John you must have some customers with long arms
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| Compensation Question http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=2709 |
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| Author: | csullivan [ Thu Aug 04, 2005 6:21 am ] |
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Hi to everyone. Although I’m not new to guitar building, I am new to your discussion group as a member. I’ve been lurking in the shadows listening to what you all have to say for quite awhile now (great wisdom abounds, I must say). Those of you who are members of the New England Luthiers group know me (though some might not admit to it). So now I have a question. I’m building a jumbo guitar with a 25.5” string length. I’ll be cutting the fret slots using an LMI template. Since they’re machined so that any slot can be used as a zero fret, they use a double- ended indexing pin, one end of which compensates for the blade width so you can cut a zero fret. However, I have read comments from some of you that suggest you shorten the distance from the nut to the first fret by as much as 1/32”. If then, I make a new indexing pin I can accomplish the same degree of compensation. Is 1/32” the magic number (sounds like a lot), or is there some sort of formula someone has derived based on string length? And question 2. In the past I have used saddle compensation dimensions for my dreadnoughts passed on to me 20 years ago by someone long forgotten. Since this jumbo has a longer string length than my dreadnoughts, does anyone out there have a formula/guideline for determining the amount of compensation required from bass to treble? Obviously, I’d like to avoid cobbling together some sort of temporary adjustable bridge and then taking measurements. I keep hearing “Oh, about 1/8” sounds good,” but I’d feel more comfortable with something with more substance behind it. Of course, action height has a bearing on this, but let’s assume this is a well-tuned guitar with a reasonably low action. I can’t wait to hear the flow of wisdom pour forth! |
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| Author: | crazymanmichael [ Thu Aug 04, 2005 6:35 am ] |
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regarding nut to first fret compensation: i have used a 0.020" shortening of the interval and found it adequate with the strings/action i tend to use. 0.031" seems a bit more than i would want but it may work for your situation. others make a compensated nut. regarding saddle compensation: the best way, to my way of thinking is to slot the bridge after it is affixed. you use temporary adjustable saddles, wire, rod, etc, of an appropriate height, or the nifty little tool which s-m sells for the purpose, to find the best intonation you can get, mark the bridge, cut the slot and make your saddle to the measurements obtained. just my $0.015 worth. the depreciation of the quality, quantity and interaction of my grey cells render me incapable of offering a full value $0.02 worth these days. |
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| Author: | John How [ Thu Aug 04, 2005 6:53 am ] |
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When I cut my slots I use a blade that is ~.023" thick. I cut first slot completely away and that is where I put the nut. So in fact I am compensating by half a fret slot or about .011. At the other end I compensate the middle of the saddle by .015 and the saddle slants about 1/8" in three inches. I have been using the same compensation for years and it seems to work pretty good for me. I'm sure that some may have a better system but till I hear one that sounds and works better I'll just keep on. I usually just use the 2 martin scales 24.9" & 25.4" and I treat them the same. |
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| Author: | RussellR [ Thu Aug 04, 2005 8:18 am ] |
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John you must have some customers with long arms
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| Author: | csullivan [ Thu Aug 04, 2005 8:30 am ] |
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Thanks to both of you for the quick response. I think I'll probably cut the zero fret as if it were any other fret, compensating the .011 you use, John. If that's not enough, I can always make a slightly compensated nut. When you said you compensate the middle of the saddle by .015, that seems like a small amount. Did you mean .15? Thanks again. Craig |
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| Author: | Don Williams [ Thu Aug 04, 2005 9:50 am ] |
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Hi Craig, I think we've met before perhaps. I've visited the NEL meetings a couple of times. 
I use a .15" compensation on the 25.4" scale, bring the length from the nut to the center of the saddle to 25.55". I believe this is what Bill Cumpiano recommends in his book. I would imagine that a 25.5" scale would not be a whole lot different from that. I'm guessing the same amount. I also add the .15" to the the bridge location, not the location of the nut. I've never encountered what I felt was bad intonation or tuning on my guitars. Don Oops corrected that....25.4 not 24.5...sorry Craig Buddy! |
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| Author: | Don Williams [ Thu Aug 04, 2005 9:53 am ] |
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For those of you who attended ASIA, while Craig was not there, he was there in spirit as the designer of the NEL T-shirts some of us were wearing. Our slogan: "Enabling Wood Acquisition Syndrome" |
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| Author: | KiwiCraig [ Thu Aug 04, 2005 11:41 am ] |
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Hi All, Reading through the LMI instruction sheet for their fret slot system they state... The saw cuts a slot of .023. The fret wire is centered in the slot (i.e.,the tang goes .010" either side of the center line). The nut, however,must butt right up against the theoretical centre line ; if this position were sawn just like a fret slot, the nut-to-first fret distance would be .010" too short. So we must shift the fingerboard .010" to increase the distance. You probably could position the nut without the shift and not even notice the inaccuracy, but it's so easy to do, there's really no excuse for not doing it. Have L.M.I. got it wrong? Why are you guys shortening the nut to first fret distance? Kiwi |
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| Author: | KiwiCraig [ Thu Aug 04, 2005 12:55 pm ] |
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Back again after a moment to think! I'm answering my own question here, but can you tell me if I'm correct. You compensate the nut to first fret distance (shorter) to compensate the sharpening affect when pulling the string down to the fret? correct? Also (another question) Do you guys radius the fret slot to match your fingerboard radius,,,,thereby leaving the F/B with a bit more material in the center?. Is it worth doing? Am I also right in thinking that on a radiused (not compound) fingerboard,if I set the cut to say 1/8", the cut would be deeper at the edge (nut end ) than the edge at the heel end? Anyone able to throw in some light on the subject? Many thanks Kiwi |
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| Author: | John How [ Thu Aug 04, 2005 3:08 pm ] |
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When you compensate the nut, you are compesating for the compensated saddle. In other words, you compensate the saddle because you are increasing the tension when you fret a string but it is still compesated when you play an open string unless you compensate the nut. The nut compesation is out of play when you fret a string. |
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| Author: | RCoates [ Thu Aug 04, 2005 3:45 pm ] |
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I shorten at the nut by .020 and at the saddle add 3/32 at the treble side and 5/32 at the bass side. This on a 25.4 scale using medium strings. My 12th fret harmonics are usually + or - a couple of cents and the fingered note at fret 12 is usually within 5-7 cents, depending how hard you press. I'm sure it could be better so if someone has a better idea spit it out. |
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| Author: | csullivan [ Thu Aug 04, 2005 11:07 pm ] |
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Hi Don I'm a little slow today, so bear with me. You said your string length is 24.5 and that you compensate at the center of the bridge by .15. Wouldn't that add up to 24.65, not 25.5, or am I confusing the numbers somehow? By the way, hope to see you Sunday. I'll have the completed jumbo body with me. Craig |
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| Author: | Mike Mahar [ Thu Aug 04, 2005 11:16 pm ] |
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[QUOTE=Don Williams] For those of you who attended ASIA, while Craig was not there, he was there in spirit as the designer of the NEL T-shirts some of us were wearing. Our slogan: "Enabling Wood Acquisition Syndrome" [/QUOTE] Wow! I'm wearing a shirt, as I write this, that says the exact same thing. What are the odds?
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| Author: | Mike Mahar [ Thu Aug 04, 2005 11:21 pm ] |
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[QUOTE=csullivan] Hi Don I'm a little slow today, so bear with me. You said your string length is 24.5 and that you compensate at the center of the bridge by .15. Wouldn't that add up to 24.65, not 25.5, or am I confusing the numbers somehow? By the way, hope to see you Sunday. I'll have the completed jumbo body with me. Craig[/QUOTE] Craig, I think Don just made a typo and ment to type 25.4. I don't think his guitars are that short of scale. |
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| Author: | Dickey [ Thu Aug 04, 2005 11:49 pm ] |
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Everytime this comes up I think Frank Ford at Frets.com or Doolin, he has a great article if you can find it. |
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| Author: | Michael Dale Payne [ Fri Aug 05, 2005 3:45 am ] |
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Mike Dollin's artical is a great tutorial. it is available on his site |
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| Author: | Don Williams [ Sun Aug 07, 2005 10:35 am ] |
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[QUOTE=Mike Mahar]Craig, I think Don just made a typo and ment to type 25.4. I don't think his guitars are that short of scale. [/QUOTE] Ummm.....yeah BIG mistake. Sorry I caused confusion! I did indeed mean 25.4" not 24.5". Don |
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