Order of Work? Re-profile neck, plane fretboard and re-fret

[tbrahan]

I really like the tone of my new mandolin, so I'd like to make it more comfortable to play. I bought the mandolin knowing it needed a re-fret. It has narrow frets with deep divots. The frets are .016 high in the divots at frets 1-5 and the ones down the neck are clean with about .024 left. I could do a partial, but five of the frets below #8 are really loose and popping up. So I know I'm going to do a full re-fret.

Looking down the neck there is a forward bow between the nut and the body joint. I have looked it over and I am sure that it's not "the hump", and there is a proper fall off below the 12th. I have cranked the truss rod as much as I think I safely can, and the relief is still .014. The action is .065 at the 12th under the G string and just less under the E. Probably could get it down a little more, but the bridge is bottomed out. I can take a bit off the saddle, but may not need it with fresh frets. Plays fine without buzz. If I wasn't going to do the re-fret I wouldn't worry about the forward bow, but since I'm going to have the frets out, I may as well address it.

The neck is fine as far as width , but it is really deep front to back. I want to thin it front to back to suit my preference. The builder says the truss rod is shallow so I am ok to take some off. I may get an xray as has been suggested here before.

My questions deal with the order in which I should do the work. What should I do first? Should I reshape the neck before I plane the board? Should I reshape the neck with the old frets still in place or take them out first? I wonder if a thinner neck would respond more to the truss rod and make planing the neck unnecessary.

When (if) I plane the board, should I relax the truss rod to increase the bow taking a little more board off to flatten it. I think this would build in some working room with the truss rod adjustment for the future.

I am optimistic that I can do the work, but I just want to make sure that each step is a step forward and that I don't have to go back and repeat to correct the effect of the next step.

Any advice is appreciated.

[mirwa]

Thinning the neck, one should always proceed with caution.

When refretting the neck, I want the truss rod to be able to give the customer the best adjustment possible, so I l do my first level on the fingerboard with the truss rod dis-engaged, next day, I engage truss rod a fraction and then re-level, then do my fretting.

Steve

[pops1]

If the truss rod is shallow and will not straighten the neck you may want to remove the fingerboard, put the truss rod deeper on the body side and reglue the fingerboard. I had to do this on a Gibson and it made the truss rod work much better. You will most likely not have to plane the finger board as it should be flat when you reglue.

[HoGo]

I agree with above. If the neck is bowed and trussrod doesn't work to get it straigth again, reshaping the neck may make it still weaker and it will bow even more... Bridge bottomed out means the neck angle may be too low to start with and planing fingerboard flat (along axis) may make you lower the bridge even more.
I would first solve the truss rod adjustment and get it working. If maker mentioned it is shallow that could explain why it doesn't work too well (of course there may be many other factors). Perhaps there is dirt in the threads that need cleaning or lubing or you need to cut more threads etc...
Only after the neck adjustment is fully working I would follow with the other work.

[tbrahan]

Adrian,

The angle is right at 15 degrees now. It doesn't look like I would lose much with the small amount of planing I think it needs. I would probably get that back with new/taller frets. The truss rod is dual action so I can't get the nut off to get to the threads, but the rod functions correctly until it reaches its limit. I did not look at the neck as being weak, but, rather, strong. Too strong for the truss rod to counter the forward bow. You may be correct. The neck is .97" thick at the nut and 1.2" at the 7th fret, which is not a baseball bat but it is thicker than my other mandolins. I will compare it carefully with and without string tension to better assess.

Steve,

That's what I thought. It builds back some of the adjustment. I just don't want to take off too much and thin the board and weaken the neck like Adrian points out.

Pops,

I was hoping to not have to remove the fretboard, but that might be the best solution in the long run. I read that the two-way truss rods were put in shallow and pretty level as opposed to the traditional rods that curved and slanted deeper toward the heel. Would a two-way rod work better set deeper in the neck?

[pops1]

No I don't think so. It may be the neck is too strong for the rod. Can you add a washer to the nut to gain some threads? I think I would still rather remove the board, plane the neck and replace the board, that may mean removing the rod as some use pressure against the fingerboard to work. Since you want to thin the neck I would start be getting it flat, then thin for comfort.

[multidon]

If it is a two way rod then it sounds to me like it is correctly installed if it is “shallow”. After all there are two rods stacked one on top of the other and the channel has to be cut into the wood of the neck twice as deeply.

Also seems to me that the rod is working properly. You say so yourself but it has a “ limit”. Have you confirmed that it works in the opposite direction? That is, can you add backbow? Or at least is there a loose “neutral” point where it feels like it’s tightening in either direction?

You need to add adjustability. What I would do is set the neck to neutral (loosest setting), then plane the board to true flatness, then re-fret (not compression). After that you should be able to have sufficient adjustability in both directions.

[sunburst]

A few things:
-A two-way rod does not need to be set deep in the neck because it does not rely on compressing the wood of the neck. It is fine, and correct to install it in a shallow slot. It will work the same wherever it is positioned in the neck. That means there is nothing to gain by placing it deeper in the neck.
-Apparently the rod is working within limits, and we expect limits, so we can probably assume the rod is not defective and that the problem is with the neck.
-While removing the 'board and planing the neck may be the best repair, that's a lot of work and potential for damage. Considering that the truss rod seems to be installed and working correctly, there goes one of the potential reasons for removing the 'board.
-It needs frets anyway, so the fingerboard will need to be planed regardless of whatever other works is done.

I believe the original plan is a good plan; remove the frets, plane the 'board, reshape the neck, and refret. I don't think the order of operation is critical (other than planing the 'board before installing frets), but if you plane the board before reshaping the neck you will get a better target for the neck size when reshaping. In other words, the slight slimming of the neck from planing the 'board will have already been done before reshaping the neck.

(I don't know the thickness of the 'board, but if it is plenty thick, planing can be done so that removal of wood is concentrated more toward the nut end and the effective neck angle can be adjusted slightly to get a slightly higher bridge.)

[tbrahan]

Thanks for all your input. The board is almost .180" at the edges by the nut. That should give me plenty to do the small amount of planing needed. John, do you agree that the truss rod should be neutral when I plane the board?

[sunburst]

...John, do you agree that the truss rod should be neutral when I plane the board?

Maybe.
The idea with a two way rod is to have adjustment in both directions. The first thought is that there should be roughly equal amounts of adjustment both directions and if the neutral truss rod position provides that, then neutral would be a good starting point.
In reality, all you really want is to be able to adjust the neck from dead straight to a slight forward bow, so the best truss rod condition for planing would be the condition that best allows for that adjustment. We seldom need to correct a back bow in a mandolin neck, except in some cases of ridiculously curly maple necks and/or poor construction, so if you have to sacrifice a little back bow correction to get better forward bow correction, then whatever condition of truss rod that gives you that might be best.

(As an aside, in light of the rarity of the need for back bow correction, my personal preference is a single action truss rod because it weighs about half of what a two-way rod weighs and it corrects forward bow just as well if not better. I feel that two-way rods are not needed in mandolins, especially when neck wood is chosen carefully.)

[HoGo]

John is correct about the double action truss rod. (I hate them and didn't even think of that possibility).

[rcc56]

In all the years I've been working on instruments, I cannot recall a single instance of having to correct a back-bowed neck, with the exception of instruments that had truss rods over-adjusted by an owner.

The laws of physics are against it. String instruments have 100 to 200 pounds of force constantly pulling a neck forward. It is highly unlikely that an instrument will develop a back-bow that was not there when it was built, except perhaps in the case of an instrument built with green wood. And in that case, the instrument will develop other problems.

[multidon]

It is not necessarily true that the only reason for a two way rod is to correct backbow. I own a nylon string guitar with a two way truss rod. With the rod in neutral, the neck is dead straight as can be. Always has been, even when brand new. The nylon strings do not pull enough to put any relief in the neck. I switched to hard tension. Still not enough (sounds better though). So I have to adjust the truss rod a little to introduce a touch of up bow so that I can have just the tiniest bit of relief.

That said, I own 2 mandolins with two way rods, and I have never had to correct back bow. I imagine all of you are correct that it isn’t necessary on mandolins. But on this one guitar at least, I find it a great thing.

[HoGo]

Classical nylon strung guitars are traditionally made with forward bow intentionally built-in during construction so no trussrod is needed if the maker thought of that.

[multidon]

Adrian- mine is a nylon string guitar, but not what we normally think of as traditional classical. It is made by a well known maker of steel string guitars, so it has some “hybrid” characteristics.

[sunburst]

FWIW, banjo necks of very curly maple can sometimes develop back bow. Banjo necks are long and thin relative to almost all other necks, and string tension is considerably less than most other steel string instruments. When maple is very curly if can be unstable in surprising directions, and I have, in fact, had to correct back bow in banjo necks.
In this thread, I was discussing mandolin necks. I'd be very surprised to see a well constructed mandolin neck made from good quality wood develop a back bow.

[tbrahan]

Did you ever have a "damn it" day? I reread the posts above to really absorb the advice. I decided to start slow and proceed carefully with the repairs. I took off the old strings and stripped the hardware from the mandolin. Figured the first step was to loosen the truss rod and decide where to set it when planing the board. Earlier I said I had that I had tightened the rod as much as I felt was safe. Well, next time I'll feel that safe is a little less tight. I had no indication but I must have reached the max stress point for the rod because when I began to turn it counter clockwise it snapped. The adjusting end nut broke off. "Damn it!!!"

Now I don't have a choice. I'll have to remove the fretboard and replace the truss rod. I've done fretboards but not truss rods, but Frank Ford, thankfully, has put up a pictoral. I wonder if I should put in a one-way rod? Haven't done that either. This is turning into a real learning experience. Glad this is my hobby.

[sunburst]

...I wonder if I should put in a one-way rod? Haven't done that either. This is turning into a real learning experience...

When you remove the broken rod there will be some sort of slot. Two-way rods are typically not set as deep and standard rods, so the slot probably won't be as deep as we usually set standard rods. It is not easy to deepen the slot in a neck attached to a body... but...

Due to the shape of the neck as well as having a (normally) very stiff fingerboard glued to it, the neutral axis of a neck shaft is much closer to the fingerboard than if the neck was a square or rectangular beam. A standard tension truss rod must be below the neutral axis to be effective, but since the neutral axis is close to the underside of the fingerboard that means that a standard tension truss rod can be effective even when it is not set very deep in the neck. As the rod is set deeper there is an improvement in it's efficiency, but you may not need to deepen the slot if you want to change rod types.

Since you have to remove the 'board anyway, the neck can be planed or whatever is needed to get it good and straight, and then the fingerboard glued back on. You should have a nice, straight neck after that and if the neck is good quality stable wood you may not need whatever truss rod you choose for anything other than minor adjustments.

If you continue to work on instruments there will be "learning experiences" on a regular basis. This will add to your experience level and to your confidence as you continue to repair stuff.

[tbrahan]

Thanks, John. Has anyone used a carpet seaming iron as a heat source to remove a fretboard? I saw one at a pawn shop. 11" long with heat settings from 140 to 450 degrees. Looks more efficient than a clothes iron, $20.00. I think I'll make one of those little circle saw tools to cut out the filler a la Frank Ford.

[pops1]

I use a 100 watt light bulb. Protect what you don't want to heat with cardboard with foil wrapped around it put the bulb in a bench light. DON"T walk away ever without shutting off the light. You can use your hand to feel hot hot the fingerboard is and it will heat it plenty so it will come off, with the frets on if you want.

[rcc56]

I use a 1" x 5" 25 watt heat blanket, available from MSC or McMaster-Carr, plugged into a Harbor Freight router control for a temperature controller. These were recommended to me by Lynn Dudenbostel. I use the same heat blanket for removing flat top guitar bridges. For guitar fingerboards, I use a 2" x 5" 50 watt heat blanket.

Heat slowly, and don't try to force your lifting tool underneath. If your spatula or lifting knife does not slide pretty easily, the board is not ready to come off.

If you don't want to try to install a new truss rod, you can lay a solid reinforcement such has ebony, very hard maple, or carbon fiber into the empty channel. Carbon fiber is hard to work and hard on tools [I don't care for it myself, but it is stiff as can be], so if you use it, you might want to choose a piece that is not quite as deep as the channel and cover the remaining gap with hard maple. If you use a solid reinforcement, you might want to blunt the corners slightly with a file-- it will be easier to lay it into the channel if it doesn't have a sharp edge on it.

[Tom Haywood]

One of the more educational things for me was the first time taking a mandolin fret board off and removing a truss rod I thought was broken. Photos and drawings simply don't convey all the information that can be gained from seeing how the slot and the metal affect that piece (or pieces) of wood called a neck, and how the neck affects the rod. It makes it easier to decide what kind of rod or other stiffener to use or not use, how deep a channel to make, and whether you need a filler strip. Also, you can get a better idea of how to judge the depth of a truss rod when you want to alter a neck. Generally, I prefer a single action truss rod on a 13 7/8" or so scale mandolin, and I like to use just a plain 1/4" steel rod in shorter necks though I'm not sure there is much if any gain from hollowing out a good piece wood and inserting metal or carbon. I don't see a need for double action, and generally don't see any forward movement with short maple and mahogany necks. On that first one, the rod was somehow bound up in the channel - not broken. A little slant to the bottom of the channel and lubrication of the threads and it worked great. It showed how and why to lubricate the threads on all adjustable truss rods, and why not to "crank" the thing. After that, you get to decide which camp you are in regarding planing and fretting the board before or after gluing it to the neck. Lots of threads here on that one.

[tbrahan]

I'm still listening to all your advice and suggestions. I've ordered a truss rod from Steve Smith, but I still don't know for sure if I want to use that. It is a straight replacement and should be easier than changing to a traditional rod or CF. Creating the adjusting nut pocket in the headstock on a finished mandolin is a challenge. How would you go about it? There is a very narrow channel now. Just enough to get an allen wrench in. There is no "shoulder" for the nut to push against. Stew Mac has a tool for new construction, but it's expensive and I don't know if it would work on a finished mando.

[Tom Haywood]

After waxing philosophically above, I'll say as a practical matter it probably makes the most sense to stick with the design you have and replace the truss rod with a similar rod - if you get one that fits. Can you post a photo showing the "no shoulder"? I have an Irish bouzouki with a double action truss rod that doesn't do much. There is nothing for it to push against on the nut end. It's the only dual action rod I've done anything with so I'm no expert on those, but it seems like a block at that end under the nut would give it more muscle. Is that what you are describing? The head stock angle to the neck and the thickness of the head stock are going to be crucial in deciding about a deeper channel and corresponding nut pocket. Another good reason to stick with what you have.

[tbrahan]

I decided to stay with the two way rod, so I ordered one from Cumberland Acoustics. Turns out it had a Stew Mac rod. The only difference is the Cumberland is maybe 3/16" longer, but that just makes the adjusting nut easier to access. I had handled guitar truss rods, but never a mandolin rod. Delicate little thing. If everyone with a mandolin got to hold one there would be less twisted off adjusting nuts. I sure wouldn't have tightened it as much.

I pulled the fretboard, removed the old rod, put in the new rod, and glued in the filler. I have the neck smoothed back out, and I am to the point where I either plane the bow out toward the nut, or I flatten it with a Frank Ford torture rack and glue the board with hide glue while in the press. I can bend the neck flat while the board is off with my hands. With the board off I measure .012" bow at the 7th fret with a straight edge from the nut to the body joint. Any suggestions as to the best route?

Another question. After I get it back together, I still may want to reprofile the neck shape. How much wood should be left beneath the two way truss rod? I've taken measurements of the thickness with the board off ( the board is .19" thick with 12" radius ) : 1st fret - .77", 3rd fret - .84", 5th fret - .91", 7th fret - .98" and 10th fret - 1.14". The truss rod pocket is .52" deep and level nut to body. That gives me from .29" to .52" under the rod. How much is the minimum to be safe?

Thanks for any input.