Neck bending troubles

[John McDonald]

I'm having some trouble getting the neck right on this mid-60's harmony archtop. This is one of those all birch jobs with the steel reinforced neck but no truss rod. I do know that this neck was probably never "right" in the first place, but I'd like to see what can be done. It had the typical mediumish bow in the neck causing a hump in the fingerboard where the neck meets the body. With this set-up the guitar was fine playing open cowboy chords but would start to get buzzy by the time you would get to the 5th fret or so. I assumed this was do to the hump where the body meets fingerboard. I went ahead and tried out Hideo Kamimoto's neck bending technique. I carefully and slowly heated up the neck with a heat gun, put two hardwood shims on the fingerboard (1st fret and 15th fret) under a hardwood straight board, set up clamps in the middle of the neck and let it sit overnight. To my surprise, it actually worked!! I thought I was all set until I strung it up and realized that I had a perfectly straight neck with no relief. I hoped that string tension would cause a little neck relief but it didn't. This was no good for playability either. Begrudgingly fired the heat gun up again and followed Mr. Kamimoto's directions for bending relief back into the neck. This also worked but pretty much put me back to where I started. Plays great in open position but gets fret buzzy if you venture into the middle of the neck. I'm wondering if I can just grind down the frets a little lower in the "hump" area so that there is better clearance? Or should I try to bend the neck again? I also wanted to see if anyone has a better technique for bending warped necks. This method that I have been using seems to work but is not too friendly to plastic fret markers or faux painted fingerboards. Would an iron be better than the heatgun? 

[onewent]

Compression fretting, or pull the frets and plane the board flat.  I've also pulled the board, routed two channels, and inlaid two carbon fiber rods. I made a jig to hold the neck straight while routing and expoxying the carbon fiber.  I've found it tough dressing just the frets to eliminate this kind of buzz.  The photo you see is the top view of the jig.  Attached is a photo of the neck jig from the side.  Tom

[onewent]

..forgot to mention in the earlier post, but you could always try raising the action..Tom

[Hesh Breakstone]

Does it need or could it benefit from a neck reset?

If the neck angle is workable... I'm currently not the biggest fan of heat treating in so much as I have seen necks that were heat treated revert to their former state...  Not all mind you but some seem to not take to the treatment over time... And in the case of your guitar you are attempting to get a steel rod to submit to a shape that is not it's intended shape.

The problem with not having a truss rod and having a neck with steel or other reinforcement is that if the neck is not right in it's shape and ability to go into relief it will never be right without compensating for poor shape somehow.

It could be, after inspection of course, that one way to get your guitar playing well would be to take note of how the neck looks under string tension, take notes and then pull the frets and mill/level the board into a shape that compensates for what the neck wants to do.  For example the hump at the body joint could be milled away/down, fall-away milled into the extension, and relief milled into the proper areas including more so on the bass side and less so on the treble side.  This can be accomplished by manipulating the neck with weights and/or clamps permitting whom ever is doing the work to concentrate on specific areas with the leveling beam(s).  Once the fretboard is shaped in accordance with what needs to be happening as observed under string tension frets slots would be addressed as needed so that they are all deep enough after the material removal to be properly refretted.

If the neck in it's natural and under tension state originally lacked any relief you would also want frets with tangs that fit easily into the slots so as to avoid putting the neck in back bow from fret tangs that are too tight a fit in the slots.  Gluing the frets would be advisable as well.

Again though none of this is what I would do if a neck reset is appropriate and much of the time even with a neck reset the full benefit is not realized until either the frets are dressed if that will do the trick or the guitar is refretted providing the opportunity to mill the fretboard into the desired shape in the desired places.

No offense intended so please forgive me if you are an experienced repair guy but I just wanted to add that the approach that I outlined is not recommended for anyone other than an experienced repair person.  Some special tools are required such as an absolutely flat set of varying length sanding beams, a small saw designed for cleaning out fret slots and deepening them as well, and everything required to properly refret a guitar, dress, polish, etc.

So in short what I might try if inspection indicated that this method was a prospect for you is to no longer fight what the neck wants to do in it's under tension state.  Instead reshape the fret board to the shape required to have relief where beneficial, eliminate the body hump, maybe mill in some fall-away of the extension (since we are at this anyway) and the refret should eliminate any and all buzzing once the fretboard is shaped as needed.

[John McDonald]

Thank you guys so much for the detailed replies. Some really great info to file away and revisit. I guess I was hoping to avoid pulling the frets and milling the fingerboard because the fingerboard is maple stained to look like dark rosewood and has a nice original look to it.

I have sanded the hump out of a couple of similar Harmony's with good result, but wasnt happy with the look of the new stain I had to apply afterword. I'm a newbie with stains (and everything else) and maple doesn't seem to want to take a dark stain evenly for me. Its because of this that I was trying to experiment with Mr. Kamimoto's method.

I should also mention that I have a number of these old 40's to 60's Harmony/Kay/Silvertones that are in need of neck resets and neck warp correction. I pick them up for about $50 and fix them up utilizing the info I get from this site and repair books. So far so good. My neck resets are getting better and better and my fretwork and setups are as well. I then sell them on local craigslist for a little more than I bought them and give that money to stewmac and lmi for better tools.

So...I was hoping to develop a good method of heat bending the necks so that I didn't have to worry about sanding off stained fingerboards, painted fret markers, mother of toilet seat fretboards, etc.

I found some info on the web on successful heat repairs using the lmi neck bending heater, but they stopped carrying it a while back. The only other device like it is made by Aria and sells for a ridiculous $900!!!

I'm interested in what Hesh wrote about the heat bent necks eventually reverting back to the bent state.

And Tom, I do have a little room to raise the action before it gets too high. I will give that a go. Thanks again.

[Ned Knepp]

When I rebuilt my Kay with the "steel reinforced" neck, I found that the steel bar was decidedly NOT flat. I also found that the bar had large burs on the ends that were pressing in to the fingerboard and were probably responsible for forcing the fret board free of the neck. I had to bend the bar flat and file the ends before I replaced it.  Once I got the bar glued back into the neck, I used sandpaper fastened to plate glass to flatten the neck before I reinstalled the original fingerboard. Once I got the neck reset, the relief, under tension, was just right.

[John McDonald]

Thanks Ned. This method seems like it would work well for me. What was your method of heating the fingerboard for removal? I had a lot of trouble getting the neck hot enough to bend with the heat gun because the stain on the fingerboard wanted to bubble and the faux shell inlay dots wanted to melt. 

[Hesh Breakstone]

John buddy don't get me wrong heat treating has worked well on likely thousands of guitars but in my own experience it's hit and miss and does not always work over time.  A guitar just came back into our shop that had been heat treated approx. 3 months ago which seemed to do the trick at that time....  Yesterday it was back in full back bow and in need of a different solution.... 

A couple of suggestions that may be helpful regardless of how you proceed or just something else to file away.

Heat guns are great for localized and highly directional application of heat.  Problem is as you already mentioned that things such as fretboards are large areas and very difficult to get hot enough in a large enough area at one time (while also not getting too hot and bubbling finish, smoking fret markers, etc...).  For localized application of heat where a gun is a good way to proceed we use the Makitia heat gun with a variable temp setting.  The gun is set to a mark on the dial that we put on it that we know from testing is below the threshold that will bubble the finishes that we encounter in Lutherie.  You still have to be vigilant however...

For large areas a heat lamp, 250 watt is what we are currently using.  You will also need something to measure surface temps so as to position the lamp close or far enough from the work so as to also not bubble finish.  It's also a fire risk so without intending to be a nag here.... please be safe and never, never, never leave anything that is having heat applied over time unattended AND have a charged fire extinguisher at hand as well.

There is a dye available to blacken fretboards that in my experience is pretty good stuff.  I can't remember if it came from Stew-Mac or LMI but the brand is Fiebing's Oil Dye.  Although this may not be the color that you are looking for (it's very black) it may be better than what you have experienced with stain to date.

Another thing that may be helpful - when wishing to avoid torching or damaging the fret position markers the highly reflective tape used in duct work, not duct tape but the very shiny stuff works great.  Cut a piece just larger than the inlay or paint that you wish to protect and this tape will work very well for you.  I also use it to take up the gaps when using a reflective shield and using heat to remove parts.  Please remember too that many tapes and adhesives become less finish friendly the longer the tape is in place.  I didn't start a fret dress yesterday specifically because I did not have enough time in the day to complete the job and remove the tape so it was not on the guitar over night.  Tape is our friend so long as we don't over stay our welcome... ;)

Congrats on the successful neck resets too!  Neck resets can be a long walk on a short pier, so-to-speak, when things go wrong.  In my limited experience with some Harmony guitars at least they had a proper dovetail joint making the neck reset AND the learning component from resetting a dovetail available to us.  Many imports today are not even worth the effort for the learning experience because of the use of non-serviceable "doweled" neck joints.  They can still be reset if you can make sense of the economics mind you but the value received by learning to set and reset a dovetail is sadly not available on some of these guitars.

[Mark Pollock]

Something I want to add to my heat lamp is a dead man switch - it's so easy to lose focus over 20 minutes and walk off. I figure if I have that, at least when I walk off the lamp will shut off.

[Hesh Breakstone]

Great idea Mark, thanks!

[John McDonald]

Thanks so much Hesh. This is all going in the notebook.

[Ned Knepp]

John, I got lucky with the Kay, The fretboard was already loose  when I got it. The guitar came to me in three parts, the neck, the body and a bag of hardware. The dove tail was a mess but the fretboard came off fairly clean.

As a hobbist, I don't remove a lot of fingerboards so I don't have a large heat source rigged for this purpose. What I use is a small flame for heat,  a couple of very thin pallet knives and patience. The method I use takes time and patience, LOTS of patience. If you rush it, there is a very good chance that you will submarine into the neck, following the grain or you may break the fret board or even both. I also use a bit of water dropped into the gap, once I get started. As I get the fretboard separated, I  keep a couple of putty knives between neck and fretboard. In other words, I don't lever the fretboard off of the neck. I slowly work it off with a hot knife. If you can figure out which way the grain run out is oriented before you start you can help avoid the submarine problem by starting at the end that won't tend to turn into the grain of the neck. IF you should find that you are moving into the neck wood, and, btw, remember to watch BOTH sides of the fretboard/neck for this, backup and find another place to start you may find that you can back the knife out and come in from the opposite side of the neck and carefully continue then move backward to separate the fingerboard where you submarined. 

 

One thing I forgot to mention at the first, I use a razor blade to cut the finish at the joint line before I start with the hot knife. The leading edge of my pallet knife is round instead of square and it is thinnest at the edge.It's not really sharpened but it's thin enough right at the edge that you could easily cut your arm if you slashed at it.   When I heat it, I only heat about an inch at the end of the blade, not the whole length of it. I use a sort of cutting motion once I get started into the joint. In this manner I have better control of what I'm applying the heat. I keep saying it but I really can't emphasize enough that rushing will not return a good result. Once you get it right you can feel the knife melting through the glue a little bit at a time. 

 

I should warn you that these necks are pretty soft. There's a fairly good chance that, whatever method  you use, you are going to have to fix some tear-out before you can actually start to work flattening your neck. You should take care  to keep any bits and glue them back into place right away. You really don't want to remove very much from your neck as you flatten it or you will find that the width of the fingerboard will also need to be narrowed. It can happen pretty quickly if you don't pay attention because of the curvature of the neck shape. Because of this, it's important that you don't fall into the trap of thinking you can just sand out any divots that may develop. I probably could have flatten mine just fine on my belt sander but I chose to do it on the plate glass so I could better control what I was removing and where. Besides, everything you take off will make the neck just a bit weaker.

I got my steel bar out of the neck but simply using a laundry iron and applying heat by "Ironing"  the neck, NOT LONG, the steel will conduct heat just fine and there is no reason to burn the wood on the face of the neck. I think there's a pretty good chance that you may not even have to do this, there wasn't much glue holding mine in place anyway. 

[John McDonald]

Thanks for the walkthrough Ned. If I wind up going this route on this one, I will heed your warning when it comes to taking it slow.

You mention using a small flame for heat. Does that mean using a small alcohol burning lamp? If so, do you or anybody else have any recommendations on where to pick one up and what kind of fuel is best to use. I recall seeing pictures of FF using one of these on frets.com to heat pallet knives for seam separation. I always imagine a metal tool turning black with soot if put under a flame.