Gap Behind a (Through) Saddle

[Brent Hutto]

Am I correct in assuming that a gap of 0.004"-0.005" behind a portion of the saddle (when under string tension) is a very dangerous thing? I made a temporary saddle to put in my newest guitar while the original one is off to the guitar's builder to be copied (and raised a bit). I know the top profile isn't quite right and the shaping and polishing is crude but I must also have been a tiny bit inconsistent with its thickness. It seemed quite snug when I installed it but now a week or so later I can get a 0.004" feeler gauge behind it (between the back edge of the saddle and the bridge slot wall) for about the first inch or so of the treble end.

This is a cut-through saddle slot, old-fashioned like a Gibson, not glued in place. Bone saddle, ebony bridge. I think what changed since I installed the saddle is that I bumped the two unwound strings up from 0.012"/0.016" to 0.013"/0.017" and the humidity in my house has dropped to around 43-46% for the past couple days (down from around 50% when I installed the saddle). Will the bridge slot get wider if the humidity drops and the ebony shrinks a bit?

At any rate, I lowered the tension of the strings a whole step and I think tomorrow I'll remove them all together. I'm worried that any lack of perfect fit at all with a through-saddle might break the bridge.

[Antonio Cotichini]

I don't thing your ebony bridge is running risks. Obviously, the sooner you'll have installed the perfect saddle, the sooner you'll have the perfect intonation.

[Brent Hutto]

Thanks for the advice, Antonio. I was kind of on the fence about whether to keep playing it with the gap behind the saddle but fortunately my new saddle arrived yesterday, a little sooner than expected. The intonation was pretty good even with the poor-fitting saddle but it's just about perfect now, only the A-string goes a little sharp way when fretted up the neck for some reason. But there's a marked difference in volume and sustain. That badly fitted saddle must have been not making solid contact with the bridge or something because the new, good-fitting one really woke the guitar up.

So I'm a happy camper now. The new one is perfect contoured to match the shape of the bridge, fits very snugly and makes the guitar sound better. Plus the action is just where I like it (about 5/64" treble and 6/64" bass at the 12th fret with near zero neck relief). I think in the future I'll stick to making simple drop-in captive saddles and leave the cut-through ones to people who do it for a living.

[Antonio Cotichini]

Yes, the action seems perfect. Did you check the nut slots? Maybe the A string is a little higher. Press the string at the third fret (close to the second fret wire) and you must see just a breath between the first fret wire and the string. If the space is more, file the slot until it's right. Do this by very little steps, otherwise you'll have a buzzing, so check continuously. If the intonation is still sharp, file the saddle backward under the A string. Again, check and do, check and do...

[Frank Ford]

"I'm worried that any lack of perfect fit at all with a through-saddle might break the bridge."

Me, too.

Keep an eye on that part of the bridge - if a gap appears or widens, it may well be a sign of a crack in the bridge below the saddle.

[Brent Hutto]

Antonio,

I did check the height at the nut and the A-string is a thousandth or so lower than the low-E and a couple higher than the D-string. The heights at the first fret are something like 0.021", 0.020", 0.018" for the three bottom strings. My saddle does not have any compensation cut into the top, the high point is right down the middle all the way across. I'm thinking it might be this particular A-string, generally other sets I've had on there did not have worse intonation on the A-string. I'll change them out in a few days and see if that helps.

Frank,

So I'm not the only Nervous Nellie about that gap. As it turns out I've got a new, better-fitting saddle courtesy of the guitar's original builder. So no worries now but in the future I will try to avoid having any gap at all showing, especially on cut-through saddles.

[Antonio Cotichini]

Brent, probably I've not expressed myself correctly. You have to check if there's a very small distance from the lower side of the string and the upper side of the first fret (the metal, not the wood) when you fret at the third space. Read and see the pictures on Frank's article about intonation at the nut on FRETS.com. It's illuminating!
Perhaps that A string isn't born well! It happens also in the best families! Change it.
About the gap: If it was due to poor shaping of the bone saddle and you didn't noticed it immediately, I still think it shouldn't be dangerous for the bridge integrity but just for the good playability (and, after all, you were going to change the saddle in a few days). If it appeared IN the wood after a week... well that's another pair of sleeves. Anyway, Guru Frank's advice is always to be followed. Check carefully the bridge to be sure you'll not have bad surprises.
Nervous Nellie... very funny!
Good Luck
Antonio