. Long blocking file Sand paper can be used with file. It is 16-inch-long and 2 ¾ inches
wide.
3. Short blocking file Its function is to sand the minor area. A 38-No. standard abrasive
emery paper can be used.
4. Special contour file It is used for concave surface finishing. Here 2 types are shown, but
many more are available in the market. Contour files are 11-inch long.
5. Bumping or slapping file It is used for various types of ridges and buckles. Blow up to an
extended area can also be imparted with it, thereby it never increases the cracks.
Solder and solder paddle
1. Body solder It is an alloy of tin and lead. It is known with 30-70 or 20-80. 20 is for tin and
80 is for lead. This alloy is used for filling; lead is not used alone as it sticks with metal. Tin has a
low melting point and has sticking quality, but if it is used alone its filling quality is poor. A solder
having more quantity of tin is expensive
20-80 solder is used for filling
30-70 solder is used for tinning
2. Solder paddle It is a tool. It is used for smoothening the corners around the contours. Its
basic aim is to stretch the solder. Solder is required in various styles. Its shape is either flat, concave,
or convex. Soldering paddles are manufactured of maple a special wood. This paddle should be
lubricated, so that the wood is neither burnt nor stick with solder, engine oil, fats, and soldering
paddle manufactured of hard rubber is called squeegex.
Pliers
It is a combination of 6-inch pliers. Its jaws can be opened up to large extent and it can hold
thick items.
1. Diagonal cutting pliers It is used for cutting wires and can be used for removal of
cotter pins
2. Needle nose plier It is used for the extraction of smaller parts from narrow holes. It is
used for holding small parts and then polishing.
3. Channel-lock plier Here the opening of the plier can be adjusted in various shapes.
4. Vise grip or locking plier When it grips and locks a small part, its grip is quite strong.
Note: pliers should not be used for the opening and closing of nuts and bolts.

Auto & Diesel 24
5. Panel pliers It has 2 types
a. vise grip welding clip two parts to be welded can be held approx. with alignment
b. C-clamp these clamps are used where adjoining parts are too thick e.g. rocker panel,
rear quarter panel
Pry bar
It is a round bar of pipe used for prying. It can bend fender brackets.
Pop rivet
2 panels are drilled and then rivets are endorsed in these holes.
Metal shears/snipes
It has three types
1.Aviation or multiple levers
2. Duckbill or circular
3 Standard or straight type
The above three are called tin snips, which are used for cutting sheet metal. Hard metals like
wires are not cut through it, otherwise, its blade becomes blunt.
Screw driver
Standard type has flat blades
Philips type has 4* ridges
• Offset screw driver
Where limited space is available, then we use an offset screw driver.
Screw drivers are used for opening and closing of screws and should not be used as pry bars.
Wrenches/sockets
These are used for the opening and closing of nuts and bolts. The smaller size is 3/8 inch, it
can be up to 1 inch or more than 1 inch. The wrench tip is 15 degrees offset from the handle.
Pull-on the wrench rather than push.
• Box end wrenches
It is either a double hexagon or single hexagon i.e 12 or 6 points. These teeth’s are engaged with bolt
heads, the copper tube should not be engaged
• Socket type wrenches
It covers one end of the nut at one side, the other side has an opening called drive, the handle driving
the socket is fitted in this drive. The socket set has different handles.
• Combination open and box wrench
One end is open and the other is a box wrench. Open-end is used for opening/closing of nut/bolt,
loosening of nut can be carried with box end, but not it is turning.
Clips
These are called molding clips. These clips can be fitted into holes or can be bolted. These
can be used on the auto body for holding.

Auto & Diesel 25
Finishing Material
The final finishing on the body of a vehicle is called paint.
It has three parts.
a. binder is that part that sticks with the body to be painted.
b. Pigment gives color to the point.
c. solvent or reducer.it is used to mix the binder and pigment. These two components are dissolved
in the reducer and such a thin solution is formed which can pass through a spray gun. Solvent
reducer evaporates and binder and pigment form body paint.
2. Thinner/Reducer. (A compound used for thinning the paint solution).
3. Primer surf acer is used as the first coat before painting. It is also called red oxide paint. it is used
for filling dents on rounded portions. it can reach only to the grinded surface.
4. Glazing putty
It is the type of primer surf acer. it is without reducer and adopts the form of parts.
Glazing putty is used on the surface through the rubber. Dents that can’t be filled with primer surf
acer are filled with putty with primer surf acer are filled with putty generally called poteen.
5. Types of Paint
A. Lacquers b. Enamel c. Acrylic
if a lacquer paint gets dry and if thinner is applied on its surface it can be removed from the surface.
It gets dry in 15 to 20. it gives a dull finish. A polishing compound is used for shine. it is used for the
reason that it gets dried very soon.
6. Acrylic Enamel
It gives a good shine on the surface.it dries in 6 to 8 hours. It is usually dried in the oven in a paint
oven, hardness can be achieved in 15 to 20 mint of the painted surface is to be dried in an oven the
fast-drying reducer be used thus wrinkling can be avoided
7. Acrylic enamel dries in two stages
a. on evaporation of the solvent.
b. on oxidation of binder
8. Urethan Enamel.
It provides the following
a. it gives a finish like a hard tile.
b. high glass.
c. Good flow over.
d. Good looking
e. Good sticking.
f. Good

Auto & Diesel 26
9. Synthetic Enamel.
It dries with evaporation and oxidation of it is dried it never dissolves in the solvent.
It is used on commercial vehicles.
10. Acrylic paint
It is different from lacquer and enamel it dries like lacquer. it is permanent. Its color never fades.
It is composed of synthetic polymers. These are used for nut changing colors and permanent special
solvents are used as reducers.
11. Polishing Compound
It is fine abrasive it is mixed in oil or another solvent. It is used for dents filling. glazing finish must
use clean and soft cloth for application.
12. Enamel Refinishing.
It is cheaper is priceless preparation is required its viscosity is higher and its look better.
It requires more time for drying it lequriesacrates place.
Due to higher viscosity reduction of spray gun nozzle is necessary.
It is reduced from 25% to 33% spots are not painted
Enamel material does not penetrate in old.
If a single panel is to be painted avoid paint an adjacent area.
13. Acrylic Enamel on the based metal surface
1. use steps 1 to 13 for alkaloid enamel.
2. Reduce acrylic enamel by 50%.
3. 50% enamel and 50 % reducer.
4. 65 psi pressure.
5. check the spray pattern.
6. Apply full weight layer.
7. wait for 15 to 320 minutes.
8. Apply 2 coats.
9. complete flash time for drying.
10. 3ed coat for final preparation.
11. Mashing on wheels.
Safety Precautions
a. Do not pull the chain through sharp corners.
b. Do not heat chain with a welding torch.
c. Do not fasten with bolts.
d. Cover the chain with a tarpaulin.
e. Ensure the safety of chain anchoring points in the system.
f. Anchor rim nut and attachments point should be in one direction and straight line.

Auto & Diesel 27
g. Use double grip hooks for hook-less chain or use double grip hook for removing slackness of
chain.
h. Use a strip of angle crone where the chain is wound around from section.
Equipment required.
a. Oxy-acetylene flame.
b. Bumping hammer with the dolly.
c. Shrinking dolly (Flat or rear low crown dolly)
d. Water and Foam.
Procedure
a. Wear goggles.
b. Select a discarded panel or a stretched panel or hammer the panel for identification.
c. Use a bumping hammer and crowned dolly to straighten the damaged area.
d. Grind off paint from the working area. Remove red oxide coat.
e. Over stretched area is the originally distorted area.
f. Switch on the flame and adjust on natural flame.
g. Heat 1/2” area on the highest point up to read hot. Do not overheat otherwise metal will
become red hot and melt.
h. Place shrinking dolly beneath the spot and hammer the hand spot and then successive
hammering on rides.

Auto & Diesel 28
1. Equipment’s Required
• Oxy-acetylene flame.
• Bumping hammer with the dolly.
• Shrinking dolly (flat or rear low crown dolly).
• Water and foam.
Procedure
• Wear goggles.
• Select the discarded panel or a stretched panel.
• Use bumping hammer and crown dolly to straighten the damaged area.
• Grind off paint from the working area.
• Over stretched area is the originally distorted area.
• Switch on the flame and adjust it.
• Heat ½ inch area on the highest point up to red hot, do not over heat otherwise metal will
melt.
• Place shrinking dolly beneath the spot and hammer the spot and then successive hammering
on sides.
2. Caution
• Use gloves to hold dolly.
• Quench the spot after it becomes greenish-black.
• Repeat the same for other spots.
Note if the filling is required lower the shrinking area for filling.
• Always repair major damaged areas before shrinking. Low spots left in panel creates problem
in proper shrinking.
• 1/8-inch diameter spot is heated for the lesser area; however, the heated spot should not be
more than 1 inch.
• Do not shrink the metal rapidly.
• Avoid over shrinking.
• It is difficult to correct damage after over shrinking.
• Don’t quench the red hot heated spot.
• Don’t overwork the heated spot.
3. Shrinking metal without Heat
A shrinking hammer having fewer groves on its face is used for small stretched areas without
heating. A shrinking hammer is used for slightly stretched metals with dollies. Without heating
several areas are shrunk with several tools.
For example
• Dolly block with proper contour.
• Shrinking hammer with the cross grooved face.

Auto & Diesel 29
• Body panel with the minor stretched area.
Procedure
• remove under coating from the repaired area with the help of flame.
• place suitable contour dolly.
• use a cross grooved shrinking hammer and apply only the appropriate number of strokes.
• don’t overwork/over hammering.
• if shrinking hammer over works or contracts more, then a standard flat face hammer is used.
Sheet metal stretches due to accidents and enlarges and occupies more space, it used to be
shrunken to occupy its original space.
The main three methods of shrinking are as follows,
1. to cut slits in bulges area.
2. Use of special shrinking hammer.
3. By use of heat.
4. Cutting slits
Slits are cut in sheet metal surface, slit edges are over lapped, then their overlapped surface is
welded among themselves. Then these welded slits are grinded or filled and then made smooth.
5. By use of heat
Heat treatment of auto body panels results in losing the springing effect of sheet metals. If
required minor parts should be heated and sheet metal should not be heated for a larger time. Too
much heating results in buckle formation.
6. Metal finishing
Observe the impact of the accident and do not start hammering the bulge area, rather find the
area initially damaged and then finally damaged area.
7. Point of the initial impact
It is the area where the paint was being removed in-depth as it is in the point from where the
damage gets started.
Procedure
• Remove dust or under coating.
• Use dolly at spots and hammer them.
• Now feel the surface level with your palm.
• Now file the surface with help of files.
• Down areas will again have hammered along with the help of dolly.
• Use pick hammer for dimple removal.
• Use pick hammer from one side and another hammer from the opposite side.

Auto & Diesel 30
8. Using pull rods
The exterior trim of a door or trunk lid in which metal braces and other structural frames are
fitted causes difficulty in the use of hammer and dolly, in that case, pull rods are used.
9. Removing paint and undercoat
Disk grinders of 7 and 9-inch disks are used for removing paint and undercoating. Apply
grinder at a suitable angle neither large nor flat.
10. Safety while using grinders
• Keep away from clothes.
• Transparent goggles.
• Remain in a balanced position.
• Ensure earth of grinder.
• Don’t use in moistures.
• Don’t wrap the electric wire around the grinder.
• Always-on/off the grinder near the job.
• Ensure the socket of the grinder is in an off position before plugging in.
• Don’t grind near the car moldings or bumper.
• Don’t use broken disks.
11. Hammering / Bumping
1. Direct hammering on the dolly
2. Indirect hammering off the dolly
12. Direct hammering
Metal is between the hammer and dolly and the hammer directly hit the circular or radial
potion. Direct hammering is done for straightening the metal or for stretching the metal. Pushing and
pulling are also done which depends on the hammer hitting intensity.
13. Indirect hammering
It is done where strain is being removed, here strain means that twist which restricts the metal
to resume its original shape. Dolly is placed beneath the lower portion, whereas raised portion is
being hit with a hammer thus the raised portion goes down, and the down portion goes up.
14. Pick hammer used for picking
If a low spot or small dent is left after filing it is removed with a pick hammer.
Pick tools are lever-type tools and use for pushing out small dents where normal tools can’t work.
They are designed in pointed shapes. These can be prying metals behind the practice and reinforcing
bars. They are used like spoons. The pointed portion of the tool is placed on the raised portion and
thus raised portion is pressed.

Auto & Diesel 31
Plastic body components
Types of plastic
a) Thermoplastic
It softens on heating and hardens on cooling e.g poly ethylene, poly propylene.
b) Thermoset (thermo setting plastics).
It degrades or decomposes on heating.
It is not repairable through heat.
It can be fused with adhesive.
Thermo plastics
Code Product
A.B.S Acriylo nitrite butadiene styrene ABS/PRC A.B.C vinyl
EPDM Ethylene propylene diene monometer
PA Nylon
P.C LEXAN
P.E POLY ETHYLENE
P.P PROPYLENE
P.P.O POLYPROPYLENE OXIDE
P.P.O NORYL
PVC POLYVINYLE CHLORIDE
TPR THERMO PLASTIC RUBBER
TOUR THERMO PLASTIC POLYURETHANE
Thermosets
Code product
Pur thermoset polyurethane
(up) polyester (fiber glass)
2. UNSATURATED POLYESTER
Any group of thermo setting resins produced by dissolving a low molecular with unsaturated.
Polythene Test
It enlarges on burning pieces will fall on burning
Cohesion test
Thermo setting polyurethane
Thermo plastic poly urethane
Ppo is a strong engineering plastic with outstanding mechanical absorption and low thermal
expansion
3. Repairing Minor Tears or Cracks in Thermoplastic
1. Chain both side of the damaged area with a high quantity of silicon wax
2. Prepare adhesive as per instruction of MFR
3. Align the sides of cracks and apply the adhesive held up to a minute
4. Let it cure up to 3-4 hrs
5. Wet sand AND then paint

Auto & Diesel 32
4. Repairing a thermoset polyurethane component when the material has been torn away
1. Clean the damaged area with the silicon wax remover
2. Clean carefully use small power grinder, medium grid, adhesive –desk
3. Remove finish up to 3+3=6 and on both side try not to remove plastic material
4. Use oxyacetylene flame or (medium propane) for not in common use heating such that the
color of polyurethane becomes light brown
Use of backing tap mat for holding filler materials of filler.
Analyses of Metal Damage
Construction of auto body is done in a manner to absorb max collision forces to reduce loss
to the passenger compartment.
2. BODY OVER FRAME
Passenger compartments are attached with the structural frame through cosmetic panels
however drive train and mechanical accessories are supported with the frame. e.g. trucks body
3. UNIBODY
Metallic sheets are welded together to form a structural frame
4. MONOCOQUE
Light weight separate chassis manufacture of pressed sheet steel panels, forms a platform
only.
5. Properties of Sheet Metals.
Genially soft metal sheets are used to achieve safety and style. Some sheets are very thin and
are not repairable and some sheets hardened and can be repaired after a collision.
6. Physical Structure of steel Metals
Steel metals have a granular structure.
7. Effect of Impact Forces
a. Elastic Deformation Steel metals spring back to their original shape after deformation.
b. Plastic Deformation Steel metals spring back but can’t attain the original shape thus a new
granular structure is formed.
8. Load & Deformation Diagram
a. Elastic Limit Deformation is controllable; here stress is elastic in nature.
b. Yield Point The minimum force per unit area that causes the material to began or
to lead thousands a permanent change in shape.

Auto & Diesel 33
c. Tensile Strength. It is the max force per unit area that causes a complete fracture in the
material.
d. Breaking Point It is a point where if the load is removed elongation will spring back tp
but permanent stress will remain maintained.

Auto & Diesel 34
Glass & Doors
Vehicles' glasses should have clear visibility and safety.
2, Types of glass.
1. Dominated
2. Tempered
a. laminated glass Consists of 2x layers is 1/8 thick. Transparent glass sheet between the
two layers. Laminated glass is used for wind shield
b. Tempered glass Can be used for rear and side windows only Weight build Sanders:
edges of glass can be smooth and resized and restructuring m/ c
3. Installation
a. Size of the opening in which glass is installed should be 100,% correct.
b. Check, the opening, especially for used adhesives, sealing’s.
c. Marking tap is used to cover and protect the outer edges of the glass for checking in the
opening.
d. 1/4 from inside, outside tap is used fig 10.6/pg.330.
e. Remove masking tape before installation of glass in the opening.
f. Use of rubber checking blocks on glass fig 10.7 pg. 330 over the flange.
g. Assistance of fellow workers in placing them.
h. No force on glass several attempts original measurements.
i. Once the final adjustment is expected, the rubber channel is cleaned.
j. Rubber sealer of uniform bed is applied in the rubber channel in the glass cavity.
k. Place the windshield, such that the inner side is placed up for safety over the padded surface.
l. Apply a strong wire around the flange cavity such heavy that its two opposite ends come in
the center.
m. IX- hand towards inner side
n. IX hand towards the outer side.
o. When glass is placed properly, apply force on the card.
p. Inspect the glass on all four sides for accuracy.
q. Cleaning of sealers with relevant.
r. Application of sealers with applicators.
Type of glass
• Laminated
• Tempered
2. Laminated safety glass
It has consisted of two layers. Each layer is 1/8 inch thick. Transparent plastic is stacked in
between the two layers of glass. Its purpose is to stop the glass from splinters (very small parts), it
breaks during collision/accidents. Heat and pressure are used for joining glass plastic. The front wind
shield is made of laminated glass, rear wind shield, window glasses are also made out of it.

Auto & Diesel 35
3. Tempered glass
It is a single layer of ¼ inch thick glass. It is quite hard as compared to laminated glass. When
it breaks, it breaks into thousand granules. Tempered glass is used for rear and side windows but it is
not used for a front wind screen. Tempered glasses are oval in flat and in a circular shape. Always
replace the glass of the same specifications after it is being broken. Weight-built sanders are found in
glass shops for reducing sizes of glasses.
4. Wind shield and rear window installation
There are two methods in use,
• A glass section is placed in a rubber channel and then fitted in a pinch weld flange.
• In new methods a synthetic self-curing rubber adhesive coaching compound is used for
sticking glass with a metal pinch weld flange.
5. Removing of glass in rubber channel
• Protective covering on seats, hoods, fenders, trunk lid, and other sections
• Examine the glass to be removed
• Remove rear view mirror, windshield wiper arm, assemblies, sun wise, internal trims
• Remove external moldings, which has gripped the glass
• Sometimes glass is found inverted in rubber moldings and thus glass assembly is first
removed from the vehicle along with molding
• In some vehicle a locking cord is used in channels, it should be found and removed
• Consult a repair manual for removing of locking cord and rubber moldings
• Untighten the lip of the rubber channel from the pinch weld flange up to the sides and top of
the glass. Pinch weld flange is a two-fold layer in which a side of the weather strip is fitted and on
the other side of the weather strip, the glass is fitted.
• Be careful not to hammer the metal tools with the glass otherwise it will break
• if the rubber channel is free pinch weld flange get the assistance of another man for removing
the glass
• place the glass assembly on a table having some pads for protection
6. Installation
• size of glass opening should be as per glass specifications
• clean all the areas of glass opening thoroughly
• keep in view water proof ness
• During checking of glass in glass opening, use ¾ inch mashing tape on glass edges. Use the
tape in such a way that it should cover the rides of the glass by ¼ inch
• masking tape is later removed
• 5 or 6 checking blocks of rubber of shape as shown are fitted on pinch weld flange of
standard rubber blocks are not oval, then 1-inch length rubber pieces of us rubber can be used
• Don’t apply force on the glass, uniform clearance will be required on 4 sides
• Each rubber channel before final fitment should be of uniform clearance without extra
parts/particles
• Use a glass sealer bed on the inner side of the glass cavity
• Place the new glass on a padded surface and cover up the rubber channel on the outer
perimeter of the glass
• Caution, don’t apply rubber channel afterward

Auto & Diesel 36
• Use a strong cord around the glass and in the cavity of pinch weld flange cavity and bring the
ends of the cord in the mid-center of the glass
• Use a good bed of glass sealer over the base of the glass sealer. Sealer can be used on body
openings
• Centre the glass with the help of another mate
• If the glass is fitted rightly use the pressure tape placatory for sealing the inner of the channel
and outer lips of the rubber channel. It will be water sealing
• Use mild solvent or mineral spirit for cleaning
Don’t use thinner for cleaning as it will damage the sealing material

Auto & Diesel 37
FIBER GLASS
1.Composition
• Silica or Silicates
• Varying composition of calcium, magnesium, and boron
Uses
• Air crafts
• Boats
• Automobiles
• Tubs
• Septic tanks
• Roofing
Other Names
• GRP Glass Reinforced Plastic
• GFRP Glass Fiber Reinforced Plastic
Use started in 1932, Games Slayter at Owens-Illinois accidentally discovered.
Characteristics
• Corrosion less
• Light weight
• Bending
• Damage on the impact point
• Steel members for reinforcement
• Weather-resistant, surface textures
Precautions
• Respirators
• Transparent goggles
• Cover all combination
• Elastic bands
• Rubber gloves
• Special protection cream
• Instruction on epoxy resin canister
• Exhaust system
• Water buckets
2. Tools/Materials
• Power grinder
• Sander
• Hack saw
• Electric drill
• Rubber squeegee
• Knife
• Screw driver
• Scissors
• Sheet metal screw
• Paste wax

Auto & Diesel 38
• Sand paper
• Plastic pin
• Card board
• Epoxy resin
• Fibre cloth
• Bending strips
• Square backing dish
• Wire(screening)
3. Scratches repair
• Remove wax, grease
• Wet sand, grit paper 400
Cares
• No use of liquid cleaners
• Surrounding areas covering
• 3 to 4 coats of primer
• Use of air gun for dust cleaning
• Enamel or liquor paint
4. Pits, small holes, surface cracks
• Cleaning area (36 grit disk, 60 sand paper)
• ¼ inch drill for cleaning patches
• Rags for cleaning
• Resin fillers and hardeners mixing
• Dry filler materials
5. Cracked body panels
• Cleaning both sides of the repairable area
• Remove rough edges
• Remove paint
• Y shape making
• Cover surrounding area
• Align although c-clamps
• Cutting or preparation of fiber cloth
• Cleaning with rags
• Drying of paste
• Regrind
• Re-inspection
• Re-finish

Auto & Diesel 39
Spraying Techniques :
Temp air and surface which is to be painted/covered are important. Thinners,
reducers, driers retarders are also important. If the spray temp booth is low, the solvent will vaporize
slowly and drying will be delayed. In this case, the paint will sag, rins. Technion may over spray and
will result in flauding.
If the temp is higher than the requirement, the material will quickly vaporize and a sandy paper
having a grains-like situation will occur.
Appropriate temp is 70 F'
Viscosity:
Paint having higher Viscosity will not flow and having lesser Viscosity will flow out,
which will result in sag and rins. Material is checked with a viscometer. Temperature is also used to
measure the paint temperature.
Reduction: user manual
Enamel paint is reduced by 25% reducer lacquer paint is reduced by 15% to 200%...
Mixing :
The facility is made available for mixing of few basic colors mixing and achieving the
desired color in the shop.
Red, green, black, white.
Seating Controls :
Fluid trip and air cap selection, selection of spray guns are important.
Air Cap:
It should be adjusted for the required vertical spray pattern...
Fluid volume control :
It adjusts the real flow of material. It depends on the selection of the selected fluid trip. A
selected pattern is got set, keeping the gun 6" to 8" away from the surface.
Spray pattern with spray control :
If you adopt the shape of an arc then a light heavy light pattern will be formed having too far
and too near patterns.
Write Action :
It is the action of write in such a manner, in which the spray gun is at 90' to spray area
as the same width of material will be on the whole surface.
Tilting :
If the spray gun is moved downward at the same angle during stroke, the material will be
lesser at the same place and more at other places.
Triggering :
The use of a trigger in each stroke is called Triggering. The first stroke is aimed at the edge
of the panel. It forms a circle shape (imaginary). The second stroke aim point is the bottom edge of
the previous stroke. Normally strokes are 18 " to 36". Spray gun strokes overlap each other.
Alternate strokes :
The direction of stroke changes alternately thus no requirement to adjust the stroke.

Auto & Diesel 40
Charge peel :
It is due to the wrong type of solvent/reducer. Paint surfaces do not find an appropriate time
for drying.
Careful use of reducer thinner can give good results.
Sagging:
This can thinner or reducer evaporates and primer starts flowing downward. Use o good
temp good humid conditions and good material.
Running :
If the material thickness is too much it might over flow it may be due to :
1 - Spray gun movement was slow on the surface.
2- Spray gun was near the spray face below 6".
3 - Viscosity of material improperly.
4- Thinner /reducer too slow.
5- Fluid volume control open too far.
6- pattern spread control too narrow.
7- Cornering techniques wrong.
Over Spray:
If spray pattern is supported to be applied on an already dried surface following techniques
are applied...
1- Use slow drying thinner/reducer.
2- Use retarder.
3- Final coat should be reduced or thinned more.
4- A mist coat should be applied for the final finish.
Film thickness:
The thickness of the film is measured through a paint meter.
Tinsley gauge is used for paint thickness. A special lightweight magnet is attached to a spring. It is
fitted in a pencil-type tube. During measurements, a magnet is in search of measurements of paint. It
is attracted by the painted surface, which modules an elastic. Force in the spray, this elastic force is
measured over the transparent glass may be graduated in force units.
Hand portable equipment.
These equipment are hand portable and can straighten the sheet metal.
This is equipped is used for pushing and pulling and for special work, clamps and accessories are
used they can remove any damage on sheet metal. fig 7.7 shows dents to remove from a car roof.
The pull is applied on a strip, which was soldered or welded with a roof panel
The underside of the sway also is pressurized when an upper side is pulled.
Special devices are used to remove the dent from doors.
Korek Straightening system:
It is a modern method of "reference plan" which can be used on the workshop floor and is composed
of specially designed steel members.

Auto & Diesel 41
These steel members provide a strong anchorage for pushing or pulling of body and for frame
damage and any part of the vehicle can be pushed and pulled in upward and downward or side ward
and straightening force can be applied simultaneously.
Stand the vehicle on a safety stand in such a way that extent of damage is observed properly. It also
provides a working height to the vehicle.
Proper anchoring is necessary with the box of the vehicle, as every push or pull has effects in
opposite directions.
When anchoring is done it would be near the supporting stand, thus undamaged parts vehicle is not
bent downward.
A force of ten-ton hydraulic ram in any direction can be applied even under the vehicle body.
Fig 7.9
Four different pulls are applied to the car's body.
Note that 3×pulls are horizontal
A force or pull is attached with the corner of the luggage opening
An upward pull at an angle
There is heavy damage at the right front of the car.
Alignment gauges are attached at the bottom of the car.
The car has been anchored with a round bar
Which runs/goes from one side to the other side of the car.
2× pulls are applied, 1+ direct forward pulls
And 1×side pull, which is a little down.
Mitek system of damage Repair:
These are portable power units, which can be moved around the vehicle.
These are anchoring holes or pots on the floor. Rollers are provided for every positioning of the
power units.
7.10 power unit applied to the door
And there are additional pot holes
Basic pilling set-ups are shown in fig 7.12
Where straight, vertical, angular pulls can be applied to vehicles.
Power units are hydraulic ram type thus provide 10-ton pulling.
The direction of the ram can be changed, the
The length of the tubing can be changed.
When the pull is large, tubing is also large for McPherson type accessories can be seen in fig 7.11
1. Spraying Techniques :
Temp air and surface which is to be painted/covered are important thinners,
reducers, driers retarders are also important. If the spray temp booth is low, the solvent will vaporize
slowly and drying will be delayed. In this case, the paint will sag, rins. Technion may over spray
and will result in flooding.
If the temp is higher than the requirement, the material will quickly vaporize and a sandy paper
having a grains-like situation will occur.

Auto & Diesel 42
Appropriate temp is 70 F'
Viscosity :
Paint having higher Viscosity will not flow and having lesser Viscosity will flow out,
which will result in sag and rinse. Material is checked with a viscometer. Temperature is also used to
measure the paint temperature.
Reduction: user manual
Enamel paint is reduced by 25% reducer lacquer paint is reduced by 15% to 200%...
Mixing :
The facility is made available for mixing of few basic colors mixing and achieving the
desired color in the shop.
Red, green, black, white.
Seating Controls :
Fluid trip and air cap selection, selection of spray guns are important.
Air Cap:
It should be adjusted for the required vertical spray pattern...
Fluid volume control :
It adjusts the real flow of material. It depends on the selection of the selected fluid trip. A
selected pattern is got set, keeping the gun 6" to 8" away from the surface.
Spray pattern with spray control :
If you adopt the shape of an arc then a light heavy light pattern will be formed having too far
and too near patterns.
Wrist Action :
It is the action of the wrist in such a manner, in which the spray gun is at 90' to spray
area as the same width of material will be on the whole surface.
Tilting :
If the spray gun is moved downward at the same angle during stroke, the material will be
lesser at the same place and more at other places.
Triggering :
The use of a trigger in each stroke is called Triggering. The first stroke is aimed at the edge
of the panel. It forms a circle shape (imaginary). The second stroke aim point is the bottom edge of
the previous stroke. Normally strokes are 18 " to 36". Spray gun strokes overlap each other.
Alternate strokes :
The direction of stroke changes alternately thus no requirement to adjust the stroke.
Charge peel :

Auto & Diesel 43
It is due to the wrong type of solvent/reducer. Paint surfaces do not find an appropriate time
for drying.
Careful use of reducer thinner can give good results.
Sagging:
This can thinner or reducer evaporates and primer starts flowing downward. Use o good
temp good humid conditions and good material.
Running :
If the material thickness is too much it might over flow it may be due to :
1 - Spray gun movement was slow on the surface.
2- Spray gun was near the spray face below 6".
3 - Viscosity of material improperly.
4- Thinner /reducer too slow.
5- Fluid volume control open too far.
6- pattern spread control too narrow.
7- Cornering techniques wrong.
Over Spray :
If spray pattern is supported to be applied on an already dried surface following techniques
are applied...
1- Use slow drying thinner/reducer.
2- Use retarder.
3- Final coat should be reduced or thinned more.
4- A mist coat should be applied for the final finish.
Film thickness:
The thickness of the film is measured through a paint meter.
Tinsley gauge is used for paint thickness. A special lightweight magnet is attached to a spring. It is
fitted in a pencil-type tube. During measurements, a magnet is in search of measurements of paint. It
is attracted by the painted surface, which modules an elastic. Force in the spray, this elastic force is
measured over the transparent glass may be graduated in force units.

Auto & Diesel 44
Spray Paint Equipment
Compressor:
a:- Single Stage (14.7 PSI to 40 PSI)
b:- Two Stage (50 PSI to 100 PSI)
=> Pressure Activated Switch.
=> Safety Relief Switch.
Working Principles:-
1st cycle sucks air at 14.7 PSI. It pressurizes air up to 50 PSI. The air is sent to a small cylinder,
which pressurizes it to 100 PSI.
Pressure Activated Switch:-
Used to maintain appropriate pressure.
Head Pressure Release Mechanism.
It releases extra air pressure.
Cautions:-
=> Low oil level cut-off switch is operational for the cut-off compressor.
=> Cut off electric supply during service.
=> Stand by pressure mechanism pressure rating.
Pressure Rating
4 ft³/min/H.P
Air Transfer Unit:-
Removes vapor, oil, corrosion from the airline.
Hoses:
Air Hose, Paint Hose
Red Color
Black/Orange
(Low pressure)
Braid Layer Of Pipe
1x innertube, 1x Braid, 1x Rubber Covering.
Types of spray gun:
1. Bladder gun ( without air valve).
2. Non-bladder gun (with air valve ).
3. External mix ( air-fluid mix outside ).
4. Internal mix ( air-fluid mix inside air cup).

Auto & Diesel 45
Parts of a Spray gun:-
A) Air Nozzle:
Automizes fluid, Gives velocity to particles.
B) Fluid Nozzle:
Control for metering the delivery of material.
C) Needle Assembly:
Stop-Start valve for material flow.
D) Side Port Control:
Controls spray pattern width by controlling air supply
E. Fluid control assembly :
Provide mechanical pressure to the needle assembly, which will be
closed when a trigger is released.
F. Spray gun body handle :
Give support to the operator.
G. Air inlet:
Air connection point.
H. Trigger :
Control air and fluid movement to the nozzle.
I. Air valve:
Control air move.
J. Fluid inlet:
The connecting point for the siphoned cup.
Parts of Spray Gun:
1 Air Cup
2. Air cup retainer
3. Fluid nozzle
4. Fluid needle valve
5. Spray pattern width spread control
6. Fluid volume control
7. Handle portion of the body
8. Air supply connection air-fluid
9. Air fluid control trigger
10. Siphon tube
11. Vent tube

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