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Thread: I'm confused, (again) about sanding scratches

  1. #1
    Join Date
    Aug 2013
    Location
    Boring Oregon
    Posts
    883

    Default I'm confused, (again) about sanding scratches

    Metal and filler is all roughed with 80 grit.

    Then smoothed out a bit to remove the deeper scratches with 120 at this point.

    I see on both the OMNI epoxy primer and featherfill G2 tech sheets it says use P120-180 on metal and 220-320 on filler before spraying.


    The confusion part is why? I assumed that the epoxy would flow out and cover the bottom of any scratches that are left and the featherfill would flow out and fill those scratches up smooth.
    So why does the filler need to be smoothed out to 320? I have heard that scratches can be seen after paint but I don't understand how or why.

    I'm not trying to get around it, or refusing to believe it, I just want to know why.

    Thanks guys.

  2. #2
    Join Date
    Jul 2016
    Location
    Denver, CO
    Posts
    531

    Default

    first off, G2 can NOT be put on bare metal,

    i finish my filler 150-180 for G2, 3.0 iwata air gunsa

    bare steel i would 80 grit, epoxy then g2

  3. #3
    Join Date
    Aug 2013
    Location
    Boring Oregon
    Posts
    883

    Default

    No, I am not putting the G2 on bare metal. First the epoxy primer, then in recoat window the g2 on top of that. The way I wrote that sentence is confusing, but my intent was epoxy the whole thing and then the G2 after the 30 minute flash. Therefore the 80 grit scratches would have epoxy in them first, then the G2.

    I have a mystery gun I bought 6 years ago and it came with a 2.0 tip so I will use that. I think it is one step above the HF purple gun but I can't find any info on where it came from.

    I think it also came with a 1.4 tip which I will probably use on the epoxy primer.

  4. #4
    Join Date
    Jul 2016
    Location
    Denver, CO
    Posts
    531

    Default

    yeah sounds like a good plan. i would recommend 150/180 on filler, 80 grit on steel

  5. #5
    Join Date
    Nov 2005
    Posts
    10,979

    Default Guess?

    Quote Originally Posted by Houndogforever View Post
    No, I am not putting the G2 on bare metal. First the epoxy primer, then in recoat window the g2 on top of that. The way I wrote that sentence is confusing, but my intent was epoxy the whole thing and then the G2 after the 30 minute flash. Therefore the 80 grit scratches would have epoxy in them first, then the G2.

    I have a mystery gun I bought 6 years ago and it came with a 2.0 tip so I will use that. I think it is one step above the HF purple gun but I can't find any info on where it came from.

    I think it also came with a 1.4 tip which I will probably use on the epoxy primer.
    I would have to guess, CHINA.

    Try it on something else first. If it works, clean it well and do what you need to do with it. Many of those unknown small guns do work well for small stuff. Keep us posted and good luck.

    Henry

  6. #6
    Join Date
    Nov 2006
    Posts
    1,988

    Default

    80 grit scratch on metal is much shallower than 80 grit scratch on filler because the filler is so much softer. The deeper scratch on filler leaves the next coat thicker in the scratch channel. When the next coat shrinks it shrinks more in the depth of the scratch and brings the paint down with it so you see where the scratch is. The goal of using different grits on different materials is to keep the scratch depth uniformly shallow so the shrinkage doesn't show. The shrinkage can be camouflaged by buzzing the scratches with a palm sander. Don't take a lot off but get rid of the long parallel lines from block sanding. the shrinkage will still be there but you won't be able to see it as a line.

    Bob K

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