Fret levelling - creating a fall-away on the upper registers

Discussion in 'Luthiery, Modifications & Customizations' started by jonsick, Nov 14, 2017.

  1. GunpointMetal

    GunpointMetal SS.org Regular

    Messages:
    1,328
    Likes Received:
    60
    Joined:
    Dec 8, 2011
    Location:
    Madison, WI
    I'm not sure what you mean by back angle. The guitars were set with the neck basically flat (as in no relief or back angle) with the strings basically a uniform low action from open to the 24th fret then the frets were finished to fall away every so slightly from 12-24.
     
  2. odibrom

    odibrom .

    Messages:
    2,094
    Likes Received:
    234
    Joined:
    Dec 2, 2014
    Location:
    Unknown
    It is not the same as compound/conical fretboard curvature, though the result may lead to similar goals - easy play... This fall away fret treatment is meant to have frets at higher register smaller than those at the nut. One can do it gradually or from some point onward. I think this may be applicable to compound radius also, though I've only done it to 16" as are those on my guitars.
     
  3. marcwormjim

    marcwormjim SS.org Regular

    Messages:
    1,669
    Likes Received:
    809
    Joined:
    Jan 15, 2015
    Location:
    Not here
    Apologies if the image is too small - It was the first result when I googled “back angle”:

    [​IMG]

    Basically, guitar necks often angle backward from the body in order to exert a downward force upon the strings - Without it, it would be difficult to keep strings in their respective saddle and nut slots, as well as to achieve a low action. The literal downside of this is in how the fret heights are necessarily staggered, relative to the string path. A difference of degrees in the angle is what can result in fall-away leveling being a necessary compensating measure - Otherwise, you can only lower the strings so much before they choke by coming into contact with the higher frets.

    Anecdote: Ibanez wasn’t using stainless steel frets; so I purchased a used Indonesian RG with poor fretwork specifically to refret. I observed that the neck needed a shim for additional back-angle, if I was going to get the action as low as I wanted.

    After refretting, leveling, and shimming the neck in reassembly, the combination of new frets and shim resulted in too much back-angle; with the strings coming into contact with the last three frets when lowered in the desired vicinity. If the guitar was brought to someone else in this condition, their first thought may be “FALL-AWAY, BRO.” Whereas I knew there was a shim to be removed.
     
    Last edited: Nov 22, 2017
  4. GunpointMetal

    GunpointMetal SS.org Regular

    Messages:
    1,328
    Likes Received:
    60
    Joined:
    Dec 8, 2011
    Location:
    Madison, WI
    Ohh, I guess thats what I thought you meant, but wasn't sure why that would effect a fall away. I see what you're saying though. In my case, the guitars were neck-through with locking nuts/trems.
     
  5. odibrom

    odibrom .

    Messages:
    2,094
    Likes Received:
    234
    Joined:
    Dec 2, 2014
    Location:
    Unknown
    I do not agree with this statement. Neck's back angle has the only purpose to compensate for the bridge height. The other option is to deepen the bridge at the body. Shimming the neck has the purpose to acquire a better action with a tall bridge in bolt on guitars and can be with or without angle. Neck's back angle and neck shimming has nothing to do with keeping strings in saddles at the bridge, nor downward force upon the strings, that is done at the headstock and at the bridge, not at the neck angle or neck shimming tricks. Also, frets heights aren't necessarily staggered in these situations, only if the user needs or wants them to be.

    Again, fall-away fret treatment isn't a necessity in guitar setup, it's a choice with specific purposes and is a refinement of a general good setup. Neck angle or shimming is something dependent on the guitar's construction and hardware and may or may not ask for a later fret fall-away. I think you've got some confusion there on the geometry and setup of a guitar, but that's only my humble opinion.
     
    Ernesto and Knarbens like this.
  6. marcwormjim

    marcwormjim SS.org Regular

    Messages:
    1,669
    Likes Received:
    809
    Joined:
    Jan 15, 2015
    Location:
    Not here
    Humility has a way of getting lost in google translation.
     
  7. Ernesto

    Ernesto SS.org Regular

    Messages:
    165
    Likes Received:
    21
    Joined:
    Jun 18, 2008
    Location:
    Verde Valley, AZ
    I only do a fall away if the person I'm setting the guitar up for likes really low action but also strums/picks really hard, and even then, I only do it if there's buzz with a normal setup. 99% of the time, or more, it's not necessary at all.
     
  8. marcwormjim

    marcwormjim SS.org Regular

    Messages:
    1,669
    Likes Received:
    809
    Joined:
    Jan 15, 2015
    Location:
    Not here
    I used to think so, too - Until someone informed me that I’ve got confusion on the geometry of the guitar.
     
  9. Ernesto

    Ernesto SS.org Regular

    Messages:
    165
    Likes Received:
    21
    Joined:
    Jun 18, 2008
    Location:
    Verde Valley, AZ
    I think he was talking about the back angle thing?? I can't say I really get your logic there either, unless it's for a tailpiece type guitar/cello/bass/violin. Most bridges for electrics and one piece acoustic bridges inherently create a pretty big angle between the string attachment point output and the saddles. Its something I actually eliminated on purpose in my constant tension tremolo eight string bridge. I'm thinking that it will significantly decrease string breakage. Everything else you've been posting seems spot on though.
     
    odibrom likes this.
  10. Lemonbaby

    Lemonbaby SS.org Regular

    Messages:
    376
    Likes Received:
    182
    Joined:
    Jun 3, 2015
    Location:
    Germany
    I think we can all agree that the clearance needed below a string is defined by physics and has a certain shape that your frets must follow for lowest possible action. No magic involved and also independent of the player picking hard or soft - this will only change the amplitude, not the shape.
     
  11. Ernesto

    Ernesto SS.org Regular

    Messages:
    165
    Likes Received:
    21
    Joined:
    Jun 18, 2008
    Location:
    Verde Valley, AZ
    The shape in action reflects the amplitude, which intensifies then dissipates as it gets further from the pick point. The Animals as Leaders official video for CAFO shows some great views of resonating strings. Same wavelength up the string, with some fundamental harmonic variations, but the string is oscillating on a larger radius closer to the pick point compared to at the nut or fret point, peaking somewhere between the pick point and midway between the pick point and the halfway point between the nut or fret point, depending upon the frequency being played. I used to fall asleep with the book Fundamentals of Mechanical Vibration so I can see this stuff in my head now. It sounds cool but it's kind of a curse.

    If they want super clean tone, people that strum open chords hard and solo hard between the nut and the seventh fret generally need a little more clearance up high if they want nice low action down low. It seems to be more of a country thing but one of my virtuoso friends likes them that way too and he plays everything, with everything he's got most of the time, and doesn't want the buzz that most people just assume is normal when flailing on an old acoustic like he does.
     

Share This Page