Resolving intonation issues - crush my ideas to a pulp, please!

[Mark Pollock]

I have been thinking about intonation problems that a couple guitars in my life have. Specifically, a 90's Martin D-41 owned by a good friend, and my own Guild D-25M from 1975.

Both guitars go sharp on the 5th and 6th strings as you go up the neck. This is due to poor placement of the saddle, in conjunction with a medium to high action that we prefer.

Of course, I cannot just move the saddle back without some serious work on the guitars, and of course, I can't just stick some more bone behind the saddle, since the break angle would end up far too steep.

But, it did occur to me the other day that I could drill a hole through a bridge pin at the exit angle I want, and reverse the pin so that it and the ball end are facing the tail of the guitar. Then I could add the piece of bone in for my saddle, and therefore move the contact point back far enough to fix the intonation.

It seems like too simple a solution, though, and there must be some basic flaw in it that I am missing. Before I start attempting this (first on the Guild, of course), what am I forgetting?

[Joshua Levin-Epstein]

Mark, Though I think I understand what you want to do, it may not be necessary. As I (must have) said here previously, I have a D-28 where the bridge was misplaced at the factory (one of many). The saddle has been mooved as far back as it can go so the low E-string goes almost straight up over the saddle. There does not seem to be any impairment of function. If you have enough saddle above the bridge, why not superglue a piece of bone to the back edge and carve the intonation point where you want it? I could see the graft popping off at some point, but you are experimenting. If you like the intonation, you can then carve a permanent saddle with a ledge on the back.

That being said, where is the break point as the saddle exists? Can you move it to the back edge of the saddle?

Joshua

[Pierre-Antoine Roiron]

You have to know that it's not the pin that holds the string : it's the ball end of the string that is against the bridge plate under the bridge. The pin is just here to unhook. See that article from our guru Frank Ford:

http://frets.com/FretsPages/Musician/Guitar/Setup/SteelStrings/Stri...

Knowing that, you'll understand that reversing a bridge pin slot direction may not work, I'm afraid the string would pull the pin out. If no one here ever tried it (you'll have to wait for some more answers), you'll have to give it a try. My personnal experience is that : if it's not a known solution in the actual state of the repair art... then chances are it's not a good repair.

Another thought : Drilling through the pin a hole for the string to pass through would weaken greatly the little part, and you'd be sure to break it a day or another. And sooner than you'd expect... these little pins are naughty!

Last, If you're afraid that the break angle would become too tight by adding the talked about piece of bone, you could glue a nice little piece of ebony on the bridge to heighten the string's level out of the pin hole. I'm not sure if my English is clear enough to explain it.

[Mark Pollock]

Pierre - that is a nice idea, I'll play with that thought too.

The wear issue with the pins is a challenging one - I'm not sure what I would do about it. I've got some thoughts, perhaps just a hot piece of wire driven through to make a wear point. That seems to be getting silly, though.

[Tim Mace]

forget the hole in the pin....

[Ned Knepp]

Personally, I don't find them desirable but you could change the break angle by using the brass pins that come with a Bridge Doctor. The string passes through the top of the pin which would give you a higher and flatter string angle going to the bridge. It would allow you to experiment with a bridge extension to get your intonation correct.

[Mark Pollock]

Ned - I agree, but that does point out that there are brass pins available - it's worth investigating. I'll keep playing with this idea. I'll post pictures if I do anything worthwhile.

BTW, does anyone know of a mathematical way to calculate the needed additional length of a string by measuring the exact pitch of the string harmonics and fretted notes? I figure I'll just measure the difference in tuning, divide the length of the string appropriately, and figure out how much to add from there. I'm guessing I'll need just about all the space I have for that low E string.

[Joshua Levin-Epstein]

http://www.frets.com/FretsPages/Luthier/Data/compcalc.html

 

Mark, This might be helpful

[Mark Pollock]

Ahh, I was using the wrong terms in my search. That is absolutely perfect!

[Jeff Highland]

Check that the nut slots are correct depth first, and that the relief is low

Check at the 3rd fret too, if that is sharp you may need some nut compensation too and that would reduce the amount of saddle compensation needed

[Mark Pollock]

Believe me, the slots are as low as they can be, and the relief is almost dead straight. The 3rd fret is hardly sharp, the 12th fret is 10 cents sharp, and the 19th fret is 60 cents sharp! (Not like anyone plays the 19th fret, really, why is it even there?)

[Tim Mace]

Would a zero fret in this situation help??

[Mark Pollock]

No, the problem is the location of the saddle, not the location of the nut.

Also, even if the nut gets adjusted, that goes out the window once a capo is applied.