Trying to correct a twisted neck

[Pilgrim]

I have a decent old Kay KB-2 bass that has a slight counter-clockwise twist to the neck. It's just enough to screw up the action and cause fret buzz. When I sight down the neck from the nut end, the E string side of the neck is twisted upward about 1/16" or a bit more.

Here's a look at the problem:


Since I don't play it often, I decided that I could try something to correct the twist. Here's what I did:

1) I removed the neck from the bass and stored the parts.
2) I clamped the body end of the neck to my workbench using a clamp with a soft plastic pad so that I wouldn't mar the fretboard.

3) I removed the top two tuners, drilled a matching pair of holes in a strip of plywood, and bolted the plywood to the headstock with about 12" of plywood extending outward on the E string side.

Here's the underside of the headstock:

4) Through a hole drilled on the far end of the plywood strip, I threaded a nylon cord; the other end was looped around a 10-pound strip of marble I use as a base for leatherwork. I sat one end of the marble strip on a workbench shelf, letting the other end hang on the loop to provide a constant weight pulling down on the plywood strip, thereby providing a twist to the neck.

5) To avoid causing a back-bow in the neck, I used some scrap wood to support it just below the headstock. The other clamp visible on the right of this pic is to prevent the neck sliding off the edge of the workbench::


I've had it in this loaded position for about a month now, and I relieve the weight every now and them by pulling up on the rope looped over the marble. While the weight is off, I sight down the neck to see if it's straight. I figure it will probably take 4 months or more to straighten it out, but I think I see some movement already. I figure that heat and humidity might speed the process, but it's a warm summer and the garage where my workbench is probably heats to 85 degrees or more every day.

Since I used only scrap materials I already had, cost for this "solution" is $Zero.

Comments??

[GlennW]

I got a lot of good advise here for correcting an excessive bow. Prior to that I had the neck straddled across a couple of chairs with 50-60 pounds hanging from it - a week or two of that accomplished nothing (other than an obstacle in the room).

Following the suggestions here I went to Home Depot and got two Phillips 250 watt Reflector Infared bulbs and the big silver things with the clamp to hold them - less than $30 total, I think.

I'd read about straightening necks, and there wasn't much to be found. Anyway, you NEED heat. The fibers of the wood need to get hot so they become more flexible and can assume the new shape. After heating for 6-10 hours turn the lights off, but leave your stuff clamped for about 12 hours. Don't rush that part.

Be careful while heating so you don't screw up the finish. I just did this on the 4th (my idea of fireworks) and cooked the neck for 11 hours. The reason it took so long was I started out the the bulbs 9" away, and I'd check every 30 minutes or so to see if the finish was melting and if the neck seemed like it was getting warm enough. I moved the bulbs closer in 1/2" increments until I got to 6" - once there I let it alone for about 5 or 6 hours just to be sure it had enough time.

You want the wood hot to the touch - hot enough so you can't hold it very long - but not so hot it messes up the finish.

That old Kay's finish might be nitro, so you'll want to keep a close eye on the finish.

I've never corrected a twist - that's going to be tricky, might even need chicken blood or something just as powerful. Seriously, I'd suggest trying it with the expectations of having to go into Round 2 and maybe 3. I'd twist it to where it's close without going too far past where you want it and see what happens. It probably won't stay exactly where it is once you remove the clamps, but it would safer to err on the side of caution. Then you'd have an idea of how it's going to act before doing it again.

The bad news is you have to babysit it, but the good news is you won't have to wait for months.

Also, with the twist you might want to cover the area that's ok. You'll have to pay close attention to what's happening and try to read it in the process - might have to regroup and move your clamps to get it to twist where you want it to, and focus the light where you need it.

I've straightened 4 or 5, but never dealt with a twist.

Again, I've never done it. Good luck.

If you can't get the lights to shine where they need too, you might have to come up with another plan for securing the neck.

[Busker]

Can this be corrected by removing frets and planing the fretboard flat? Or is this what you're trying to avoid having to do because of the amount of work involved?

The neck on my Schecter isn't 100% perfect. It has a very slight hump on the treble side around the 10th fret. And the E string side has more relief than the treble side.

It actually plays good enough, so I'll just live with it for now. But I really want a better neck for the bass. I just can't lay down $200 clams right now.

[62bass]

I've used the heat and clamps method to correct for excessive bowing for many years. Yes, you must have heat and as Glenn W says you have to keep an eye on it. I scorched the finish on one neck I did and had to refinish it.

The idea to correct for a twist in the neck could work and is worth a shot. But use heat or nothing will happen. When the neck is heated right through and the twist is gone, turn off the heat and let it cool on its own before removing your jig. Try to heat the whole neck evenly and not just one part of it.

[GlennW]

Just looked at your pictures again. The fretboard binding might try to escape if it gets hot enough.

[Pilgrim]

I'm playing a very long game here - I don't need to use the neck any time in the near future, as I have a half-dozen other basses. So for now I'm going to use time rather than heat, and see what happens.

I can certainly keep GlennW's recommendations in mind, but I'm not sure what it would do to the finish or fretboard glue. So Plan A is to be patient and work with lots and lots of time. If nothing has changed in 4 months or so, I'll have to make up plan B and try it...and it may be the plan GlennW suggests.

Of course, in the meantime I'm also keeping an eye on Ebay for a trashed SG-style Kay with a usable neck.

[PilbaraBass]

there are definitely more "gentle" forms of heating than heat lamps...for instance...an electric blanket...

[62bass]

I'm not sure of the exact temperature needed to affect a change in the neck, but it's just around the point where your hand would get uncomfortable if left there for more than 15 seconds or so. Not very scientific, I know, but I've never set up a thermometer when doing it.

My first try doing this to correct a permanent bow in a neck was around 1978 when a friend brought over a very old Martin acoustic flattop that had no adjustable truss rod and a very bad bow. I devised a clamp system, tested it, then got a heat lamp, and throwing caution to the wind, went ahead and did it. I went strictly by estimate and changed the position of the heat lamp until I got it to where I thought it was hot enough. I left it for about 4 hours checking it frequently. After about an hour and a half the neck started to get a slightly rubbery feel, showing that it was working. I probably could have turned off the heat at that point but continued to about 4 hours. Then I shut the heat lamp off and let it cool while still clamped up overnight. Strung the guitar up to tune with new strings. It was perfect. My friend was very happy. When I checked with him a couple years later he said it was still perfect. There was absolutely no damage to the finish or fretwork.

This heat method is used quite often by woodworkers to laminate wood into a permanent curve and by boatbuilders to get wood to conform to the many curves needed. In fact, I got the idea from watching and helping my father build a wooden boat when I was a kid.

Pilgim, if you have all the time in the world, there's no harm in using your method. It's certainly safe for the finish and bindings. Your clamping system is brilliant. I don't think it will work without enough heat myself, but let us know 4 months down the road on how it turns out.

[T-Bird]

Hi.

+1 for the doesn't probably work department.

I've tried that same kind of method some 20 years ago and while it can work for a short period of time, the wood just twists to the same shape it was prior to the rapid bending. Rapid considering the time that was needed to develope that twist it has now. Wood tends to have a "memory" and that memory is IME quite good .

BTW, IME quite a few (70% ) of those Kays, Ekos, Cimars, Applauses etc. etc. came with twisted necks from the factory because of the incorrectly sawed stock and incorrect humidity of the wood when the neck was made. If that's the case, the only solution that I've found is to take the neck apart and to glue the fretboard back with a slight counter twist. Did a few when I was young, but wouldn't even dream of doing anything like that in these days. Just not feasible.

I also tried the method of soaking + twisting and that worked a bit better, longer, but after a year or so: back on the bench.

Nothing beats the heat however and I don't think that You're going to see any permanent results without applying heat to the neck.

IME that kind of twist can be compensated in the nut, with the saddles and with the relief. It jus takes a lot more work to find the right combination than with a non twisted neck. Definitely worth a try though, saves a lot of work and time in the end.

Just my 0.02€
Sam

[GlennW]

The disadvantages of a heat blanket are that you can't feel it to get and idea of how hot it is and you can't see it to monitor the finish. I was going to try one used for bending PCV pipes, but felt safer with the lights.

[202dy]

If one puts money in an investment that appreciates more slowly than inflation one loses money. People do this knowingly for reasons of their own. Others cannot fathom why they do this. Guitar collecting is mostly like that. People do it because they love guitars and their investment pays a dividend beyond money, that is pride in ownership. While it is true that there will be a gain, that gain, in a monetary sense, will not be enough to justify the investment. And while the gain may be acceptable it may not reach the desired goal.

Attempting to bend wood sans heat or steam and waiting for it to take a permanent set is a lot like that. While it will eventually bend to a point that is acceptable it might not bend to the point that is desired. Or it might bend in ways that are unexpected. If held in position long enough it will take a set.

Then there is the question of spring back. When bent to desired point C the bent item will normally spring back to point B, closer to point A where it was at the beginning. Therefore the bent piece must be bent further than the end point to eventually and permanently arrive at the end point. If, when attempting to bend wood for the first time this is not understood, the workpiece will not be bent to the desired shape.

How much heat to use is an often asked question. The answer is simple. The right amount of heat to apply to a bending project is one degree less than the temperature it takes to do damage to the project. That could be to the wood or to the finish. Electric blankets are great for warming up pieces to be joined with hide glue to gain a little extra open time but are totally inadequate for bending. The heating elements in a blanket are spaced too far apart to be effective. Quadruple wrapping with a blanket could be a fire hazard. That is unacceptable unless the original goal was to burn down the house. Heat lamps, in various forms, are recommended to those that do not wish to invest in silicon rubber heaters. Rubber heaters are refined idea similar to gutter heat tape. However, when using the heaters caution must be exercised as they can achieve heats beyond the combustion point of wood. It is prudent to insert a control in the line to limit the temperature of the heater.

This is a project that must be babysat through for the entire event. Using heat correctly can turn a six month project into an hour and a half on day one and a setup on day three. For most folks, this is a desirable way to conduct a procedure.

All of this is scary, frustrating, and time consuming for the first timer. And those who have done it often. That is why the almost universal choice is to apply heat. Those with experience realize that the first (or second) attempt may not be successful. Ultimately, the idea is to complete the repair, not to see how long one may take to complete the repair. Or as one might observe on the bumper of a passing pickup truck: "Git'er done!"

[Pilgrim]

Good thoughts above! I recognize that it took 30 years for the neck to get where it is (although the twist may have appeared much earlier than that) and therefore even a 2-4 month corrective process is a "fast fix" by comparison.

Also, I have been contemplating the "spring-back" issue, which I recognize is inescapable. The question becomes, regardless of correction method, how much PAST the desired point does one bend the neck in order to allow spring-back to a point where the neck is actually useful? Of course, there is no correct answer. One must simply make a best guess.

There are some interesting thoughts above about possible ways to apply moderate heat. I will give them serious consideration. Although I have LOTS of time available, achieving a result sooner than later would free up workbench space and allow me more time to re-try if I get too much spring-back.

[202dy]

Originally Posted by Pilgrim

Good thoughts above! I recognize that it took 30 years for the neck to get where it is (although the twist may have appeared much earlier than that) and therefore even a 2-4 month corrective process is a "fast fix" by comparison.

Also, I have been contemplating the "spring-back" issue, which I recognize is inescapable. The question becomes, regardless of correction method, how much PAST the desired point does one bend the neck in order to allow spring-back to a point where the neck is actually useful? Of course, there is no correct answer. One must simply make a best guess.

There are some interesting thoughts above about possible ways to apply moderate heat. I will give them serious consideration. Although I have LOTS of time available, achieving a result sooner than later would free up workbench space and allow me more time to re-try if I get too much spring-back.

Estimating spring back is difficult. Unless you have a lot of experience with the type of wood and know how it was sawed it is simply a guess. On an unknown wood start at 120% and go from there.

Having lots of time is a luxurious situation. You are to be applauded and respected for your ability to schedule yourself so well. Having so much time, though, might it not be better put to use learning the details of wood bending rather trusting to the whims of the environment?

BTW, the method you have chosen for correcting the twist is ingenious. Clamping schemes suffer from the temptation to introduce more force than necessary causing cracks in the neck or headstock. Your way applies a predictable amount of force that can be increased as needed. Kudos for original thinking.

[Turnaround]

It's probably worth noting that it takes a fair bit of effort and time to bend the wood unless one is using steam or heat.

Next time someone asks if it's OK to remove all the strings at once......

[Pilgrim]

Originally Posted by 202dy

Estimating spring back is difficult. Unless you have a lot of experience with the type of wood and know how it was sawed it is simply a guess. On an unknown wood start at 120% and go from there.

Makes sense to me! I'll use that suggestion as a good place to start...and no reason I can't just eyeball it.

Originally Posted by 202dy

BTW, the method you have chosen for correcting the twist is ingenious. Clamping schemes suffer from the temptation to introduce more force than necessary causing cracks in the neck or headstock. Your way applies a predictable amount of force that can be increased as needed. Kudos for original thinking.

Thanks. I wanted to be able to apply constant, even pressure - and it occurred to me that the headstock was a place where I could generate twisting force by attaching to it, then extending a lever outward to the point where force was applied. Then I just started looking for heavy objects. The marble chunk was something I could tie onto, but I thought it was too heavy to simply hang from the lever. Putting one end on a shelf 'felt" right to me.

[the low one]

I started a similar thread recently about a twisted neck problem I've got. I'm tempted to leave it alone though as it doesn't affect the way it plays.
http://www.talkbass.com/forum/f18/neck-twist-380540/#post4919302

[jrfrond]

My feelings are:

a) It won't work

b) If it DOES, you might bend curves into the neck that otherwise were not there.

I think it will be "a" though.

Twists can be awfully hard, if not impossible to correct without yanking the frets, planing the board flat and refretting. Even simple over or back bows can be difficult with a neck heater. I've used my neck heater a lot over the years, and it does not always work. The principle behind correcting a bow was to get the neck hot enough so that the fingerboard glue joint would soften and let the FB slip a bit. Then it would cool in the new position. This is assuming that a thermoreactive adhesive was used. If an epoxy or CA adhesive was used (as well as others that won't melt), you might correct it temporarily, but I've seen them come back lots of times.

It can't hurt to give it a shot though. Wood can be flaky and unpredictable. Who knows what might work?

[Pilgrim]

John, always a pleasure to hear from you!

Well, I did it - left it under load for a couple of months, than finally added a heat lamp for the last month or so to help the process along. Total time under load: about 4 months. Result: the neck is still straight (no unintended curves as far as I can tell), but it actually un-twisted MORE than needed. Now I have a slight twist in the opposite direction.

If you look at the sixth picture in my thread-starting post, you can see I did put a support under the neck so that I wouldn't be bending the neck downwards at the headstock as well as applying twisting force. In that pic, the clamp kept the neck from pulling off the workbench, but above it, I positioned some wood shims under the neck to give it support. I wasn't sure how it would work..but it seems OK.

Here's the pic:


I have it re-assembled and sitting (hanging) to allow the neck a month or two to spring back, since it's reasonable to assume that it will spring back to some degree - that's what I was trying to allow for, but I may have over-done it. If the twist doesn't come back enough, I may have to do the same process again, but load the neck the opposite direction.

One observation: if you use a heat lamp in a portable clamp-on work light, check the light fixture's maximum wattage rating before proceeding. Most of the clamp-on light fixtures are rated 100W max, and most heat lamps START at 150W and go up. I forgot to check that, and although I didn't cause a fire, I did fry the heck out of that work light. When I went to press the off switch in its base, the light socket crumbled. I'm glad I stopped when I did! I'll buy a porcelain-based light fixture rated for the wattage of the lamp if I have to do that again.