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?
How high are your strings, Mark?
The way I have this pictured in my mind is that the intonation problem is brought about by the string height at the saddle. I'm wondering if you can add a bit of relief to the neck and lower the strings at the bridge a bit while keeping the high string feel you like. On the other hand, I could be all washed up. I like my strings to be low so I don't have much experience with this sort of a setup.
On my Guild, the action is pretty dang low - a bit too low for my tastes.
On the Martin d-41, the owner likes a nice high action with little relief on the neck.
We are actually going to try just setting up a bridge pin as a saddle, since the amount that the saddle needs to move is really close to where the pin actually is. I'll just turn a new pin from bone, and we can file and play with it until it is right. I suspect he will eventually want to replace the bridge and have the saddle placed correctly, but this would work for now. The nice this is that, if we fail, there will be no damage to the guitar and everything would be reversible.