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A friend of mine came to me with a Gibson 335 with a severe up-bow. The "relief" is 0.9mm (0.035") at the most without strings and with the truss rod loose. Even with fairly soft strings and a tightened truss rod, the relief is more than acceptable, and with my friend's super heavy wires the guitar is not playable at all. I think that the fret board must be absolutely straight without any tension in either way to be able to fight against these strings. Is there a better solution than sanding the fretboard down these 0.9mm? Removing the fretboard to remove the relief from the neck itself is out of the question. I am also skeptical to hammer in overdimentional fret tangs to straighten the neck as I find too tight slots difficult to handle.

Bob

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IF it has a functioning truss rod, the simple way to reduce relief is to tighten the rod. Since you say the rod is loose, I suspect that may be all that's needed.
Thanks for answering, this has, however, been tried. I'm afraid that my English, for me a foreign language, has not been sufficient, so I will try once more. When the neck is influenced by no artificial tension, neither from the truss rod nor from strings, the fretboard has a 0.035" sag (measured with a slotted straghtedge). This measurement, I think, should normally be zero or close to zero. With the truss rod tightened as far as I dare risk, the neck is almost straight without strings, and with strings, the relief is too much to accept. I hope I am better understood now.
What's in my mind is for instance heating the fretboard while clamping the neck in a backbow position. Is this worth a try? Is this a possibility? How? Are there other possibilities? I will, regardless of solution, do a refret.

Bob
Without wishing to offend: this is a valuable instrument that need proper repair: if you are unable to do an appropriate repair you should tell your friend to send the instrument to a repair facility that does professional level repairs. Otherwize, level the fingerboard against the bias before refretting, use high frets and try to take out the remaining relief in the final fret level. Doing a dodgy heat and slip repair on a heavily stressed 335 neck is not adviseable. Rusty.
Before you judge the "feel" of the truss rod, you should remove the truss rod nut and lubricate the threads and the face of the nut where it contacts the steel washer. Then, when you replace the nut you may well find that it works much better.
Ditto on Frank's advice. It can make all the difference.
Bob, another thought: if the wood has compressed at the truss rod adjustment end, try slipping an additional washer over the rod and replace the nut. It may give you an extra couple of turns on the threads, which could make the neck adjustable again.
Bob, here ("heat and slip repair") Russel is talking about a possible repair if all trussrod care proposed in the following replies fail : heat the fretboard with a heating blanket or light bulbs to soften the glue, back-bow the neck and let it cool back-bowed.
Considering you've got less than a milimeter of up-bow and it is a guitar (not a bass, believe me it's far more complicated due to the massive up-bow it can take), maybe the fingerboard+fret levelling is a good option.
Is the "heat and slip" repair the same as the method described in "Complete Guitar Repair" by Hideo Kamimoto? (Heating with a lamp and clamping?) The guitar will certainly get the best treatment. I am used to the procedures described here, but this time I would like to know alternative ways to solve the problem, this mainly because the fret markers in the binding, especially those marking the 19th and 21th fret, are quite close to the rim already.

Thanks for advices, gentlemen!
Bob
Bob,
I am familiar with Kamimotos procedure and consider his book to be one of the best available - his setup procedures should be tattooed on luthiers arms. His gentle heat procedure works for a lot of guitars but 335's with their skinny necks and low frets seem to be in a world apart when it comes to neck movement - someone out there knows why older Gibson 335's seem to have chronic neck twists, bends and loose frets but it's got me stumped. LP's which are somewhat similar don't seem to present with the same pathology. I've also come across the skinny binding strips which also seem a 335 hallmark - this makes getting the twists/bends out these necks by flattening the board particularly difficult. Try 55 thou' height frets (54x100 is a commonly available size) and level it out with the neck stressed a little against the bias. But, heavy strings (11+) will really test these necks once they have taken a set. Good luck Bob, yr not alone with this one. Rusty.
The neck was levelled, clamped to my work bench and with a string pulling down at the nut. It was heated with a houshold iron. Two rounds of ironing did the trick. The neck got straight without help from the truss rod, new frets were installed, and my friend could put on his .013 wires stringed to pitch. Even with these strings on, the truss rod has more to give if the neck should move. Now, after more than four months, my friend claims that the neck has not moved at all (I have not seen the guitar since January, so I have to take his word for it), and I have hope that it will remain straight.

The ironing can be done with the frets on. The frets seems to distribute the heat well (also said by Kamimoto in his book). This means that even necks with MOTS inlay can be straightened this way. I have straightened the neck of a -61 Hofner archtop, so far with success, without melting the MOTS inlay. Flattening a back bow is just as simple, just leave the neck on a neck rest and clamp the upper part of the body.

Later, I have used this method on more guitars. It does not work on all. One 60's Yamaha and one 70's Yamaki did not respond, probably due to a heat resistant glue under the fretboard. The experience is, of course, limited, but so far it looks good.
Thanks for the comments!

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