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Anyone see this happen? Its happened to me twice in the last week. Customer calls back a few days later and says there is buzzing on the open strings so I ask him to bring it back and sure enough the D string on one and then the E on another are way too low. I cannot figure out what is going on. I play the guitars and make sure everything is tip top shape before they pick them up.

Only thing I can think of is maybe after filing the slots some debris was left in the slot that worked it's way out? I always blow air after filing but still, it's the only thing I can think of. And if that is the case why now all of a sudden twice in one week?

Can it be that the bottom of those slots were not wide enough so over time the strings work themself down to the bottom of the slot. But right after setting them they were OK.

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http://www.Harvestmoonguitars.com

A change in humidity can change the thickness of the fretboard, but the debris in the slot is a good theory. I think you would have noticed if the nut wasn’t totally settled in its slot. Every now and then, I get a blank that’s a bit porous in a spot or two. I’ve had them crumble at the edge.

You haven't told us what the nut was made of...

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"Act your age, not your shoe size" - Prince

Ah yes they were both Gibson's so it was what ever plastic it is that they use.

That is a good hypothesis too. I do use gauged files now and make sure to cut a bit wider then the string gauge but I suppose I could have grabbed the wrong file too.

This is possible if one forgets to set relief before, before cutting nut slots.

So we cut them low when there is too much relief and then when we (or the client) straightens the neck some the slots are too low.

As such I always set relief and sometimes with a bit less relief than I really want so I have a cushion on cutting the nut slots too low.

Another possibility is the slot was not relieved enough for the string. For example for a .013" string I cut the slot to handle a .014 and maybe a .015". My technique is to scrape the sides, left and right of the nut slot on the first couple of down strokes. This is also why we don't like needle files for nut slots, V shaped slots pinch and bind strings and strings may not sit in the bottom of the slot.

I had one a few weeks ago that someone had filled with superglue and dust which never lasts especially with wound stings and a tremolo.... I didn't recognize that I was cutting into a fill that would not last and it didn't, instrument came back and I cleaned out all the dust and CA and did dental fills, problem solved.

You might have had some prior work with a substandard fill that would not last with an owner with new found excitement about playing his/her guitar.

Yeah could be. I'm just bothered that it happened twice like all of a sudden I am doing something wrong or something is wrong with my files. I did check the relieve on return and it was the same. Bah! Oh well. I'll probably just have to let this one go without resolution.

Time to invoke Occam's Razor? V-shaped slots would be susceptible to string vibration working the string down. Any idea if any strings liked to go flat more than the others on the instrument?

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Peter Havriluk

Had a PRS in that had profoundly.... V shaped nut slots and you have to be very careful because as I reshaped them to a U shape that can accommodate one string size larger (that's how I cut slots) progress was very fast. Kind of like drilling with a pilot hole.

So thinking about Peter's post here I can see that happening too. Good thinking Peter.