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Block sanding/final sanding question..

Discussion in 'Luthier's Corner' started by suraj, Jul 21, 2012.


  1. suraj

    suraj

    Oct 1, 2008
    Mumbai, India
    I may be close to final sanding my build soon, so the question is -

    Up till what grit should one use hard blocks(wood) and when to switch to soft blocks(rubber) ?

    Say i'm sanding the flat region of the body with 80 grit paper attached to a flat wooden block, can I use this hard block up till 220 grit ? And then lay two coats of varnish, wet sand uneven areas with 400 grit with wood/rubber blocks.

    The reason why I am asking is, i feel sanding a finish with a fine grit paper attached to a hard block might produce witness lines, where as soft blocks wouldn't. At the same time a soft block could compromise the surface flatness under a gloss finish ?

    Also at what grit can one sand without a block and just use fingers without compromising surface flatness or quality ?
     
  2. praisegig

    praisegig Supporting Member

    Jul 7, 2008
    Stephenville, TX
    When prep/level dry sanding the body flats, I use a hard block with cork attached to bottom, up to 320 grit. Using a rubber eraser to do the sides. Fingers to do the edges.

    When dry sanding the sealer coats, I use the same as above. When wet sanding the clear coats, I will go to the rubber eraser for the flats and sides, starting with 800 grit up to 2000 grit.

    I never have seen witness lines when level sanding, as the next finer grit will remove any scratches from the last grit and should be level with an even sheen.
     
  3. suraj

    suraj

    Oct 1, 2008
    Mumbai, India
    thank you :) that makes a lot of sense. Although is the cork necessary under the hard block ?
     
  4. praisegig

    praisegig Supporting Member

    Jul 7, 2008
    Stephenville, TX
    No, not necessary, but my sanding block was made out of a 2x4 to fit my hand and I wanted to have a little cushion between the block and paper. Its only 1/8" thick. Less chances of the block digging into the surface, to me. Anything can be used as long as it is flat.
     
  5. suraj

    suraj

    Oct 1, 2008
    Mumbai, India
    thanks for your response :), I guess my question is answered..
     

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