Thread: advice on sandpaper grit

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I just got my model A , needs body prep before paint, my question is what grits do I use and when, I do have some filler to knock down and some welds to smooth out, after that what do I finish with before primer, then what is next to be done before sent off for paint? block sanding? wet sanding?

thanks,
simon

I'm sure there will be other input on this but here's mine...36-40 for the welds and old filler(grinder) 80(on a hand block) to shape new filler working your way to 180 before primer. And I like 320(some like 400) under base coats. Then you can do 600 between clear coats if you choose to do that. Then 1500-2000 before buffing..Just be sure not to oversmooth between products because they all need something to hook up to.Always use a hand block if you don't want waves.Keep in mind the timeframe for fillers, they sand very easily when they first harden. Hope this helps.

Read this, I think it will give your some good pointers-

http://www.a2zautoforums.com/showthr...sandpaper+grit

Cut your filler with 80 grit. Work your way to 180, prime. Block again, most likely will need to prime again. Wetsand with 400-600 (all depends on what you like, everyone has their own ways of doing things). Lay your base and clear.
This is just a quick way of telling you and it's about 2:00 in the mourning so I am tired and may have left some things out sorry.
Buy some 36 grit, 80 grit, 180, 220, 400, 600, 1500, 2000. That is what I use. My process may be different than some here or may be the same, we will soon see once they post their oppinion. The best person on these forums for paint help is SprayTech, I have learned lots from him.

If you lay filler like me, get some 36 to shape it. I also got a rasp for cutting down the high ridges, I read to let it harden about as much as cheese and then you can just trim the high spots.

Sean

Yes the 36 grit before the bondo fully cures is a great time saver and will cut it flat. If you use too high of a grit then you will not be shaping or cutting the filler down flat or to the shape you need, it will just smooth out whatever shape is there or take a long time getting the results you need.

First of all we need to know the shape your Vehicle is in before some one can give advice .
Is it rusty ? Is it pre primed ?
If its primed I would recommend having it blasted with Aluminum Oxide and see what is under it all , some scary stuff can be hidden with Fiber glass , Bondo and other fast fixes . If its clean and in fairly decent shape after having it Aluminum Oxide blasted , prime it with PPG's DPLF Primer Sealer and then you can do your repairs with filler . The few replies here have very good info and you can go with that .
But I wouldnt do anything till I knew what shape the body was in . it could come back and haunt you after spending much time and money not knowing what shape its in .

They have what is called Cheese Graters for shaping bondo .
There is a right time to use the Cheese Grater for shaping to soft & it will just rip it off the panel , to hard and it will not work . This will take some getting used to to find the right sweet spot for shaping

Hope this helps

SprayTech has some good info, the cheese graters help cut down time and get it flat. As for starting, yes make sure you start with bare metal to see what you are working with. Like he said, you dont want to spend all this money and spray over rust or anything and have it come back later down the road to bite you in the ass and lose all that work for something that could have been dealt with.

SprayTech wanted to know what shape the body was in , well it has no rust has been taken down to bare metal and coated with ppg DP90 the body work was started but does need quit a bit more, the roof has some low spots don't know if it is from too much filler in some places or just needs more and then some shapeing , there are also some areas on the body that need some smoothing out. I havn't sanded any of it yet so I don't know how much filler is on the car but I am very sure that the body is rust free and preped pretty well, they gentleman that was building the car sold it to me so he could buy a 37 ford that would accomidate his growing family (grandchildren) I can definatly see that there is filler in places but havn't really taken any paper to it yet to see how much, Since I have never really done any body work but am willing to take my time and learn and get it right. does this help any SprayTech? here are a few pics of the car at the link below you may need to copy and paste it.

thanks,
simon

http://s170.photobucket.com/albums/u...9%20Model%20A/

That is one fine hotrod you got yourself there !!!!!!!!!

I would get some white spray paint and just lightly fog a coat over the body ( called a GUIDE COAT ) then get a long sanding board and block sand it with 180 or 220 grit , and see all your highs and lows . Some areas may only take a skim coat to get it straight , and other areas may require some bigger attention , but the block sanding will give you a good visual on the work involved to get it right !

Its easier to work bondo if you can hammer and dolly the dents and get the metal as straight as you can ,then to try and fill .

With it having the DP on it you can ruff it up ( the block sanding will be sufficient ) and put your filler over it , as this is how PPG recommends a good repair as the DP is an excellent ground coat for repairs !

I use only 80 grit to sand my filler & then just before I have it where I want it I then go to 180 grit for the final cutting ( This will also help on filling with primer as it doesnt take as much to fill the deep scratches ) , as I can usually spread the filler smooth and not have to cut it with any thing courser .
A cheese grater will cut fast so be sure to use little pressure to shape as you dont want to cut it all off . keep it a tad high & use your blocks & 80 to get it straight .
Hope this helps

Thanks SprayTech could I use an aresol type primer for the (guide coat)? and if so what would you rec. I use? I have some spray equipment and a 60 gal compressor but I think that I would rather just get the body work done and get it to a painter to have the base and clear done. The area that I build up should I buy some ppg D90 and respray those areas? Or again could I use some sort of arisol can primer? like I said I have never sprayed is it possible to prime outside with just a respirator? the reason I don't want to paint is well two reasons one I have never done it before and two I have heard that you really need a good booth and a fresh air hood so not to kill yourself.

thanks,
simon

Yes an aerosol can of light colored primer will work as a guide coat . This will show Highs & Lows when you run a block over the panels .
Sanding in an X pattern as it will not cut groves the size of your block in the panels Use this method through every blocking process !

I would not use a spray can primer for priming your body work , use PPG's K36 for your priming & blocking process , and I would stick with PPG products as this is what your ground surface is , I am not a big believer in mixing products as you never know what is or is not compatible with each other . Even though many mix products with great success .
It may take a few primings and blockings to get it ready for paint .
PREP work is 80% of a paint job .

When you have it ready for paint I would leave it in the K36 primer and let the paint shop use the sealer and base coat and clear . Hopefully finding a shop that shoots PPG .

SprayTech sorry don't mean to be a pain in the A** but one last question, I have been reading up on saftey of painting, I read that a active charcoal face mask is actually sufficent is this true? Here is my plan and I want to know if you think this and a face mask respirator would be okay not a risk to my health since I already smoke cigs. I am buying a 20 by 30 protable car port to put in my back yard ( large yard) and store my 1992 mustang that lost its place in my garge to the 29 model A. I was going to get a 20x30 tarp and errect the fully enclosed car port over it. I thought I could make some sort of houseing out of 2x4s and plywood that could house 2 box fans about 2-3 feet off the floor, and put that in the entrance way closing the front of the carport on it then have the fans blowing in with house hold a/c filters on the front of the fans, then have the back door of the carport 1/2-3/4 open. do you think this would be an okay enviorment for painting and a safe one with enough ventilation and use of only a carbon filter face mask?

thanks,
simon

I use the 3M Charcoal respirator every day , but make sure you get one that fits snug to your face and seals ( S, M & L sizes ) , can NOT be used with facial hair ! Mustache is ok but not goat -T or beard .

I also use the 3M full face Charcoal mask too , uses disposable charcoal filters that can be changed when needed ( and you can buy to replace them ) , and I buy a package of tear offs to keep the lens clean of overspray . I like it better as these high solid clears bother my eyes , and Isocyanates ( catalyst or hardners ) go towards moisture
With these masks , make sure you seal them in a big zip lock baggy to help make them go farther as once they are opened they will filter air constantly and therefore reducing protection & made useless .

Any one of these will work for a person that doesnt spray all the time & everyday . No need to purchase a high dollar fresh air unit for a few times spraying . I have been breathing this crap for 30 years and havent died yet , but the lungs dont have the capacity they once had and I dont have 3 arms or 15 toes , and not bald ........ ha ha ha