Official Luthiers Forum!

I made a couple shelf nuts for nut compensation for a player with a death grip left hand, a heavy pick right hand, tuned 1/2 step down and guitars with narrow straight saddles inadequately compensated with saddle placement.
It was a pain. Anyone have any suggestions on how to mill a shelf on a bone nut blank considering various fretboard radii, nut seatment differences and fretboard thickness?

Thanks
Dave

Shorten the fretboard at the nut end?

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Instead of radiusing the underside of the shelf remove the radius from the fretboard under the shelf, just to the top
of the binding in your pic. Then it's a more straight forward process to fabricate the nut.

I saw an article where there were just individual little pieces wedged under the strings at the nut. I do no know if they were glued in.

We don't use or believe in shelf nuts and even nut compensation. Feiten, Earvanna, etc are BS to us. One of us has been trained and certified in one of these compensation methods in the past and we still think it's BS.

Instead we cut nut slots very low and at least on steel strings we've never had a client who had any intonation issues after we cut their nut slots and set the intonation at the saddle (saddles) as we do.

To give you an idea what we know to be a properly cut nut slot is as follows. For the high e for example if we fret and hold the string between the 2nd and the 3rd and then pulse it over the first the gap over the first when we are done is around .0005"..... As you can see there is virtually no difference between our string height leaving the nut here and how a string naturally will bend over the subsequent fret when fretting anywhere on the board.

That gap, that .0005" gap is very difficult to see and impossible to measure easily. We still want to hear the "tink" sound when pulsing the string to be sure that the string is not in contact. This example is again for the high e only, other strings are higher.

Subsequent strings of greater gauge get more clearance.

We do see nut compensation as useful on classical guitars because nut slots and action are generally WAY higher with much more possibility for string stretch.

Your nut looks great but we've found that 99.9% of the time if you cut nut slots very low for effortless playability and set the intonation at the saddle side correctly intonation complaints go away.

Also what kind of guitar is this. You have every string compensated and a great deal too what's up with that?

And if the owner decides later to go back it looks like crap. I say NO to that. Don't do something that can't be undone.

_________________
"Act your age, not your shoe size" - Prince

Noo, can't be no going back.

Truthfully, it never occurred to me to make the fix reversible. This denotes the difference in thinking between a builder only and a person who repairs, I guess. So, I agree with Chris, not a good idea as a possible temporary solution.

Thank you for your responses so far. Still hoping for a milling idea.
I did not want to do anything invasive and irreversible. I am sure the owner would not be happy if I did.

Hesh... Thanks for being predictably helpful. I learned to cut nut slots (Charles Fox) exactly as you do them, and, although I don't do as many as you do, nor as fast, these are suitably low. And I agree that this eliminates most noticeable intonation issues. This was nowhere near enough for this case.
As for the type of guitar, a major USA made company, probably the most recognizable name in acoustic guitars in the US. It has a 3/32" saddle that is at least .1" short of where it should be for correct saddle intonation even after shaping it to push the string contact as far back as possible. This contributes to the need for compensating every string (compensation at the nut reduces the amount of compensation required at the saddle). The year of manufacture is not in the range of "misplaced bridges" it is just a typically (incorrectly) built guitar that is acceptable for 95% of the people but not for everyone.
The main challenge, really, is the player's preferences. He tunes down 1/2 step for vocal reasons. He plays primarily in first position. His grip on the left hand pushes the strings almost to the fretboard or possibly to the fretboard. He makes strings go sharp even when playing with a capo. And he uses a pick, hard, so the action needs to be fairly high to stop buzzing. Add all these requests and guitar limitations together, and nut compensation (I know you don't believe in it) is the appropriate solution.
A search on this forum would yield a post by Alan Carruth about a similar situation with a 12 string.

thanks again
Dave

So.... all this drama and work because the clients' technique sucks. Had a couple of those guys once.... ONCE. Get my drift?

_________________
"Act your age, not your shoe size" - Prince

Dave I am sure you have already thought of this but I'll throw it up anyway. Could you cut a new saddle slot to allow a wider saddle that would enable proper saddle compensation? I realise you have to have enough room in front of the pegs but maybe it is a possibility.

Cheers Dave

Dave
yes.

But based on a lot of research and theory, that would have solved only half the problem, and not the half that most interested the player. There still would be several strings noticeably incorrectly intonated on frets 1-4. Because this player was almost not at all concerned about intonation above say fret 7, I could accomplish (and did accomplish) what I needed by only compensating the nut. Plus the pucker factor of slotting a bridge in place if you don't own a Collins Saddle Slot mill.
To be 100% correct, I would have needed to do both but doing only the nut fixed the main problem and actually also helped (not completely) intonation at some higher fret locationsl

Dave

Thanks Dave I appreciate the details. It sounds like you have the perfect storm of a client with not one but many of the things that keep us up at night all combining to create an intonation nightmare. The drop tunings are also as you indicated problematic. Capos are also something that it's very easy to have user created intonation issues with too much or not enough pressure and some capos have a radius that does not match the fret board.

Thanks again Dave I hope you and yours are holding up OK in these terrible times.

Almost forgot about this, it's been so long since I read it.
This was my original introduction to the idea of nut compensation.
Stephen Delft used a series of shims, adjusted by paring some off as necessary.
Full MIMF article reprinted - https://www.mimf.com/nutcomp/
Hope that helps.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

the issue with compensated nuts is just like any other system. IF you are the only one in the group with this compensation method you will sound out of tune with the other band mates. It is all or none.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Further to what John said, if the saddle is out of position by .10 of an inch and you intonate at the half scale position
and move the nut by that large amount the remaining frets, other than the twelfth assuming a standard guitar, are all now in the wrong position making tuning difficult at best. Since you are only concerned about the lower fret positions it seems you are
fudging things enough to satisfy the owner. So I needn't say any more.

As for milling the shelf nut, here's one approach. Use a carrier and router or laminate trimmer mounted in a table or temporary
setup to do the job. Take a piece of 3/4" stock say a foot long and route or sand the fretboard matching profile into the side a couple inches from the end. On top route or saw a rabbet for the nut blank to sit, the fretboard profile will now be under the
nut blank. A drop of CA to hold the nut. Use a top mount bearing flush cut router bit and make a temporary fence from a piece of scrap with a slot cut in center so as to cover the bit with a little clearance. Route the blank by incrementally moving the fence
exposing a little more of the bit with each pass. When the bearing reaches the bottom of the fretboard profile you're done. Some acetone will release the CA. Any ole smallish flush cut router bit probably could be used with a slightly different approach.
Nothing beats a drawing, I know. Hopefully you get the picture though.

Ken
Thank you for the good idea. Have you had success using a router on bone? Do you use full speed or slow it down some? I was concerned about chipping and heat build up with a router approach.
Dave

Nut compensation will solve several problems but can cause others to emerge I had an issue with a saddle too close to 12 th fret on a students guitar and we added about 1/16" shelf nut and were able to get thew 12 fret intonation correct. Here is an article I found while researching nut intonation, it jumps around some but good information. http://setitupbetter.com/Understanding- ... nation.php Basically what ever you shorten nut to 12th causes the saddle contact point to move forward also so if the 12 fret intonation needs the saddle back farther this is a good quick fix.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Bone will saw and route somewhat like wood , except for the smell... small 1/2 or 3/8" bit, shouldn't need slowing speed, slow feed rate and take small bites, 1/32nd or so at a time.
I've never had to make a shelved nut so for the purpose of this post I'm just an idea man. All the best.

I make my compensated nut using an end mill. I think if I was trying to do what you are I would mill a straight cut at the dept of slightly shallower than the final depth at the edges of the final nut shelf and use a scraper to put in the radius. Scraping and checking, repeat until it fits.

_________________
http://www.Harvestmoonguitars.com

John
Thank you. Do you have any details on the mill setup? Speed, bit type/size etc? I will likely be using a drill press but any info would be helpful. thanks.
Dave

I have done it two ways. One with a router in a bishop cochran router base and a jig that allowed me to hold the nut and guides that allowed me to move the router parallel to the nut. That gave me the two axis of control I need to make a shelf. I used to use the same jig for my saddle slots.





Now I have a mini mill. That I use for a lot of stuff. It gives me three controlled axis to work with. More with special vises.



I run everything full speed. Bone mills, cuts and scrapes well.

I have use 1/8"-1/4" end mills depending on what I am doing. To make the shelf I would probably use a 1/4"

_________________
http://www.Harvestmoonguitars.com

Perfect. Thank you so much.

Dave

Dave B , yes I am still grappling with the issue of nut compensation but have finally grasped it's importance, particularly with the lower frets. My major source is Trevor Gore's explanation.

So leaving aside your actual question of how, technically to do it, I would be very interested in how you arrive at the distances you need to move the nut edges, and roughly what those distances are.

Please let us know how you get on.

Cheers Dave M

Dave M
I'm not qualified to do anything other than re-quote what I read from other sources, if it made sense to me and fit my experience. There is some stuff out there that did not meet both those criteria. A couple of the links by others further up this thread have great info. There are some very good posts in the archive of this forum. And an online search will get you some good (Trevor Gore) and not so good, info about this.
1) The most widely used method for getting the correct distances involves trial and error. There is a very wide range of distance values depending on a bunch of factors.
2) One starting point for getting values is to figure the total compensation needed (ie a regular saddle compensation calculator) then divide that in half and use half at the saddle and half at the nut. I think there is a post on this forum that explains that you can get very close by just doing this method and making the nut face flat and parallel to the saddle angle. A search should find it for you.
3) there is a sequence for getting intonation correct on all frets from 1 to say 14. a) intonate the saddle using the string at frets 2 and 14 (instead of open and 12). b) find the nut compensation values by trial and error using open and fret 2.
4) there is a way to actually calculate the required nut compensation but I don't have the formulae and I suspect that there are enough variables involved that it will only get you close anyway.
5) This follows from some info in this very thread... unless you are going to do this a lot and can come up with a jig and process for easily machining the buik of the material away consistently, only use it when the usual correct setup procedures do not get the job done. Some people do it routinely (Trevor for instance) and tool up appropriately, you probably will not be able to be adequately compensated for your time if you only do it occasionally without tooling. It is not easy unless the guitar is designed for this (Trevor again) or you can make invasive irreversible changes to the guitar (like cutting off the fretboard).
6) gluing pieces of bone on to the face of another piece of bone to form the shelf did not work for me. If you want to try this, I suggest you practice on some scrap pieces and put some severe shear stress on them as a test.

I hope this helps.
Dave
Dave