Body Filler Question

BrianS

Promoted Users
I did a search and did not find a thread that addressed this question directly.

I am not a big fan of filler, 95% of the filler I put on ends up on the floor. So the other day my neighbor was over and I was blocking down the skim coat on the rear quarter of the RR and he was giving me a hard time (in fun) on how much filler I was blocking off. Like myself he always seems to have a hobby car in the garage and I have seen his work which looks pretty good. What ensued was a conversation on max filler depth and how you see the guys on TV slather on 1/2" of filler. I was taught never go over 1/8". After he left I looked it up on the web and found a video by a 3M "application engineer" that said 1/4" for 3M filler was acceptable, 1/4 inch would keep me up at night......

What is the rule of thumb most of you guys use on thickness of filler????
 

JimKueneman

Mopar Nut
There are places on the Duster where it s likely more than 1/4 because the one fender was tweaked and I can form filler much better than I can work metal. My unprofessional opinion is if you have it sealed top and bottom with epoxy so it can never absorb moisture why not. I tend to put a coat, block it, a few coats of epoxy and the next day do it again so my cars have a sandwich of 1/8 of filler then epoxy then 1/8 of filler then epoxy until done.
 

texasking

Promoted Users
In my opinion, where the filler is, has a lot to do with what is acceptable. On restorations, I strive for 1/8" or less anywhere, but 1/8" on a door edge, or any panel edge, is too much. 1/4" (in spots) out in the middle of a panel I doubt would ever give a problem with today's fillers, but a little more time working the metal is time well spent to avoid it, imo.
 
The less filler the better but not all of us can work metal like a pro does.
I use black epoxy to seal the metal. Then lightly block sand the panel to reveal lows and highs. Next is hammer and dolly to try to get the lows and highs taken care of as best my ability and time charged will allow.

If the panel has a number of issues I will then shoot 2 coats of polyester primer using a 2.0 tip. When that is cured I guide coat and then block sand the panel with 80 grit to remove the guide coat. At this point most of the polyester primer is being removed and the black epoxy begins to show.

I then circle with a pencil the areas that need skimming with filler. Once marked I lightly sand the guide coat from the low spots and then skim with filler. Once satisfied with the filler work, I move on to the 2k build primer, guide coat, block sand to remove guide coat and then begin my finish sanding.
 

Chris_Hamilton

Trying to be the best me, I can be
For me when I was younger I used more filler, as my skills progressed I used less. Do the best you can with where ever you are at skill wise. Don't be satisfied too easily.

As for how much is too much I will say this. Generally when you have to go 1/4" there is something wrong that should be corrected in metal. Ideally you never want to go over 1/16" (ideally) to 1/8" (max) just from a Craftsmanship standpoint but depending on your skill level that's not always possible. Filler has a bad name because of how much it has been abused by guys over the years. Used correctly and with epoxy over metal there is nothing wrong with it. Conversely skimming an entire vehicle and having nearly an 1/8" of an inch on nearly the whole thing is not my idea of Craftsmanship either.
 

jcclark

Oldtimer
It's a moot point, if filler is done correctly, the thickness won't matter and will
outlive the car as long as it doesn't get wet.
I've seen filler 3/4" thick done over 20 yrs ago and still looked fine.
I strive to keep it as thin as possible using a stud welder but it's really only for self satisfaction,
1/4" or 1/8", it won't make a difference.
 

dhutton01

Promoted Users
I think some of the bad rep filler gets is due to the old filler products. Some 45 years ago I recall watching a body tech apply filler from a five gallon bucket that used no hardener. It was a long time ago but I’m pretty sure that is what I saw. That stuff swelled and looked like crap in no time.

Don
 
1965 Buick that needed a "little work and paint" according to the owner.

Left Quarter Panel Front:

Quarter Left Front.JPG


Left Quarter Panel rear:
Quarter Left.JPG


Turned out that most of the back half of the quarter panel was well sculpted filler:

Deep Bondo.JPG


This is just one example of what guys do with filler. I have found holes stuffed with old shirts and then window screen forced into place over the shirt and covered with filler.
 

theastronaut

Promoted Users
I don't go over 1/16" but have seen plenty of shops use however much filler is needed to correct body lines and sweep lines on show cars that have to be 100% straight and correctly shaped, and the metalwork isn't that great.
 

MikeS

Camaro Nut
'68 Coronet R/T, how thick was that filler in the bottom picture?o_O It looks like the traditional pink color filler below and a light blue filler on top?

Mike
 

texasking

Promoted Users
1965 Buick that needed a "little work and paint" according to the owner.

Left Quarter Panel Front:

View attachment 14855

Left Quarter Panel rear:
View attachment 14856

Turned out that most of the back half of the quarter panel was well sculpted filler:

View attachment 14854

This is just one example of what guys do with filler. I have found holes stuffed with old shirts and then window screen forced into place over the shirt and covered with filler.
With the price of filler these days, a quarter panel would actually be just as cheap as doing that :)
 

NextGen Classics

Floor sweeper
If you must use filler in any thickness remember this, bolt your fenders on and get everything aligned before filler work.

Then I drill 1/8 alignment holes in inconspicuous places, so reassembly is spot on. If you have to tweak or realign anything you will put stress on the filler and it may crack down the road.

This is another reason to put epoxy under any filler because if it cracks,you have an opening directly to the bare metal and you know what will happen next.....
 

RosharonRooster

Promoted Users
1965 Buick that needed a "little work and paint" according to the owner.

Left Quarter Panel Front:

View attachment 14855

Left Quarter Panel rear:
View attachment 14856

Turned out that most of the back half of the quarter panel was well sculpted filler:

View attachment 14854

This is just one example of what guys do with filler. I have found holes stuffed with old shirts and then window screen forced into place over the shirt and covered with filler.
Man. That looks like cutting into a birthday cake...
 
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