Sanding Grits Thru the Complete Process.

ffltstn

Promoted Users
I've read so much its running together.
This will be done over time (months / years).
Assuming straight panels-
I used 80 on rusty areas, then 180 and spray epoxy. If longer than respray window what grit before 2k?
To block 220 or 320? Then 400 for Base or 600 for metallic? Then 600 or 800 before clear?
On hard to sand areas what color scuff pads?
Sound about right?
 
Make sure all of the rust is removed after 80 grit. Epoxy over 80 grit. If after 7 days, 180, red scuff pad, then 1 coat epoxy. Wait overnight before 2K. I usually sand 2K with a coarse grit initially(120) and if everything looks good, guide coat, block with 180 till 120 scratches are gone, guide coat again, block with 320 till 180 scratches are gone. At this point you can sand with 400 to 600 wet. If during these steps you hit metal, stop, spray epoxy on the metal, wait overnight then spray more 2K in that area or panel, then continue to next step. Most of the time it will take more than 1 primer session to get things right, so starting with a coarser grit speeds things up. Usually 120, 180, reprime. Then 180 or 220, 320, wet sand 400 to 600. Gray scuff pad in hard to reach spots before base. If sealing, red is ok.
 
I would only buy the coarser grits at first unless the project was small. No bodywork was mentioned but I would assume some 40 would be a good bet for roughing in filler. In the projects we do, 40, 80, 150, 220, and a box of red scuff pads will get a car almost to final primer. No use having fine sandpaper lying around picking up contaminants and abrasive particles while the project gets to that point.
 
Most of this car was in epoxy when I got it and looks very smooth. I don't anticipate any or very little filler. I may try 180 first then and see how bad it it is.
Thanks
 
I would block the epoxy that is on it right now with 180 on a long board and find your highs and lows. You can then dolly them out and repeat the process tell they are all near flat. Then finish sanding with 180 and spray epoxy. Now your bodywork can begin. Oh and bolt it all together and check your gaps first. You may need to weld or seroiuly do some adjusting,better now than when in primer and filler.
 
I agree with the above, I wash everything with Dawn dish soap before sanding.
Sanding the epoxy with 180 will get it straight,
Then the 2k with 400 to 600 will get it smooth for paint.
600 is as fine as you ever need before paint.
 
It's the little jewels like this post that make this forum so great for rookies like me. I've got pages of notes from stuff like this!

Cheers,
Chris
 
This is a very helpful thread, thanks!

In the projects we do, 40, 80, 150, 220, and a box of red scuff pads will get a car almost to final primer. No use having fine sandpaper lying around picking up contaminants and abrasive particles while the project gets to that point.

I noticed Crasthech does not use 180? I already bought a roll of 150 & 220. Now, reading back through other threads, most people use 180, then apply another coat.

If I block epoxy with 150, should I follow with 220 or 180 before spraying another coat of epoxy? Thanks...
 
I use 150 for primer sanding all the time, a couple coats of epoxy covers it quite well
and go to 400 or 600 for the final sanding. I always guide coat it too.
 
150 or 180 is pretty much personal preference. But it's just my opinion that those who use 180 would probably be better served using 240 as their next grit, because 180 and 220 are too close together. 240 is not as easy to find theses days though. Back when I worked for other people in collision, they were trying to make finishing in 180 the standard, but I said I would rather stay with 150 and finish with 220, because 80 to 180 is too big a jump for large areas imo, where 80 to 150 is just about right.

It's really all about the grits that bracket the 180, not the 180 itself. If we block with 150, we usually will lightly go over it with 220 and red pads before primer, mostly because I am a bit OCD more than any real necessity.
 
I'll have to try me some 150. Old habits die hard, but I can relate to the jump between 80 to 180 being rather large. I just recently started blocking 2K(on restorations) with 120 initially, guide coat, and then skip to 180 and like the results. It seems to get flat real quick.
 
Back when I was just a Pup, the summer after I graduated from High School, drove cross country to see my Dad in California. While I was there I spent the better part of a month bumming around in the LA and Bay area's visiting Shops. I spent a couple of days at Hershel "Junior" Conways Shop. Junior was one of the guys that worked for Barris in the '50's. His work was/is some of the absolute best Paintwork out there. He was gracious enough to me to let me hang around and watch him and pepper him with questions. (he did make me sweep the whole Shop though:)) One thing I saw him doing was doing his initial blocking of 2K with 80 grit. THink he went 80-150-220, then 2 wets 320-400 or 500. Hard to remember the exact grits but I do know he always started with 80, because it would level so well and quick, although Junior wasn't worried about the quick part. :) Wish I had stayed in LA a little longer and pestered him a little more as I would have loved to start out working and learning from him and the crew he had in his Shop.

120 is an excellent grit to start blocking with. I've had good luck going 120-180-320 (all dry) then 400-600 wet. Alternatively 150-220-320 works well too.
 
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Something else to consider with grits is how much time spent with each level and how sharp & fresh a section is. Also how much pressure you use.

For example an aggressive courser grit like 80 may be used by someone as a first step in primer or 400 to 600 with thick clearcoat, but not with much pressure or for as long or as complete of a sanding before jumping to finer grit & spending more time with it. Could refer to a courser start with less pressure & time spent as trying to get the best of both worlds in results.

If you ever try to fabricate, then bring up to polish a super hard surface such as granite, you really begin to understand the importance of grit progression & time spent on each step. Work up to finer too quickly & you're basically polishing over scratches without removing all of them, resulting in a smooth but hazy finish.
 
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