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-   -   How much time do you spend 400/600 sanding? (http://www.hotrodders.com/forum/how-much-time-do-you-spend-400-600-sanding-232456.html)

Lizer 05-02-2013 01:25 PM

How much time do you spend 400/600 sanding?
 
I'm just curious how much time you guys spend when you're final sanding before sealer or base. I'm sanding 400, then 600. My final block was with 220. I'm dry sanding because my panels were sprayed with Slick Sand and I don't want to get water on that. I'm using 3M paper. I'll be putting lightly reduced epoxy on as a sealer, and my basecoat is a metallic blue.

However, it's taking me HOURS per panel. So far I've done a fender and I've now spent half a day on my hood already, plus some time on previous days. Granted the fenders on my 67 Mustang have several body lines, and I have a scoop on my hood which takes more time as well. But I'm sanding with 400 until every last detectable scratch I can see is gone.

I'm just trying to figure out if I"m doing something wrong, being too anal, or this is just how it goes. The last time I prepped something was a fender years ago and I don't recall how long it took me.

mr4speed 05-02-2013 02:53 PM

Well yeah the fussier you are the longer it will take. Dry sanding will also wipe out and clog up your paper faster than if you wet sanded. Don't think you are really doing anything wrong, and yes the more contours and body lines a panel has the longer it will take to sand for sure. Are you going over the 220 scratch with a dry guide coat? If you are going to seal I don't really see the need to go all the way with up to 600 grit, 400 should be fine enough before a seal coat. Now if you were going straight to a metallic basecoat then I would go to 600 grit.

mitmaks 05-02-2013 03:10 PM

Are you using guide coat? I would definitely wet sand with 400 and then seal. Sealer will cover up any tiny 400 grit scratches.

33Willys77 05-02-2013 03:13 PM

I usually final block with 180 grit, give it 2 light coats of primer and final sand with 400. If you are putting on a sealer, no need to go any finer than 400, and if its epoxy as a sealer, probably be fine with 320.

Irelands child 05-02-2013 03:28 PM

Why are you dry sanding? As another said, the paper clogs - and I've found almost instantaneously. Also, when it does clog, it will usually form a bunch of globs on the paper that are digging furrows in your poly primer, 2K or even the epoxy if using a sandable like SPI. If you are worried that it will cause rust if you wet sand - it will only if you cut through the substrate then leave it for an extended time. Soak the torn, not cut paper pieces a half hour in a bucket of luke warm water with a couple drops of Dawn or similar dish soap, then alternating between several pieces, resoaking and cleaning in the bucket, go to work with whatever sanding blocks and pads blocks you have along with a constant water source(you aren't doing it without blocks are you?). You might not save a lot of time, but you will save the cost of lots of paper plus really have a 600 finished panel (I finished my last car with 1000 before paint:eek:).

Now, how long does it take? As long as it takes to get a perfectly prepped surface ready for paint and often that's dependent on how slick you put the undercoat down and to cut the 'nubbies' down smooth :sweat::sweat:

John long 05-02-2013 03:49 PM

Josh, I am not a professional painter so maybe I should not contribute here but...... If you are going to seal I agree that 400 should be fine enough and also believe that you should be fine to wet sand it. I am sure you started out with Epoxy on your bare metal so you have protection from rust there.

Hopefully Ray, Henry, Brian or one of the true experts will join in. You could also check with Barry K at SPI. He would be more than happy to give you sound advice if you are in a hurry.

John L

Lizer 05-02-2013 04:02 PM

Why am I dry sanding? Because most of the panels--except the fenders--have poly primer on them. I'm not real crazy about wet sanding polyester 'filler,' essentially. I have spoken to Barry on that issue before and he also wouldn't do it in a million years. Evercoat says the Slick Sand is dry or wet sandable but I just can't get brave enough.

I am constantly blowing the paper off with air. I sand a little bit, blow off the paper and panel, sand a few more strokes, and blow off some more. This avoids sanding with the paper completely clogged.

I am using blocks. On a tricky contoured spot that my round blocks can't do I'll cheat and use a piece of paper folded over several times and scuff out the area by hand.

I am not using guidecoat for the 400 sand. Someone here once (it was a professional) told me it wasn't necessary and I don't think we did it in some tech school classes I took a long time ago either. But I am sanding it outside in the sun and the light dances off the scratches well, so they have high visibility. That is if you were referring to guidecoat for scratch visibility as opposed to panel straightness.

I've visited with Barry about this in depth already which is why I've been doing what I've been doing, but was starting to really wonder on the amount of time it's taking me.

I'll seal a panel after just 400 and see how I make out.

Lizer 05-02-2013 05:37 PM

Quote:

Originally Posted by Irelands child (Post 1672214)
Why are you dry sanding? As another said, the paper clogs - and I've found almost instantaneously. Also, when it does clog, it will usually form a bunch of globs on the paper that are digging furrows in your poly primer, 2K or even the epoxy if using a sandable like SPI. If you are worried that it will cause rust if you wet sand - it will only if you cut through the substrate then leave it for an extended time. Soak the torn, not cut paper pieces a half hour in a bucket of luke warm water with a couple drops of Dawn or similar dish soap, then alternating between several pieces, resoaking and cleaning in the bucket, go to work with whatever sanding blocks and pads blocks you have along with a constant water source(you aren't doing it without blocks are you?). You might not save a lot of time, but you will save the cost of lots of paper plus really have a 600 finished panel (I finished my last car with 1000 before paint:eek:).

Now, how long does it take? As long as it takes to get a perfectly prepped surface ready for paint and often that's dependent on how slick you put the undercoat down and to cut the 'nubbies' down smooth :sweat::sweat:

I went out and started the other fender with this (it's one of the few panels with 2k and not poly) and it was SO much faster needless to say. The paper cuts better, faster, longer. The problem is I can't see the scratches very well when doing it wet.

33Willys77 05-02-2013 05:48 PM

Use a guide coat. Just take a can of spray paint - any color that will show up good and spray a very light dusting across it. When sanding, you will see your high and low spots (scratches). When its all one color, you sanded enough.

Lizer 05-02-2013 07:20 PM

guide coat also worked awesome. I did this fender in a fraction of the time and used a fraction of the paper! :thumbup: And it's so much cleaner. I thought I hate wet sanding but I have clearly forgotten how the experience actually was.

John long 05-02-2013 07:32 PM

Why did Barry say not to wet sand a poly primer? I don't misunderstand. I am not arguing just trying to learn something here. As long as it is given plenty of time to dry and breath I don't understand what the liability is as long as it is not over bare metal.

John

mr4speed 05-02-2013 08:03 PM

Quote:

Originally Posted by Lizer (Post 1672230)
Why am I dry sanding? Because most of the panels--except the fenders--have poly primer on them. I'm not real crazy about wet sanding polyester 'filler,' essentially. I have spoken to Barry on that issue before and he also wouldn't do it in a million years. Evercoat says the Slick Sand is dry or wet sandable but I just can't get brave enough.

I am constantly blowing the paper off with air. I sand a little bit, blow off the paper and panel, sand a few more strokes, and blow off some more. This avoids sanding with the paper completely clogged.

I am using blocks. On a tricky contoured spot that my round blocks can't do I'll cheat and use a piece of paper folded over several times and scuff out the area by hand.

I am not using guidecoat for the 400 sand. Someone here once (it was a professional) told me it wasn't necessary and I don't think we did it in some tech school classes I took a long time ago either. But I am sanding it outside in the sun and the light dances off the scratches well, so they have high visibility. That is if you were referring to guidecoat for scratch visibility as opposed to panel straightness.

I've visited with Barry about this in depth already which is why I've been doing what I've been doing, but was starting to really wonder on the amount of time it's taking me.

I'll seal a panel after just 400 and see how I make out.

On the rounded areas that a block won't work try the small 3M sqeegee they work great for those tight curved spots, there just flexible enough yet stay flat to the surface your sanding, I use them all the time in those complex curves. If you are using guide coat after the 220 grit the powdered version works much better for showing ANY imperfections or sand scratches.

Lizer 05-02-2013 08:12 PM

Quote:

Originally Posted by John long (Post 1672302)
Why did Barry say not to wet sand a poly primer? I don't misunderstand. I am not arguing just trying to learn something here. As long as it is given plenty of time to dry and breath I don't understand what the liability is as long as it is not over bare metal.

John

Would you wet sand body filler? My answer to that question is 'No,' which is why I elected not too. Apparently it's the same answer as Barry's. My fear is the poly primer absorbing too much water and not getting out. I think deadbodyman has actually discussed situations where it lifted when wet sanded. This clearly needs googled. I'd consider spraying 2k over it, blocking and wet sanding that but a concern of Barry's was having too many different substrates on there.

How long is long enough to breathe? After sanding these I'll be sealing in good time and I think it would be devastating to have that moisture trapped in there.

Lizer 05-02-2013 08:14 PM

Quote:

Originally Posted by mr4speed (Post 1672322)
On the rounded areas that a block won't work try the small 3M sqeegee they work great for those tight curved spots, there just flexible enough yet stay flat to the surface your sanding, I use them all the time in those complex curves. If you are using guide coat after the 220 grit the powdered version works much better for showing ANY imperfections or sand scratches.

won't that powdered stuff wash right off when it gets wet? I've always just used a cheap can of black spray paint, or better yet, aerosol primer since it sands a little better.

mr4speed 05-02-2013 08:22 PM

Quote:

Originally Posted by Lizer (Post 1672329)
won't that powdered stuff wash right off when it gets wet? I've always just used a cheap can of black spray paint, or better yet, aerosol primer since it sands a little better.

NO water (wet sanding) will not touch the dry guidecoat only sanding it off will get rid of it. If you are using the old flat black spray paint technique, trust me hands down the powder works and shows much more because it gets into every crevice there is.


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