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I’m finally doing the body work on my 59 truck ! I plan on sand down to bare metal and was wondering what is the best grit to use before applying epoxy primer ?

Thanks for your help !
Clem

Doesn't matter. Epoxy will stick well regardless of paper grit used. Use whatever grit accomplishes the task with least amount of effort.

The remember that the coarser the grit the deeper the scratches will be. The best paint job in the world still looks bad when the sand scratches show.

Depends a lot on how thick the paint is and what your using for a sander? I start with 40 grit and go over that with 80 grit. I use a dual action sander. You may want to check out 3M paint remover disk, takes off the paint without removing metal. They come in different shapes and work good in tight areas.

If you are using a D A (dual action air sander) then 80 grit is fine. But using 80 grit by hand will leave scratches in the metal.
If you are doing it all by hand, I would finish with at least 180 grit before primer. If you are using a good 3-part primer, it will fill scratches to a certain extent. But with any primer and paint, it will shrink somewhat and the blemishes will show up later.
Another tip is to wet sand the primer with 320 or 400 grit, and use blocks. Maybe prime and sand 3 times. A good guide is to use a spray can of black paint and just lightly fog over the primer each time. This will show the low and high spots. Wet sand until all the black is gone. If you get bare metal showing in spots, re-prime and do it again and again. Whenever you get the primer slick as glass...you are ready to paint. Remember, paint hides nothing, just makes the blemishes show up more.

I totally agree with the 3M Roloc advice but,if I have 3 or 4 layers to remove my choice would be NO DA just pure circular and 36 or 40 grit till I reach the last layer of primer.
No deep scratches to worry about if you develop the feel and stop before you hit metal. I shoot for the original primer coat.
Then I switch back to DA with 80 grit or the roloc disks.
Your not gonna strip 3 or 4 coats or paint by hand unless you cook meth...

Nice thing about epoxy is you can do one panel at a time, spray or brush three coats of epoxy on it and come back in three years and it's still good to go. Sand it down some with 80 grit to give it some tooth and start your body work from there.(assuming all the proper prep was done)

Watch out for what you use as guide coat. Some spray bombs just gum things up and waste paper. That's another reason I like epoxy. No guide coat required.

I'd agree with CASO on starting with a regular slow speed circular sander with 80 grit. I use a 7" myself. Would stay away from edges or ridges with it. Then when you see it just starting to show a little metal here or there switch to a DA orbital sander with 80 grit.

John

Thank you all ! What do you recommend for a DA and Circular Sander ?

Thanks for all your help !

I think most air DA's have a way to work in both actions but I don't 'know' it for any but mine.
A Circular is faster at stripping but a DA leaves less of a scratch pattern. I guess that's why they make em that way?

If you have a variable speed buffer like a Makita or something you could use it. a screw gun/drill will do for a roloc disk.

I screwed and glued a dewalt 5" hook and loop pad to my old porter cable that took 1/4 sheet and like it better than either one before. I use it more than my air DA now when I'm finish stripping.
Figure out a process that works for you that's easy to repeat.
For my working comfort I pulled the panels and set them on saw horses or whatever worked.
A plywood panel bolted to an engine stand can hold doors or fenders. I had both rears mounted on a piece of 1/2" ply I traced and cut to fit the profile. Since my bed was off, I had it setting on a piece of plywood across the back of the truck. It was accessible from the ground or standing up on the plywood.

3M makes a bristle disc for Right angle grinders,5"& 7", goes right on the 5/8-11 holder and they make roloc style in 3",2" and 1" diameters.
They come in different grits and are extremely quick at removing paint, getting into corners and crevasses.
they leave very little witness marks and are easy to blend out.
I have used these a lot and really like them.

All good suggestions, but many are lost on me. If you are taking the body to bare metal, then sanding scratches are a moot point. Certainly no one will be painting on top of the first coat of any primer. The first primer coat will be an initial protective coat. Then you have to find your high and low spots and fix those. Then more high build primer and careful block sanding and so on. So, scratches in the metal will be long gone short of using a grinder.

Thanks Everyone !

Clem

I do this a lot on frames, cabs, fenders, all of it. Maybe its just me, but I find it impossible to really feel what is straight, and what is not if I use mechanical or pneumatic sanding equipment. In fact, I have spent just as much money in long board hand sanders as anyone who buys DA's and the like. I have 36" long boards, down to the small ones. I use PSA stick on paper in only 3 grits until its time for wet sanding the clearcoat at the end. I use 80, 220 and 400 then I rely on the PPG primers and paints (Rage Gold filler and Polyester plastic) for the finish. Without long boarding all body parts, there is no way to ensure you have straight panels.

To get the old girl to bare metal, media blasting is my choice and I have learned to do that myself if I want it done right. #1 Silica sand removes all the paint/rust and there is NO scratches involved to discuss in the first place. IF I were to use a DA to get the truck down to bare metal, it would be 80 grit or higher. Paint and primer has a tendency to shrink over time and using anything more coarse than 80 is asking for trouble. Truth is, this whole discussion is not for just anyone. There is a lot of finesse to this kind of work and takes years to perfect. Once you have done about 5 to 10 entire trucks, you can call yourself worthy of even doing it in the first place. Its just like anything else, practice makes perfect. I am in my 35th year of practice (on these trucks)with no end in sight!

I was in the middle of researching body-work posts- that is hilarious!!!

Brad