lowest grit to sand clearcoat before shooting 2 more coats

C

coletrain777

What grit should I use to sand my clear down before I shoot two more coats. I have always used 400, but recently several people have said to only use 600... what is the lowest possible grit you can/should use without sand scratches showing up later???

I have heard that some people use 320 and have no problem several years down the road, but I have never gone that low.
 
320 dry works great. As long as u plan on using a high soilds clear. I just finished a 62 impalla and used 320 dry. 3 coats of universal sand and 3 more coats. Just make sure you body work is real straight! If not u will cut thru pretty quick with 320. But 320 will get u super straight for the next coats. Have pics posted in the restoration forum of the impalla.
 
Would there be a problem with doing it with the 320 wet instead of dry, I don't really care either way. I guess it is easier to see progress sanding dry though.
 
I personally use 400. What you can get away with depends on your sanding. 320 imo is slightly too coarse if blocking dry but not if its on a da. 600 works but slightly too fine to cut really flat. 400 seems just right.
 
If Universal covers 320 or so why am I still seeing 6-800 scratches with two coats?
 
AAE;2399 said:
If Universal covers 320 or so why am I still seeing 6-800 scratches with two coats?
Click to expand...


Not possible.
Sounds like trapped base solvents.
When do you see the scratches in relation to when you shoot the clear.
 
AAE- are you seeing base scratches or clear scratches?

Now I am worried! I already sanded with the 320 (wet), I sure don't want to see sand scratches later on. Scoty77 sure looks like he does good work and has for a while, I would think he would be able to see sand scratches later on if 320 was too course. That being said, I know for a fact that Jim knows his stuff so...

I guess I will go this route on this truck and kind of use it as an experiment. I am good friends with the owner and I will be able to see the truck for several years. I will be sure and put down at least 3 coats.

Keep the discussion going guys, even if we disagree on an issue, it's the way that we all learn to better our self at this craft.


Oops, Barry answered while I was typing... that makes me feel better.
 
not gonna happen. i use 400-600 and have yet to see a scratch. if you do it's in your base.
 
I totally agree, at 600 and above there is no way possible you are getting scratches showing on your clear. They have to be in the basecoat and the clear is just enhacing them so you can see it.
 
Unless you're overthinning the clear and putting on just a light "flow coat"
(yes I did that.........once!!)
 
I use P400... I used to use P320, but I could see faint lines of straight sanding marks in just the right light on some colors.. When I switched over to P400 those imperfections went away.. I think you could probably get away with P320 on a DA, but not sanding by hand on a block from my experience..

You have to remember, that we all grew up using the Cami scale ( US grit scale ) for our paper grits, which i would say almost all if not all manufactures have now switched over to the Fepa scale ( European grit scale ).. Which means you have that P notation in front of the number..

The grits are the same with or without the P up to 220.. After that it changes and is no longer what you read per say.. For example.. P400 is really like the old 320 that all the old timers used to use.. However P320 ( Fepa scale ) is more coarse than 320 ( cami scale )..

With that understanding of the grit scales it gets screwy once you get to color sanding grits too.. See its just a Big F'n confusing mess really.. For example P1200 is TECHNICALLY around 600 on the old cami scale ( read US grit charts ) if you are looking at a chart.. However all the colorsanding grits I buy, like the 3m finishing disk, Nikkens paper etc.. all have the cami P notation, yet they have the abrasiveness of the old US cami scale..

Confused?? I can see why.. I can also see why many people use such higher grits now than they used to..

Lets not forget paper quality.. the better the quality of paper, the more uniform the grit is and the more even cut you get.. I also believe that using higher quality paper allows a person to use a lower grit and get away with it per say, than someone using cheap paper of the same grit choice..

http://www.abrasiveresource.com/resources/gritcomparison.pdf

Well that is my 2 pints worth for today..

Happy sanding, I metal calling my name :)
 
I think Bondo has a good point, I have in DA paper the following in 320 velcro.
Norton Champagne
Norton yellow
Indasa red.

All three are different as far as coarseness.
 
The material the grit is made of also makes a difference in scratch.
Just as the type of sanding, wether random orbit (RO),
dual action (DA) or straight line hand sanding.
I see a difference in wet verses dry but I think that's due
to the different material used, not the water.
The color of the grit is how it's identified, and there
are quite a few different ones, each has an advantage
at something. If you look up sanding grit specs on
the net they explain the differences and why.
My woodworking paper isn't great for automotive
and vise versa.
 
I think that the brand of paper makes a huge difference. buy cheap line paper and I believe that the grit material is not as consistant as high quality paper, ie: 280 grit abrasives in the 400 grit that the paper is labelled as. A direct result of poor quality control.
 
AAE;2444 said:
I use the champagne. What end of the coarseness spectrum is that?
Click to expand...

I think it depends on how much of it you drink.

"Well I prefer bourbon, either way, after a few drinks
eveything always looks better."

I only have a beer budget. I hope that works as well. LOL

Aaron
 
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ADTKART;2463 said:
I
I only have a beer budget. I hope that works as well. LOL

Aaron
Click to expand...

Yeah right!!!
We all know that you "metal men" make all the money
(and you call me cheap???)

Just remember, that case or two of beer you drink everyday
costs more than what I drink!!!!! (LOL)
 
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