hot wire foam cutter for releasing a fingerboard

[Bob Hammond]

Hello,

I just removed a fretboard that I'd glued a few days ago.

I used the hot caul & putty knife technique, but halfway through, I thought of using a hot wire that is used for cutting Styrofoam.

Has anyone done that yet?

[Eric Baack]

the hot wire is not nearly as strong as a hot putty knife and will probably break easily if you have one thin enough to actually get between the board and the neck. It can also get hot enough to burn the wood if you aren't careful.

I think a hot knife of some type wouldn't be too hard to do but you may need a very stout power supply and there could be a significant electrocution risk.... But hey, it would be interesting.

[Bob Hammond]

I think that there is a way to do it, and do it safely. I'll think about it.

What is needed, is a hot leading edge (the wire) followed by a non-conductive, slippery blade that prevents the glue from re-fusing- congealing. The hot wire would not be used to mechanically pry the fingerboard away from the neck -- its purpose is to liquify the glue -- and then the following blade separates and prevents re-adhesion. Probably, paper could be used to create an easily splittable joint if a plastic blade was not available. The electrical heating power could be delivered at a reasonably safe low voltage, probably about 6-12 volts DC.

About the removal today, I had used hot hide glue on the fingerboard, which did require supplying moisture at a moderate temperature (below 100C). Most epoxies release at a somewhat higher temperature, but not too much hotter. I was concerned that the moisture would warp the fingerboard or neck, but afterwards, I realized that the water was absorbed mostly by the hide glue, and not by the wood. After a bit of scrubbing and scraping, the wood of the fingerboard (grenadillo) and neck (vertical-grained maple with a CF/SS reinforcement) didn't seem to be seriously affected. But tomorrow things may look different.

[Barry Daniels]

Many years ago in my stupid youth I took someone's advice for removing a fretboard with a wire strung tightly in a frame. You were supposed to saw it back and forth and the wire would get hot as it removed the fretboard. It sort of worked but it left a very rough surface on the fretboard and especially the edge of the neck where it chewed various grooves on the show edge. Total disaster in my opinion.

Now I use a putty knife and an electric blanket laid on top of the fretboard.

[Bob Hammond]

I think that the energy of frustration that was applied, was much greater than the energy of friction that was delivered.

[JC Whitney]

I haven't used a hot wire for fretboard removal, but I did put a lot of hours in a few decades ago building architectural models out of foam. Horrendous fumes...
I'd second the concern about keeping the wire tracking true. In my experience even easy to melt foam would often distort a well tensioned wire and send it off track. (Side note: I eventually discovered that old unwound guitar strings were a nice cheap alternative to the manufacturer's cutting wire.) With that said, I just googled "industrial foam hot knife" and there's quite a few offerings out there with nice flat fairly thin looking blades. Perhaps one of these trailed by a flat pallet knife to do the work of keeping things apart once separated?

[Barry Daniels]

I think that the energy of frustration that was applied, was much greater than the energy of friction that was delivered.

You can say that again! Half way through the job I was swearing "never again".

[Michael Lewis]

We are ever in pursuit of better and easier ways of doing things, and removing fingerboards is one. By preventing damage in the process the completed project becomes easier and less tome consuming. Some fingerboards come off without much difficulty but some do not come off well at all. I recall a Guild fingerboard that was particularly problematic, and had to be replaced because it came off in pieces. Some others glued with hot hide glue can take a bit of time but usually come off very cleanly with the use of alcohol. Heat generally does help, especially for epoxy and aliphatic resin glues.

[Todd Stock]

I've hot wired foam for aircraft wings, and even with pretty low density stuff, there's a lot of drag...trying to do that through Titebond would be interesting. Also going to be a challenge over the body, where that wire is going to have to stay clear of the finish.

[Bob Hammond]

Michael, thanks, that's interesting information about the use of alcohol to remove hide glue. Over what temperature range does it work best? Hmm, if an instrument has a shellac/french polish finish, then the use of alcohol might be risky.

[David King]

I've heard the alcohol trick and tired it but it never worked for me. How about tying a cinderblock to the fingerboard and throwing that cinderblock out of a high window while you sit in a chair holding the guitar facing the window?

[Michael Lewis]

It is probably best to heat the fingerboard to help drive off any moisture content before starting with the alcohol. The alcohol further dries the hide glue and breaks down some of the molecular bonds, so it fractures. That is what you want to hear as the joint separates, the pop and crack of the glue letting go, NOT wood splintering.

Yes, alcohol is the solvent for spirit varnishes, so much care is advised.

[Bob Hammond]

Here's another chapter:

I was dissatisfied with the HHG re-gluing of the fingerboard, because the fingerboard had crept a little bit underneath the clamping caul.

So this time I laid a sidebending blanket on a board, plugged it into the HF router speed control, and slipped an electronic thermometer probe under it to monitor the temperature and keep it around 300-320F. Then I laid the spring steel bending slat on the blanket, and then a sheet of baking parchment paper on the slat. I then laid the neck with the fretboard down so that the entire length was heated.

This time, I used an Incra 6" x 3" perforated layout rule instead of a putty knife. It is made from stainless steel and is thin (0.008"). It worked well for separating the fingerboard from the neck. I removed the blobs of glue from the wooden surfaces and then spritzed them with water, and laid them on the parchment paper to heat them again. When the glue film became warm and tacky, then I quickly placed the fingerboard with a tiny bit of rubbing, and then carefully clamped it again without the caul. This time it worked.

Notes: The baking parchment paper has a siliconized surface and the paper is resistant to 450F. It did not seem to contaminate the wood. The Incra layout rule was not damaged -- I just soaked it a few minutes in hot water and then the HHG came away cleanly.