So, my friend Ray came over today, and we went to work on his Martin D-41. The intonation on the 6th string was pretty terrible - at the 12th fret, it played 10% sharp.
What we ended up doing was making a new saddle with a notch in it, and turning a bone pin to act as a saddle and pin combination.
It now intonates almost perfectly. He can capo and it stays in tune, even at the 9th fret. harmonics and fretted notes at the 12th fret are about .5% different now, very slightly flat. If I was to do this again, I'd make sure to leave plenty of meat on the pin so that we could dial in the intonation perfectly, but this is a major, major improvement. Watching him barre chords all the way up the neck without any problem was wonderful. There was no loss of tone, and we didn't have to make any changes to the bridge at all. The string is in very solidly, with no appearance of slipping out.
Thanks everyone for bouncing some good ideas around. Ray is giddy with excitement now that his guitar FINALLY plays in tune.
I blogged the process.
Nice Blog entry. Well done.
I wouldn't have given it a try... you prove me I would have been wrong!
They aren't as egregious in their out-of-tuneness. That low E was horrible, the others are not nearly as bad. I was able to compensate them at the saddle in the typical way - a big notch to the back for the B, way forward for the high E, and moving to the back for the rest. I don't think this could be done for any other string. Also, if I was to switch to extra-light strings, or a lighter 6th string, I'd probably have to switch back to the saddle. I've also wondered about turning a pin with a flat top that is closer to the saddle for really picky intonation, but at the point the pressure fluctuations of a finger will make it rather moot.
Actually, now that I think about it, it makes sense to move that A (5th string) as far back on the saddle as possible. I tend to have it slightly forward of the low E on the saddle, and now I wonder why. Habits are so strange.