Hot Rod Forum banner

Trying to understand filler work

11K views 98 replies 11 participants last post by  glhx 
#1 · (Edited)
Having a hard time with this. There's about 4 layers in there
They get sanded down and every time it's too low or not the right shape. I rough it out with 36 then go to 80 and polish it up with 180
There's still a lot of 80 scratches in there. There are 2 spots.....one is on a curve and the other on a flat panel. I thought it was done so I put some high build on there, guide coated and found lots of low spots. I was told you can't put filler over high build so I took the high build back off. The next 3 times I just put some epoxy on there to find low spots. Epoxy doesn't build and takes a 24 hours recommended to dry.
.....so I can't run high build because I can't recoat and it's taking forever with the epoxy because of drying times......not to mention having to keep the epoxy at 75°F for 12 hours at a time which is costing a fortune to heat the shop. I'm going through a vicious cycle. This picture is as close as I've come....I think high build will cover this.

image by -glhxturbo-

It still seems like its low in the top left corner.
image by -glhxturbo-

Here it is sprayed with a thick coat of epoxy. There's no build on this so it's not saying much
image by -glhxturbo-


The flat panel at an angle.*
image by -glhxturbo-


Any thoughts on this.
 
See less See more
4
#4 ·
Ok, here is a "Basics of Basics" on filler work that others have found useful.

Bondo Basics - Autobodystore

Something not mentioned in the "Basics" I don't remember but I don't think so is how you need to remove the paint back aways from the filler work. And of course you don't know how far sometimes when you start but lets just say it's most always further than you think. You want the paint removed back away from your work so when you feel the filler you aren't having to figure out what is filler and what is paint. Because YES just the thickness of the paint can be felt and it can be confusing.

But print out that "Basics" and sit down on the couch and read it a few times. And clean up your spreader with a thinner soaked rag when you get done.

Brian
 
#94 ·
Ok, here is a "Basics of Basics" on filler work that others have found useful.

Bondo Basics - Autobodystore

Something not mentioned in the "Basics" I don't remember but I don't think so is how you need to remove the paint back aways from the filler work. And of course you don't know how far sometimes when you start but lets just say it's most always further than you think. You want the paint removed back away from your work so when you feel the filler you aren't having to figure out what is filler and what is paint. Because YES just the thickness of the paint can be felt and it can be confusing.

But print out that "Basics" and sit down on the couch and read it a few times. And clean up your spreader with a thinner soaked rag when you get done.

Brian
I have a question on something mentioned in the article linked here on final skim coats. About 2/3rds of the way down the page it says:

"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 offiller 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. "

He seems to advise against it but is he saying it is possible to use fiberglass resin to thin bondo as a final skim coat? If not is it possible to thin duraglass with a little resin to do the job?
 
#6 ·
That helps a lot. Makes a lot more sense than what I've been doing.

I also think part of my problem is speed. I'm trying to make it perfect the first time. So when I lay the filler I'm getting edge marks from the spreader. I'm always trying to take these out with the spreader instead of knocking them down with paper. This in turn has me caught off guard. When the filler cures it drags holes in pattern. The more holes I get the more I'm trying to fix.

I probably need to spread it and leave it alone. Then knock it down and then run that skim coat.

Will you look at the metal......the metal is in a circular pattern surrounding the filler. Are those the high spots I need to knock down. I will admit I am not proficient at pulling dents with a hammer dolly. It the pushing of the dolly from the back side. I'm knocking down highs but not pushing hard enough on the back side.....maybe I don't have to......I don't know
 
#7 · (Edited)
Another question maybe rudimentary In nature,
How do you correctly use a long board? Hold it from the middle and apply light pressure.

Hold it from the ends and apply medium pressure.

The reason I ask this is becUse it seems when I hold it in the middle.....the ends ride up and it doesn't stay straight..

When I switch to the circular long board it seems to stay more straight and hold its shape better.......I'm using dura block. Need to clear this up.

I could be using this wrong. For the flat panel I'm using the 16" block

For the curved panel I'm using the circular block.

I'm thinking of going to a thick dowel rod that stays straight

All that being said......the bondo basics talks of 8" panel.....what it fits larger?
 
#10 ·
I wrote that so long ago I had to go back and read it to see what you were talking about. I am referring to is if you are doing a small area that is as coarse a paper you need. On a larger area you could go to 40 or even 36. But I have actually gone to only using 40 or 36 on VERY large areas with a long board. On the areas you are working with you don't need anything coarser than 80. But using the 40 isn't a big deal, if it helps you CUT that filler flat go ahead and use it. You just have to be careful to blow all the dust out of the scratches and to use pressure when spreading out new filler or polyester putty to be sure you don't bridge over the scratch as it can shrink up later after you are done and ruin your nice work.

Remember, use ONLY 2K fillers, polyester putty and fillers that require a hardener. Don't ever use putty that doesn't use a hardener.

Brian
 
#11 ·
You haven't removed the paint out away enough. And the very sharp edges on the bare metal tell me that is high OR the filler is low, that edge of metal to the filler should be literally transparent. It should taper off getting thinner and thinner, THAT is when you know you are getting close to having it smooth. If it jumps from metal to filler like that with a sharp line you know it isn't right. I don't even have to feel it to tell you that isn't right.

Brian
 
#13 ·
And Evercoats "Metal Glaze" or "Glaze coat" polyester putty is a great product for that "Skim coat". Spread it on thin literally looking at is as a coat of primer, it works great.

Brian
 
#14 ·
I think your explanation at this point shows me the next step and explains a lot. Along with the article and the definition of the current state I know where I'm at and where I need to be from here. This to me .....now....is the first stage of filler......now I need the skim coat to cover everything. Then finish that.

This has been driving me nuts
 
#15 ·
Brian is correct on the fact of all the high spots on that bare metal is showing too much, as Brian states you should just barely start seeing the high spot and stop sanding. When you just look at it you can clearly see there is a considerable high spot causing you a hard time. On the A pillars I find that a large 3M sqeegee works great for blocking the filler and primer and follows those contours while staying flat. Using the round durablok (tube) on those areas is tough because there is not as much contact point while you sand, making it difficult to get rid of the high spots. I find those little sqeegees work the best on all those tough spots even for the tops of fenders right by the winshield area.
 
#17 ·
Very true, this is one reason to use NICE, NEW, SHARP, QUALITY paper so it CUTS and doesn't "polish" the filler.

Very good point Mike about the flex.:thumbup:

Brian
 
#18 · (Edited)
I've been using the 8" and the 16" dura block because it covers the whole dent.
image by -glhxturbo-

The 16" seems to flex a lot in the middle and dig into the dent sort of sticking up on the ends so I stopped using it.............but Im not sure. I was told to hold it in the middle and apply light pressure. I think I'll try to use the paper to create the contour for the flatter panel. It does have some contour to it.

I stopped using the flex block because it was too small and following the wave. That particular pattern has several different contours. The flex block has been good in some areas. Might have to get more creative

I'll put a skim coat on it and as soon as I see it break metal I'll stop there
Probably need to change the paper more often as well

I've also had problems with creasing the paper with the flexible blocks.
 
#33 ·
I suspected You were using dura blocks, theres your problem right there. You need a stiff aluminum backed board file to do filler work..about 8" not the full size one. Those dura blocks are great but will flex slightly they're more for primer blocking and dings but they DO have their place. I have all of them too with the exception of that super long one ,I never saw a need for that one.
 
#19 ·
the problem is the metal work, body work, and inexperience. the blocks are fine as long as you are picking the right blocks for the right contour. I use a 3m 16" block that's a lot harder than those dura blocks but that's not the issue. Getting new blocks isn't gonna fix the issue. Getting straight body work is not easy and comes with experience. Just keep trying it and you'll get it. I hope I'm not discouraging you but to offer good advice means to NOT tell you to go spend more money but to just spend more time. My bodywork looked like that at one time so did everybody else's.

Go check out some of my videos. Lots of stuff on filler work. Go to youtube and type in "sanchtech". There's plenty of bondo tips in there.
 
#24 ·
yep. you'll think you have taken a step forward when your body work gets good but then there's an entirely different animal and another step you have to take to get hoods consistently good. I remember my bodywork getting decent but not on hoods til I really focused on the details of EVERYTHING, even how it sits on a stand.
 
#25 ·
Working body panels is an art, no doubt about it. The best advise I received came from the fellow who taught me to work with lead and Bondo in 1973 (H.S. auto shop). He said as soon as you find there is a need to add filler to a panel, you become a sculptor. Once you realize that, you will also need to realize that you are no longer shaping the panel, you are sculpting the fill.

In other words, once you spread fill, forget the panel until you are happy with the shape of the fill, or when you *JUST* see the panel again as it's high spots poke through. At that point you have a decision to make. Either stop or add fill to the low spots and sculpt some more.

Most of the trick to sculpting anything is knowing when to stop removing material.
 
#26 ·
Working body panels is an art, no doubt about it. The best advise I received came from the fellow who taught me to work with lead and Bondo in 1973 (H.S. auto shop). He said as soon as you find there is a need to add filler to a panel, you become a sculptor. Once you realize that, you will also need to realize that you are no longer shaping the panel, you are sculpting the fill.

In other words, once you spread fill, forget the panel until you are happy with the shape of the fill, or when you *JUST* see the panel again as it's high spots poke through. At that point you have a decision to make. Either stop or add fill to the low spots and sculpt some more.

Most of the trick to sculpting anything is knowing when to stop removing material.
Very true, that is NUMBER ONE the absolute NUMBER ONE mistake guys make, taking off too much. Newbes very seldom leave too much, they always take off too much. That edge of the filler should literally be transparent, it should transition from filler color getting thinner and thinner like a fading color to the surrounding metal. VERY seldom does it go from filler to metal with a definite line like in these photos and still be smooth. It does happen under certain conditions, but it is VERY seldom.

Henry (Tech69) has some great videos but I don't know where to find this particular lesson so I grabbed one off the net. This guy has some great explanation of the process. Click on the second video down on the page. I wanted to post a photo here showing the proper look that blocked filler should look. I googled images and found this image but it ended up being a video, which is cool, the video is very good. I don't like using the course paper as long has he does but other than that it is some great basic info. I also don't like how close the paint feather edge is to the work but there are lots of different ways to pull it off. You will notice he warns of hitting the filler when you feather edge the paint away after the repair, well if you feathered it further to begin with there wouldn't be a problem. But check it out, it's a darn good explanation of the process.

Body Filler - How To Block Sand Bondo On A Auto Repair

Brian
 
#27 ·
I studied the pictures again and was going to ask the question of fading into the metal and becoming transparent. Brian already answered it in his last post and that tied things together

It should feather over the metal and there are a few small spots where this has been done it looks like. It's the solid line transitions that are problematic and need more filler.

I also see why the paint needs to be further back.....you can see the high spots and you know the inside of the circular pattern is low. You don't know if outside of the circle is low because the paint is covering it so you pull the paint back to see?

This is finally starting to make sense. I've only used 3/4 of a gallon of rage extreme on these spots and a few other small ones that were covered by the primer. Hopefully they won't shrink. They were more like dings.

Basically what I've taken out of this is that you finish the filler to almost perfection BEFORE high build. You last coat of filler should be like your first coat of high build.

I have 2 questions.......if the primer is going to shrink and sink down into body work filled by primer. How long will that take with the car sitting in the shop?

Mine has been sitting there in high build for 2 months on the first coat and 3 weeks on the second round of blocking with 180....I had to buy a new gun to spray the primer more evenly. The blocking is taking shape though.

Second question is......since the body work has been sprayed with high build.....then glazing putty put over the high build. What now.....if I want to put more filler in there should I take it out down past the high build and start over?
I was told glazing putty can be put over high build.....but regular filler should not be.
 
#29 ·
"I have 2 questions.......if the primer is going to shrink and sink down into body work filled by primer. How long will that take with the car sitting in the shop?"

This is NOT the case at all, if applied properly it hardly shrinks at all. The biggest mistake with primer is asking it to do more than it is designed to do! Asking it to fill 80 grit scratches is MORE than it was designed to do. Asking it to fill low spots that weren't properly filled with your "last final skim coat" is asking it to do more than it was designed to do.

"Basically what I've taken out of this is that you finish the filler to almost perfection BEFORE high build. You last coat of filler should be like your first coat of high build."

You are getting this wrong. You use your high fill to fill the majority of the damage, the HUGE majority. You then use a skim coat of polyester putty as a "primer coat" to catch all the small, tiny imperfections like pin holes, small low spots, coarse sand paper scratches, that sort of thing. You don't have to use polyester putty for this last skim coat, but it spreads and sands SO much better than regular filler it isn't even a thought for me.

Brian
 
#28 · (Edited)
I'm just going to take most of that back off until I get back to the base filler without the high build on it and more or less start over. .....and not run high build over it until it's done.

Then it won't shrink too bad....I won't have the deep scratches and there won't be any high build on there.
 
#31 ·
At first I wanted to do this on top of the epoxy. In my inexperience I went through to metal over and over and over again. So I sprayed the metal with more epoxy as opposed to putting the filler direct to the metal. My shop is 75 miles away from my house now (it wasn't when i started this) so I go back every 2 weeks for a day. Trying to get the filler work done on the epoxy working like this has taken forever because it's recommended by spi to let the epoxy cure for 24 hours. So I literally was going back and filling.....sanding....spraying.
Then 2 weeks later filling....sanding....spraying. I always had to wAit to do every little step. I think now it's time to go direct to metal with the filler. It's not feasible at my level with the amount of time I have and the amount of time it takes to let the epoxy to cure, to wait every time I hit a metal spot. It's really holding up the project. You guys put it on the metal for years....can I still go that route and seal it up with epoxy before the high build? Do I need to hit the metal with 40 or can I hit it with 80?

I'm block sanding all other parts of the car already ....but these two large pots are giving me trouble.. I'm almost done with the first round at 180 block sanding.
 
#39 ·
At first I wanted to do this on top of the epoxy. In my inexperience I went through to metal over and over and over again. So I sprayed the metal with more epoxy as opposed to putting the filler direct to the metal.

My shop is 75 miles away from my house now (it wasn't when i started this) so I go back every 2 weeks for a day.

Trying to get the filler work done on the epoxy working like this has taken forever because it's recommended by spi to let the epoxy cure for 24 hours. So I literally was going back and filling.....sanding....spraying.
Then 2 weeks later filling....sanding....spraying. I always had to wAit to do every little step. I think now it's time to go direct to metal with the filler. It's not feasible at my level with the amount of time I have and the amount of time it takes to let the epoxy to cure, to wait every time I hit a metal spot. It's really holding up the project. You guys put it on the metal for years....can I still go that route and seal it up with epoxy before the high build? Do I need to hit the metal with 40 or can I hit it with 80?

I'm block sanding all other parts of the car already ....but these two large pots are giving me trouble.. I'm almost done with the first round at 180 block sanding.
HOLY CRAP, that is a hard way to get something done!

If you were really proficient there is no reason you can't do filler work in two applications, one to fill and then the second as a skim coat to finish it. WHAM BAM. Two applications is all you need on 95% of jobs, but this takes some experience. To do what you are doing AND learning, that is a toughie, you have my respect. If you read that "Basics of Basics" for bondo work over and over it may stick in your head when you get there, two applications is the whole basis of the "Basics". Using those guidelines WILL get you there.

Brian
 
#34 ·
That makes sense now that you say it. Those blocks were flexing on me but I thought it was me not knowing how to use it. It was working well for the blocking and the small stuff.

Not nearly as well for the larger one. It pushed down in the middle and rode up on the ends.....even with the 8" and more so with the 16"

Can you send me a link of where to get the file your talking about. I looked online and saw a lot of wood files. And does it still have the stick on sand paper.

I have the rolled stuff for the dura blocks and the regular large square sheets. I would like to get this stuff ASAP.

I looked over the videos brian recommended and feel more confident with it.
 
#35 ·
I actually got a good one at HF and was surprised at how well it worked its exactly like My expensive (name brand) one They have a wood handle screwed to an aluminum backer under 10 bucks if I remember right. but any place that sells auto paint would carry them...but expect to shell out 20-30.00 for name brand.
also I believe your pulling the filler too tight and not leaving enough on so try slobbering it on just to get it on there and with one pass level it then one pass in the opposite direction and leave it, dont try to get it all pretty ,let the sanding do that. If you want the filler to sand a little easier you can mix some of the poly putty with the filler. metal glaze or EZ sand use your blower (full blast) to clean out the sand paper as it clogs and get more life out of it.
doing filler work was the hardest thing for me to learn too so don't feel too bad ,it'll come to you...
DONT BE AFRAID to grind it all out and start over again now that your armed with some new ammo...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top