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Old 09-27-2007, 12:50 AM
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Sanding down to bare metal anyone have any tips?

I just got a DA air sander and plan on sanding down my 67 Mustang down to bare metal but Im going to practice on my dads 73 Datsun pickup first. Anyone have any tips on sanding down a car to bar metal. What grit should I start with? How much pressure do I apply to the body with the DA sander? How can I prevent warping the body panels. Any thoughts are appreciated. Thanks.

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Old 09-27-2007, 01:30 AM
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I am just doing the finishing touches on my el camino this comming weekend. I had Seven layers of paints and primers. I used a 41/2 inch grinder and lots of sanding disks. I found that 60 grit was perfect.

I also tried 80 and 40 grits but they were either not strong enough (80grit) or they wore out Way to quickly (40 grit wore out within 10 minutes). 60 Grit is the way to go. I

am even going with 60 grit to get rid of some small surface rust and thin patches of paint and bondo, a.k.a "the finishing touches". This should give me a good surface to apply primer to, and then bondo. Im also going to try my hand at some old school body work, except I'll try it with a sludge hammer cause its the only thing Ive got lying around, j/k.

Good luck, and wear a filtered mask, goggles, and wear a shirt (it gets real itchy without a shirt, keep your pants on too!).

-Matt
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Old 09-27-2007, 07:16 AM
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DA is going to take you a long time. We go down to bare metal on repair area's only with a DA and we use 80 grit followed by 120 before starting the repair. For over all stripping we use a sand hopper with walnut shells for a media. If I were you that would be the route I'd take. You can pick up a cheap one at Harbor Freight and they also sell the walnut shell media there. By the time you by all the sand paper, you probably could have bought 4 or 5 of those sand hoppers.
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Old 09-27-2007, 07:51 AM
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Start with a coat of air craft stripper. Get it soften up. Then sand it off with 36grit. Do one or two panels at a time. Keep it soft. It will be messy!
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Old 09-27-2007, 08:32 AM
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Quote:
Originally Posted by duallybuster
DA is going to take you a long time. We go down to bare metal on repair area's only with a DA and we use 80 grit followed by 120 before starting the repair. For over all stripping we use a sand hopper with walnut shells for a media. If I were you that would be the route I'd take. You can pick up a cheap one at Harbor Freight and they also sell the walnut shell media there. By the time you by all the sand paper, you probably could have bought 4 or 5 of those sand hoppers.

do you have a pic of the hopper
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Old 09-27-2007, 09:29 AM
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Wow, there is a lot of unnecessary hard work going on here. First off, does it REALLY need to be stripped? That is one of the most over thought of mistakes there is. What are your expectations? Are you building a show car? Does the car or truck have many paint jobs on it, or is it failing in some way?

Most cars can simply be sanded and painted. There is NO need to strip and paint every cay.


Using "AirCraft stripper" you do not put it on to "soften" the paint, you put it on to REMOVE the paint. It is a horribly messy, dangerous way to go and you don't "mix" it with sanding. You put it on, strip ALL the paint off down to bare metal then sand the bare metal.

Which ever way you go, for a home hobbiest, do ONE PANEL AT A TIME and get that panel into epoxy primer before going on to the next. A bare metal body can be very overwelming!

One step at a time, one baby step and you can get a lot done on a car. Bite off more than you can chew and it ends up on Craigs list as a project car.

Brian
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Old 09-27-2007, 09:59 AM
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Quote:
Originally Posted by MARTINSR
Wow, there is a lot of unnecessary hard work going on here. First off, does it REALLY need to be stripped? That is one of the most over thought of mistakes there is. What are your expectations? Are you building a show car? Does the car or truck have many paint jobs on it, or is it failing in some way?

Most cars can simply be sanded and painted. There is NO need to strip and paint every cay.


Using "AirCraft stripper" you do not put it on to "soften" the paint, you put it on to REMOVE the paint. It is a horribly messy, dangerous way to go and you don't "mix" it with sanding. You put it on, strip ALL the paint off down to bare metal then sand the bare metal.

Which ever way you go, for a home hobbiest, do ONE PANEL AT A TIME and get that panel into epoxy primer before going on to the next. A bare metal body can be very overwelming!

One step at a time, one baby step and you can get a lot done on a car. Bite off more than you can chew and it ends up on Craigs list as a project car.

Brian
Very eloquently put Brian.
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Old 09-27-2007, 10:10 AM
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I have a 69 Dart factory 4 sp conv that sat for many years in a barn. It had 90% original paint but it had many tiny scratches & nicks before it was stored; so it had light surface rust in each nick.

Being the car has some value, I decided to go to bare metal to find all those nicks. I don't care for stripper unless it's got many repaints, so I went with the DA. The BEST DA discs I've tried are the green 3M in 40? or 60 grit. They last a REAL long time and do not hurt the metal. You don't need to put a lot of pressure on it, let the grit do the work.

They are pricey at $10+ for a 5-pack but it is worth it. How many did I use? : I used 4 discs so far and only have one door & one front fender left to do. The hood was off another car and has 3-4 repaints so I will use stripper.

I am now using the green ones for filler and they last forever and they don't seem to get cake up like a regular DA disc.
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Old 09-27-2007, 11:49 AM
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For my 55 Chevy truckrod, I took it all down to bare metal. I worked on one panel at a time, outdoors, off the frame, using Rock Miracle paint stripper to remove the old layers of paint. This stuff is great, it softens the layers of paint quickly, then I wire-brushed (manually) the paint off. I repeated the process to get down to bare metal. Usually took 3 applications due to all the layers. After washing the panel with soap/water, I DA'd the panel to get off any remaining pieces of paint. My DA uses 100 psi pressure and I used 80-grit peel-and-stick. I found a box of 100 disks for $12 at a Good Guys show. I think I used only 20 disks. (I didn't do the bed panels this way, I sandblasted it).

Anywho, if you decide to go this route, be careful of the stripper, it's VERY NASTY stuff and burns skin easily. Don't ask me how I know!

Antny
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Old 09-27-2007, 02:33 PM
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going down to bare metal- quickest and less messiest(comparing to chem stip) is to use a grinder with a wire brush attachement. dont work about worping the panel . I hav down this plenty of times with out warping
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Old 09-27-2007, 08:12 PM
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A wire brush on a grinder will create quite a bit of heat. And honestly, it works horrible compared to other means. For instance a 3M "Clean and strip" disc or a 3m ROLOC "Surface conditioning disc". If you used either of these, you would never touch that wire brush again.

Brian
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Old 09-27-2007, 11:05 PM
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Thanks for the reply. The body has light surface rust. I just wanted to get the 40+ year old paint off. I also have a electric grinder from harbor freight also. Would that work better with a sanding disc attachment than the DA sander. Thanks.
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Old 09-28-2007, 12:56 AM
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Thats exactly what I did. I used these sanding discs (I forgot the brand, ill post tommorrow) that screw right into the grinder. I went through six 9 dollar disks. $65 and the car is sanded.
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Old 09-28-2007, 09:15 AM
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You really have to be careful, any "grinding" disc style tool and disc that spins as opposed to orbiting like a "DA" is going to create a LOT of heat and WILL on occasion warp and damage metal.

Especially around body lines! You can cut the tips off of body lines in a second, BE CAREFUL.

An orbiting sander with 80 to cut thru the bulk of it, then switch to 120 is a safe way to go. And even that can warp a thin late model hood.

Brian
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Old 09-28-2007, 10:26 AM
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I would suggest heeding the advice of MartinSR and would also suggest NOT using a DA or sand paper IF you are going to take it to bare metal. I have previously used this method but have SEEN THE LIGHT and now use the strip-it style discs on an angle grinder. Here is a link to what I am recommending:
http://www.abrasives4sale.com/strip-clean.htm

I do not own the company so I am not trying to sell these but rather provide a heads up to an alternative.

I recently purchased the same type of disc but with a hook & loop backing. It is a 6 inch backing pad and replacable discs. I run this on my large angle grinder and it saves lots of time and does not heat up the metal.

Much quicker than sanding. Always wear breathing protection and eye protection when doing ANY body work.
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