Sand paper grades..how do they work?

[Austin-182]

Ok, so does anybody know exactly how the different grades of sandpaper works? And whats the difference between sand paper and wet and dry?

For example, if i want to spray something plastic i understand i need to "prep" before i go spraying paint on it, but how is it done?
Il use a gear insert as a example as thats something i want to spray, what would i use and what grades etc?
Have wondered for a long time the process of sanding things so cheers if you can clear it upfor me
Austin

 

[mx1_champ]

sandin pads n wet n dry are pretty much explain themself's, generally the higher grade papers are wet and dry as they get clogged up easier and the ''wet'' helps lubricate and clean the paper.

grades work in the ammount of grit per inch. p2000 very fine p40 being very corse.

generally you can base coat over p320, although can be slightly scratchy and need more basecoat. p400 and above is fine to apply base coat on top of , although some prefer 600. there is no need to flat with stupidly high papers as the finish will be the same either way.

if your using below p320 you are going to need to use some sort of primer. general 2k primer is ok upto about p240ish but much more that that say p180 , p80 +p40 etc you will need a high fill primer to cover the deep scratches.

however if you are confident enough you can use say p240 then go over it with p320 or p400 to smoothen it out enought not to need primer, although i wouldnt really advise this in most cases

 

[Austin-182]

Cheers mate,
So wet and dry are higher grade meanin p2000 being the highest?
So if i get some say p400 or p600 to go over my gear insert etc, would that need to be wet while using it?
Anything below p400 would not really get the surface smooth enogh to paint i take it?
Lol sorry for all the questions, just like to make my head clearly understand haha

 

[mikekean]

Im not sure you will notice to much on interior parts but i wouldnt use less than 600 gritt to prep pannels or you will get horrible sanding marks in the paint once it has fully cured and sunk. I normally use 800 grit for pannels as your pretty much garunteed no sanding marks after you have painted.

 

[Austin-182]

Would i start with (?) grade and then move onto (?) grade, or just use one grade through the whole of the process?

 

[mx1_champ]

what you start with depends on what your trying to achieve ? remove a scratch ? sand filler ?

 

[Austin-182]

Just basicaly plastic parts allredy painted that i want to re paint...
I smoothed some bullets and dont even know what grade i used, i used 2 different grades but dont know what either of them were lol, they were just what was lying around in the garage

 

[mikekean]

Depends on the condition of the piece your prepping, whether it needs filling or not etc. If its something that just needs keying up for paint then i would use 800, remeber not to put the paint on too thick or it will chip badly.

 

[sidey]

I did my interior bits anth. recently, prepped with 400, 800 and briefly 800 wetted cos i'm a bit anal. Then 2x primer, 3x colour, added decals from n2graffix then 3x laquer. Once cured for a couple of days i polished with AG paint renovator to get rid of the orange-peel finish (probably caused by my amateur spraying), SRP and waxed the fecking things. Told you i'm anal!

 

[Austin-182]

Lol, cool ive got a better understanding now of what grades i should be using, and painting aswell which would of been my next thread lol

 

[mx1_champ]

what sidey said aint bad for what you want tbh, for the base coat dust it on very lightly for the first coat then give it a few decent coats.

on the parts you smoothed was it plastic ? and did it have like a bobbly texture to it after sanding ?

 

[Austin-182]

Yea it was the plastic bullets, its quite smooth tbh no bobely bits, mite go over again with some 600 then give spraying ago

 

[mx1_champ]

id use some filler primer first give it a dust coat then 3 good coats then p600 before paint. ake sure you use high fill primer or it would look a tit