Clamping a neck into a back-bow

[eliya]

Hello everyone, I'm new to this board and also fairly new to guitar repair. I tried using the search function to find previous threads about the subject, but came up empty handed (I'm sure it's been discussed, but I just couldn't find it).

I have a Guild S300 (24 frets, 24 3/4" scale, set neck) that has a set of 11s on, and even with the truss rod maxed out, the neck isn't straight. Instead it has an up bow, which isn't drastic, but probably too much for my liking. I plan on bringing this guitar back to a playing condition (including a refret), but first I want to get the neck straight. I've seen Dan Erlewine demonstrate clamping a neck into a back bow in one of his videos, and he made it look easy and like something that's done more often than not. However, he doesn't go into very specific details.

How loose/tight do you keep the truss rod nut?

Do you clamp with or without strings on? (With strings seems to make more sense)

How long do you clamp it for?

Is it really something that's done more often than not?

Is this the right thing to do in order to get the neck straight? I've also seen the method of pushing down on the headstock while turning the nut in order to bring the neck into a back bow. I'll probably try that first.

Some helpful info about this guitar: It is a real road warrior. Its frets are worn all the way to the 14th fret, and the finish is almost completely missing from the back of the neck. When I first got it it had too much back bow, and the luthier who used to work on my guitars suggested stringing it with heavy strings to compensate for that. I used to use 013s with it (but tuned low) and went back to 011 in the last two years. I don't know if the neck's ability to go from one bow to the other is a good or a bad sign, but I thought I'd mention it.

Thanks! I really enjoy this forum.

[eliya]

So a thin one is ok? (i.e. not as thick as the original half-moon).

Thanks again for all the help, everyone! I'm going to attempt this process soon.

[Andrew]

Id say it depends on how thin. If its too thin/poor metal quality, it may deform under pressure. This might result in a bit of binding of the nut, or other issues that could affect the feel of the adjustment. Also you obviously want enough thickness to give back the amount of threads you need.

[eliya]

I got a few more washers and threw one in, so there are two washer between the nut and the wood. I was able to get the neck to back-bow a little and then brought it to straight. I was excited to try and clamp it, but the best repair is the one that's easiest and take the least amount of time.

I still don't understand the "science" behind this (especially since I didn't run out of threads).

[eliya]

The washer trick helped with one neck (on the Guild guitar), but didn't help as much with the Fender-esque neck. With the original truss rod nut, I can barely get the neck straight. Adding another washer isn't an option because the nut will stick out and I won't be able to get the neck to fit the neck pocket. I have another nut (which is longer, therefore unusable in this situation) with which I can get the neck into a back bow, so it's possible that I can get it to be straight with strings on.

Anyway, I think I'll try clamping this neck, but have a few questions. Does it matter if the blocks I put on the neck are the same height and size? I saw some pictures of Dan Erlewine doing this, and the blocks seem to be different sizes (with the one that's by the neck-body joint being shorter than the other). Also, the gap between frets gets very small in the area of the neck-body joint. It's so small that I don't know if I can cut the block that size. Is it ok to just file a little notch so the block can fit over a fret?

Thanks!

[Andrew]

Stew macs truss rod rescue kit will help the fender style neck; it can cut the recess deeper and add more threads so the nut doesnt run out of them, then you can add a washer and not have the nut stick out, and be certain youll have plenty of threads to work with. Clamping the neck wont help til you do something like this because the nut cant provide the compression needed to hold the neck in the clamped configuration once the clamps are off.

Also, it may be possible to get around the rescue kit by simply carving some room in the neck pocket for the protruding nut. Depends on whether you feel this would be kosher for the guitar, and whether there are any other factors that might come into play, like pickup cavities and pickups, etc. would require some judicial measuring.

[eliya]

I'm not too keen on paying as much as I paid for the neck for a rod rescue kit. This is a new neck (I bought it 8 months ago), so I hope the problem isn't as severe.

I also don't want to carve into the neck pocket, I'd much rather shave down the nut itself and add another washer. I bought a new nut that is supposed to be a little shorter than the one I have right now, so I'll see how that goes.

The question still remains -- how come I can get a back bow with one nut but not the other?

[Jeff Highland]

Are you using closed end nuts?

Rather than running out of thread, the end of the rod is probably bottoming out inside the nut

That would explain why the longer nut works.

You could  cut a clearance slot in the neck pocket

[Andrew]

Id be pretty tempted to just make some room for it too. It should be no big deal if youre careful about it. Unless its vintage, or something high end/classy, I wouldnt consider that a bastardization.

There must be some difference between the nuts, theres no other explanation (that I can think of).

[eliya]

Yeah, I think Jeff is absolutely right, the nut doesn't have enough threads. I bought a new nut online, so I'll see if it fits better.

Do you guys have any input regarding the blocks?

[Jeff Highland]

Yes or even two thin ones if necessary

[Bob Steinarsson]

If the washer trick doesn't work, see this link: http://fretsnet.ning.com/forum/topics/noobish-question?commentId=21...

[J R Emmett]

If you have access to a lathe, an alternative to a stack of washers is turning a cylindrical spacer.  ID should be slight clearance for the major diameter of the truss rod threads.  OD should match the nut.  Material can be Aluminum, Steel or Brass, which is preferred as it runs well on steel without lubrication.  Have rescued a number of necks in this fashion.