Londons Autobody

Bondo Basics – Apply and Sand

Bondo Basics – Apply and Sand (part 2)

This is a follow up to:  Bondo Basics – The Art Of Body Filler

When applying and sanding bondo your gonna want to be fully assured you know what you’re doing. This will save you time and materials in the long run. Don’t bother starting with the bondo until you have made sure your damage is pulled, patched, ground down, blown off, wiped clean and ready.

To Begin you have to make sure your area you are applying the body filler to is completely roughed up. Grind the area thoroughly with 36 grit sand paper or at a minimum of 80 grit. Take your air gun if you have one and blow off all the dust and grit from grinding. There are steps people like to avoid, I’m guilty too, but you learn some shortcuts pay and some don’t. Here’s one commonly overlooked. Wipe it down. Take the wax and grease remover and treat it as though you were painting it. The bondo has to stick completely or it will chip and flake, in other words it won’t feather for you and it will tick you off and waste time and materials. If your damage is repaired right you shouldn’t have to apply more than two or three coats to have a finished repair.

Alright, to the tools needed. Generally you want a 5 – 9 inch sanding block. The sandpaper you need will be the common 36, 80, 120 works well sometimes, 180 then 320 for feathering before primers etc. A DA Sander is used by some, but the same sandpaper applies, choose the same grits.

The methods: Depending on the size of the damaged area, mix only enough to fill the damage completely. Be sure to apply enough – this takes a little to get used to. One important note is that you will not spread the bondo perfectly, it shrinks in an you will end up with a low spot. Apply enough body filler so it’s built up a 1/8 or so. Not more than that, you will be sanding your butt off, this gets old Take your 36 grit or 80 grit, depending on the amount  of area you will be sanding. If you think you can lightly sand and feather in one or two coats, then stay away from the 36 grit unless you know when to stop. It puts some pretty deep scratches in the bondo and the area around the bondo where you will be sanding over. Use 80 grit to avoid excessive scratches. For most larger dents you will want 36 grit and your larger or largest file board.

With the panel prepared and the bondo spread,  let it harden. If you have a mess you can carve on it with a knife to get some of the stragglers you slopped on it off. If you wipe on body filler when it is not set up it will surely stick and you’ll have to sand them off. Let it harden and pick it off later.

For large dents that you know will need at least 3 coats of body filler it’s best to have a rasp or body file hand plane. It works somewhat like a cheese grater. Let the bondo set up real good, feel the bondo and it should be a little warm but not cold….if it’s cold it will be too hard for the rasp if it hardens.  Take the plane and begin filing in one direction. This is very rough but effective way to cut your panel. This takes a little getting used but it will save you quite a bit of time, sandpaper and your lungs from tons of dust. Use it on the first coat only, the rough coat. You will be turning right around and spreading another coat of bondo over it, after you blow it off real well of course . This is used to help get the filler straight. The low spots will not be filed. Note: To help Identify the low spots… spray the filler with a cheap flat black paint, the cheapest fastest drying kind you can find. DO NOT USE ENAMEL SPRAY PAINT, you don’t have all day to let it dry. Find a cheap lacquer paint, Walmart brand works good at .94 cents a can. Simply dust it, don’t put a full coat of paint on, just enough to add contrast to the body filler to identify where you have sanded. This will greatly assist you identifying what and where you are  sanding. High spots are gonna sand first of course. Keep attacking them as you sand until  all the guide coat paint around them is off. If you have sanded the filler and panel is free of the spray paint you applied, chances are you are real close to a finished repair. But there are other things to look for and consider.

Take your inline sander or manual long board of choice or hand sander and begin sanding in a criss-cross (X) pattern. This is extremely important if you do not want waves. Sand at a 45 degree angle in all directions to each other. This helps cut the filler evenly. If you sand in a straight line…. you get a straight line. This is not rocket science and there are no tricks. You have to watch what you are doing. Don’t go nuts sanding, do it methodically. Sand And Feel, Sand And Feel. Pay attention to body lines. They will have to be included in your sand and fill process. For straight lines use tape and sand up to it, reverse and sand down to it. Use tape when applying bondo to get a straight line. Apply the body filler over the edge of the tape and remove the tape before it hardens. If the filler hardens you’ll be sanding the tape too, so pay attention.

Apply bondo as many time as it takes to fill the low spots. If you have high spots you’ll know it. If the metal is showing and the bondo isn’t sanded… you have high spots. These will not go away. There are two ways to deal with this, only one is the right way. You can fill the whole panel up with body filler and sand and sand, or you can take your pick hammer and carefully tap them down. Tap them down!!! Don’t be afraid to use the hammer, you will need it until you are finished and satisfied. Don’t cheat, if it’s high… tap it down lightly…tap, tap, tap.  All the bare metal showing is high so tap the bare metal and beyond an inch or so. Stop sanding if you see this, they won’t go away and you’ll be getting further from straight. You’ll have to tap them all down and apply more body filler.

When you know your getting it close switch to the light grits. Use 80 grit paper and feather all the edges of the bondo and the paint together. It may feel a little rough and that is normal. You are filling the dent, the primer you use next will take care of the small scratches.

Another note: When mixing the bondo try to avoid flipping it over like taffy. Roll it over and spread mix it. You don’t want to let air get trapped in there. You will end up with pinholes eventually. Pinholes are just that. Small little pits in the bondo. These can be filled later with a glazing putty, but try to avoid excess air when mixing.

After the 80 grit sandpaper begin to taper down on the sand paper. Use 180 to feather any scratches in the paint near the filler. Finish with 320 to assure you won’t have sand scratch swelling later on down the road. The smoother you get the panel from here on out the nicer the repair will be as a finished project.

Wipe it down, look for pinholes, fill them with glazing putty if you have them. If not get that primer ready and spray on 3 good coats. Dust your primer with the black spray can and begin sanding again. I’ll write about the primers next.

Good Luck with your project. You’ll learn from experience, you can’t screw it up if you know these basics to bondo. It’s easier to do than explain

For further reading on Body Fillers  go here:   Bondo Basics – The Art Of Body Filler (part 1)

Tags: autobody techniques, body filler, Bondo, corvette repair, fiberglass repair, heavy weight gold filler, pinholes, sanding techniques

Remember Those Old Classic Cars

Remember Those Old Classic Cars

Remember Those Old Classic Cars by Len Roe
Can you remember back to a time when cars were real? I mean when they were made of good heavy metal. A time when they all had their own character. They didn’t all look the same. A time when you could tell a mile away that a Chevy or a Ford was coming because of the identifying characteristics. The rumble or roar of the engine. That special sound a Pontiac made as it rolled down the highway. Every car had its own specific sound and we knew all of them.

That was a time when all cars had a class of their own. They all had their own shape and look and each year we waited for the coming changes wondering how we could modify it and make it look even better.

We could chop the top, add some fins or cut in some vents. We could change the paint design and add some flames and a lot of pinstripes. We always had a new idea to make our car an extension of ourselves.

Back then we all had our own favorite car and we worked on it everyday to make it shine, run smooth and stand out in the crowd because it was ours and we were proud of it.

There was the 51 Merc, the 57 Ford convertible, the 57 Chevy. And don’t forget the Charger, the Transam and the Firebird. All classic cars in a classic time.

A time when it was fun to go to the drag strip and show everyone what your car could do. It was great to pop the hood and show off the powerhouse that made that puppy roar. To see all the chrome shine and sparkle.

Remember when we hooked a sparkp…read more
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Tags: autobody techniques, automotive industry news, classic cars, muscle cars

The Basics Of Dent Pulling

Our first lesson today will be on the basics of dent pulling.  After all, dent pulling is one of the most challenging and rewarding of all aspects in the body shop. Let’s create a scenario. Grandma just hit the garage again backing out and you’ve got to help her out. Well first of all you give her crap and remind her how good her cookies are. First you’re gonna want to analyze the damage. It’s in a good 2 inches and creased about a foot. With any luck you’ll be able to hammer it out. Open up the trunk and take a look. Find yourself a decent hammer, body hammers are essential but of course anything will work. If the dent is creased your going to need to reach around with a contoured dolly. A hammer and dolly sure work well together in these situations, you may need a helper to do this or your “go-go gadget arm extension”. From the inside of the trunk, begin tapping gently. You’ll want to walk the dent out together. Starting in the middle of the dent is NOT what you want to do. Take a good look at it first. It’s a good rule of thumb to pull the dent out working your way back from the way it went in. When you have the right combination you should hear the hammer hitting the dolly, nice and clear (clean). It takes a bit of practice, but with the right tools you’ll get it. There are a variety of hammer & dolly combinations, so find yourself a cheap set of these, check out my store at Begin Autobody.com The more time you spend doing this the better. Again, just take your time. If the hammer and dolly technique don’t work, grab the biggest hammer you have. No! You certainly will make it worse. An assortment of pry bars can help you out, but only so much. It can be tedious and time consuming, an you’ll need something to pry against. Use caution and take your time. There is no shortcut here, just poke around a bit, it usually helps, if only a little.

That’s not working though? O.K. here’s the secret if you have a few bucks laying around especially if you enjoy doing autobody work and pulling dents. You’ll need to find yourself a stud gun uni-spotter. This is a must have in the shop if people (grandma) keep on hitting the garage. It’s a hand held spot welder that will weld pins to the damaged area. This can be quite fun, but make sure you grab your basic essentials. “SAFETY FIRST“. You need to grind the damaged area down to the bare metal, the pins will just spark if you don’t have a good contact. Be careful of sparks especially near the gas cap door. If the damage is near this then wet a rag with water and shove it in there, just to be safe. Watch what you’re doing, you certainly do not want the grinder where you don’t want it. NOTE: Use duct tape if you have to, a couple pieces here and there will assure you that you won’t cause any extra unnecessary damages to fix while you’re at it.

Alright, back to the Uni-spotter. I’ll assume you know how to use your stud gun if you already own one. For a few bucks if you need one, you may be able to ask the nearest autobody shop near you if you can borrow theirs. They may look at you funny, but oh well, it never hurts to ask. To begin, run a row of pins in the crease about 1 inch apart. Grab the slide hammer and begin pulling, in this case she backed out and hit the garage. You want to then start at the rear of the car where it’s damaged and begin pulling and tapping gently all the way to front. NOTE: When you begin pulling on the dent, take your hammer and tap anything around the dent down, this allows the metal that is streched to come back down where it should be.  Always begin pulling from where the dent starts and move along to where it ends, tapping down any high spots along the way. You can do this as long as it takes, you want it as close to the original contour as time allows or humanly possible. Remove the pins with a side cutter pliers. Usually the head of the pins remain on the car. These can be ground off with a hand held grinder. NOTE: Pick up the pins you cut off. They may find their way into your tire Okay!!! Great, you should be good to go. Don’t tap any harder than you have to, tap lightly and often. “lightly”. With the uni-spotter put away, your not gonna want to haul it back out again. Tap all the way around the dents (high spots) using the pick side or dove tail side of your favorite body hammer. You need a good hand to feel. Give er a good rub. The use of a rag, or by simply putting a clean cotton glove on will assist you in determining what’s high and what is not.It will be rougher than a cob at this point, but you’re looking for the outies (high spots, nipples). These you do not want. Now it may be time for that hammer and dolly again. NOTE: you’ll be putting a lot of body filler on trying to form your way around high spots or by having to pound them in after each course of body filler. Do your best, it challenges the most advanced autobody tech, but persistence pays off. Are you satisfied? Congratulations! If you did these simple steps thoroughly, you should be about done with this step. Take a breather for now, it’s time for some fresh baked classic grandma cookies.:).  “Keep in touch, we’ll bondo it up real soon”.

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Tags: autobody techniques, dents, dolly, hammer, hammer and dolly, how to pull dents, pulling dents, slide hammer, spot welder, stud gun, uni-spotter, welder