Straightening a Neck with Heat

[rhino55]

I came across an old Harmony H165 with a cracked nut and 3 strings.

 

I put a new bone nut on last night and a fresh set of strings with some modified golf tees to replace the bridge pins that were missing. It sounds really good, but boy howdy is that neck bowed. I'm not wanting to spend the $300+ it'd take for a neck reset. In looking for alternatives online I came across neck bending by heat. Does anyone have any experience with this? Does anyone know where I can order a neck heating bar?

 

In all the articles I found about this the links to the heating bars are no longer good. Could the same thing be accomplished with some stewmac heating blankets and leveler?

 

I'm thinking it might be nice to get setup to do this because I know lots of folks with cool old guitars with bowed necks.

[Freeman Keller]

Rhino, please clarify some things for me. First - is the neck itself bowed - ie if you lay a straightedge on it how much gap is there at the middle (assuming its resting on the first and 12th frets? Pictures of H165's show that they have adjustable truss rods - that is what it is there for. If you can't adjust the relief down to something reasonable (less than 20 thou, preferably 10) we'll come back to that.

 

If the fretboard is relatively flat but the angle of the neck to the body is too great (ie the neck is actually folding at the body joint) then the normal repair is to remove and reset it at the correct angle. This is the old lay the straightedge on the fretboard and see where the end hits the bridge trick - if it is significantly below the level of the top of the bridge then the angle is wrong.

 

With most guitars removing the neck and shimming/shaving the joint to change the angle is relatively straightforward but does take some equipment and time - that's why it costs so much. Some kinds of neck joints (Spanish heels on classical guitars) can be "slipped" by heating them to soften the glue but this is almost never done on a dovetail. The other way to change the neck angle is to saw it off and convert to a bolt on - this is occasionally done when the glue won't come apart. (Obviously the last way is on a bolt on neck where it is simply unbolted - your Harmony is a dovetail). I don't know of any widely used method of changing the neck angle other than these (people do shave bridges but most repair people consider that very wrong).

 

OK, if the neck is seriously bowed and you can't adjust that with the t/r then the common fix would be to remove the fretboard, plane the top of the neck flat and then either replace the f/b or try to reuse the old one. Here is an article by Frank Ford doing exactly that - note that he also removes the neck from the guitar before removing the board

 

http://www.frets.com/FretsPages/Luthier/Technique/Guitar/Structural/NewFingerBoard/85hd28board.html

 

Here is the heating blanket that he uses (SPBL4)

 

http://www.lmii.com/products/tools-services/bending/heating/heating-blankets

 

Looks like a whole lot of work too me.

 

Another possibility for a badly warped board is to pull the frets and level it with a long straight sanding block, then sand the radius back in, cut the fret slots a little deeper and refret. If the neck angle isn't quite right you could probable sand a little more at the nut end to bring it down but you are working with a complex three D geometry and it would be really easy to screw up completely.

 

So, short story - if its the neck to body joint that's bad, pull the neck and reset it. If the neck is seriously bowed, pull the f/b and plane it. You might be able to find a luthier-in-training (like myself) who will do this for less than the going rate for practice

[rhino55]

Thanks for chiming in Freeman. I was hoping you would. It might not be an H165. I see some pics online of ones that have a white truss rod cover on the headstock. The one I have has a steel reinforced neck but it is not one of the ones that has an adjustable rod.

 

Thanks for the links. Here is a link to what I was talking about.

 

http://harmony.demont.net/kamikazie.php?page=033

 

I'll take some pics and post them so you can see exactly what I'm talking about.

 

Do you think a neck reset is something a novice can handle? I'm relatively handy, but have never tried something like that before.

[Freeman Keller]

I had heard of that some where and seemed to recall that they actually clamped it in a slightly back bowed state - the idea was that it would be spring back or something. In theory it should work, however I doubt that you really are bending the neck - more likely softening the glue and letting the fretboard slip a little. The only thing that I want to point out is that whether it works or not, its not a very common method. Before about 1980 no Martins had adjustable truss rods (they did have square or tee shaped rods however). It is not uncommon to plane the neck or f/b to take relief out and talented repair people use a technique called "compression fretting" to remove relief. Basically that means replacing some or all of the frets with ones with wider tangs - that force slots apart slightly and bends the neck back a hair. But I never hear of this being used.

 

Not saying it won't work - its just not a common technique and I think it would be hard to control.

 

As far as a newbee doing a neck reset - it is as a dear friend likes to say "figity-{censored}ity". There are lots of photo essays on the web. Basically you pull the 15th fret (assuming a 14 fret guitar), drill a couple of holes thru the fret slot into the neck pocket and inject steam (I use an old espresso maker). The glue softens and the neck comes off. Then you need to put some little shims in the pocket so you have some material to work with and using a chisel and sandpaper you change the sides of the pocket until the neck angle is right. Glue the neck back in place (using a glue that can be removed in the future), replace the fret, clean things up and bingo. I would say it is worth while learning if you want to do more, but for a one off it just isn't worth the hassle.

 

Last comment, a neck reset will not fix the problem that your link addresses - a neck that is bowed between the nut and 14th fret that can't be adjusted with a truss rod. Take some measurements and pics and lets discuss more.

[Terry Allan Hall]

I had heard of that some where and seemed to recall that they actually clamped it in a slightly back bowed state - the idea was that it would be spring back or something. In theory it should work, however I doubt that you really are bending the neck - more likely softening the glue and letting the fretboard slip a little. The only thing that I want to point out is that whether it works or not, its not a very common method. Before about 1980 no Martins had adjustable truss rods (they did have square or tee shaped rods however). It is not uncommon to plane the neck or f/b to take relief out and talented repair people use a technique called "compression fretting" to remove relief. Basically that means replacing some or all of the frets with ones with wider tangs - that force slots apart slightly and bends the neck back a hair. But I never hear of this being used.

 

Not saying it won't work - its just not a common technique and I think it would be hard to control.

 

As far as a newbee doing a neck reset - it is as a dear friend likes to say "figity-fuckity". There are lots of photo essays on the web. Basically you pull the 15th fret (assuming a 14 fret guitar), drill a couple of holes thru the fret slot into the neck pocket and inject steam (I use an old espresso maker). The glue softens and the neck comes off. Then you need to put some little shims in the pocket so you have some material to work with and using a chisel and sandpaper you change the sides of the pocket until the neck angle is right. Glue the neck back in place (using a glue that can be removed in the future), replace the fret, clean things up and bingo. I would say it is worth while learning if you want to do more, but for a one off it just isn't worth the hassle.

 

Last comment, a neck reset will not fix the problem that your link addresses - a neck that is bowed between the nut and 14th fret that can't be adjusted with a truss rod. Take some measurements and pics and lets discuss more.

 

I knew someone who did the "compression fretting" thing on a 50's D28, and, as I recall, it took him several tries to get it right...seems like he started with 5 or 6 frets towards the middle, strung it back up, added 1 or 2 more above and below those at a time, until he liked how it played. Lot of experimenting, and he let the neck rest for a week or so between "adaptions".

 

No idea if that's the correct way it's done, as he was pretty much making it up as he went along. Worked, though.

[Freeman Keller]

 

 

I knew someone who did the "compression fretting" thing on a 50's D28, and, as I recall, it took him several tries to get it right...seems like he started with 5 or 6 frets towards the middle, strung it back up, added 1 or 2 more above and below those at a time, until he liked how it played. Lot of experimenting, and he let the neck rest for a week or so between "adaptions".

 

No idea if that's the correct way it's done, as he was pretty much making it up as he went along. Worked, though.

 

 

There is actually a pretty good description in Dan Erlewine's book on guitar repairs - apparently Martin makes several different frets with different tang widths - the trick is choosing the right ones for the job at hand.

 

And lookie here - the real TAH has returned. Welcome back Terry!

[Terry Allan Hall]

 

 

 

There is actually a pretty good description in Dan Erlewine's book on guitar repairs - apparently Martin makes several different frets with different tang widths - the trick is choosing the right ones for the job at hand.

 

And lookie here - the real TAH has returned. Welcome back Terry!

 

Yeah, it's good to be able to use my own name again... smiley-lol

[WRGKMC]

Guitars with steel reinforced necks are not instruments designed to be repaired. They are throw away instruments sold in

mail order catalogs and designed as children's beginner instruments. They figure kids will either learn to play and upgrade

or use them as baseball bats so they don't spend much time or money on the builds.

 

They are often epoxied together and cant be steamed or heated to repair them. Look inside the body. If the glue is white its

bone or wood glue that can be removed. If its dark or yellow, don't waste your time. Chances are that harmony guitar cost $25

back when it was sold by sears of Montgomery Ward and its nothing but a wall hanger at this point.

 

If it had a truss rod then it might be worth salvaging if only to get the education in the process.

For the cost of the tools alone its cheaper to buy a real guitar though.

[Freeman Keller]

"Guitars with steel reinforced necks" include some of the finest guitar made. Every Martin prior to about 1980 had a steel reinforcement, either a square or tee shaped bar, it its neck. Adjustable truss rods appeared on Martins about 1980 - it too provides reinforcement as well as the ability to control the shape of the neck. Obviously adjustable rods appeared on many other brands far before - Gibsons date back to the 30's - again both for reinforcement as well as adjustability.

 

For that matter, epoxy does release with heat and that is one problem using it on fretboards and repairs (my source is Dan Erlewine's book of repairs). Granted, it is a bitch to get apart when used for neck joints but some people are able to do it.

 

I also think these are the best guitars to learn repair on - so much better than trying to do a neck reset on a prewar OM-28.

 

Oh, and don't forget that a 1930's Martin OM-28 cost $28 when new, a fairly princely sum during the depression.

[rhino55]

Lol at "buy a real guitar." Whatever dude...

 

Freeman, hopefully I'll be able to get some pics up soon. Between work, St Pat's gigs last weekend, and this weeks normal gig load it feels like I've had even less time than normal.

 

 

[DeepEnd]

Lol at "buy a real guitar." Whatever dude...

At the same time, beyond a certain point a guitar--or anything else--simply becomes a money pit. So far you've got an old guitar with a cracked nut and a bum neck that needs at minimum a lot of TLC. Personally I'd pass.

[riffmeister lives]

I haven't read everything in this thread, but I have two classical guitars (no reinforcement in the neck) where heat bending worked well to correct some minor neck issues. Carried out by two highly competent luthiers.

[Freeman Keller]

I haven't read everything in this thread' date=' but I have two classical guitars (no reinforcement in the neck) where heat bending worked well to correct some minor neck issues. Carried out by two highly competent luthiers.[/quote']

 

It is fairly common to heat the neck to body joint slightly on classical guitars with Spanish heel necks as a way to reset the angle - its called "slipping the neck". I'm still waiting for the pictures from Rhino to help him decide whether its a neck angle problem or too much relief, and what the best approach is.