What grit to use?

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PostPosted: Wed Jul 07, 2010 12:29 pm
I thought these were helpful in understanding grit & comparable differences between types. I was recently trying to figure out what the Marine Trizac disc's were equivalent too in the Automotive versions as they rate Microns vs. grit count.
The differences between "P" rated sandpaper & "standard" were quite surprising to me as well, hopefully these will be helpful to some & maybe Chris can find a place for these somewhere.

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PostPosted: Wed Jul 07, 2010 3:41 pm
Yeah, I had pulled these same charts a few years ago over in the Cut and Buff section. I think Chris should put them up in the What Grit to Use sticky, just a suggestion.
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PostPosted: Wed Jul 07, 2010 4:55 pm
Down the road we are going to have a couple of additional options for information like this but for now that sounds like a great idea. Thanks edp and DarrelK!
PostPosted: Wed Jul 07, 2010 5:12 pm
nice sheet. as u can see p grade is finer than american.

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PostPosted: Wed Jul 07, 2010 11:01 pm
lild wrote:nice sheet. as u can see p grade is finer than american.


thats an interesting take on the charts as my thought was "wow, P grades a lot courser then I thought!" if 320P = 250US I found that surprising, maybe more so that they were that different.

conversely, could I take US 250 & then say 320 & base over it?
PostPosted: Thu Jul 08, 2010 6:53 pm
if you look at the standox copy, you'll see p-400 = us 320, so p grade is finer and it feels finer. and yes you can as long as it's on a da. i paint over p320 scratches on a da all the time. if you hand sand it, the scratches are too deep. however you can hand sand p400 and paint over that.

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PostPosted: Thu Jul 08, 2010 7:40 pm
lild, if P-400 = USA 320 then maybe another way to say it is that you need to go to a higher number P to get equivalent to USA.

I wish they'd just state the micron size on the paper...if I want 35 micron scratches then I buy either P-400 or USA 320. The lower the size (in microns), the finer the scratches :-)

-Chris
PostPosted: Thu Jul 08, 2010 8:39 pm
yep that's it. if you use pgrade you need to go higher in number. and really p grade isn't bad, it will actually keep you form going to low on the refinishing side of things. so if you go to the store and ask for lets say 3m 320, and then p 320, and feel the diff. you'll notice the p will feel finer.
so when you got the feeling thing down, and your on a tight budget and ask for some cheap as you got 400, feel it. i did this once, ordered from the store, and when i used it, it was more 800. i was pissed. so when getting cheap paper feel it, and go lower on the pgrade scale. becuase you may think your saveing money, but you won't. you'll go through it like a sat. nite crack whore. also not p grades are equal.

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PostPosted: Thu Jul 08, 2010 10:09 pm
lild wrote:if you look at the standox copy, you'll see p-400 = us 320, so p grade is finer and it feels finer. and yes you can as long as it's on a da. i paint over p320 scratches on a da all the time. if you hand sand it, the scratches are too deep. however you can hand sand p400 and paint over that.


If P400 = US320 then its not a finer grit, its the same. Thats the point I was making about being surprised by their ratings. The only thing that makes sense on the P ratings is that the grit is positioned more uniformly on the paper then the US, other then that the grit ratings are just confusing. then of course getting used to thinking in Microns is a whole nother ball game.

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PostPosted: Sun Nov 21, 2010 10:51 pm
I would wet sand with 600 if you are going to add more clear any time your paint has cured. How many coats of clear to use is dependent upon the paint system you used and/or what effect you are after ie: do you plan to scuff and buff or are you painting "the old pickup" etc.

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