DIY - Radius-sanding Blocks

Discussion in 'Luthier's Corner' started by opus1956, Mar 1, 2010.

  1. opus1956

    opus1956 Senior Member

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    Thought I'd share this cool way to build your own radius-sanding blocks. This is a 12" radius block.

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    First, use a piece of MDF or plywood (whatever you have) and attach your router to one end. Mine is just as wide as the router and about 22" long.

    Then from the center of the router bit, mark the length of each radii you want to make. I marked my board at 9.5", 10", 12", 14", 16" and 20" so I can use this same board to make all these different radius-sanding blocks. Then drilled a 1/4" hole at each length. Make sure these holes are in the center of the board.


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    Next take another piece of MDF and cut it to the width you want the sanding block to be, mine is 2-3/4" wide (StewMac sanding block width). Then mark the center line of the board and lines equal distance apart. Mine were 3" apart.

    Depending on how thick your MDF is will determine how many pieces you need to cut to make your sanding block. If you want an 8" sanding block and you're using 3/4" MDF, you'll need the board to be at least long enough to cut 11 pieces plus an extra 15". So for the 8" sanding block you'd want to start with a piece 2-3/4" wide and 48" long.

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    Drill 1/4" holes at each of the 3" lengths starting 15" back from the edge of the board. Drill as many holes as pieces you going to cut plus an extra 5. I used a 1/4" straight cut bit in the router.

    Bolt the two pieces together at the 12" mark and make your first cut. Then unbolt it and move to the next hole to cut off another piece. So the bolt doesn't come loose as you pivot the router, I tighten two nuts against each other.

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    After your pieces are cut, use double stick tape, line them up and stick them together.

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    Then cut the block in half.

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    Hang on to the piece you cut off w/ the convex radii...you'll use that later.

    Take the piece with the concave radii and glue it to a backing board. I used a piece of 1/4" MDF.

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  2. opus1956

    opus1956 Senior Member

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    Then take 1/8" masonite and glue it to the radiused side of your sanding block. Use the leftover convex piece you just cut off as a caul to bend the masonite.

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    Once it's all glued, clean up and smooth the edges...then you're ready to throw on some self-adhesive sandpaper.

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    Enjoy!
     
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  3. dougk

    dougk Senior Member

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    COOL!

    Thats a really great idea. I'd seriously consider trying to make one 16 or so long. I take my long blocks and screw them to the bench radius facing up. Then I can work the neck over the block (if its separate from the guitar). Seems to be easier for me for some reason.

    Anyways, absolutely brilliant idea!
     
  4. landsharkey

    landsharkey Senior Member

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    Yes, nice job. Here's a little different approach I used making a template first for an 18" long block-
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  5. w666

    w666 Senior Member

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    Way cool....I wish I had thought of this!

    What I did was to use my Stewart Mac 12" sanding block to create a convex sanding block, and then used it to shape clamping cauls. Very labor intensive!
     
  6. Guitarsquirrel7

    Guitarsquirrel7 Senior Member

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    :applause:GENIUS!:applause:
     
  7. NateM

    NateM Senior Member

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    Nice trick!

    I used a bandsaw in place of the router for mine and pivoted the piece of wood I was using for the block through the blade. It worked pretty well though I didn't think of the masonite for the bottom.
     
  8. opus1956

    opus1956 Senior Member

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    Thanks...yeah, I need to make a 16" - 18" one next.

    Thanks for sharing your method!

    Thanks guys.
     
  9. slapshot

    slapshot Senior Member

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  10. Tardis

    Tardis Senior Member

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    Dude, I was not liking the idea of buying radiused blocks, but I could think of no alternitive. Thanks for sharing this with us, me Cheapo side really appreciates it :):)
     
  11. SteveBassett

    SteveBassett Junior Member

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    The initial router method is a brilliant approach. Good work. But you'll have to measure from the center of any given radius pivot hole to the FARTHEST EDGE of whatever diameter router bit you're using, NOT to the center of the router bit to get an accurate radius. Maybe that's what you meant?

    I'm going to try this same structural approach but on a band saw with a scroll blade. I've got a lot of blocks to make and suspect the router bit would overheat cutting that much MDF. I'll measure from the blade kerf to the pivot hole. I think I'll have Home Depot cut my strips of MDF first on that nice, big panel saw they have. I may just strip rip a whole 4x8 sheet!

    Thank you for sharing the excellent method.
     
  12. fatdaddypreacher

    fatdaddypreacher V.I.P. Member

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    i can't believe someone else spent as much effort making a sanding block as i did. i made mine doing essentially the same thing that you did, only i used a radius cutting jig on a bandsaw. worked out fine, till i used it and found out i had a brain fart and set the jig for a 6" radius and ruined a perfectly fine piece of wenge.

    can't wait to see the effort you put forth in your builds.
     
  13. LPBR

    LPBR Senior Member

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    Unburing a very old post, I know, but I just found it. Anyway, I really don't think that the half width of a router bit will make any difference in this case. This is the kind of perfectionism that won't drive anywhere.

    :hmm:
     
  14. Freddy G

    Freddy G V.I.P. Member

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    Hey nice one!

    I made this 9 1/2" block about 20 years ago and it's still accurate and stable (albeit a bit beat up :D)


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    The precision will indeed matter if you are using a matching radius caul to press the frets in. If hammering then no big deal if the radius is out a bit.
     
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  15. nicolasrivera

    nicolasrivera Senior Member

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    nice Opus, always wanted to know how it was done..... and it is bit of work to do to save $16 bucks.
     
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  16. mountainwhimsy

    mountainwhimsy Senior Member

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    Nice trick. Though I just bought a pre-radiused and slotted fretboard, put sticky paper on it, then ran a hardwood blank back and forth over the top of the fretboard until it had the the pre-radiused profile. The cost was a little more for the pre-radiused fretboard, but I needed it anyway. About 5 minutes of total work.

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  17. LPBR

    LPBR Senior Member

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    Very nice approach Tony! Sometimes we need to look out of the box!

    :)
     
  18. emoney

    emoney Senior Member

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    Me? I just spent $10.00 and bought one off Ebay. Took all of 9 seconds flat.
     
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  19. scottop1972

    scottop1972 Premium Member

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    ^thats what i did! Buy it now!
     
  20. mux164

    mux164 Senior Member

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    great ideas, i just took my stop tail piece and traced it onto a cork sanding block then used the belt sander to get it to the line. then i use 40 grit up to 180
     

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