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What do you guys think of the concept of filling the fret slot so there is no true empty space beneath the fret vs wicking in thin CA which does leave an air space?

As I mentioned earlier in the thread I could swear I heard a difference with slots filled with hard hide glue. I had previously just used water or thin CA and occasionally Tightbond.

I let the glue dry for at least 24 hrs before filing and beveling the ends and the actual leveling does not get done until after finish. I have not observed any significant change in the contour of the fretboard from the water in the glue.

Many paths to a good outcome eh?

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It's not what you don't know that hurts you, it's what you do know that's wrong.

IIRC an old school trick was to inject a bit of water in the slot to drive the fret in and then the wood expands holding it. I've never had a problem using water based glue either and in fact always thought of it as a good idea. But you know cats, and many ways to skin them. CA is fast though that's for sure and the thin stuff gets in there really good.

I can't claim to notice any difference in tone dues to air space under the frets. I do try and cut them as short as possible though unless I am doing a bound fretboard then I make them a bit deeper. I think of the fret slot as a sort of kerf like in the linings we use. Once you fill that slot with a fret then the full strength of the board comes back. the glue just ensures that it stays there. But who knows, maybe there is a tone function. I know one exceptionally talented guitarist who swears by bar frets probably under the same assumptions.

We had a customer that - having received his guitar after a refret - complained about a single 'dead' note on the D string. We changed the string, checked the fret shape, security, saddle, and pretty much anything that can impact a fretted note, then finally pulled the fret. Beneath the D string was an air bubble in the hide glue fill...we raked out the slot and reset the fret. A few days later, the customer picked up the instrument and noted the issue was resolved and he was seeing the same volume and sustain along the string and across.

We see a big difference, which is why it is the standard practice here, and why we use hide versus CA for the purpose. i can only suggest trying it on one of your instruments.

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A constellation only takes shape when one maps the whole.
- Beth Brower

I deal almost exclusively with re-frets. Fingerboards taking up water can be managed to some extent with wait times if building but I would ask why?
we patiently wait for dense fingerboard woods to acclimate to 45%rh, avoid gluing them to necks with water based glues for fear of backbowing necks, then, during the process requiring the highest level of precision, let the endgrain straws of both sides of the fret slot drink up a bunch of water? I suspect, if you set a fingerboard with such a wet bedding of frets on a sensitive scale it would continue to get lighter (and smaller) for a long time. I wouldn't expect the moisture to be gone the next day.
When gluing a fingerboard to to a neck with hide glue against a granite plate, it will be severely back bowed 24 hours later but, if left for a week, very little.
I have seen quite a few fretted boards that have gone through a cycle of extremely high humidity then returned to normal. The board has puffed in thickness, lifting the fret crown with it, then dried and left the frets all partially raised away from the board at the high tide line. This simply has to be happening at some scale when using water laden glue during fretting.

I carefully pool the thinnest CA on one side of the fret until I hopefully see it capillary up to the opposite side of the fret. That means it has wicked along the entire interface between fret and slot. The fret displaces glue when it's in so unless the slot has to be deepened, or the new wire has a radically different tang size, I don't find much to clean. What is the point of cleaning to bare wood beneath the wire?

As far as getting CA on a sensitive finish, that's just one of the many things you learn not to do. There are many things I find difficult about lutherie but keeping CA running under the fret and not over the side doesn't rank very high. I use a small, cut back pipette, gripped close to the tip so there is no springing or flicking going on. I keep a piece of clean paper towel in in one hand to quickly wipe any that might get away. If you wipe it up right away, any damage is very superficial. and can be invisible fixed with some 2500 grit and buffing without much drama. This all assumes pressing not hammering.


I just tune any air bubbles under a fret so the frequency tends to couple with the main top mode. Boom! Done!

Exactly. My prior comments being not as illustrative as Woodie.

Andy

I've seen that behavior on guitars before with dead notes on certain frets but it seemed to be that the fret was actually loose. It doesn't even have to be popping up but just loose enough to sap the energy out of the note.

It would be an interesting experiment to weigh a fretboard continually after fretting with water based glue to see how long it takes to come out. My guess is taht it's not that long. I glue the fretboard on with HHG or in the past with Titebond and clamp over night and I can't remember ever having an issue with weird twists or anything like that. But I'm not doing this every day either.

If ebony takes a while to lose moisture, it takes as long to gain it, so the fear that enough water might be added to cause a bit of wiggle and waggle is not supported by what we've seen on either repair or new construction. Those necks which seem to pretzel after the board goes on may not have been glued up on a strongback. It seems as though StewMac's fingerboard band clamps and a few of the build reference methods are content to leave the issue of a straight neck to chance, but a strongback and 36 hours of time under clamps avoids the issue entirely, as well as the need to resort to epoxy and other challenges for future repair people.

As to acoustic properties, I wonder how many of us are content to have a nut or saddle which is air-gapped for some fraction of its contact area with the neck or saddle slot? That would seem to be the case for tanged fret wire, with its thin band of contact across the underside of the crown and at the barbs. Avoiding that air gap and the abrupt density changes seen across it would seem to be as desirable as properly fitting the nut and saddle.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Moving to the topic of fret bedding, wouldn't leaving more wood under the fret be the ultimate move? That's what I have been doing with my old style LMI manual fret slotting box. It is able make radiused cuts by customizing the top saw stop. It took me a while to figure that out. I used to do it by cutting a shallow original slot, then after radiusing i re-cut the slot with the screw-on plastic depth stop. However the old LMI rig is much easier. Same can be done with cnc.

Anyway, filling the big gap with glue sounds less than ideal. Of course all slots need to be at least slightly deeper than the fret and could be filled, but having .075" gap under the middle of the fret doesn't seem like the best way to start. Someone, i think it was "the boss" suggested that strength wise it didn't matter, but as far as tones, who knows...

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Pat

With the exception of compression fretting, the fret tang will not fully fill the fret slot. In the case of standard Martin vintage-sized 0.080" x 0.037" wire, the tang is 0.0195" with nominal width of the slot at 0.023". Assuming a perfectly milled slot in width and a mere 0.002" excess slot depth, the tang is air-gapped on the bottom and sides by at least 1.5 mil...the only contact between tang and fretboard is at the barbs. If the fret is perfectly set, there will be an additional band of contact along the underside of the crown, with contact area somewhat reduced should the fit be less than perfect. The feeling here is that once the fret is air-gapped, the damage is done.

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A constellation only takes shape when one maps the whole.
- Beth Brower