Some people whack a little bit off the theoretical first fret distance to compensate for the string stretch sharping caused by the nut. The fraction of a mm you lost -might- actually improve intonation.
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| Fretboard out of square - where to fudge? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=46982 |
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| Author: | bcombs510 [ Tue Jan 05, 2016 4:25 pm ] |
| Post subject: | Fretboard out of square - where to fudge? |
Hello, I'm not sure how this happened, but the nut end of my fretboard got out of square. I was probably just sloppy on the sander when sneaking up on the line. I'm using a 24.9 scale which puts the nut -> fret 1 spacing at 35.51 according to my plans. I was using a 5mm gap between the headstock veneer and the start of the fretboard per the Robert O'Brien video, which should have created a ~5mm nut slot. However the nut slot is (understandably) wider on the end where the fretboard appears to be short. The fretboard centerline lines up well with the centerline of the guitar, so it doesn't appear to have swung during glue-up. Best I can tell I just bumped one too many times on the sander. Here is my setup. The gap between the headstock veneer and the fretboard on the "low" end: Attachment: IMG_0079.JPG The gap between the headstock veneer and the fretboard on the "correct" end: Attachment: IMG_0080.JPG The distance between the nut and first fret on the "correct" end: Attachment: IMG_0081.JPG The distance between the nut and first fret on the "low" end: Attachment: IMG_0082.JPG Question - Is there anything I can do to correct this? Or, does it need to be corrected at all? Could I just make the nut a little wider on the one end? The fret slots are square to each other and spaced correctly going down the rest of the fretboard. So I'm thinking that it could just be fine, but I'm not sure. Thoughts? Thanks! Brad |
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| Author: | Clay S. [ Tue Jan 05, 2016 5:03 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Some people whack a little bit off the theoretical first fret distance to compensate for the string stretch sharping caused by the nut. The fraction of a mm you lost -might- actually improve intonation.
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| Author: | bcombs510 [ Tue Jan 05, 2016 5:07 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Clay S. wrote: Some people whack a little bit off the theoretical first fret distance to compensate for the string stretch sharping caused by the nut. The fraction of a mm you lost -might- actually improve intonation. So now the $20.00 question (I'm cheap) is - Do I try to square the fretboard off at the shorter length or leave well enough alone? 
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| Author: | Colin North [ Tue Jan 05, 2016 5:21 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
That's actually pretty much how I compensate my nuts, maybe a little more if you intended 5mm nut. You could - a) fit a tapered nut and see how the intonation works out b) cut a ledge or back slope on the F/B side of the nut to lengthen the distance from the nut break point to lengthen the string slightly if it's too much compensation (this can be done for individual strings as nut compensation) c) put a tapered slice of ebony in to fill the "gap" and "nut" as normal. I take it this guitar for yourself/a friend, not for sale? |
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| Author: | DennisK [ Tue Jan 05, 2016 5:25 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
In the future, saw the nut end as a fret slot, and then cut it all the way through. AFAIK that is the standard method used by factories and just about everyone. Guarantees accurate spacing since it's registered off the same template or ruler as the rest of the slots, and has the side benefit of making the nut to 1st fret distance about .011" shorter (half the saw kerf). As Clay says, that improves intonation a bit. So flatten it out and you should be fine. Alternatively, you could cut it all the way to 2 or 3mm short and try out nut compensation If you do, remember that the bridge moves closer to the 12th fret as well. Shortening from the nut end alone will make the 12th fret harmonic higher pitched than the 12th fret note.
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| Author: | bcombs510 [ Tue Jan 05, 2016 5:26 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
This is my first guitar build. It will be for a family member. Thanks for the help! Sent from my iPhone using Tapatalk |
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| Author: | kencierp [ Tue Jan 05, 2016 5:28 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Here's Mike Dooling's intonation and nut compensation guide http://www.doolinguitars.com/intonation ... tion4.html |
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| Author: | wbergman [ Tue Jan 05, 2016 6:13 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
If I see this correctly, the slot is wider at the top, That is actually a design some high end classical builders do to drop the nut in and not have it drop to the floor during string changes, though I suppose they take the extra wood off the headplate veneer. |
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| Author: | Quine [ Wed Jan 06, 2016 1:19 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
So you're about 0.4mm off on the low side? That might not really matter for the bass strings, but I would shim it anyway. It should be pretty easy to hide on the black fingerboard and its in a spot that will never see any wear. Fit the nut based on the correct side. Then fill the gap on the bass side with ebony dust or plane shavings. Fill with CA and sand it all smooth |
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| Author: | Tom West [ Thu Jan 07, 2016 10:18 am ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Brad: Did you make the end cut off line with a square against the edge of the finger board.............??? I think if you follow Colin North's at (a and b) you will be OK and no one will know except you and us. I actually like to see a bit of taper in the nut slot but only a few thou. That allows a push fit from the side and holds the nut very firmly. Tom |
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| Author: | bcombs510 [ Thu Jan 07, 2016 2:11 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Tom West wrote: Brad: Did you make the end cut off line with a square against the edge of the finger board.............??? Tom Thanks, Tom. The procedure I followed was: 1) Run one of the fretboard edges through a jointer to get is cleaned up. 2) Used the jointed edge to cut one end of the fretboard on a chop saw. 3) Attached the fret slot template from LMI to the fretboard using double stick tape. I used the same jointed side on the edge of the template. 4) Moved the fretboard into the miter box until about 1/2" past the cutting slot. 5) Made the first cut, which became the end of the fretboard. Cut the rest of the slots as usual. Where I may have made my mistake was that rather than cutting all the way through on this first cut I only cut to the fret depth on the miter box and then later bumped up to that cut on the belt sander. My guess is that I got out of square or was just not paying attention while using the sander. My thought is that next time I'll go ahead and cut all the way through on the first cut using the fret saw instead of trying to do it later. Thanks! Brad |
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| Author: | phavriluk [ Fri Jan 08, 2016 12:30 am ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
Teachable moment here: Power tools aren't my friends. I can mess up work instantly by using them. I've had good success cutting a zero fret slot in the fingerboard and then using that slot as a guide to (hand) trim the top of the fingerboard. |
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| Author: | alan stassforth [ Fri Jan 08, 2016 11:00 pm ] |
| Post subject: | Re: Fretboard out of square - where to fudge? |
I like the tapered nut advice here. Carefully shape it, leaving it long, cut it,lay it out, then tap it into place from the wide end. I might start making nuts that way on purpose. |
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