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Using these radius router bits

Discussion in 'Luthier's Corner' started by erikbojerik, May 31, 2007.


  1. Ask, and you shall receive!

    OK, so I had these router bits custom made for me by a machine shop contact, to the tune of $200/ea. I'd got a bunch of quotes from commercial manufacturers that were all in the $265 to $315 each, so I think I got a good deal in that respect. They are a bit pricey but because I am finding my free time is not what it used to be, I am reveling in the fact that I can now radius a fretboard in ~5 minutes.

    bits.jpg

    1) These are used in a router table (mine's a fairly cheap Craftsman), I'd never use them in a hand-held. The bearing runs more or less along the centerline of the fretboard blank. First bit of business is to plane square and true a block of wood longer & wider than the fretboard, so that you can mount the fretboard centered on one side and not have the edge of the board touch the router table. I used a 4x4 mailbox post for this, planed & squared up on the jointer. Fingerboard blank has already been planed flat by this point; the board pictured is a birdseye maple fanned-fret board with integral binding, slotted but not yet tapered.

    FB53.jpg

    2) I'm using the 16" radius bit for this board. I raise the bit so that the lower edge of the bearing is on the centerline, then make two passes, flip and make another 2 passes. Normally this does the job on the outer half of the board, you can see there's a strip down the center that hasn't been radiused yet, and this is clearly shown by the radius gauge.

    FB54.jpg
    FB55.jpg

    3) Now iterate...raise the bit, make a pass, flip and make another pass, keep raising the bit a little at a time until you just eliminate your centerline on the board. This leaves a subtle ridge down the center of the board that is ever so slightly high, easily knocked down with ~10 strokes from a sanding block (I used a radius block I already had on hand).

    FB57.jpg
    FB58.jpg

    The result is a radiused board with a precise uniform radius that is even across its width...no more fretboard with assymetrical radius!

    FB59.jpg

    The surface here is very nice. This was a board that I got a fair bit of tear-out from the jointer, so I had to use a drum sander to bring it to proper thickness. I got no tear-out at all with the radius bit, even though the board was already slotted. Here's a shot of the surface, after knocking down the center ridge.

    FB60.jpg
     
  2. Phil Mailloux

    Phil Mailloux

    Mar 25, 2005
    Brisbane, Australia
    Builder: Mailloux Basses
    Damn that's hot! I gotta get myself some of those made :eek:

    Did you check the length of the fretboard with a straightedge to see if it did come out flat after radiusing?

    How long is the cutting edge on the bits?
     
  3. pilotjones

    pilotjones

    Nov 8, 2001
    US-NY-NYC
    Cool.

    How many instruments do you make? That's quite a bill for bits!


    That fretboard looks "pre-bound," I was wondering whether anyone did that.
     
  4. Foamy

    Foamy

    Jun 26, 2006
    Sac Area
    Oh you %#$$^!!!!!!
    ;-)

    Seriously though, very well done!

    I wonder, did you see this machine?
    http://www.grizzly.com/products/g0574

    Seems like it is less money than the bits, but a bigger footprint. But you can't drop it. ;-)
     
  5. Phil, yep its still straight along its length. The depth of cut is 2", they are 1/2" diameter shanks.

    PJ, for me the issue right now isn't how many guitars per year. Its how many years per guitar. Both speed and accuracy have been achieved in one fell swoop.
    Yeah, integral binding=saw off the edges+slot+glue 'em back on (paying attention to match the grain). After tapering I'll have ~1/8" uniform thickness on each edge of the board.

    Tim, I've paid ~$150 for a single bit before. Still, for this many bits at this price point, I did ponder a belt sander and its versatility. But I just don't have the room right now for even one more large power tool.
     
  6. scottyd

    scottyd Commercial User

    Nov 17, 2006
    Waco Tx
    Builder/owner Redeemer Basses
    Congrats, Im happy to see that they worked for you, even on a slotted board! Although at that price I would be too scared to even use them! Way to think outside the box Erik, there are so many ways to skin a cat.
     
  7. Erik,

    Thanks for taking the time to do this, looks great. Completing a board in around 5 - 10 mins is fantastic. As you indicated, this is an excellent time and space saver.
     
  8. Foamy

    Foamy

    Jun 26, 2006
    Sac Area
    I'm just really impressed.
    Business opportunity?
    I wonder if we (or you) could make a larger order and get something in the neighborhood of $100 a pop - prepaid, or something like that.
     
  9. I don't know how many this guy'd be willing to make, but I can't imagine they'd be as cheap as $100. Big 1/2" specialty carbide bits routinely run over $100.

    But I've already blazed the trail as far as setup goes, so I'll ask about a quantity discount.
     
  10. Luke Sheridan

    Luke Sheridan Commercial User

    Dec 30, 2004
    Yonkers, NY
    I build guitars and sell them. Strings, too
    Count me in. I just spent three hours doing a 16.
     
  11. I finished a 5 string 20" radiused fingerboard in two hours straight with 40 grit paper and this was just to get the radius, finish sanding followed. I was buggered and my hands were hurting, so there was not much productivity after that. Where time is money, hand power just doesn't cut it with this job. I'll also be in it for at least one bit.
     
  12. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Feb 26, 2021

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