JP Style Fretboard Radius Jig

Discussion in 'Luthier's Corner' started by count_funkula, Dec 22, 2004.

  1. I recently built a router jig like JP uses to radius his fretboards. I just tried it for the first time and it worked great! It sure saves a lot of time and it's very acurate. Of course there is a bit of sanding to do after using the router.

    I don't know if JP came up with the idea or got it from someone else. Either way, thanks JP!
  2. Bassic83


    Jul 26, 2004
    Texas, USSA
    Please elaborate!
  3. Suburban


    Jan 15, 2001
    lower mid Sweden
    Regardless the majesty of our beloved JP, the credit for this jig is to Martin Koch (

    Martin is the author of one of the best books available on building solid and semiacoustic guitars - IMHO the best available.
  4. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    yep, this is where I got the idea! ;)

    Also I amost only build basses with flat (no radius) boards now.
  5. JP,

    Where did you get the idea for your necks? That layered method you use is very interesting. I can see a lot of benefits in doing it that way. Is that a common technique?

  6. Another quick question -

    What amount of compensation are you using for the radius in your jig. By that I mean, your arched platform has a radius and the tip of your bit rests on the plane of another. What is the difference between the two or does it matter too much?
  7. Hambone,

    If that question is directed at me, I'm not sure. The base of my platform is about a 16" radius. The router bit was around 1/2" below that, maybe a little more. I guess the actual radius of the fretboard would be around 15". It feels really good so thats all I'm concerned about.

    The hardest part of making the jig was the router base. I had to make an entire jig just to create the radius for the base. I had an arm made from 1/2" mdf that attached to my work bench with a single bolt. It was raised up 1/2" off the surface of the bench. On the orther end of the arm was a platform where I mounted my router. The distance between the bolt and the router bit was 16". The arm could be moved in an arc to cut a piece of mdf. That resulted in the template I used to make the router base out of some red cedar I got from home depot.

    I have another really cool jig for routing the truss rod and graphite rod channels. It has cut the amount of time it takes me to do those routes in half. It's far more acurate as well.

    It takes a long time to build these things but the rewards are tremendous. I have a couple more jigs to design and I'll really be set. :bassist:
  8. The reason I asked is that I've drawn up some plans for a jig/apparatus for radiusing fretboards that takes the opposite tact by moving the fretboard laterally while the router swings in a fixed plane around the neck at a precise radius measured at the tip of the bit. JP's design actually looks like it's easier to get set up to a precise radius especially if you could raise or lower the fretboard mount or you used a known distance below the router board and compensated your curve for that. It's all cool - I like this one enough to maybe try to incorporate it into this master neck jig I've built. Knowing how he sets it up would help me figger it out quicker. Just thinking out loud here.
  9. That sounds cool. I'd be interested to see how it works when your finished.
  10. Suburban


    Jan 15, 2001
    lower mid Sweden
    Well, good on ya!!
    I assume you mean the J-neck, which JP has discontinued. He nowadays seem to have become lazy, and work with single-piece necks...sigh...;)

    The "parallel to fretboard" lamination is not very common among luthiers, but there are a few. Some got the idea from old, meaning ancient, instruments, others from the Internet(! - sites like Linc's et al). I ,and I believe JP as well, got it from tech school, where laminations were tought with examples mainly from automotive industry.

    I can't really comply with the thought that JP actually went to onepice, scarf joints...and didn't stick with the three-lam, and added a scarf joint head! :D
  11. The reason I ask is, I would like to try that method on some of my basses. I didn't want to "steal" the idea if it's JP's signature method of building necks.
  12. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    As Sub said, I got the idea from my tech studies. you can use the method if you'd like of course.

    Sub, I stopped using this method just because sticking to well selected neck woods, I have the stifness and stability needed. Horizontal lams should add stifness and used right improve stifness to weight ratio but I haven't noticed any audible difference on my instruments.

  13. budman

    budman Commercial User

    Oct 7, 2004
    Houston, TX
    Formerly the owner/builder of LeCompte Electric Bass
    I just had an idea. You could use this same method to make radius sanding blocks, but instead of the concaved arched pieces that mount to the router base one could make convex arched pieces that would cut a concave arc in a block of wood...instant radius block. Or has someone thought of this already?
  14. In fact, if you were shrewd in your design of the platform for the radiusing jig, you could use it for doing the radius blocks by turning it upside down and putting a pair of rods on the base of the router to ride on the arched rails. Put your blank between and go to town.

    I just built this jig into my neck jig setup. You guys won't believe what this device can do now. But in doing it, I came up with a neat way to make perfectly smoothed radius rails for your router base without having to resort to making a swinging radius device for your router to make a perfect arc. The idea is to make your pattern on the computer and figure out all of the geometry first. Then take the pattern and cut out your rails using a band saw. Be very careful to follow your pattern as closely as possible. If you get off a little it's OK, but avoid large errors. When that's done, just use double sided duct tape to attach a strip of thick plastic to the rail as a friction surface. This covers any imperfections and smooths the curve. I used 1/8" UHMW for my friction surface but you could easily get a nice piece of plastic from a 5 gallon plastic bucket. That stuff is tough and slippery against a metal tube rail.
  15. Hambone,

    Can we see some pictures of your jig? Thanks.
  16. Bass Kahuna

    Bass Kahuna

    Dec 3, 2002
    West Lafayette, Indiana
    Luthier, Custom Builder
    CTH Luthiery offers a very similar radiussing jig for $275...

    Go to his site at: and click on "Tools".

    His version uses the radius guides under the router mount, thereby allowing any combination of radius guides for doing any combination of compound radius (if desired) with a router jig.


  17. Yep, now that I'm free of certain encumberances, I'll be a little less secretive with some of the stuff I've alluded to here on the boards.

    This setup has several parts and lots of capabilities so I want to organize the shoot to make the most sense for everyone. I'll get things together here in a day or two.
  18. Uh, yeah.

    I wonder if it radius's any better than my $4 setup? :confused: :D
  19. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    I also still like that radius jig that somebody made about a year ago, that used a belt sander.