| 1. |
Q. Are
dents easy to remove?
A. Most are, some are
not. Depends on the nature of the dent and the skill of the person
performing the repair. Dents that are easy to access from behind are
usually easier to repair. |
| 2. |
Q. What
is the best way to remove dents?
A. If you can gain
access to the back of the dent, try pushing it out with a pry bar
or other object. If access isn't easy, you can use a slide hammer
or pull rods. |
| 3. |
Q. What
are some of the tools that can be used to remove dents?
A. A hammer and dolly
are the most common tools. Other tools include pry bars, a slide hammer,
pull rods, stud gun. I've even use the back of a baseball bat inside
a door once to pry out a dent. It depends on the nature of the dent
and what tools you have at your disposal. |
| 4. |
Q. What
is a stud gun?
A. It's a tool used
by autobody technicians to remove dents. The stud gun itself is basically
a handheld welder that spotwelds a metal stud, similar to a common
nail, to the dented metal. Several studs can be applied to a dented
area. A slide hammer or pull handle can then be attached to the studs
and the dent pulled out. The advantage of this system is speed and
quality. The dent can be pulled out from outside (without removing
door panels, etc.) and no holes are drilled into the sheet metal that
might lead to rust down the road. Every body shop has one. They're
available for a couple hundred bucks and a worthwhile investment if
you plan to take up autobody refinishing as a serious hobby. A good
stud gun is an H&S Unispotter kit. |
| 5. |
Q. What
about a slide hammer?
A. It's a tool with
a piece of heavy metal that slides on a rod and creates a blow when
it reaches the end of it's travel. They're relatively inexpensive
and work well for pulling out a whole range of different types of
dents. Most slide hammer kits come with several types of pulling attachments
connect to it's pulling end. |
| 6. |
Q. I've
seen these dent-pulling rods with handles, are they any good?
A. Yes, they work well.
They're a inexpensive and versatile alternative to a stud gun. They
work particularly well for long creases. The main downfall is that
the holes must be drilled in the sheet metal to insert the rods into.
The holes should be filled before performing bodywork to prevent moisture
from entering the filler. The holes are easily filled with solder
(using a large solder iron) or body filler or seam sealer. Most bodyshops
use a stud gun because it's faster. For home autobody use, pull rods
work great. Steck Manufacturing
Company makes a very nice, sturdy set that will stand up to years
of hard dent pulling. |
| 7. |
Q. If
I drill holes in my panels, will it cause it to rust there?
A. It may, especially
if moisture is allowed to get through. When doing bodywork, seal up
any cracks, seams, or holes to prevent bodywork from becoming wet.
Body filler absorbs water and can cause metal below it to rust, even
though you can't see it. Cover holes with seam sealer or undercoating. |
| 8. |
Q. My
vehicle's fender/door is damaged, can it be repaired?
A. Impossible to tell
w/o seeing. Most sheet metal panels with light damage such as small
dents or creases can easily be repaired. When damage becomes severe
it is usually faster and cheaper simply to replace the entire panel
such as fenders and doors. |
| 9. |
Q. What
are my options if I have a panel I can't repair?
A. Replace with a new
panel from the dealer or aftermarket source. Used panels from auto
salvage yards can be used if available. Sometimes on doors, the outer
door skin can be replaced. It's a matter of removing the outer skin
and welding on a new one. It usually is only economical to do on newer
vehicles where outer sheet metal damage is severe but the rest of
the door is undamaged and affordable alternatives are unavailable.
|
| 10. |
Q. I have a rust
hole over my truck's rear wheel well, what should I do?
A. If you fill the
hole with fiberglass it won't last very long. The best repair is
to cut the rust completely away and replace with new metal. Luckily
they make patch panels to make such repairs easier. A patch panel
is a small partial panel made of steel that has matching bodylines.
You can buy them from online sources like Raybuck or JC Whitney
or locally from autobody supply stores.
To install, cut well around the rust
area with a snips or cut-off tool. For doing a rusty truck rear
wheel well, I've found that you're better off cutting away the entire
wheel lip from front to rear and about 5" up because the rest
of the wheel well is probably rusty on the inside and may rust through
in short time anyway. An air cutoff tool works great for cutting
the metal away w/o warpage. Grind away any burrs. You'll get a more
flush fit and a better looking job if you can create a flange at
the edge of the metal around the hole you cut out. An inexpensive
flanger tool (also available from JC Whitney and other sources)
or even a pliers can make a nice flange. Next, cut the patch panel
to fit in the flange. Drill some holes around the perrimeter of
the patch panel so you can weld the vehicle's metal through the
hole, then fill the hole with weld. Then weld in place with a wirefeed
welder or use an alternative but just as effective method of fastening
the panel with metal adhesive. A lot of shops are beginning to use
metal adhesive these days for panels. It bonds as strong as steel.
You can hold the panel in place with a few screws until it the adhesive
dries. For best results, try to get the new panel to fit as flush
to the surface of the old metal as you can. If you can't create
a flange, cut the patch panel so it overlaps the old metal by at
least 1/2". If you have some high spots on the seams, tap them
down with a hammer. Then perform bodywork to hide the seam. The
last crucial step is to apply seam sealer to the rear of the repair.
It's less critical if you glued the panel to the vehicle. But you
need to reach up inside there and get seam sealer on the seam to
prevent moisture from gettin in the seam. That will create more
rust. Tape a small brush on a paint stick to reach up there if you
need to.
|
| 11. |
Q. How
hard is it to replace a door/fender?
A. On most vehicles
it's a matter of simply unbolting the old fender or door and installing
the new one. Generally it's simple and anyone with moderate mechanical
skills could do it. Door panels usually have to be removed to unhook
wires and that increases the amount of time/skill. Replacement fenders
or doors should be painted, or at least it's jams painted prior to
installation. |
| 12. |
Q. Should
I paint a replacement door or fender on or off the vehicle?
A. That's
a judgment call. Some argue to paint off the vehicle. Others suggest
to paint on the vehicle. I personally feel it's better to paint the
jams first, then install and paint the rest on the vehicle. For one,
it eliminates the possibility of scratching the panel during installation.
In addition, on most newer vehicles with metallic paint, a paint blend
into an adjacent panel is often required to make an undetectable repair.
|
| 13. |
Q. How
do I remove trim/emblems?
A. Most trim and emblems
on modern vehicles is adheres with double-sided tape. They can usually
be removed with a thin paint scraper or long razor knife. To reuse
an emblem, remove the old double-sided tape and apply new automotive-grade
tape to the emblem. Trim around it's edges with a razor knife. Reapply
emblem. |
| 14. |
Q. Do I need to
remove the old paint to repaint my vehicle?
A. Not necessarily.
If your vehicle's paint is in good general condition, you can paint
over it with no problems. Body shops do it all the time. If the
original paint is old and cracked, show signs of delimitation or
is worn away to the primer in places, it's advisable to sand the
old paint off before repainting. That will prevent possible adhesion
problems down the road.
|
| 15. |
Q. Can
I sandblast my vehicle?
A. It's not an advisable
way to remove the paint. The peening action of the sand, and heat
buildup will very likely to cause the sheet metal to become badly
warped. When that happens, it's almost impossible to get straight
again. The sheet metal on modern vehicles just can't withstand sandblasting.
With great care, and gentle sandblasting it can be used to remove
rust on some rust spots. If you were to watch someone sandblast metal
in the dark you would see a shower of sparks at the metal's surface. |
| 16. |
Q. I
have some rust spots, can I sandblast them?
A. Most small rust
spots can be sandblasted clean if light blasting is used and care
is taken not to heat or overwork the metal. Blast at sharp angles
using spurts. Allow time for cooldown. |
| 17. |
Q. Should
I strip the paint to bare metal or leave the factory primer on it?
A. That's a debated
question and it's done both ways. Generally it's difficult to sand
an entire vehicle or even a panel to the primer and not sand through
the primer in at least a couple places. In addition, new primers,
particularly self-etching primers have outstanding rust prevention
qualities. But you could save time and money by sanding only to the
primer and eliminating the self-etching or epoxy primer stage but
you risk having compatibility problems between the original primer
and new primers. Some say the original vehicle's primer is better
at preventing rust than aftermarket products but again, that's debatable. |
| 18. |
Q. What's
the best way to strip all the paint off my vehicle?
A. A couple methods
widely used are: mechanical (sanding with sandpaper on a DA sander
or a mudhog) or blasting, or Chemical (using stripper). Most bodyshops
and restoration shops just sand the old paint off with 80 grit on
a DA sander or Mudhog (8" geardrive sander). It's fast and effective.
Chemical strippers are used on poly and fiberglass panels. Taking
to a blaster and having your vehicle blasted with plastic media is
another alternative. |
| 19. |
Q. What
is a mudhog that I keep hearing about?
A. It's a tool similar
to a Dual Action sander (DA) but instead of having a freely spinning
6" pad like the DA has, it has a gear-driven 8" pad that
follows a set path. The advantage is superior sanding action and a
much more aggressive tool than a DA. You can use one for quickly grinding
away bodyfiller and hence the colloquial term, Mudhog. With skill,
a mudhog can be used for doing quality body repairs. |
| 20. |
Q. How
can I cut/drill out spotwelds?
A. They make special spot weld cutting drill bits
that make the job relatively easy. |
| 21. |
Q. Can
working on a vehicle set off it's airbag?
A. Anything's possible
especially if you're hammering near the sensors or working on sensitive
electronic parts. In some cases, a minute amount of static electricity
passed to an unrelated component can even set it off. In general,
however, it's not a common occurrence. Each manufacturer has a procedure
that disables the airbag restraining system. To be safe, you can call
your dealer for the exact steps. |
| 22. |
Q. What
is the secret to doing good metalwork?
A. The biggest piece
of advice is to take your time and go slow, particularly if you haven't
done a whole lot of dent repair. In most cases, it's helpful to leave
the original paint on the panel until the dent has been removed. You
can use the shiny paint surface to gauge high and low spots. Also,
a straight edge, something like a metal yard stick is very useful
to actually see where you are in the dent removal process. Nearly
all body panels have a gentle outward curve to them. It provides strength
to panels. A straight edge should roll gently across the panel. Compare
with a panel on the other side of the vehicle too. When hammering,
use a dolly behind the dent. Don't become frustrated if it's not coming
right away. Take your time. Often, bodyshops will bump out nasty dents
for not a whole lot of money. |
| 23. |
Q. Do
any bodyshops use lead anymore?
A. Virtually none do.
Very, very few restoration shops use either. Plastic fillers, even
some that contain metal, have come a long way in recent years. For
99.99% of the repairs out there, there's no reason to use lead. Plus,
lead has health risks associated with it. Even on classic cars, plastic
fillers are nearly always used to make repairs. It is easier to work
and stands up over time. |
| 24. |
Q. How
do I get my bodywork straight so I can't see any waves?
A. Start with good
metal work first so very little filler is needed. Secondly, use a
long 17" board sander and sand using long strokes. Sand at angles
to prevent grooves from forming. Take your time. Often it takes several
time just to get it 'right'. Check your work periodically with a straight
edge. When finished, apply a high-build urethane primer, sand with
a sanding block when hard. I prefer to apply a guidecoat of paint
over the primer and wetsand with sandpaper wrapped around a wooden
stir stick. The guidecoat will allow you to see where you have sanded
and have yet to sand. It'll also allow you to see any dents or short
body waves that might exist. For doing bodywork on really long panels,
make a long sanding board from a common 1x3" board of 30"
long or so (try to find one that is gently bowed). Put some handles
on it and have a friend help if necessary. It's a two-man sander!
|
| 25. |
Q. What
do I do once the bodywork is finished?
A. Spray bare metal
surfaces with a self-etching primer and apply a high-build urethane
primer over the area of bodywork or entire panel. A light mist of
paint applied over the primer (of a contrasting color) can act as
a guide coat for later sanding and is a really good idea to achieve
really good bodywork. Block sand the primer either dry or using water
(wetsanding). If you should sand through the filler and it becomes
wet, allow it to dry before applying more primer. |
| 26. |
Q. What
is this self-etching primer I keep hearing about?
A. It's a primer that
contains compounds that etch the metal and improves adhesion. In addition,
they are very rust-inhibiting. I've left metal coated with self-etching
primers outside for years and they've yet to rust. Used as an undercoat,
they help prevent rust even when chips develop in the paint. |
| 27. |
Q. What
is urethane high-build, or 2K primer?
A. It's a primer that
when applied builds much thicker than regular primers. Therefore,
they allow a body technician to easily sand out surface imperfections
like shallow dings and rings around bodywork and get bodywork much
straighter. In addition, they use a special activator or hardener
and harden via a chemical process rather than by evaporation like
lacquer primers and therefore don't shrink with age. And because it's
a urethane-based product, it has much greater durability. It's a bodyman's
dream product. Sometimes also called a 2K primer. |
| 28. |
Q. What
is epoxy primer?
A. A primer that uses
a hardener or activator to set up, usually urethane-based and non-sanding.
Epoxy primers are waterproof (unlike laquer primers) and have outstanding
adhesion properties which provide a good base for new paint to adhere
to. Sprayed over a vehicle's existing finish they also produce a uniform
color on which to spray the new paint and form a tough barrier which
reduces solvents from new paint from penetrating into the vehicle's
existing finish thereby reducing potential problems such as lifting.
Epoxy primers are usually sprayed over new panels or existng finishes
which have been sanded with 320-400 grit sandpaper. Many epoxy primers
are non-sanding and act like a sealer. Can be sprayed underneath a
high-build primer but do not build as thick as a 2K high-build primer.
Therefore, for bodywork areas, most shops apply a 2K high-build primer
over filler. |
| 29. |
Q. Can
I just use spray can primer over my bodywork?
A. You
can, but it's not a good way to go for making quality repairs. Spray
can primer is very weak stuff, despite what the can says. They're
usually over-reduced lacquer or enamel -based products. They don't
build up very thick and almost always shrink over time exposing your
bodywork beneath. Finally, they are often not durable enough to withstand
aggressive solvents found in automotive grade paints. For quality
repairs and reduced problems, stick to automotive-grade primers. |
| 30. |
Q. What
is the difference between high-build primer and epoxy primers?
A. Mainly the thickness
that it sprays on at and weather it's sanding or non-sanding. Both
are waterproof but a high-build 2K primer goes on thicker and be 'worked'.
Therefore high-build primers work great over bodywork for finish sanding
of filler and dings. Epoxy primers don't build nearly as thick and
are intended to improve adhesion, reduce corrosion, create a barrier
between the old and new paint, produce a uniform color and fill small
sandscratches. They can act as a sealer and can be topcoated with
paint. If you were to repaint a vehicle and had it properly sanded
and ready for paint, use a sealer or a epoxy primer over the existing
finish before applying the first coat of paint. It will provide better
adhesion and reduce the chances that solvents will penetrate into
the old finish (which can sometimes lead to problems). |
| 31. |
Q. These
urethane primers are expensive, are there any alternatives?
A. Some companies sell
'universal' high-build urethane primers at reduced cost that work
very well. One such product is Morton
Easywork 2K Xtra High-build primer. Other companies also produce
universal urethane primers. They advertise they can be topcoated with
any paint. |
| 32. |
Q. My
bodywork is smooth, can't I just paint directly over it?
A. You can but it'll
look like crap. Body filler is porous and it'll absorb paint like
a sponge. Areas of bodywork will look very dry and anybody with even
moderate vision will be able to see each area that contains bodywork.
Primer that has been sanded fills the filler's pores and provided
a smooth surface. In addition, even the best bodywork isn't truly
smooth. The edges of filler can only be feathered so much. If you
spray paint over filler you'll be able to see it's edges. Those edges
can be filled and made smoother by coating with primer and sanding
with a sanding block. Once the repaired area has been primed and properly
sanded, it'll be impossible to detect that bodywork was done. |
| 33. |
Q. What
does it mean to "block out" the primer?
A. It's a process of
sanding the primer with a stiff rubber or wooden block. It allows
the high spots to be sanded down. When done properly, it leaves behind
a nice, smooth surface with no high or low spots. It's a process used
by auto restorers and good bodymen to produce high quality, straight
bodywork. A sanding 'paddle' is a similar process that is basically
made by wrapping sandpaper tightly around a wooden paint stir stick. |
| 34. |
Q. I'm
painting my entire car, should I prime and sand the whole thing?
A. It depends. If the
paint surface is smooth - there aren't any dings or dents (or you've
already repaired any dents), you can sand the paint, apply a coat
of epoxy primer or sealer and then the paint. The sealer will produce
a smooth uniform surface that will adhere well to the existing paint.
In addition it will also create a barrier between the old and new
paint which will prevent the paint's solvents from lifting the edges
of the existing paint/primer. If you've done a significant amount
of bodywork to a vehicle or you're restoring a vehicle and you want
a nice smooth surface when you're finished, it's advisable to primer
the whole vehicle and sand it's surface. It'll guarantee that you
didn't miss any dings and ensure a really nice, smooth surface. |
| 35. |
Q. What
is wetsanding?
A. A process of sanding
down paint or primer using water and waterproof sandpaper. The reason
you often need to wetsand is because, some sandpapers like 400 or
600 grit are so fine that their surface would become clogged up with
dust after only a few strokes and be useless. Water carries the dust
away and one can sand continuously. |
| 36. |
Q. What
is better, to wetsand or sand the primer dry?
A. It depends on what
grit you're sanding with. Fine papers clog up faster. Also, some prefer
to wetsand while others don't. I myself prefer to wetsand. |
| 37. |
Q. What
grits of sandpaper do you recommend when sanding primer?
A. It depends on the
quality of the surface and if you plan to use a sealer before painting.
If you're sanding smooth a bodyworked area and did a good job on your
bodywork and it was pretty smooth prior to priming (say you final
sanded it at 120 grit), I'd start out block sanding the bodyworked
area with 280 grit and switch over to 400 grit. If you are sanding
surfaces that didn't require bodywork and plan to use a sealer under
your paint (which will fill in some sandscratches), I'd wetsand it
with 320 and maybe do the tops of the fenders and hood with 400 just
to be on the safe side. You wouldn't have to use a block or paddle
when you went to a finer grade of paper. But I prefer 400 grit for
final sanding. If you plan to make a color blend and paint directly
over nearby painted areas and the primer, I'd finish sanding those
areas with 600 grit. |
| 38. |
Q. My
car was in primer and I've been driving it around for a while and
now it seems to be rusty underneath, why?
A. Lacquer primers
are porous. Water can seep through and rust the metal beneath unbeknownst
to the vehicle owner. Urethane primers are not porous and water will
not seep through. I can't stress this enough, for quality autobody
repairs, stay away from laquer primer. |
|
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