Everything you need to know about Autobody Repair.

#1
harmonator84 wrote:
I figured that a walkthrough of everything from dent repair to mixing the paint would be needed. I typed most of this up the other night, so if you find any mistakes thats why. Now I am not trying to say this is the ONLY way to do bodywork. Everyone has there own way, its just this is the way I was taught. I attended a 2 year technical college for autobody and repair.

PREPARING SURFACE FOR FILLER
One of the most important steps in applying fillers is surface preparation. Begin by washign the repair area with soap and water to remove any dirt. Then clean the area with wax/grease remover to get rid of wax, tar, etc. Make sure you use a cleaner that will remove silicones which is often found in automotive waxes.

Mask any trim, parts, or other panels that could be damaged by grinding and sanding. Use masking tape or duct tape to protect them. Grind the area to remove the old paint working 3 to 4 in around the area to be filled. REMEMBER...Never apply body filler over paint! Only apply filler to bare metal. Filler will NOT bond properly to paint, causing problems later down the road. Use 24 or 36 grit grinding disc to remove paint. Grinding also etches the metal to provide better adhesion. But make sure you only grind to remove the finish. Grinding to much will then and weaken the metal.

After grinding away the finish from the repair area, blow away the sanding dust wtih compressed air and wipe the surface down with a tack rag to remove any dust. Make sure no solvents are used to clean sanded area before applying filler. This could cause pinholing and adhesion problems.

MIXING FILLER
As soon as you open a can of filler you should mix the can to a uniform and smooth consistency. It must be free of lumps and not wet on top.

Now take the cap off the hardner and let all the air out. Put the cap back on and then you want to "Knead" the hardener...this is done by squeezing the tube back and forth with your fingers to mix the material. The hardener should be like toothpaste when you squeeze it out.

MIXING FILLER AND HARDENER
You want to use a clean putty knife or spreader. Place the filler on a smooth, clean filler mixing board. You can also use sheet metal, glass, or hard plastic to mix the filler and hardener onto. Whatever you do, DO NOT use carboard as a mixing board. It is porous and contains waxes. The waxes get dissolved in the mixed filler and cause poor bonding. Carboard also absorbs some of the chemicals in the filler and hardener. Remember to put the lid back on the can of filler right away. This will keep dust and dirt out of the can.

Add hardener according to the proportion indicated on the can, usually 10 percent hardener. Too little hardener will result in a soft, gummy filler that will not adhere. Too much hardener will result in pinholing. A tip I found was for each golf ball size glob of filler use a inch of hardener. If the filler is as big as a baseball, use about a six inch bead of hardener.

With a clean poutty knice or spreader, use a scraping motion going back and forth to mix the filler/hardener together.. Scrape filler off both sides of the spreader and mix it in. Every few back and forth strokes, scrape the filler into the center of the mixing board by circling inward. What ever you do, DO NOT stir the filler. Stirring causing air to get trapped into the filler, which causes air pockets and pinholes.

You want to use clean tools when removing the filler and mixing the filler and hardener together. So total you will need 3 spreaders/sticks. 1 for removing the filler from the can to the mixing board, 1 for mixing the filler/hardener together, and the other for applying the filler to the surface. This will save you from getting hard lumps in your filler or soft spots in the cured filler.

APPLYING THE FILLER
Apply the mixed filler as soon as you are done mixing. First, apply a thin coat of filler to the repair area. Press firmly to force filler into the sand scratches and holes. Work the filler in two directions, left to right then top to bottom. This will greatly reduce pinholing. Spread filler around 3 in beyond the repaired area. This will give you better adheasion, and allows you to featheredge the patch.

When this layer cures, apply more coats to build up the repair area to a proper contour. Allow each application to set up before applying the next coat of filler.

Build up the final layer of filler slightly above the panel surface. So you can sand the filler down smooth on an equal with the existin panel. For your final coating of filler, make sure the spreader has a smooth edge. If worn or nicked it will not make a smooth layer.

Avoid using filler in cold temperatures. When the filler, shop, or panel are cold, the filler will NOT cure properly. Filler should be stored at room temperature. You can use a heat lamp to warm cold surfaces if you need.

FILING THE FILLER
Allow the filler to cure to a semi-hard consistency. This usually takes 15 to 20 minutes. Scratch the filler with your fingernail. If the scratch leaves a white mark, the filler is ready to be filed. Filling is usinga "cheese grater" or body file to rough shape the filler. You will knock off the high spots and rough edges. Since the filler is only partially hard, the body file will quickly remove excess filler. If you do NOT rough shape the filler with a grater, you will waste time and sandpaper. Sandpaper will become laoded quickly.

To use a chees grater, hold it at a 30 degree angle. Pull it lightly across the semi-hard filler. Work the file in several directions. Stop filing when the filler is slightly above the desired level.

APPLYING FILLER TO BODY LINES
Maintaining sharp lines when doing filler work is difficult. The best way to get straight, clean lines is to file each plane, angle, or corner separately. Apply masking tape along one edge. Then apply filler to the adjacent surface. Before the filler sets up, pull the tape off. This will remove the excess filler from the body line.

After the first application is dry and sanded, tape the opposite edge. Apply masking tape along the body line and over the filler. Then, coat the adjacent surface with filler. When the tape is removed and the filler sanded, the result is a straight, even line or corner.

APPLYING FILLER TO PANEL JOINTS
Many panels have joints that are factory finished with a seam sealer to allow the panel to flex. Often, both panels of the join suffer damage and require filler. NEVER cover the seam with bodyfiller. The filler will crack when the body flex. You can fix the joint buy taping off alternate sides. Just apply tape to one panel. Then apply filler to the other panel. Pull the tape up to remove excess filler. Then fill the other panel the same way.

SANDING THE FILLER
After filing, you want to sand out all the file marks. Use a 36 or 40 grit disc on a sanding board or block first. Then, follow with 80 grit sandpaper until all scratches are removed. Finally, smooth the filler with 180 grit sandpaper. Be careful not to oversand.
After final sanding, blow with an air gun and wipe with a tack cloth. Doing this removes the dust and also exposes holes. These holes and sand scratches must be filled in(if any found).

Run your hand over the surface to check for evenness. Do not trust "eye balling". Paint does NOT hide imperfections, it highlights them. A true bodyman looks with his hands. Do not be satisfied until the repaired surface is perfectly smooth, and remember if you can feel the slightest bump, paint will make it show up much more. The dull surface of filler and sanded paint does not visibly show surface imperfections.

FEATHEREDGING
Featheredging involves sanding the repair area untill the filler and old paint blend smoothly into each other. You must use fine sandpaper, 180 grit or finer. Sand until you rmove any small lip where different materials on the surface meet. Featheredging is commony done with a DA sander.

PRIMERS AND SEALERS
Primers come in different types- primer, primer-sealer, primer-filler,epoxy-primers, etc(cannot remember them all). A plain primer is a thin undercoat made to provide good adhesion for your topcoat. Primers can be used when the surface is smooth and there is no protectial problem with "bleeding".
You may ask, well what is "bleeding"...Bleeding is where your colors in the undercoat/old paint seep into your topcoat. Which in turn will discolor your new paint.

A self-etcing primer has a type of acid in it to treat bare metal so that the primer will adhere properly.

A sealer is a innercoat between the topcoat and the primer/old finish to prevent the bleeding you can sometimes get. Sealers are different from primer-sealers because they cannot be used as a primer. Sealers are sprayed over a primer/old finish.

A primer-sealer is a undercoat that improves adhesion of the topcoat and also seals the old painted surfaces that have been sanded. So it pretty much solves two potential problems(adhesion and bleed) at once.

A primer-filler is a VERY thick form of primer. It is used when a very pitted or rough surface must be filled and smoothed

There is also a epoxy-primer, which is a two part primer that cures harder and faster then normal primers. It greatly increases body filler adhesion and corrosion over metal. The epoxy primers are the closets thing to OEM primer.

A thing to remember about primers and your topcoat. Always use a complete system. Meaning all the materials(primer, paint, etc) are compatible and made by the same company. You do this because they are designed to work properly with each other. If you mix materials from different manufacturers, you can run into BIG problems.

PRIMING
Priming is done directly after filling to cover any bare metal as well as filler. After using filler, primer is often sprayed on the repair area. Since primer is very thick, it will help fill small sand scratches in the filler and paint.

For best results when applying primer, spray 2 to 3 coat. You will actually save time by following flash recommendations versus spraying coats wet on wet. Wait a hour or more before sanding the primer.

After the primer dries, you can dry or wet sand the filler to check your work. Now you are ready for a step called "guide coating". You just need a cheap can of spray paint ( I use walmart 99 cent stuff)and spray a LIGHT mist over the full coat of primer. Also you will want a color that you can see well...black, red, etc. Then, by sanding the area, you can easily find high and low spots. If the spray paint does not sand off, you found a low spot. If it sands off too quickly, you have found a high spot. Ideally, the primer and spray paint should sand off a the same time. This shows that the surface is flat and ready for sealer.

APPYING GLAZING PUTTY
Once the primer is dry, small pinholes and scratches can be filled with glazing putty. Just mix the putty and hardener according to the back of the tube. Place a small amount of putty onto a clean rubber squeegee. Apply a thin coat over the primer. Use single strokes and a fast scraping motion. Glazing putty will dry very fast.

ATTENTION: A common mistake is to use glazing putty as a filler. Spot putty is NOT as strong as filler. Only use putty to fill small imperfections in the primer. Do NOT apply it to bare metal or painted surfaces. Most are designed to be applied over primer.

Allow the putty to dry completely before sanding smooth with 240 grit sandpaper. The repair is now ready for final priming, sealing, and painting.

PREPARING THE CAR FOR PAINT
When painting the entire car you will need to sand the car down for the topcoat to adhere. You want to use 400 grit wet for almost all your topcoats. Light sanding should be done on all areas where the old finish is in good condition. The purpose is to partially reduce the paint gloss to improve adhesion. You want to use a sanding block to do this. Never use a grinder or sander. For the base coat/clear coat finishes, you will want to sand all surffaces with 400 grit followed by 600 grit. Wet sanding is faster and requires less sandpaper then dry.

Remember every inch to be painted must be sanded. If you dont scuff any glossy surface the paint will peel off.

PREPARATION
Check all masking tape and paper one last time. Make sure none of the tape has pulled up or paper has been torn. Inspect all edges and paper closely for openings that could allow overspray leaks. Blow off any dust with a air gun. As you blow off surfaces, wipe the vehicle down with a tack cloth. After wiping down be careful NOT to touch the surface being refinished. Before applying the topcoat, carefully read the paint manufacturer's directions that appear on the paint can. Each has specific formulations for its products. For this reason, the best source of data on how to apply a specific brand of paint is the label. You want to check...
1.) Viscosity recommendations
2.) Air pressure recommendations
3.) Use of additives, reducers, thinners, and activators
4.) Application techniques
5.) Number of coats required
6.) Polishing and compounding recommendations
7.) Clean up procedures

DETERMINING TYPE OF OLD FINISH
Before planning any refinishing job, you must find out what type of paint is on the vehicle. The vehicle might have its original paint or it could have eben repainted with a different type of paint. Here is a method I use to find out. Rub the paint wiht a white cloth soaked in lacquer thinner to see how easily the paint will dissolve. If the paint film dissolves and leaves a mark on the rag, it is a type of air dried paint. If it does not dissolve, its either an oven dried or a two part reaction type paint. The easiest way to see if a car has been painted is to inspect closely for signs of repainting. Look for masking tape created paint lines, overspray, and other signs of repairing. If the vehicle has not been repainted, you can use the body color code identification plate to determine the type of paint on the vehicle.

SPRAY GUN APPLICATION STROKE
You want to apply in a side to side movement of the spray gun to distribute the paint evenly. You want to practice on masking paper to get it perfect. Any problems with the spray pattern must be corrected before painting the vehicle.

To use a spray gun, hold the gun 6 to 8 inches away from the surface. Normally, hold the gun parallel and perpendicular to the surface. Keep the gun at a right angle to the vehicle. This should be done even when spraying curves in the body. If you tilt the gun when spraying the sides of the vehicle, an uneven paint film will result. On flat surfaces such as the hood or roof, the gun should be pointed almost straight down.

Avoid fanning the gun with your wrist. Fanning the gun will deposit an uneven paint film. The paint film will be thicker right in front of your gun and thinner on the sides. The only time you should fan the gun is when you are trying to blend a small repair spot. With a spot repair, you want the paint fim thinner at the edges to blend out the spray.

Spray gun triggering involves stopping the paint spray before you stop moving the gun sideways. When you pull halfway back on the trigger, only air blows out of the nozzle. When you pull all the way back, paint is atomized and sprayed out.

During the application stroke, release halfway on the trigger right before you stop moving the gun sideways. This will prevent too much paint being deposited when the gun changes direction. It will also keep air moving through the nozzle to help prevent sudden burst of paint. Release the trigger halfway at the end of each pass, then pull it back when beginning the pass in the opposite direction.

Move the gun with a steady, deliberate pass, about one foot per second. The speed must be consistent or it will result in an uneven coat. Spray edges and corners first. Aim directly at the corner or edge so that half of the spray covers each side of the corner or edge. After all the edges and corners have been sprayed, spray the face or front of the panel.

Generally, start spraying at the top of any upright surface, such as as door panel. The gun nozzle should be level with the top of the panel. The upper half of the spray pattern should hit and cover the masking paper. Move the gun all the way across the top of the panel. Make sure you hold the gun square with the panel and keep it the same distance from the panel.

You want to make sure each spray gun coat cover about half of the previous coat of paint. Make each pass in the opposite direction. So one half of the spray pattern overlaps the previous coat. The other half of the paint pattern is applied to the unpainted area. For a double coat, repeat, making sure to allow flash time of several minutes between coats.

TYPES OF SPRAY COATS
The easiest way to control thickness is by changing how fast you move the gun sideways. If you move the gun slower, a heavier, thicker coat will be applied. If you move faster, paint thickness is decreased.

A tack coat is a mist coat applied to the surface first. It allows the application of heavier wet coats without saggin or runs. THe tack coat dries quickly to bond and form a lightly textured paint film to hold the next coats in place. The tack coat will flash quickly, usually in a few minutes.

OVERALL REFINISHING
There is no universal way for overall refinishing of a vehicle. However, most experienced painters agree that the following method is an excellent technique. Start by painting the roof, then the rear, then the driver side, front, and finally the passenger side. It will produce minimum overspray on horizontal surfaces. This will also help keep a wet edge when starting a new section.

Wet edge means that the area just painted will still be wet when starting to paint a new adjoining area.

APPLYING BASECOAT/CLEARCOAT
More and more cehicles have basecoat/ clearcoat finishes, it is very important to become fmailiar with them. You must first spray the color basecoat over the repair area.

When spraying, two medium coats of basecoat should be applied. The basecoat does NOT have to be glossy, and only enough should be used to achieve hiding. Two or three medium wet coats of clear should be applied next. Allow at lwast 15 minutes flash time between coats.

Avoid sanding the basecoat. If sanding must be done because of dirt or imperfections, allow the paint time to dry. Wet sanding the 1000 grit sandpaper will minimize sand scratches. The sanded area must then be given another coat of basecoat to prevent streaking. On panel repairs, only spray the basecoat where needed. You do NOT have to basecoat the whole panel if the existing color is acceptable. Use as much of the existing color as possible to help avoid a color mismatch. Do NOT load clearcoats on heavily. Because they are clear, it is easy to use too much trying to increase the desired glamour effect. As a result, the thick clear will hide the color. Also do NOT use thick viscosity clearcoats. Clears do NOT perform better when they are under-reduced. THin or reduce clearcoats according to the label.

REMOVAL OF MASKING TAPE
After you are finished with you base/clear, pull the tape slowly so that it comes off evenly. Take care NOT to touch any painted areas because the paint might NOT be completely dry. Fingerprints or tape marks could result. Never allow paint to dry thoroughly before removing the tape. This could cause the paint to peel off along with the tape.

After all this its time to clean your gun. There are many different ways to clean your gun properly. Just make sure you follow the steps in the instructions that came with the gun.

WET SANDING...AGAIN
You will need to wet sand to smooth the paint surface on larger areas to remove orange peel. Wet sanding should normally be done with a rubber sanding block. For finishing, 1000, 1200 and finer grits of wet sandpaper are used.

Wet sand in a small circular motion. Use plenty of water to flush away paint debris. Dip the block in a bucket of water or use a hose to flow water over the area. You also want to use a drop of soap in the water to help clean the surface as you sand.

You do not want to cut too deep into the finish so you want to check the area often while sanding. If you cut through the clearcoat or color, repainting will be necessary.

BUFFING / POLISHING
Polishing involves using very fine compound to bring the paint up to full gloss. Many finishing systems recommend the use of different buffing and polishing pads. It is important to use a slow-speed machine to avoid static build-up and high surface temeratures. Do not push down on the buffer. Let the weight of the machine do the work.

Because the compoud has a tendency to dry out, do not try to do too large an area at one time. Always keep the machine moving to prevent cutting through or burning the topcoat. As the compound starts to dry out, lift up a little on the machine so pad speed increases. This will make the surface start to shine.

You can hand polish small or hard to reach areas. Machine polish larger areas to save time. Instead of a circular action buffer, you should use an orbital action machine for you final polishing. It will move the polishing compound in a random manner to prevent swirl makrs left from machine compounding. Final polishing should always be done with an extra fine polishing compound.

CARING FOR YOUR NEW FINISH
A newly refinished vehicle must receive special care, as the paint can take several months to cure. Each paint manufacturer will have specific recommendations for caring for a new finish. You should avoid commercial car washes and harsh cleaners for 1-3 months. Hand wash using only water and a soft sponge for the first month. Dry with cotton towels only. Avoid waxing and polishing for up to three months. After that time, use a wax designed for basecoat/clearcoat finishes. Avoid scraping ice and snow newar newly refinished surfaces. Finally flush gas, oil, or fluid spills with water as soon as possible for the first month. DO NOT wipe off.

Hope this helps. Thanks for reading and if you have any questions you can post them up on here so the same questions are not always asked.
Thanks
Matt
all credit goes to harmonator84 on ht.
Image

.saint, the honda EK parts jdMuseum.
i hope i grow to be half the man my grand father is.
poop.hell sideways.brigade
http://www.frightmarestudios.com
Post Reply

Return to “exterior. engine bay. interior appearance”

Who is online

Users browsing this forum: No registered users and 3 guests

cron