Custom compensating nut

Construction and repair of Classical Guitar and related instruments
Robert Goodwin
Student of the online lessons
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Custom compensating nut

Post by Robert Goodwin » Fri Mar 09, 2018 12:21 am

Is it possible to just get a compensation type nut made to a set of specifications? I am thinking of the nut type described in Greg Byers paper on intonation. I just need basic forming; length, string slots and recess cutout for the extension. I can do minor adjustment to allow for string type etc. It's just that I don't have a workshop (bandsaw, etc) to do the bulk of the work. This would be for a 580mm scale guitar, not for the 650 scale Greg originally wrote about and provided measurements for. I have been experimenting with temporary wedged extensions and find a 3mm extension makes everything about right with some adjustment on some strings. It seems the shorter scale makes compensation more necessary. I think it has to do with the ratio of string deflection to scale length when fretting a string. The open strings are tuned spot on as measured with a meter but markedly sharp when fretted. I'm sure this is not fret placement but more the need for compensation. I can provide specs for the needed dimensions.

Thanks in advance for any advice or directing me to someone who could do this work.

Best regards,
Bob G.

Alan Carruth
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Re: Custom compensating nut

Post by Alan Carruth » Fri Mar 09, 2018 5:07 pm

Maybe for a steel string guitar, but not for a Classical. 'Nylon' is not a single thing, like steel, but a class of chemical polymers that vary a lot from one to another. Each different string maker uses ones that work to give them the sound and other characteristics they want. To properly intonate a Classical guitar you need to know what strings are going to be used. Also; A compensated nut moves the contact point closer to the first fret. You either have to cut some length off the end of the fretboard, or make a nut that overlaps it somehow. Either way it's not a DIY project unless you're fairly skilled, in which case you could make your own rather than ordering one from somebody.

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Michael.N.
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Re: Custom compensating nut

Post by Michael.N. » Fri Mar 09, 2018 7:51 pm

You can buy bone veneer that is very close to 1 mm thick. Either that or befriend a piano restorer. You only need a tiny amount because it can be glue to the front of the existing saddle, creating an overstep. File back, the amount dependent on the string. If you need it thicker than 1 mm either glue two together or use spare saddle material. You can also use ebony veneer if you wish to do some quick experiments.
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Catire
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Re: Custom compensating nut

Post by Catire » Sat Mar 10, 2018 1:34 am

I make mine using a dremel tool. Not all that difficult.
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Trevor Gore
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Re: Custom compensating nut

Post by Trevor Gore » Sat Mar 10, 2018 3:02 am

Robert Goodwin wrote:
Fri Mar 09, 2018 12:21 am
Is it possible to just get a compensation type nut made to a set of specifications?
I do this sort of thing all the time:

DSCF9472cs.jpg

You do have to be cognisant of Alan's comments, in that a compensated nut has to be made for a specific string set and set up. In the picture, the nut-to-first-fret distance is shortened by 3mm, then the compensation is added by cutting back into the nut from there. Of course, complementary saddle compensation is also required. Some string sets appear to be designed so that a common (equal) nut offset can be used on all strings. Either that or the strings designers just got lucky! One such set is (well, I should say was when I measured last) Savarez 500AR Corum Alliance. For a 580mm scale length guitar, a forward shift of the nut by 0.8mm on all strings and then adjusting the saddle compensation should get you pretty close, if the rest of the guitar set up is pretty normally. It shouldn't be too hard for you to give that whirl.

In the book I give a variety of options (six, I think) on how to do nut compensation, going from very mathematically involved to hardly any maths at all. I modeled the results of each method, so you can choose how much effort you want to put in for the benefit you get.
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Trevor Gore: Classical Guitar Design and Build

Robert Goodwin
Student of the online lessons
Posts: 63
Joined: Mon Dec 25, 2017 9:25 am

Re: Custom compensating nut

Post by Robert Goodwin » Sat Mar 10, 2018 4:11 pm

Thanks to everyone who has offered info or opinion regarding this question. :merci:

What I found particularly interesting was Trevor Gores' approach although I had a slightly different concept in mind. I've seen examples where the lower portion of a standard nut was undercut so that the top was shifted forward over the finger board and then the top cut back as needed (if that made sense.) The compensations depicted in Trevors' picture just in terms of which strings got more compensation and which strings got less was exactly what my experimenting indicated for my guitar. I also liked Micheal.N's idea of using 1mm bone to build forward. the trouble is I don't have a workshop where super precise cuts for slots and such might be made. I live in an apartment so small, you have to step outside to change your mind :lol: I can picture all kinds of buzz from a badly formed nut.

I have successfully replaced a plastic nut with a bone nut in the past. It required shortening and thinning the pre-made nut to get the string height right and even needed cleaning up the slots to eliminate buzz so I do have some understanding of what might be involved. I've also read everything I could find online about this subject. I feel strongly that because of the short string scale, this is something I need to do. The strings all have a lovely tone individually but there's always that sense of 'out-of-tune' when played against another string when fretted.

Best regards,
Bob G.

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