body work

[izzys75]

hello i am doing some work on my truck, and need some info can someone help. when working on bare metal can i skim coat over it or do i have to primer first. im new to this and don't know too much but am a quick learner. i live in a small town but there is a napa auto store and a carquest. what is a good primer and body filler for a skim coat. and also how long can it stay primered before i have to paint it, i ask because i am a boiler worker and am out of town quite a bit so working on the truck will take time.

[jonkmbll89]

If your referring skim coat as bondo or body filler, you put the bondo on the bare metal then primer. Be sure to scuff up the metal pretty good so the bondo will stick good. As long put a good coat of primer on your truck it will not rust. You can leave it primered with out painting your truck.

[izzys75]

thanks jon, does it matter what grit of sand paper i use to scuff the metal. and what is a good primer  you recommend i should use. also what body filler is best. 

[Blazin]

Welcome izzy,
 First off you should get the metal as close to original shape as possible, and strait as you can. This minimizes the need for body filler. I sand blast all my welds after I am done grinding all my welds if its patch work. the I personally use fiber glass filler ( Dynalite, Evercaot, Marglass ) over all my welds. Then Body filler ( same brands as glass ). If its dents I go strait to body filler.I use 24 grit 5" wheels on a high speed air grinder to bare metal up for filler. Go quite a ways out past the actual dent or weld area. Finish your filler with 36 grit on a 10" mud hog then to 8" mud hog, then an air file with 36 grit, then an air file with 80 grit then hand block with 80 grit. Feather edge all paint scratches left by grinder at edge of the bare area.
 Primer. I use a self etching primer Martin senior has a good 2 part self etching primer ( called Etch Filler ) SEM make a single part one, and the same stuff in a spray bomb. Prime it with one of those.
 Next I use is a urethane primer, if its a show piece  I block sand out the urethane primer with 180 grit. Then reprime if needed, once thats dry I finish sand primer. I don't recommend primer sitting for much more than a few months unless it is an epoxy primer.

[izzys75]

awsome blazin, but as i mentioned im new to this and don't have hogs, files and everything you mentioned. as i mentioned it's the rear fender to a stepside bed. it has a few small dings nothing major thats why i want to skim coat it. i will be doing the whole fender but want to know how to do it with small amount of tools. i live in a small town and all there is, is a napa and carquest auto store. it will not be show quality but i want it to look nice. so blazin thanks but can we bring it down a notch and give me other options to getting the job done. blazin you are great at giving detailed job describtions and i've seen the work you've done it looks awsome but you have 15+ yrs and i have none. as a beginner what else can i do and thank you.

[Blazin]

You should be able to do a decent job with a hand board and a few rubber sanding blocks. Always work from one end to the other of your repair area and work the filler at a 45 degree angle switching back and forth 90 degrees from the last sanding pass. You will need some sort of DA sander. They make pretty  good electric ones. That is the only way you are going to be able to feather edge the paint to the bare metal. Also you should have bare metal all around you body filler area. The filler should not touch or cover the paint. As for a grinder electric is fine as well but you need around 24 grit. When grinding the metal keep the wheel speed down and keep it moving. Biggest thing to remember is the more filler you put on the more you have to sand off. Several thin coats are better for sanding and for not getting pinholes etc., also for a larger area a bigger / wider applicator works better. Keep it as smooth as possible when spreading. Remember where your low spots are so yo can ease up on the pressure of the applicator. Keep the edges of the repair thinner as that is not where you need the filler. Keep in mind that even if a panel looks flat ( a step side fender is a good example of this ) it doesn't mean it is perfectly flat. They have a bit of a bubble shape to them. Basically every time you step up a grit you are removing the scratches from the previous step but still leaving smaller scratches behind for the next coat of material to have a mechanical bond.

[izzys75]

as i said before blazin you have good insructions and i really appreciate the feedback. when it's done and the fender looks good i know who to give thanks to. do you have a good body filler you recommend that i can get from the stores i have mentioned before. napa or carquest, only asking cause i'd rather be safe than sorry. oh and will this also work for other parts of the truck. thank you a whole lot blazin i will keep in touch and always keep you in mind.

[Blazin]

I use Dynatron. Rage is not to bad either, I have used the NAPA brand before with decent results. If you are not real familiar with filler mix a smaller amount for the first few coats to get a feel how much hardener to put in. Also a trick I do for my last two some times three coats is add some polyester resin for fiberglass to make the filler creamier. You also need to up the hardener a bit when you do this. The liquid stuff in filler is polyester resin. The hardener reacts with it not the actual filler it self. The filler basically gets trapped in the process and hardens with it. Another thing is blow it off real good before appling another coat to make sure any pinholes are cleaned out.