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Sanding scratches

Discussion in 'Getting Started' started by Tim Deal, Sep 25, 2020.

  1. Tim Deal

    Tim Deal

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    I'm relatively new to woodturning and would appreciate advice on how to avoid those tiny scratches that remain on my spindle turnings after finishing with friction polish and beeswax/mineral oil. Am I starting out with too course of a grit. I typically start with 80 or 120 grit and go up to 220. The scratches are barely perceptible but if you look closely enough - there they are. I see many turnings by other apparently more experienced folks that don't have those scratches. Thanks for the help!
     
  2. Robert D Evans

    Robert D Evans

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    You're stopping too soon with the sandpaper grits. After 220, go to 320 and then 400 grit. Then the friction polish and your finish. For most projects, I find that 400 grit is high enough but you can certainly go higher.
     
    Charles Cadenhead likes this.
  3. Mark Jundanian

    Mark Jundanian

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    I think deciding at what grit to start your sanding sequence can be hard and gets better with experience. But a guess, for a spindle that is long grain work 80 grit may be more coarse than you need unless your surface is very rough or you need to tweak the shape.

    The scratches you are seeing may be from the 220 abrasive, or from earlier grits.

    When I start at 80 grit I usually progress from there to 100, 120, 150, 180 and 220. Some might consider these half steps, but I find this better addresses any sins I might have left behind from earlier grits.

    At the fine end of my sanding routine I will continue from 220 to 320, 400 and 600 (and lately even finer). Around 400 to 600 scratch marks are supposed to be invisible to the naked eye. 220 grit scratch marks are still visible. In flat work 220 is an endpoint grit, but in that instance sanding is usually with the grain which obscures the scratch marks. Turned work is more often sanded across the grain, but with some pieces it is possible to do a final sanding with the grain.
     
    John Freund and hockenbery like this.
  4. hockenbery

    hockenbery AAW Advisor Staff Member

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    The final sanding I do with the grain.
    With the lathe the stopped I sand parallel to the lathe bed.
    I do not sand features I could round with the sanding.

    The starting grit will go up with your skill level. You may need to start with 180 or 120.
    If you are using a sharp spindle gouge and cutting with the bevel lightly on the wood you might be in the 220 starting range.
    If you are trying to scrape spindles you may need to start with 80 grit.

    when I do finials using a skew and spindle gouge I sand Usually with 320 and 400
    I do have to use 220 on some coves when I miss matching the cuts from the opposite sides..
    The key to having a crisp Look to finials is minimal sanding

    lastly with friction polishes it is easy to leave drag marks in the finish.
    The application of the friction finishes takes a lot of practice.
    I rarely use them easier to just use a rattle can lacquer.
     
    Last edited: Sep 25, 2020
  5. robo hippy

    robo hippy

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    Well, pretty much all solutions have been covered. If you can avoid 80 grit, do so, because some times the 80 grit scratches are worse than the tool marks you are trying to sand out.

    I use the same progression that Mark does. Mostly when you do leave some scratches from two grits ago, if you are going in half steps, you can get those scratches out, without having to go back another grit.

    Having good lighting and glasses really helps. We all see differently, but I like the natural light spectrums. The main reason for that came from a quote from a turner on another forum. "Never take a finished piece from the shop into the house on a sunny day. Sunlight causes scratches." If nothing else, if it is a sunny day, take it outside to look at it for scratches. Been there, done that, more than once. I do wipe my pieces off by hand, or some times use a rag, because the fine dust will go into scratches and some times that highlights them.

    I prefer more flexible abrasives to the stiff ones. The edges, especially of the coarser grits can leave scratches. This is more of a problem if you are power sanding bowls and are working on concave surfaces.

    robo hippy
     
  6. Mark Jundanian

    Mark Jundanian

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    I might also add that we seldom build a dresser or table with the thought that someone will pick it up and fondle it. Small objects just get closer scrutiny, hence the finer grits.

    To add to the above, when you think you're done sanding wipe the piece down with mineral spirits. This highights the surface irregularites and cleans off the swarf prior to finishing. It also gives you an idea what the grain will look like under a coat of finish.

    As mentoned, strong raking light can also demonstrate the defects.

    I frequently employ the pencil trick. Lightly scibble on the surface with a pencil, then sand with a particular grit until the pencil mark is gone. I have been surprised to discover that what I though was plenty of sanding wasn't enough.

    And one last note, (appologies to Jaques Vesery) the sandpaper is not precious. It gets dull and you gotta make yourself throw it out and take a fresh bit.

    Sorry if you knew all this already, but it's just the tid bits I had to scratch together for myself when I was starting from scratch.
     
    Charles Cadenhead likes this.
  7. odie

    odie

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    Hello Mark.......Don't think I've heard of the "pencil trick" before. Can you explain a little more in depth please?.....:D

    -----odie-----
     
  8. Mark Jundanian

    Mark Jundanian

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    @odie it's something I learned from the flatwork community. You lightly mark the wood surface with a pencil before sanding. When you've sanded enough to remove the pencil marks then you have sufficiently abraded the wood surface to advance to the next grit (although some people say to do it twice).

    If you are generous with the distribution of your pencil marks it is also helpfull to make sure you have sanded the entire surface.
     
    odie likes this.
  9. Timothy Allen

    Timothy Allen

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    The pencil trick is commonly used for "fairing" a surface (flat or curved) with a "long board" -- where the graphite has been sanded away, those are the high spots; where the graphite remains on the surface, those are the hollows. You then either have to keep sanding down the high spots, or fill the hollows with fairing compound, and repeat the process.... (it seems I have to do this to the keel of my sailboat every year!)
     
    odie likes this.
  10. Rob Fridenberg

    Rob Fridenberg

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    The same process is used for automotive bodywork. You use either a black powder guide coat or spray a very light coat of black onto the grey primer and start the tedious process of block sanding and priming until the surface is flat.

    It is the only way to ensure a flat finish for a high gloss paint.
     
    Roger Williams, odie and Bill Boehme like this.
  11. Tim Deal

    Tim Deal

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    Thanks everyone for the replies! Good information!
     

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