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Thread: Compound radius fretboard

  1. #1
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    I am in the planning stages for building a mandolin from a Siminoff kit. #I would like to try a compound radius fretboard on this one. #A search here on the forum had several articles about jigs for making compound radius fretboards, but as I am only going to be doing this one (at least for now), I was wondering if any of you builders that are already setup would make one for me or know of someone who could. #I have not made a definite decision about deminsions yet, but was thinking about something like 7 1/2 - 8" at the nut to 16 -18" toward the bridge. Am I nuts for attempting this? Any suggestions appreciated.

    Michael

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    Here's a link to the developer of the compound radius, you might want to email Denny a few questions. Nice guy, easy to work with. Here's the link to some info about it.

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    I haven't looked at the other methods, but here's mine. Get one side of your tapered-to-final-size-fretboard flat, then attach it to something flat and longer. Make a negative template of your 8" radius and plane near the nut til it fits.
    Then plane flat across the centerline of your fretboard, longways end to end.
    Then, you'll need a positive template of your bridge radius, 16-18".
    Slice it and fit it (fixed at exact the scale length from the nut) til the fretboard plane meets your template at center, using a straightedge. Now plane lightly the edges to center, both sides (avoiding the nut area and the centerline which are both already done at this point) til your straightedge goes all around straight.. You have to sort of arc your straightedge as you measure from side to side, in the same planes you planed at, sort of in a sun-rays pattern.
    Hope that makes a smidge of sense.....

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    Thanks Brian and Neal. #That gives me something to mull over. #Brian, your method with the radius template at the bridge end got me to thinking about using the same type positive template on the nut end and using a long enough perfectly straight sanding block that would ride on the templates. #One problem with my idea would be that the templates would have to be placed some distance away from the ends to allow motion for the sanding block so the sandpaper would not ride on the templates. #The radius would have to be adjusted accordingly. #Guess he radius does not have to be exact anyway...just close. #Just an idea. #Thanks for the responses.

    Michael

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    Registered User PaulD's Avatar
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    Here I go overthinking the problem again, but maybe there will be something useful in my ramblings. What if you made the sanding block so it has two holes drilled lengthwise for two steel rods. The sanding block would slide back and forth on the rods. The rods would ride on the templates and would follow the radius as the block is moved side to side. I think you could set this up in such a way as to not require much distance between the template and the ends of the fretboard, and I also think it could prevent the rounding over of the edges of the fretboard that folks say is common with sanding blocks. By changing out the templates you could do different radii or compound radii.

    I might be missing something in my brain dump... I wouldn't know until I thought it out some more or tried it. I would probably opt for marking the ends and handplaning the fretboard or setting up a power tool fixture, but for a sanding block solution this might work.

    pd
    "... beauty is not found in the excessive but what is lean and spare and subtle" - Terry Tempest Williams

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    Paul, take a look at this. You can change the arc-shaped pieces for different radii, and move them lengthwise for fine adjustments, and cut any compound radius you want. It's a similar principle to what you're thinking about.

    The literature that you see on the table there lists the web address as www.ctluthiery.com . I would link to it, but it won't come up, so the server might be down, or, who knows.



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    Thanks Paul and John.
    John, that router fixture looks like a great idea for producing numbers of fretboards accurately. #I did a websearch and found the website Cth Luthiery
    He sells the fixture for $275.
    Paul, the steel rod idea sounds great. #I will have to do some experimenting and see how it works. #
    Thanks for the input.

    Michael

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    Dyslexia strikes again!
    Thanks michael, the literature does, in fact, list the address as www.cthluthiery.com
    It's hard enough to get all the letters right when it's something I can pronounce!

    He had one set up at the ASIA symposium. I thought "that looks like something I could make." Then I found out it was $275, and thought, "I ain't building one for that!"
    I think he has the price just right. It's easier to buy from him than to make a copy.

    I've wondered If I could modify it for a nice quiet block plane rather than a screaming, dust slinging router, though.

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    John; I was rereading OldTymer's post and I think he's on to something. He's using a template for the outfeed side of his planing jig to keep the plane from cutting too deep. I'm thinking if you use a larger plane like a #5 or even your jointer and put another radius template at the nut end you could have "limiters" that would allow your plane to cut down to the radius but no more. You would want a longish plane for this and obviously would want to avoid hitting the templates with your cutting iron.

    In case that's not clear, I knocked out a "quick" sketch; I hope it posts okay... it's a Windows Paint jpg. The fretboard would be attached to the bed, and the interchangable templates would be screwed to the ends of the bed or set into dados. The top of the fretboard blank would need to be flush with or higher than the peak on the templates. Make sure your cuts always start and end with the plane on one of the templates. It looks simple but I think it would work.
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    "... beauty is not found in the excessive but what is lean and spare and subtle" - Terry Tempest Williams

  10. #10

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    I've built a couple of radius jigs for stationary sanders, but I remember someone else making a very simple version. I went to search, put in compound radius, and spec'ed this year, and sure enough, at the bottom of the list was a post by Ragamuffin showing a simple but effective jig.
    Now, someone tell me how to do a link to it so I don't have to write so much.

  11. #11
    Registered User sunburst's Avatar
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    Here it is

    Jim, select (highlight) the URL of the page then 'edit-copy'.
    Click the http:// button above the window your typing in.
    'paste' the URL right over whatever is in the little window that shows up.
    Another window will show up, and you can type in whatever you want to call the link.

  12. #12

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    Here is a shot from Frets.com. This is Collings old radius jig. I think they may use something else now. A couple piece of iron are fixed at each end. The jig which holds the fingerboard (in collings case the whole neck and fingerboard) has blocks attached at each end with a radius of choice milled into the bottom side. You plop it down and rock it. Seems like another decent idea in this category.

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    oops. here is the pic.
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