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Thread: Can CAD calculate fret spacing on fingerboard?

  1. #1

    Can CAD calculate fret spacing on fingerboard?

    I use my little cnc to cut fingerboards, wondering if there are CAD software that can do the calculations for fret spacing. The formula is to multiply the scale length by the 12th root of 2, that gives the first fret. Then the same with the remaining distance for subsequent frets.

    There are easy fret calculators on line, but it's no fun copy and input the dimensions (accurate to 3 decimal places) Would be great to have the formula in the CAD and just plug in scale length and generate a fingerboard. Any way to do that? I've been using Fusion 360.

  2. #2
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    Yes, that could be done in solidworks using a formula to calculate the spacing in the background. I suspect it could be done in fusion or others as well, but I am not familiar with those. Look into parametric programming for fusion and post some images and I might be able to help with the forumla's.

  3. #3
    Thanks for the reply Brad. I also posted this query on a luthiers forum and just discovered that there is Facebook group - Fusion 360 Luthiers, where this is discussed, just signed up, waiting for approval. Gotta love these forums!

  4. #4
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    I had a few minutes so I mocked up a solution in the software I have. It might not be exact as I am not a guitar builder, but it should get your creative juices flowing. In this, I can change the width, fret width, scale, or any of the variables and the part will automatically update. You can add tolerance variables or any host of other things you might need.

    FRETq.jpg
    I see the image comes out too small, so I added an image of just the formulas for you to look at.
    FRET_VAR.jpg
    Last edited by Brad Shipton; 02-08-2019 at 12:30 PM.

  5. #5
    Quote Originally Posted by richard newman View Post
    Thanks for the reply Brad. I also posted this query on a luthiers forum and just discovered that there is Facebook group - Fusion 360 Luthiers, where this is discussed, just signed up, waiting for approval. Gotta love these forums!
    Thanks for posting this, Richard. I have been wanting to do that very thing but haven't stopped long enough to work it up in Fusion 360. And I rarely use FB but I'll go to that group and see if I can be approved, as well. I had not thought about doing parametric modeling on this, just figured I'd draw it up. But having it as parametric sure makes it easier for different scale lengths.

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
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  6. #6
    David, I also hate FB and the whole social media data grab conspiracy, but there are some groups worth checking out. The parametric aspect of Fusion should make it great for this sort of thing.

    Brad, thanks for giving this a try. Not sure you got it yet, in the drawing it looks like all the fret spacings are the same, they should be getting smaller and smaller. Have to apply the formula to the remaining distance after subtracting each previous result.

  7. #7
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    Ok, I see the goal now that I look at a finger board image online. I think it would still be possible, but the location of each fret would need its own formula. I see the formula in the youtube video below, so that could be easily used.

    youtube video: https://www.youtube.com/watch?v=zGVw8Q-2UgI
    Last edited by Brad Shipton; 02-08-2019 at 3:22 PM.

  8. #8
    Interesting the way he laid that out but man oh man can I do without the clicking sound on his keyboard and mouse! LOL!

    I was thinking of doing this a different way but I may try his way, as well.

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
    YouTube Woodworking Channel for David Falkner (just search for me by name)
    Romans 3:23

    Etsy shop - CurlyWoodShop

  9. #9
    There are two listed on the Shapeoko wiki:

    - LoboCNC Fretboard.exe at http://jrkerr.com/lobocnc/userapps.html
    - http://efguitars.s3.amazonaws.com/fr...generator.html

  10. #10
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    Not knowing as much as I probably should about this, having built a few instruments but being only a very mediocre musician, does the formula actually give the ideal intervals? I ask because in piano tuning anyway one "stretches" the octaves so they are not mathematically perfect but sound better to the human ear. I don't even want to think about how temperament translates to a fretted instrument; presumably a guitar natively sounds better in some keys than others, do really good players compensate by bending strings on the fly to achieve better intonation when playing in "off" keys?

  11. #11
    Roger, you're right, the simple math of fretboard calculation doesn't even work scientifically, much less to the satisfaction of the ear. The stretch induced by fretting a string sharpens it, and each string behaves differently. Builders deal with this with compensated bridges and nuts, but it's still a big compromise. There are some very sophisticated systems that take it way further, but I know nothing about them.

    But when it comes to satisfying the ear, obviously what might work in one key would be even more off in another. I'm sure some players can bend on the fly, maybe even subconsciously.

    Making banjos, I don't really worry as much, banjo players are just not as fussy. And if they are, they can play a fretless banjo and get just what they want. Plus all the notes in between! And many of them do.
    Last edited by richard newman; 02-09-2019 at 11:47 AM.

  12. #12
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    Hey, I resemble that remark! Building a banjo was the project that led me down the rabbit hole of woodworking some 40 years ago (picture below). I copied the spacing from a Whyte Laydie they had at Gryphon in Palo Alto at the time, tweaked with advice from Frank Ford who had a whole collection of scales. Subsequently I bought pre-slotted fretboard blanks from LMI. I am one of those non-fussy (or at least have an insufficiently good ear) players, so that it works for me. When I play a fretless banjo fortunately no one is around to hear. My thinking about this is pretty purely theoretical!

    IMG_0997 (1).jpg IMG_0998 (1).jpg

  13. #13
    Nice looking banjo Roger! How many instruments have you built? Still doing it?

    I got started by making a 5 string neck for a tenor pot while in engineering school in the early 60's. Long story short, wound up leaving to pursue furniture making at the School for American Crafts in 1966. Got back to banjos as a side trip in the early 70's, had a little success and notoriety. There was an article about my banjo making in the first issue of Fine Woodworking, with the below photo. After my daughter was born in 1977, had to give it up and get serious about my furniture biz. Returned to banjos after burning out turn of the millennium. Consider myself semi-retired, but still have a big shop. Semi-retired is great, gives a lot of latitude and allows indulgences. I haven't made any furniture for 10 years, not ruling it out, but only doing banjo stuff now.
    Attached Images Attached Images
    Last edited by richard newman; 02-11-2019 at 1:39 PM.

  14. #14
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    How cool is that! I remember that article.

    I've not built much, only the one banjo so far, but it's something I hope to do a lot more of in retirement. It was my favorite project ever, and I still like to think of myself as a proto-luthier. I hope it's not just fantasy. I've been thinking about a gourd banjo for some time now, and would very much like to make something with a 12" hoop and frailing scoop in the neck. I made my son an electric bass, did a number of hammered dulcimers back before you could buy them, and I've got two mandolins under way (for a painfully long time now), one maybe 50% and the other about 85%-- I try something on the A shaped one first and then try to transfer what I've learned to the F. I also play with organ pipes.

  15. #15
    I'm really good at math. Like really good. Algebra, not so much. Up until getting our router, that was fine, you really don't use it that much, and when you do, it's extremely basic. Any time I build a part in cad, even if it's a one off, I try to do so parametrically so something in the variable table can be altered and easily change the part. It might never get used again, it might get used a thousand times. This has REALLY exposed my weakness in the algebra department, my geometry is dog vomit too. I wish I would've paid more attention in school. You can make the software do just about anything if you know how to write the formula.

    Far too often, I know what I want, I just don't know how to express it. It's like being a two year old again.
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