Ive started my filler process and I dont think its going well. I'm working on a the rear quarter.

once I locate the area in need I dx440 sand with 36 grit and dx330 then apply filler and sand down with a 12" block on a 8" area (for example) with 120 grit. It seems to take forever. I probably have 9 hours in 3 7" spots!

it seems like I can never get the middle part of the area sanded before the edges. I seem to be making a nicely blended dome of filler where the low spot was??!!or another low spot, this is really starting to get fed up with FUN poject.

I think Ive got it down to 2 problems I need answers.

1. any low spot whatsoever you can feel needs filler or is K38 meaty enough to take care of small imperfections?

2. when sanding filler do you go side to side with the sander or in a strait line.

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does any body know what the h*ll im talking about.. cant wait until the body is done!!!!!

Hello, I am a former collision technician. First off you are now using coarse enough sandpaper to cut your filler. You should completly strip area around damage where filler is to be applied. 24 or 36 on a grinder will work well. You have to use a rough enough material to give the filler something to bite to. Only then should you apply filler. Apply in a area just larger then damage or dent tapering edges. This makes sanding much easier. After filler has cured or is just beyond tacky it's time to start cutting. Use a 40 grit to sand to shape. The paper has to cut filler or it will load up & skim over it like has happened to you. That will just cause high & low spots.
After you have it sanded to shape you can use a lighter consistancy filler for a final skim coat. Such as Evercoat # 417. After that has completely dried ( the longer it sits the better it sands ). Use 80 grit to sand this off. When done you ahould have a nice product ready to feather edge & prime. You can also lightly sand after 80 grit w/ something finer such as 150. Just DO NOT use DA sander on plastic filler. It will give a uneven surface. Also, don't use primer as spray on Bondo. Make sure it's ready to be primed before or you will waste alot of time & materials. If you have any further ? email me @ Johnbondo69@aol.com. Good luck, John graemlins/thumbsup.gif

First off you are now using coarse enough sandpaper to cut your filler

Had to make a correction! You are NOT using coarse enough paper. John

Our Auto-body teacher always taught us to sand filler diaglally in an "X" patter. I usually use 80 grit to sand my filler.

Somewhere in Team Chevelle Arcives you'll find MartinSR's Filler Basics.
It's a GREAT over view of the steps to take in application of Filler.. Look it up it's well written.

I myself like to ROUGH and shape the frist coat of mud with 36 and use 80 on the final skim coat... Save your DA for feather edging the surounding area with 180

Here is your "Basics of Basics" to filler use.

John, I am with you on your description in all but one point. 24 grit grinder (and even 36 in most cases) is MUCH too course. It will damage the metal unnessisarily.
I hardly ever even use a grinder at all. Usually just my 8" "hog" with 40 grit sand paper on it. Modern fillers just don't need an open coat grinder disc to stick.

Think about this, how to you feather the filler out? You have to have some much finer scratches than 24 grit out on the edges right? I mean, if you didn't you would have to fill them with primer! :eek:

So if you filler is feathering out on metal that is finer than 24, why us it at all? Unless you are doing a real big filler job where it was going to get to maximum thickness or that sort of thing. For instance, as I said I hardly ever use a grinder to prep my metal for filler. This past week I had an unusual job. It was an old Toyota and instead of replacing the quarter we repaired it. It was a 16 hour dent (I did it in 4 smile.gif ). On that job, I was using much more filler than usual with the damaged area being about 18 x 18 inches. THAT repair I used a grinder with 36 on it to rough up the area, NEVER getting near the areas where I would be feathering.

But usually, I am doing very small areas more in the area of 8 x 10 inches or something like that. Those areas I just rough up with 40 grit on my "Hog".

For that matter, many times I only use 120 on a palm DA because polyester putty is going to be used.
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Plastic filler basics;

What ever tools you use the trick is to not add the last "skim coat' till you KNOW that it is all you need. Don't try to block out that first coat, just use it as a base for the LAST skim coat.

I was taught this procedure after doing bodywork for a number of years and it really works well:

Just apply a nice coat of filler (what ever brand, whatever style, we will put that aside right now). Cut that coat NOT to make it perfect, but to get the basic shape and filling you need as a base for the skim coat. You can cut it with 36 40 or 80 depending on how big the area you are working is. In other words, if you can cut it fast with only 80 then do it. But I would say that this would be limited to an application that is no larger than about 8 inches.

If you happen to have a few high spots, see if you can tap them down.
If you have a few low spots add a bit more filler to ONLY those spots.

Re-cut these last low spots you have just filled with the same grit you have been using (most likely 36).

If you now have a surface that ONE skim coat will fill, then apply it. If you don't work with it a bit more, but NEVER add a little here or there and think you will finish it without a skim coat.

If you have a surface that is very close with only a few VERY MINOR low spots like poor feathering onto the metal, poor transitions from one application of filler to another, or from the metal that is "poking" up here and there you can do the LAST skim coat.

This skim coat is very important, you want it to extend over the COMPLETE area, this is well past the damage you have been working. Maybe as much as 3 inches past the plastic that you have applied to "rough" it out.

This skim coat can be regular filler or a polyester glaze like "Icing" or "Polyester glazing putty", that is your choice, I use both depending on the size of the area being worked. Do not use anything that doesn’t mix with a hardener. NO, “Spot putty” in a tube, only polyester putties or fillers. If it uses a hardener, it cures to a hard film. The “spot putties” stay soft and can become even softer when the solvent from the primer coats it.

You now run a block, long board, or hog even over this skim coat with a little bit coarser paper than you plan on finishing with to cut off the resin that has surfaced in the filler. I usually just use the 36 or 40 or whatever I have been on the "rough" work. BUT take CAUTION not to cut much off, you want to JUST take the very top, don't really sand AT ALL.

Now finish sanding with your longboard or block or hog or whatever using the finer paper like 80 on a large area or 120 on that small 8" sized area. Block it out to perfection with a nice feather edge to the surrounding metal.

I can't stress enough, the trick is to know when just ONE LAST skim coat will do the job. And apply it COMPLETELY over the surface. If you only one little low spot in the middle, DON'T just do it, skim the ENTIRE thing. You HAVE to have one LAST skim coat over the ENTIRE thing every time. If you get in the habit of this you will do it over and over on every dent you repair and find that you can do just about any dent with just
two applications.

As you sand the filler let the board or block you are using run over the surrounding metal. If you only work on the filler you will sand it too low. You need to keep it as high as the surrounding metal, so use the metal as sort of a straight edge that you run the block or board off of.

Don’t worry if you cut through this skim coat here and there. In fact, you WILL most likely cut through. The point of that "LAST SKIM COAT" is that after you add it, you don't add ANY MORE filler. That "LAST SKIM COAT" is just that the LAST filler you add. If you hit a little filler below, or metal, that is normal and fine. The only thing you are looking for at that point is if the panel is FLAT. The filler skim coat is serving no other purpose than to finish you filler work, it is not a "sealer" or anything like that.

You can add fiberglass resin (“A” coat if you have a choice) adding the resin was exactly how I learned from the great Emery Robinson (my personal hero in the auto body world). But remember there was no products like polyester putties back then. When you add resin, that resin comes to the top of the film of filler. It is then something you have to deal with. The whole purpose of the SKIM COAT is to put a layer of filler over the top that is easy to block out with as little effort as possible. You want to be able to concentrate on making the panel FLAT not fighting with gummy resin, sand scratches and the like.

So the polyester putty though expensive is what I use.

How is this for an idea, a co-worker of mine showed me this very obvious tip. smile.gif

Add pour-able polyester putty to the regular filler! What an idea! LOL A little pour-able squirted into the "bondo" really thins it out nicely.

The "LAST SKIM COAT" should be left to cure a good long time. Where you may jump on filler and sand it as soon as it is hard, the skim coat should be GOOD AND CURED for an hour or more. If you can of course, in the production shop you may not be able to wait that long. The benefits of the procedure will not be diminished.

A little added note, I have found that I don’t use 36 or 40 grit at all anymore. I went to work at a shop that didn’t use the coarser grits so I had to learn not to also. I have found that using just the 80 and then finishing the Skim coat in 120 or 180 works great, even on large panels.

At this shop it was the first time that I wasn’t doing my own primer work. This meant that I couldn’t “cheat” with a lot of primer and blocking the body work “one more time”. I found that I had to get the work PERFECT, then give it to the painter. I did this in an interesting way, I look at the last skim coat as even a more “final” step. I now look it as “primer”. You see I have used polyester primer, which is like spraying “bondo”. They are both polyester resin based and act and sand very much the same. So, I figured why not just “spread out my primer” as the skim coat! It has worked GREAT, the painter jokingly says, “do you think I’ll need to prime this or just paint it?” I tell him, “Just clear it, it’s a shame to hide that work under primer”.

This method has worked great for me, it’s more of a state of mind than a procedure.

And don’t be afraid to buy the best sand paper and use a lot of it, the cost of the paper will be nothing next to the time and muscles saved. Find the paint store in town that services the PROS the Body shops in town, that is were you will get the right stuff and the right info.