I know this is a bit different of an article, but if you read my articles then you know that if a reader of my articles asks a question I usually try to answer it if I can. Today I had a reader ask how to do the bodywork after the rust patches, or replacement panels are in place.
In this article, I will try to answer his question. I don’t know if this is exactly what he was looking for but I will wing it. The question is how to do body repair after the welding incomplete. I will start right after you turn the welder off.
A 5″ air grinder with 36 or 24 grit disks.
A 2″ angle air grinder for the detail work, you will need 80 grit disks for this grinder.
A 5″ DA sander, DA stands for dual action sander.
A long hand sanding board with 24-36 grit stick on paper.
A 12″ air file to get you through the bigger part of the sanding, you will finish by hand.
Sandpaper: 24, 36, 80, and 180 grit.
Plastic filler (Ever Coat)
Metal glaze (Ever Coat)
After you have faced off the welds around the patch panels, you will begin to spread the plastic filler. This is my standard warning with the plastic body filler; the filler should never be more the 1/16″ – 1/8″ thick. If you load it on you will have problems later on.
What you need to do here is make sure that you pay very close attention to what you are doing when you spread the body filler. Plastic filler is not a magic wand, it’s quite simply a tool to help you get the job done, and like any other tool when used right it will do amazing things.
Now down to the real business of finishing the rust patch process. Most classic cars do have some rust in them simply because they have been running around for 30 years or more. Rust is just a side effect of the ageing process of the car.
Remember the toll list above? The first toll that you will use from that list is the 5″ air grinder, and you will need to be very careful with this tool as it will grind the metal out very quickly. You need to use your eyeballs and your hands in unison to do this right.
What you need to do here is making that big weld that is sticking off of your car as flat as you can without grinding through the metal on the car. This may sound like an easy task, one that you don’t need to pay much attention to, but it takes some learning.
I know people who do this every day for a living and still grind too much every once in a while. So please don’t take this lightly, you need to get to know your tools you to develop a feeling for how they operate, and what they can do for you or to you.
You need to focus the grinder on the weld trying not to slip off of it and grind the car body. This takes some getting used to when you’re using the 5″ air grinder. If you have to make a couple of weds on scrap metal and learn the process that way before you graduate to your pride and joy.
Now the warnings are all done, what you should see when you are done with 5″ air grinder is the weld should still be a little high because you about to move to the final weld finishing stage of the process.
If you have a nice even weld you should never need to go with more then the 36 grit disk on your 5″ grinder. But if you had a problem with dirt, oil, or toxins on the metal and the weld piled up in some places you may need the 24 grit, but I would try to stay away from it if possible.
By now you should have the weld ground to the point where it’s just a little high all the way around. Now you need to change tools, but the process is exactly the same. It’s time to fire up the 2″ angle grinder and load it with and 80 grit disk.
The finishing process could take a lot of 80 grit disks so spare no expense buying the 80 grit disks. You looking for a flat smooth weld after this process. As a matter of fact, if your weld is perfect it should almost disappear.
Once you have gotten your weld to this point you are ready for the plastic filler. Heed my warning from above not more the 1/16″ – 1/8″ of plastic filler. Get out your mixing board and scoop out about a golf ball sized portion of filler on to the mixing board.
By the side of the filler squeeze out about a 1″ line of hardener and mix them together. Do not take to long doing this or the filler will harden while you are working with it. Get you spreader and begin spreading the filler on the area that you have repaired.
After the area is fully covered with filler you need to give the filler a few minutes to kick off, I’d say about 10 – 15 minutes depending on how much hardener you used. I don’t let it dry rock hard before sanding it, I prefer it to be a bit malleable.
It just seems to sand a lot quicker if you don’t let it dry all the way. Although this may take some getting used to, it’s a great tip to help you save some time that may be better used elsewhere. The first sanding will be done on with the long hand board, and 36 grit paper loaded on it.
You should sand the filler using an “X” motion this makes the work come out looking much better. I try to stay away from using the air file to sand the filler because this is not a production process, and you pay a lot more attention to what you are doing when you sand by hand.
Again you should not use the 24 grit paper unless you have to. After you have sanded the plastic filler with the 36 grit paper you should feel the repair work with your hand and see if there are any high spots or low spots.
Although I would plan on going with another spread of the filler because you have to at this time. If you got lucky and felt no high spots or low spots you can use metal glaze to fill the 36 grit scratches in the first coat of filler. If that’s not the case you will need to spread more filler.
For this article we will go with the second scenario, you have discovered some minor high spots or low spots. What you will do now is mix more filler the same way as I told you above, and spread it over the work area again.
Paying close attention to not letting it dry all the way. There will be a slight difference this time. What you will do here is start the rough finish with the 36 grit paper on the long hand board, but this time leave the filler a bit high on your work area.
Here you will finish it with 80 grit paper, then go over it with metal glaze. The metal glaze is a finishing substance not designed to fill small dents and waves. This is only for the finish work. It is watery in comparison.
You mix it the same way as you do the filler, but it’s a little harder to get a feel for how much to use because of its thin makeup. After you have spread the metal glaze you should let it dry all the way, and then sand it with nothing more than 180 grit paper.
If you have to use 80 grit just to break the surface that is fine. But after you have removed the smooth hard surface you will need to sand it with 180 grit paper only. Now we are at the end of this article, I hope this helps you out.
The next step is a primer, and I have covered that a few times already
I’ve been in the automotive business for about 20 or 25 years, I have worked in all facets of the industry, from parts to restoration, all different makes and models.