Sanding body filler. Newbie question.

I am a total newbie when it comes to bodywork and body filling, so these questions may seem rather basic, but how smooth should body filler be before priming? What grit should I use to finish off? Do I wet sand?

 

It does not have to be as fine as wood working, 400 grit should do it. you usually do have to sand primer again after spraying, at least once. You shouldn't have to wet sand, or color sand as some call it, until after final coat. Wet sanding is to keep the paint or clear from cloging up the paper.
Are you using single stage or bc/cc?

 

good primer should cover 180 grit

 

Every one will have a different answer.. some use 120.. which is a little coarse.. 180 for me would be the finest.. you have to have tooth for the primer to bite in.. start with a lite coat for proper flashing.. the go heavier on the second coat for your primer..

 

I'm with 53sled, I go to like 320, and then put some dp40 on that bitch and lay paint.

 

yup 150, 180 ,400 to smooth may not bite..

 

180 before primer, 400 before paint

 

Like others have said 180. Never wet sand bondo, it absorbs moisture and it'll rust behind your filler, then one day when you're driving down the road your quarter panel falls off.

 

We rough the bare surface with 80 grit then spray DP40. Then rough it again with 80 before doing filler. I usually run 40, 80, 120 then prime. Block sand it, with 80 or 120. Prime again then 120, 180, 220, 320, 400, 600 and then seal and paint. After paint usually color sanding starts at 1200 or 1500 and goes all the way up to 3000 before buffing.

It's a lot of steps but it is worth it in the end.

 

i usually block filler to 180, prime (2 coats depending), then block to 400 seal and paint.....if you dont seal you need to block to 600

 

one good tip is to use a good filler. If you use the bondo brand or cheap stuff, the surface stays tacky and you will go through tons of sandpaper or discs due to clogging/clumping on the paper.

 

depends how big the area is. small dents the size of a 50 cent piece area easy to fininsh in fine paper like 150


if you have a whole qtr skimmed, thats another story, 80 grit would be fine there. a common mistake is to try to go to fine on the paper, and you loose your flat cut, and or make it to low.

commercial body men are supposed to finish in 150 grit , but many dont.

if you want to make a car real straight for paint, you need to block it with 80 1st anyway, so going to fine on the mud is un-neccessary


skull

 

I'm loathed by most painters for leaving my mud in 80. Now at a production shop, 90 percent of the painters DA you bodywork with say,180. So by leaving it in 80 they cut down the 80 scratch without screwing up the work you have done. I have been working at using 120 to finish my plastic. Never wet sand plastic.

 

I leave mine in 80 as well. Sometimes I'll go higher, but most often its 80. Primer, then 150 on a block, up to 320 wet then sealer. Done.

 

I go to 120. Then a light 150 so I can feel it better. Epoxy then surfacer.

 

Hey,

A 1/2 round "Surfform" blade can be used in the basic shaping of your fill, just as the filler starts to kick. This makes your 36-40 grit a thing of the past, prevents any clogged paper due to un-semi kicked resin, and gets you well on the way to the use of 80 grit, with less dust in the shop. It does fill the shop with little bits of ''confettie'' ala plastic shavings, though.

If you get in the habit early, of using plastic filler as more of a putty, than a ''fender-in-a can" type product, move on from your 80-180-220 grit and don't lean on ''high-build surfacers to ''straighten'' that which shoulda been bumped out further, you'll enjoy better results. Usually, you can bump out, and straighten the metal to within 80-90% of where you need to be much faster than 2-3 coats of heavy filler and spot putty. Good ,high grade brands of filler and spot putty are not very cheap, today!

Swanky Devils C.C.
" Humpty Dumpty was pushed!"

 

another tip is to take a used piece of paper and scuff all the mudd to get the mentioned tack off it, and only mess up that one piece of paper, then a new piece will go along way toward finishing the job.

that paper can burn up like dollars in a slot machine if you're not careful

skull

 

you guys prime over 80 grit??? that is nuts never heard of that. teachers at school told me that the 80 grit grooves are to deep for the primer the settle all the way down in and it will just skim over the grooves causing air pockets

 

I use u-pol fiberglass fine hair, reason for using this product is becuause glass doesnt absorb water at all! all other "bondo" type stuff will ... use a decent amount of hardner . its takes 40 to knock that shit down becasue its hard as a rock than ill move to 80 than like a 60 ...when i get it where i want it ..i dont use bondo ill use a glaze ..dolphin glaze (if you cant get a glaze try and get like a flyweight product ) is usually what works best for me ..do a nice thing skim coat to get out any air pockets you have ...(if your new at this i 100% guarentee youll have air bubbles ) than smooth sand it down ,the glaze usually can be sanded with very fine grit paper and it sands like butter man ...then id prime it and sand i always finish my primer with at least 400 dont forget when you prime it ... to prime in one color than go over it with a different color rattle can and just very lightly leave speckles everywhere .....reason being is that when you block it ..sand it just untill the speckles are gone ... if you are sanding it and there is a area where there are spckles left 9 times out of ten your body work isnt straight or you didnt sand it right .....

.also quick reminder ....if you use a primer with a hardner suck as a laquer primer or those rad ass ratlle cans that you activate the hardner on the bottom .. you CAN wet sand it .. which is what i recomend if you are going to paint it pretty ....IF YOUT GOING FLAT BLACK THAN SCREW IT ! dry sand that hoe wipe it with prepsol and bombs away!

good luck i hope this was helpful also keep in mind bono is godd for about 4 years thans it turns to shit so if you plan on keep her id use glass or cut weld and glaze it

AND DONT PRIME OVER 80 GRIT UNLESS YOU WANT YOU CAR TO LOOK LIKE A BADGER RIPPED INTO THE SIDE OF IT THATS JUST LUDACRIS

 

Also if you are using bondo ...use a cheese grater to shape it (you do this when its tacky) if your bondo is tacky for more than 15 minutes you didnt put enough hardner in it i can guarentee you that ...

 

decontrol you took the words right out of my mouth that is exactly how i learned

 

Thanks for the advice, I'll keep it in mind...

 

Oh boy!

More misconceptions! I'm getting to really HATE these bodywork and paint threads!

 

I love these bodywork threads! Let me hit that pipe too!

 

you know what's really sad is, this FNG comes on here for advise, and when guys that actually know what there talking about, take the time to post their knowledgable advise and try to help out the FNG, he actually dismisses their advise to some knuklehead who for whatever reason, goes on a senseless rant that about how it really should be done. i can't even understand half the shit decontrol spews, and then the original poster agrees with him!! sheesh, some people just don't get it!! ya know, maybe i just don't get it!!

 

If you want to do a job that you can be proud of for many years follow these directions.

1. Body filler needs to be mixed at 2% by weight with hardener (100 grams filler and 2 grams benzoyl peroxide hardener). You see some people will add or subtract the hardener amount based on shop climate, this is foolish. Too much hardener will make the dye used to allow you to know when it is mixed, to bleed through the final finish. This might not happen right away and then all of a sudden one day you will see it. Too little hardener will not completly cure the filler. Things will look good for a few months and then the filler will adjust itself on a hot day and it will look like you didn't block properly.

Keep in mind that polyester filler will not cure in the presense of oxygen so you will always have that greesy skim on the surface before you sand. use an old sheet to sand that off so that you don't clog up a brand new sheet.

2. The grit that you need to finish the body filler in is based on the tech sheet provided by your paint manufacturer. I use Autocolor (PPG) and they reccomend 180 - 220 grit before primer. DO NOT TRUST WHAT ANYONE SAYS!!! Paint manufacturers will not warrantee any deviation from their tech sheets even if their paint rep said it was okay. I have been burned by this before.

3. Do not cheap out on your primer and primer surfacer. I have seen many "show" jobs fail because the guy wanted to spend his money on candy paint or whatever and save $$$ on the undercoats. Remember that each paint manufacturer has different lines of paint for different price points. Just because you bought a good brand does not ensure that you have a top quality material.

Good luck.

 

exactly..............maybe i've been doin it all wrong for 40 years as well, lol

maybe they need to go join one of 'ole nash's threads

 

Wear a mask, everything is toxic.

 

you wanna avoid the use of the old style red hardner when using any ureathane paints, or bc/cc jobs

thats why they switched to the blue-green stuff many years ago. i can agree with the rest of the mixing info


as for the priming over 80 causing a lack of warranty........i guess that depends on who you deal with, i have had ppg warranty stuff for just that, same with pcl and morton.
it really isnt the material failing as a rule, usually it was misslabled, or misrepresented. (or missused, lol)

for those who cant prime over 80 grit, fine, but please dont try and convince those of us who have been , without failures for many many years.
now , i wouldnt rec 80 grit over paint, but on metal ,or filler, thats a pretty fine feather.

ive been told by the old guys who showed me lead work, not to go finer than 80 g or risk a greater chance of lead injestion. i ve always followed that, not sure how accurate it is, but i dont do alot of lead anymore.
do alot of prime over 80g though


skull