Questions on Bodywork/Painting Cont.

[4x4n In A Cherokee In Colorado]

You guys have sent me like 20-30 emails asking me to put up a post on bodywork/painting in more detail, so here goes I'll try. I know the other post was hard to follow as I was trying to help Roadgrime and also trying to answer everyone questions along with it.

I figured with all the mail I better try to make all this clearer. This may take me 10 days or so to do, all I can do is a little at a time. I work too many hours.

First off, before you do anything you need to decide the condition of the origianl paint and if its been repainted, also what kind of bodywork/rust repair is needed. Do you want to keep the original color or do you want to color change it? Are you going to park the rig or still drive it? Do you really have the tools available to do this project? It takes a lot of tools, garage with nice neighbors, and a sizeable compressor to even get involved. There are some more questions you need to ask yourself, but this will get you started.

I'm going to start off with finding out the condition of the paint and if its been repainted. This will help you decide on stripping it or just repainting over the old paint.

I use a mill thickness guage to check paint thickness. The cheaper ones look like a ink pen. They have a magnet on one end. You stick the magnet on the vehicle and pull the outer portion of the guage slowly, watch the window, it will have numbers going to 20. Just when the magnet pulls off the surface, it shows the reading. You will want to do this several times and check the rig in like 10 different places to get an idea what your working with. A virgin/factory paint job will be in the 6-8 range....Anymore than that, and its been repainted unless its been striped. Most 2nd jobs will be in the 12-15 range and 3rd time jobs will be 18 or over.

You can also take a sander and feather edge a spot. This will reveal the coats in front of your eyes..You would want to do this is several spots, because the vehicle had maybe just been repainted in one area. You would see metal, ecoat primer, factory sealer, paint, then possibly clear coat all in layers. If its been repainted you will pretty much see this again on top of the factory paint. I have feathered spots on a few rigs that I counted as many as 15-16 or more layers...

Also a razor blade on a blade tool works too..Find a high body line or edge and cut the paint to the metal...You will also be able to count the layers.

Still for speed and reliability the paint thickness guage works best.

I generally plan on stripping if its been repainted even once. I never trust what the other guy done. Most of these rigs are now old enough that they will probably need stripped anyways to get a nice job..Most of these rigs have hazing/fading/dulling. Crazing(very small cracks in the paint) Peeling, or bad rock chips. Seperating or faded clear coat. Any of these items I just mentioned will require stripping to get a new long lasting paint job.

It is possible to use a thick coat of primer and then try to fill all the problems of the old paint, but then you will have a problem of brittlement. Thick paint has a brittle problem and it will chip and peel way easier then factory(and we all know how easy the factory paint chips)

If youve noticed over the years paint doent chip as easily as it used too. They used to use many coats and everyone still thinks the more paint, the better. That used to be a good quote, not anymore.

In the world of paint these days the less is better now. The paint is much harder now than it used to be and requires a final total coat mill thickness of 12-14 or less mills to be chip resistant. If you stay within these limits, a repaint can be just as chip resistant as the factory and many paint MFR's will put a lifetime warranty on the paint if your under the 12-14 mill thickness. A mill is very close to the same thickness as a cigarette cellophane wrapper.

Im going to go into stripping first, as 90% of us will require this.

I'll take a hood and go into that and tell you everything I do to a hood. For instance the hood on my 80 chero is single stage(no clear) enamel. It is still pretty shiney with no visable craking or crazing. Its in pretty good shape for 24 year old paint. I can see it was garaged for a portion of its life. It has some small dents and a few waves in the sheetmetal.

It has major chipping in the front. Its actually starting to surface rust in the very front. It has rock chips varying from alot to a little the further you go back on the hood. I would rather strip it that try to feather edge out all the rock chips. The rock chips need to be removed some way as not to see them thru the new paint. Anytime you are feather edgeing paint you will probably need primer in that area to get it straight again.

Think of a wood table with a scratch. If you sand out the scratch, then look accross it, you will generally see a low spot where you sanded the scratch. Feather edging paint is simaliar. You will need a very gradual feather not to see it when your done. That is why all but the very experienced will need to use primer to fill the low spot you just created.

Beacuse of all the chips, and the body waves and dents, I will strip it, and start a new foundation from bare steel up.

Well I'll get into more as I get time....For now, I'm out of that......Have a Great Night!!
Carey

[TexasJ10]

Perfect. This is kind of like the old Charles Dickens pickwick papers. I anxiously await the next installment.

[4x4n In A Cherokee In Colorado]

Well I figured I maybe better mention tools, as we cant strip the hood without them. I think I will go ahead and mention everything you may need, so I bet this post will be nothin but tools.

First thing youll need is a decent size 220 volt compressor. The bigger the better. Minimum would be 5hp 30 gallon. You really need to pay attention to the volume of air it makes versus air pressure...In body work we need lots of volume. You may run a 6cfm air tool for hours and there is nothin worse than waiting on the compressor.

Most air tools run best on 90psi, any more than that, then youll have trouble contolling them. Most MFR's recommend no more than 90 psi max to the tool, but we all push that every now and then. You will need a decent water seperator plumbed in.

You may look into getting 220 to the garage wired in also, I wouldnt get less than a 50 amp service. I used to run a heavy extension cord to the dryer outlet and get by with that...On weekends though it can be a conflict with the wife, unless you like wearing dirty clothes! lol

If your rig needs welding,I would seriously consider taking a welding class at your local Community College. This would teach you the basics, and can generally be fit into most peoples lives. Probably like 1-2 hrs, 3 days a week, nights or days. I was involved in FFA as a kid in HS, that taught me the basics. I'm greatful for that!

For types of welders, probably best for someone new would be the 110 volt gas or gasless(gas is better) mig welders. You can pick these up under 500.00 and will get you started pretty good. Many bodyshops do all there welding with a 110 mig. You will not be able to weld anything thicker than about 3/16ths steel so you may consider that if your looking at building bumpers, or something heavy also.

A oxy,acetelyene gas set up will also do well if you now the basics of welding. Whats cool about a gas setup is that you can cut steel with the torch set up, use the small flame tips to take out hail dents or other small dents, shrink, stretched metal, and do all kinds of either brazing or steel welding for doing patch panels, clear up to a full panel replacement if your careful. Us guys here in Colorado wouldnt know what to do without a gas set up as these are the very best at removing hail damage. We get tons of that here. A oxy,gas set up is really almost a requirement...I'll get into welding some more in depth in later posts.

I'll probably see a flame or two on this one,
I have used an ARC welder for years also. So you may look into that also(cheaper welder) You really need to have some experience in welding to use an Arc welder for sheetmetal. It really works pretty well, but it does have some limitations. I only use the DC side on about 20-30 amps with 1/16th high quality fresh rod. Plug welds work best, also overlap welds works to..Just dont try butt to butt or try to do any filling work with them. Like I said they have limitations, but when you drag out the 1/4 or 3/8 steel for you heavy work, they flat will smoke a weld and you can buy these for 300.00 or so. You can also get an attacthment to fit your Arc to do factory like spot welds, another +

A mig that could do the same will be 1300-1500.00. So you may look into learning how to do sheetmatal work with an Arc welder...

I'll get into more welding later so hang in there!

Ok, on Air tools. You need to look for quality tools if you want quality work. For air sanding, Hutchins are awesome, they are made in L.A. and are of the best quality! Very smooth(little vibration) long lasting tools. But very pricey, a DA is around 175.00 other sanders are more than that.

Snap on and Mac sell some pretty nice ones too...Most are just rebadged CP or other name brands. Both Snap on and Mac do not make very many body tools. Most are some one elses brand with there pricey name on them so pay attention, alot of the time you can pick up the same tool cheaper. They are both getting into making more of there own body tools so there is more of a selection than there used to be. But for machanics type tools including air tools, you cant beat either!!

Craftsman makes some decent body tools also, I would say more now than ever. They have a huge factory in Colorado Springs!(plug for the locals!)

I would try and stay away from the chinese/taiwan look a likes but thats another option also...If your just doing one rig and are not looking for a showy job, then they will work.

It is somewhat hard to do any real nice feather edging with the cheaper tools. But like I said they would get you by.

Youll need a nice hammer and dolly set up also. I own a Mac set up and I like it. Get something of quality. The cheap hammers break after the first swing.

If you have several big dents, you will need a way to pull them. I call it a Spitz tool or stud gun as they were the first, and the name stuck. They are a small welder that fits in your hand, that welds a stud to the body(bare steel) This allows you to pull the dent with the welded stud, then you cut the stud off and grind it smooth. That way you havent made any holes to fill. Be careful here. I have seen several bodymen light the insulation behind the panel on fire, then we had a carbque in the shop! The tool gets the metal cherry red in a small spot and if that touches anything behind the panel you will have a fire....Cars a VERY flamable! Please remember that!

Dang!! Out of time again!

I had a big day today, so I may have missed some tools. I will be mentioning other tools we will need in later posts in more detail.

If you guys have any comments or questions, post em, I can just tell my experiences here. I know I'm pretty biased! lol I have learned my own way of doing things. You all may have your own way also..Please elaborate some though.

I had alot of guys telling me they are wanting to learn the basics from the start and were very anxious for an in depth post on body/paint work.

I enjoy sharing what I have learned thru the years, maybe a few of you will get some use out of it.

Next post will be on stripping that hood, getting the dents out, straighting out the waves, and getting it ready for undercoats.

I will also have a post on taking a hood with good paint, fixing some dents, and doing some striping to the front, and sanding/feather edging the rest getting it ready for undercaots.

Carey

[TexasJ10]

OK, I have to ask one very basic question. Does DA stand for dual action? I'm also curious about two stage compressors. These usually run at around 175 PSI, but seem to provide much higher cfm at 90psi as well. Any drawbacks that you know of to a two stage?

[JeepBountyHunter]

D/A is Dual Action...Great post! Gives me flashbacks from my AutoBody days...

Originally posted by TexasJ10:
OK, I have to ask one very basic question. Does DA stand for dual action? I'm also curious about two stage compressors. These usually run at around 175 PSI, but seem to provide much higher cfm at 90psi as well. Any drawbacks that you know of to a two stage?

[RailSlide]

I will be keeping my eye on this post.

[scott f]

Definitely educational as I am stripping my Wag down to metal.

[4x4n In A Cherokee In Colorado]

TexasJ10, A DA is like Bounty said, a Dual Action Sander. The sanding disk wobbles as it spins. It uses a counterweight on the drive to do this. So instead of grinding like a grinder, it woks in an oval motion, this slows the rpms down to like 100-200 rpm's. It softens the grinding action, allowing you to do precision sanding...This allows you to feather out an area much more level than a grinder could.

On the Two stage compressor. It is just that. It compresses the air at around 125psi in one piston cylinder, then the air is sent to another piston cylinder to further compress it to 175psi...If you can afford to buy a two stage, it really is the way to go....They provide much more air than the single stage compressors. Even your low end two stage compressors can keep up with two men at once, decently.

I only have a 1 and 1/2 car garage, I wanted a two stage, but I didnt have the room for it. I bought a 60 gallon Campbell Hausfield Quadzilla..Its 4 cylinders, but single stage...I paid like 800.00 for it....Ive owned it over a year now and have painted a couple cars with it...I'm pretty happy with it..I dont have the high pressure, but I have pretty good cfm flow...If you can get a two stage, that is the way to go!!

Ok, on stripping the hood.
First off, with the hood shut, get a marker, grease pencil, or a charcoal pencil. Get down on a level plane with the hood. Look for any high spots or low spots, dents, dings, etc. Use your marker to mark these spots. On the high spots you see, it would be good when making your circle around them to put an H in the circle. That way you can quickly distinguish whats high and low. Since this panel has good access to the bottom side, you will be able to hammer and dolly most any dings/dents you find.

Some rigs will require hood blanket removal.

On small dents, maybe up to quarter size or so, you can use a flat faced dolly hammer, to hammer the dent against the dolly. Go gently, and make sure the hammer is flush with the dolly. This method is called Hammer on Dolly, you only want to use it on dents up to the size of a quarter or so...Hammer on dolly is only used to make small adjustments to the metal. The dolly is placed on the low side of the dent(ouside) The hammer is placed under the dent. (inside)

On a high spot, you will need to go vice versa, dolly under the hood, hammer on top.

This will generally remove the dent close to flush. Youll have to play with it a little, go easy. Stop and feel the area with your hand flush on the top gently sliding your hand back and forth, you will feel any imperfections. If your real close that will be fine....Make sure you have now not created a high spot where the low spot was. If so, hammer the high back down, a pick hammer will help here using it gently.

You can use a little filler or glaze to finish it off later..The more experience you get, the less bondo/filler you will use in time.

On bigger dents, you will be doing the hammer OFF dolly method, you will be using the dolly more around the outside of the dent and hammering starting on the outer portion of the dent and working your way to the middle not hammering against the dolly. So basically on bigger dents, theres a rule. First in last out. So what caused the dent, will be pushed out last. So if you have a dent with a point in it, you will want the very point of the dent to be pushed out last. This is done to reduce stretching the metal. If you push the center of the dent out first, you have just stretched the metal, then we will have either a permanate high or perminate low spot. Youll end up with alot of mudd/bondo!

On bigger dents, you will have some minor stretch. Once you get the dent close to flush, you can go back to hammer on dolly method. And remember, Hammer on Dolly is only used for the small stuff. I generally will now use a shrinking hammer while using the dolly here to strenghten and shrink the metal back. Use your hand alot to feel the area. On bigger dents, you can also use a small straight edge against the hood to see what you need to do.. I will alternate dolly to the bottom side, dolly on the top side getting out any high/low spots.

Youll want to keep the area to just below flush to be able to coat it with a coat of bondo and not end up with a high spot afterwards. The bondo is used to fill the imperfections only and blend the low back to flush.

Bondo can be used up to 1/4 inch with absolutly no problems, so if you feel you cant get the dent all the way out without alot of stretching then quit there, and mudd it up to final it out. I will fully explain how to use bondo in the next post.

You can also use a torch on dents up to a golf ball size....I will post on that later....Very Tricky!!

So we only need three body hammers....A flush faced hammer, a pick hammer, and a shrinking hammer. One straight dolly and one curved dolly will get you by.

Now that we have the hood looking straighter. You are going to need to grind all the areas that are needing a coat of bondo/filler/mudd, whatever youd like to call it...I call it mudd. On bigger dents sometimes its easier to do your grinding first, as sometimes you end up with lots of little highs and lows and it makes it hard to get all the paint off...

Well as usual, I'm out of time!! Sorry, but if i'm on the computer all night the wife and kids get worked up...Plus one of the kids always have a project that uses this computer...I'm sure thinking about getting ME a laptop....Till then I only have an hour or so a night...So hang in there!!! It will take a few nights to get the hood ready for primer, so hope your all patient!! Carey

[J10/J20 Project]

very good info.
I can't wait for the next lesson.
How much to make a Truck look pretty [img]smile.gif[/img]

Thank's
Paul.

[4x4n In A Cherokee In Colorado]

Onward! Now that we have removed the dents, most of them will need a light coat of mudd. There are several ways of going to the next steps.

First thing, get a dust mask and put it on!! Old paint generally wont hurt you much, but many old cars had high amounts of Lead in the paint formulas..So its really a good idea to protect yourself...Plus it sucks, the next day after your done, and you are still blowing the color of your rig out your nose..The paint dust is so fine it really gets way back in your sinisus's. Some people are bothered by that, some are not...Just put the mask on, OK!!

For prepping the areas for mudd, you can use a 4 ich air grinder with a 24-36 grit disc for most areas. It spins at around 5000-10000 rpms + so eye protection should be worn. These are a small hand held grinder that most guys cant live without. They are fantastic at removing paint quickly, and getting the area ready for the bondo. Dont let these grinders sit and spin on the panel for long, you will create lots of heat quickly and can ruin a panel in no time. Just keep the tool moving, if you missed a little spot continue in the area and come back and get that spot just a few seconds later...This is called controlling the heat.

You can also use a 9 inch air grinder with 24-36 grit disc for large areas, these big grinders also spin at 5000-7000+ rpms, and can help in straightening the panel. You can create LOTS of heat, but with some heat control, will draw the metal back to flush, and help in doing final shrinking. It depends on what your working with, these work great on hoods, roofs, and large areas that had some small dings you have fixed and were just a smudge high or low. Hail especially!!

The disc is so big that it will naturally straighten as it grinds. Alot of times, this is all the panel will need to get it straight and ready for primer. You can work this tool a little slower becuase of it big size, it removes material just a little slower, allowing you to use the tool in your advantage in some instances.

You could also use a 90 degree angle die grinder with a 24-36 grit 3M rollock disc, the disc's are about 2 inches in dia, and they spin at 20000 rpms. They are good at removing paint out of nooks and crannies. Removes material Very QUICKLY!! Be careful!!

I like to grind my damaged areas first with high rpm in either 24 or 36 grit..Some people like 16 grit also... Then after I have grinded every spot I'm unconfortable with, I like to finish stripping with 40 grit. That way when you have the panel down to metal, you can easily distinguish what needs mudd and what dont from the difference in grit/grinding marks left on the hood. You can lose the damage areas if you just use one grit to strip. Its really hard to sometimes remember every little spot you just worked on....At least it is for me!! lol.

For Stripping I have tried about every tool available...I like an air polisher used for buffing paint...Mine is a Chicago Pneumatic(CP). It spins at 2300 rpm. I like an 8 inch sticky backed 40 grit disk on a 1 inch thick 8 inch diameter, foam 3M sanding back up pad. It spins slow enough that you wont build heat real quickly, this setup flat shucks the paint off!

If you let this combo just sit and spin, you will do much damage...It will warp a hood in no time! Keep the tool moving at ALL times! You will not be getting to bare steel the first pass in most cases, its ok..Just come back and get those spots in a few secs..Like I said, we need to control the heat...Doing this all day will wear you out, so be ready for a workout. It doesnt have to be moved real fast, just kinda...lol(you all are saying, uh?) Yea it will take a bit to learn, but anyone can do this. Stop and feel the panel with your hand, if it Hot to the touch, let it cool a sec...You dont want to go past warm. You can destroy any panel with too much heat.

Another tool that works pretty well is a (several words for this) Bondo Buster, Mudd Hog, etc. It is a large 8 inch sander used to grind mud off in large areas...It is simaliar to a DA. It uaes a simaliar oval type pattern but in a much bigger pattern...These are very nice in removing mudd quickly....They also work very well in stripping. They build heat a little slower than the tool I just mentioned above...But are also slower...They work well on newer thinner steel cars. I also use the 8 inch sticky back discs with these.

When grinding, or stripping, be very careful around trim and edges, one mess up and your trim is wasted...Use several layers of duct tape where you know youll be close to trim...Always be watching just ahead of were your going with to grinder or stripping tool.

If you are seeing sparks, you need to protect the window glass...The sparks will cause pitting just like follwing a Semi on a dirt road...I have seen many guys totally waste a windshield or door glass on a brand new car....All it takes is a little masking paper, or blanket to protect it...

You need to remove ALL the paint in the areas using bondo. Bondo does not stick well to paint.

If you get 75% of the paint removed you will be fine. You need to get rid of the topcoat and sealer coats completely. If there is still some e-coat left, you will be fine...

I like to go over the areas I stripped with some 80 grit on a DA to finish feathering any ecoat I left..This will aid in not having to use so much primer later.. Just leave you bondo grinded areas alone, as bondo needs a deep tooth to attatch itself with.

I will go into applying and sanding bondo next....I think!! lol.......If anyone has a question.....nothins stupid in my book!

Good Night!!

[TexasJ10]

It seems like the grits used are very course. Doesn't this make it hard to get rid of these marks later? Can an electric 4 1/2" and 7" grinder be used instead of the air grinders?

[4x4n In A Cherokee In Colorado]

Yes TexasJ10, the grits are very coarse. for bondo, the coarser the better..The deeper the scratch, the better the bondo will hold. Every body shop out there uses right around these same processes. Remeber everywhere you have grinded in less than 40 grit gets covered in bondo..Youll blend the bondo into 40 grit, which has been gone over in 80 grit. Makes a very good blend from bondo to steel with this process.

The primers we now use will fill an 80 grit scratch in two coats, without ever shrinking back into the scratch. Actually when your stripping, 40 grit really doesnt make a very deep scratch on bare steel...I have stripped alot of panels to about 50% steel, paint showing, then feathered it with 80 grit, then use 220 to further feather, then 320 to finish it out....Then just epoxy sealed it, and painted it...works great!

I will explian in the next post, finishing out the bondo...you will get your mudd work straighter using the coarsest grit that can be refinished..which is 80 grit...I will help you understand why this works, when I get some more time..

Before urethanes, you could only finish your work in 180 grit...Lacquer products are very thin, and it would take 3-5 coats of lacquer to equal 1 coat of urethane. Urethanes are much harder than the old lacquer products...Our urethane primers have about a 30-45 day window that they stay soft enough to get them ready for paint...If you let urethane primer sit for a few months after spraying, youll see that they are like sanding concrete...I will get into that later...

You could use electric. The dust is very hard on the electric tools...electric tools are much slower, so maybe that is why body shops only use air tools...The only major reason I could think of having trouble is the weight of electric tools, versus air tools....If your grinder was real heavy, with the heat created, you would warp panels much easier. Air tools are very light in Horsepower verus weight....Electric arent..Panels arent able to support a heavy tool with out caving as you sand/grind...

[scott f]

I have most of my wagoneer down to bare metal with aircraft paint remover. Now I want to over it with a DA. If I use 24-36 grit will that leave scratches that are too big for primer. By the way, this is probably some of the best info I have read on this forum. Thanks again!

[4x4n In A Cherokee In Colorado]

No, Just use that corase grit for putting bondo over. Bondo really needs 16 to 24 grit to hold well..I have always used 24- 36.. After the aircraft stripper...Just use a DA with 80 grit if there is still quite a bit of paint...You can also use 100 or 120 grit...It doesnt matter..Your primer shouldnt have any trouble filling any of these...I will be getting into the coats needed and how I prep primer for paint in later posts...so hang in there..

I took the day off to install my BJ's lift today/weekend...My garage is just starting to warm up!! Cant wait to go play in the grease!!

[mountainlander]

Keep it coming, this is REALLY great stuff.