I was just wondering how much tension should I put on the truss rod before leveling the fretboard? I'm thinking between 1/4 and 1/2 a turn. 3/8ths...
I'm about to start yanking the frets off of my neck. This neck has a back-bow even with the truss rod completely loose. So I'm going to take the file to the board.
I just noticed this neck already has quite a bit thinner FB in the middle than it has at the ends. With the truss rod loose the ruler along the edge of the fb only has a tiny bit of back bow, but the seam of the FB aganst the maple has over a mm. In that case I guess it doesn't matter much if that difference will become even greater...
Top two pics is with loose truss rod. bottom is 3/8 of a turn. That feels about the right resistance...
Why bother? Remove the frets, set up a temporary neck clamping jig, jack the headstock up until the board is level and start leveling.
The question, really, is how much relief is there under string tension? If there is adequate relief and some modicum of adjustability, say, between .000 and .012"±, you don't need to level a backbowed neck. You can take Tadej's advice and proceed happily. If, however, you have backbow, or zero relief under string tension, a small amount of leveling will suffice, but you don't need to, nor would I advise taking that particular F/B flat. That's a LOT of mass to lose for nothing. You need take only as much as minimally possible to achieve an acceptable amount of relief under string tension. You'll likely end up with a neck that still backbows without any tension on it, but every Martin made before 1983, of which there are countless thousands, all exhibit this characteristic.
Depending on the glue used under the FB, heating the neck under tension may straighten the neck. In cases like this, I clamp the neck to an up-bow and iron the FB (preferably with the frets still there) until the back of the neck is warm to the touch. Let it cool. If the glue used is a decent one, the neck will be staighter. It's worth a try if you don't know for certain that there has been used epoxy or other evil sorts of glue to fasten the FB. If it doesn't work, nothing's lost, and it will take you no more than 20 minutes to try it.
What Bob doesn't say ( sorry if I am treading on your toes Bob!) is many times this process has to be repeated multiple times. Though I have only done this job only on 4 necks, there has been not one that I did not repeat the process at least 4 times. It does work eventually though. Do not expect it to be perfect though. Guaranteed there will be some sanding to do, and so you need a proper radiused block to get the board back to spec .
And the frets have to be in for this process to conduct the heat without damaging the fretboard/or lacquer/ or possible binding....
I have done this on different guitars with great success, but you are right, Kerry, you may have to repeat the heating one or more times, and in this case, as the back bow is huge, I also think that will be nessecary. Perfection is a rare thing, but if a decent glue has been used in the neck, I think it should be possible to make an up-bow. I have straightened necks this way without having to refret afterwards. One of them, a Gibson 335 that had a severe up bow is still straight as an arrow after more than two years in spite of the .013 set tuned to pitch, of course as long as the truss rod is able to withstand the high tension.
You may also have a look at this discussion:
Any iron will do. As long as the frets are still there, don't tell your wife, and she will never know. The jig is easy: Clamp the body close to the neck and leave the other end of the neck on a rest of some kind. Don't use maximum temp if the guitar has a bound neck or MOTS inlays. Heat till the back of the neck is warm, not hot. Let cool. loosen the clamps and check progress. If nothing has happened the glue is evil. If it has helped some, repeat till you are satisfied. Good luck!
Well, this is a Strat neck, the heel and the back of the headstock are in one plane.
Just need to find something straight enough to not introduce some other warpage.
Inlays look like pearl, but so do bowling balls. Anyway.
So, I did two passes, first one didn't do much, second one I clamped the 5th fret down and it is now almost straight with some tension on the truss rod and no strings. Most of the twist looks gone too! I'm so stoked about if it'll still be this way tomorrow!
I'm going to do another pass tomorrow and see if I can get the rest of the twist out. Then it's yankin' time! I want SS frets.
I did another two passes and the neck is totally straight! I clamped it to my desk, which is the straightest and most rigid board I could find. I put some folded paper (1.5mm) underneath the headstock to give it some twist in the other direction than it was twisted and the twist is totally gone! just laying the headstock and heel on the desk there is no wobbling!
It's untwisted now! Sighting from all angles doesn't look twisted in any way!
It has cooled down after every pass. Can I be certain it will stay the way it is now? Should I wait and see a couple of days before I move on with the frets?
I'm pretty stoked! Thanks everyone and Bob especially!
Now to put the iron back before it's missed.
I don't think a couple of days will tell you anything. The neck may want to go back to the backbow state, but if so, this will take a long time. I have experience only from upbowed necks which of course will be forced to behave well if they have a truss rod. I have, however, an old archtop without truss rod that got this treatment two years ago, and this needs a new ironing soon because the neck has started to bow up again. The relief is now about 0.015. I consider filing the FB flat and refret, but this is a lot more work than ironing it every second year. This guitar has .012 strings tuned to pitch.
However, if the neck warps again and the frets are good, all you need, is to do this ironing again, maybe many years from now. The frets don't move because the neck does.
I guess we'll see. In a couple years...