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Thread: Slotting a nut

  1. #1
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    Default Slotting a nut

    Is it best to slot the nut in line with the fret board, or angle the slots toward the post the string will be attatched to.
    Bob Schmidt

  2. #2
    Adrian Minarovic
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    Default Re: Slotting a nut

    Quote Originally Posted by irishmando View Post
    Is it best to slot the nut in line with the fret board, or angle the slots toward the post the string will be attatched to.
    Both at the same time.... Start the slot in line with the string and smoothly change the direction towards the tuner post.
    Adrian

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  4. #3

    Default Re: Slotting a nut

    What Adrian said.

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    Default Re: Slotting a nut

    OK this makes sense since it distributes the side load over a wider area and away from the fretboard end of the nut, but now for a dumb question. What tool do you use to cut the channels since all of the nut files are straight?
    Bob Schmidt

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    Default Re: Slotting a nut

    The slot's not curved. It's straight. Start it on the fingerboard side with just a little notch and then, keeping the file in the notch, rotate the file and aim it at the tuner. If it helps, you can put a slight back bevel on the top of the nut. It's not unusual to file the top of the nut down a bit after the slots are cut anyway.

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  9. #6
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    Default Re: Slotting a nut

    OK thanks, I think I understand it now.
    Bob Schmidt

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    Default Re: Slotting a nut

    I cut them straight in line with the strings, so strings won't bind on the front edge. Then slightly widen the opening on the back edge toward the tuning machine, to avoid binding there also.
    It's not possible to cut a parallel, curved, slot with a straight file.

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  12. #8

    Default Re: Slotting a nut

    Make sure you protect the frets. I didn't...

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    Default Re: Slotting a nut

    Hewines, thanks for elaborating; I think that is the same thing Adrian is indicating. At least that is the way I understood it.
    Bob Schmidt

  15. #10
    Adrian Minarovic
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    Default Re: Slotting a nut

    Quote Originally Posted by Hewines View Post
    It's not possible to cut a parallel, curved, slot with a straight file.
    It is possible to cut curved slot on nut. It's not flat and not parallel to anything (at least on the instruments I worked on)
    You need to shape the top profile of your nut so it copies the future path of the string towards post (plus depth of future slot) which is somewhat cylidrical shape and use file just to file the shallow string slot. Since you are working shallow on curved (convex) surface you can cut the slot with straight file.
    I usually cheat a bit and leave a bit more meat on top of the nut (just eyeball the rounding) and just file the curved path without looking at the edges of the resulting slot (they may be perceived a bit jagged, though only when looked at with some magnification). After I arrive at correct depth (sting up and test - if necessary I remove one string at a time and deepen slot) I remove strings from nut and reshape the top of nut to desired shape. If I worked well on slots just the bottom of the slots remain (typical half of string thickness for wound and 3/4 string thickness for plain). Sometimes during this shaping I remove parts of some slots towards string posts that I didn't cut deep enough so I recut them carefully. Often I finish with tiny swiss round file and widen the half of the slot towards the post to relieve any unnecesary friction.
    After conversation with a strng manufacturer I even started relieving the upper edges of a/e string slots with tiny square file (only works if the slot is more than half string diameter deep). Actually he advised to cut the entire slot with square file to form 90 degree v-slot for the plain strings (don't use 60 degree file the strings will bind) - he noted that this prevents accumulation of junk in tight slots that may be problem with conventional U shaped slots.
    Adrian

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  17. #11
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    Default Re: Slotting a nut

    One an active Cafe member, the late Paul Hostetter taught even interested amateurs like me. Fortunately for us, his family has maintained his website. Personally, I found his "bell" analogy to be most helpful:
    http://www.lutherie.net/nuts.html
    - Ed

    "Then one day we weren't as young as before
    Our mistakes weren't quite so easy to undo
    But by all those roads, my friend, we've travelled down
    I'm a better man for just the knowin' of you."
    - Ian Tyson

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  19. #12
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    Default Re: Slotting a nut

    Ahh, i think I'm on a different plane! Hogo, i get what you're saying. I was thinking of the direction of the slot when viewing the mandolin from the front.

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  21. #13
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    Default Re: Slotting a nut

    Thanks for sharing all of this insight. I see that making a nut is a lot more precise then just cutting slots. I agree that the Paul Hostetter link is most helpful, and that site is now in my bookmarks.
    Bob Schmidt

  22. #14
    Adrian Minarovic
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    Default Re: Slotting a nut

    Quote Originally Posted by Hewines View Post
    Ahh, i think I'm on a different plane! Hogo, i get what you're saying. I was thinking of the direction of the slot when viewing the mandolin from the front.
    My slots change direction both when viewed from front and side. The curved surface allows for that tiny amount of change. On mandolins it is really not much and most folks would not notice at all, but when you insert the file in the slot you can see it clearly where the tip points.
    BTW I mostly start the slot by scoring just tiny scratch with triangular file (60 degrees) then deepen it a bit with the same file if I'm happy with the scratch position and angle and do final deepening with my nut "saws" which are made of feeler gauges with rounded edge and tiny teeth cut into it. These are flexible enough that they will follow the bottom of started slot. Sometimes I polish bottom of slots in pearl nuts (those that appear rough, crumbly in the slot - some pearl just does that) with 1200 grit paper wrapped around smaller size feeler gauge. I finish the slot at headstock side (widen) with a pointy round file - I don't know what it is, my FIL gave it to me it is marked with swiss and no other mark it it's 4" long and tapers from barely over a 1mm thick to fine needle tip that is marginaly thicker than e string. Just prefect tool for mandolin strings - covers the whole range. I've got one that is a bit thicker that I use for guitar and sometimes for thinner cello strings.
    Adrian

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  24. #15
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    Default Re: Slotting a nut

    Thanks Adrian. Now that you mention it I remember reading about modifying feeler guages to slot nuts and I can see how they would allow tracking a bend in the slot.
    Bob Schmidt

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    Default Re: Slotting a nut

    Rob Meldrum describes making nut saws out of feeler gauges in his book, "How to Set Up a Mandolin". Search this forum for a link if you don't have it.

  26. #17

    Default Re: Slotting a nut

    I guess artfully cut nuts are demonstrations of builder and repairer skill, but zero frets make a lot more sense, for function, mass production, and durability I M H O. I did a little web searching - most of the discussion concerns guitars and also regional practices, with only a little fantasy about acoustics and osteo materials thrown in.
    Thinking about it just now, it occurs that the zero also offers the opportunity to vary the effective break angle in both directions, not that I’m sure about any advantage that would ensue.
    Howsomoreover, the optimum nut slot shape Hostetter suggests might be easiest to create with an abrasive string of similar diameter to the playing ones, and that’s easy to do, including the outboard shaping. But winding up with depth accuracy in the region of a few thousandths is still finicky.

  27. #18
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    Default Re: Slotting a nut

    Please email me at rob.meldrum@gmail.com and put Mandolin Set Up in the subject line. I will send you my free ebook that will show you what you need to do. And, yes, making nut slot files out of inexpensive feeler gauges is one of the tips in the book.

    Rob

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