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Some recent posts regarding epoxy to glue fretboards has me leaning towards HHG.
I have been using HHG for a while now to glue bridges with excellent results.
Thanks Hesh and Woodie for the guidance on that. (I used to use fish glue, and had some failures)

Regarding gluing fretboards, my question is:
Do you need to apply the HHG on both the neck and the fretboard before assembly?
Noting of course the limited open time I am a tiny bit concerned about time to apply to both surfaces.
Of course I would be completely ready for assembly (and a dry run) before applying the glue, so assembly would be quick.

Any thoughts?
Thanks!
Rob

I cover the truss rod channel with masking tape so no glue gets in there and there is a bit of a border around it for squeeze out. Then I place my fretboard on a hot iron and use a heat gun to heat up the neck which is positioned in a vice with all the clamps and cauls ready to go. Then I apply a nice coating of hide glue to the entire neck, rip off the tape, then do a rub joint with the FB that is fresh off the iron and nice and hot. Then I clamp everything shut.

I like to use the Bitterroot Martin style truss rods and make sure to not glue them in so that I can remove them as needed. So far this method has worked out well for me.

Robbie--

A few thoughts for you:

1. It is not a complete deal-breaker if you only put glue on one of the surfaces, but it is probably a good idea to be liberal with the glue if you only coat one of them. I personally put glue on just the neck, since it is facing up, and I put plenty on there. I've never had a problem.

2. Heating the parts with a heat gun (low setting) right before you apply the glue and put the parts together is a great way to avoid the glue gelling too early. Using more glue than a thin line, and letting the extra squeeze out, is also a good way to keep the heat in there.

3. Using location pins is a good idea. You don't want to be fiddle-farting around with where the parts go while the glue is cooling on you.

4. If you are worried about glue getting into the truss rod slot, one thing I have done on occasion is to make the slot just a smidge deeper than the height of the rod and glue a spline on top. Very little glue is needed for gluing in the spline, and it can be as thin as a piece of veneer. Then you plane it down, and you have a perfectly flat, 100% wooden surface for gluing on the fingerboard. Or, using a wrapped rod is probably good enough protection. I tend to not worry about this too much, and it all works out fine.

5. You should probably include in the clamping sandwich something that will stay straight, like a level, and leave it clamped until all the extra water is gone. The neck will move a bit from the water in the glue, and it is good to try to minimize that effect.

I use HHG glue for literally everything meant to hold the guitar together. This is not one of the harder jobs to glue up with HHG. If you have worked out where the parts go with locating pins, you will be fine.

I heat the neck and fingerboard, spread water on the outer surface of the fingerboard to counteract cupping, spread glue fairly thin on the neck and fingerboard, and reheat after the clamps are on.

Glue on one surface should be fine if you're working fast, but my glue is gelled by the time I get pressure on it so it's better to have both surfaces wetted in advance rather than counting on the reheated glue to wet the other.

I use HHG for fretboards most of the time. I use locating pins and a thick, very stiff caul on both repairs and new builds. The caul focuses pressure at the edges of the board - I find the amount of moisture involved can cause the edges to curl a tiny amount and lead to a wider glue line if the caul isn’t shaped in this way. Even a radius caul matched perfectly to the fretboard surface seems inferior to this caul. I was also taught to dampen the upper face of the fretboard but I have forgotten on occasion and notice no difference…

I heat the fretboard prior to applying glue and work in a warm room. I find I have no problems getting the clamps on in time.




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Not too high-jack thanks Robbie for the reports of more fish glue failures on bridges. By my mental count you are number 13 who has reported what we reported that it's poor choice for steel string bridges especially if higher RH is in the picture.

One thing to note about the photo Josh posted above is that he is gluing on a fretboard as part of a repair, so the fretboard is laterally arched and has frets already, and the neck is attached to the body. The job is a lot easier with a new build if you glue the fretboard onto the neck before it is attached to the body, and you postpone the arching and fretting until after the fretboard is glued on the neck and the neck is attached to the body. This allows you to use flat cauls and something very rigid to keep the neck straight while the glue completely dries. And as Hesh will tell you, this sets you up for doing a much better fret installation, because the flattening and arching of the fretboard is done after the water in the glue has had its way with the neck.

Thanks Josh, I am going to build a similar caul as what you have posted.
Don, my workflow differs slightly to what you have recommended.
As suggested, I always install the unfretted fretboard on the neck before installing on the guitar for the reasons you mention.
The neck is still square, with the headplate installed and profiled, and the initial taper on the back side cut using the Safe-T-Planer.
What differs is that after I cut the fret slots and install the position markers, I arch the fretboard with the appropriate radius block.
This allows me to precisely mark, drill and install the side dots.
After installation, I do a final level sand with the radius block, (dialing in a bit of fall-away per Hesh) re-cut the fret slots, then install the frets.
This time, I am going to use HHG, my fancy new caul, and ensure everything is nice and warm - not like the temps outside right now, -27 C with the wind chill....!

...if you let it dry for a day or two. The first time I did a non-radiused fingerboard, I flattened it too soon and it went slightly concave (as it remains to this day, since it doesn't actually cause any problems). Probably did the same thing on radiused ones before that but just couldn't tell.


Warm room is the key. I do all my glue work in winter when the humidity low, and I have the coldest room in the house. Glue usually gels on contact unless I preheat things, and even then I only get 10 or 20 seconds of open time.

Not surprisingly, I did my last one different. I roughed the radius first. Then I cut the slots, board still square not tapered. Then drill locating holes to get the placement. Then glue and clamp. That's the easiest part of the whole job!
Then sand the radius smooth and pond in frets going back and forth. The frets are all flat. The board is very flexible with the slots in. Maybe it.stays flatter.
It is a bolt.on neck.

_________________
Why be normal?

Rob,

Just a couple of thoughts:

Why not use Old Brown Glue (or equivelant)? It's designed to have a longer open time (by the addition of some urea) and will hold a fretoard on just fine as there is no lateral stress on the FB.

To pre-warm the surfaces, I just paint on water from the glue pot right before I apply the glue and the FB. Since hhg cures by evaporation and heat loss, this helps with an even longer open time. After 24 hours I flatten/radius the FB, so any miniscule warpage is taken care of. Seems to work for me.

Steve

I agree it is a little easier on a new build. My main message I guess is, don’t be afraid of HHG for fretboards! It is totally viable even with weird shaped fretboards, necks already attached where you are gluing the extension simultaneously and so on. I even used higher gram strength (270g) HHG on the one pictured, which has a shorter open time than the 192g I would normally use but had run out of.

Even on a new build with an uncarved neck and unradiused board I prefer a caul like this which bears on the edges of the board. But I’ve used all kinds of things as cauls in the past, including a steel beams and had success.

Thanks for all of your tips and guidance!
I was ready today to glue up a fretboard so I build a caul similar to Josh's.
By warming everything up prior to glue-up the actual glue-up was a breeze.
The 192 gram strength glue flowed on nicely on both surfaces and I got some nice liquid squeeze out when clamping.
And cleanup is so much easier than other glues.
This is what I am using from now on...sold!

I have read in other posts that some of you use a squeeze bottle to speed up the process.
Do you squeeze it out then use a brush it even it out?

Here is a picture - I am building 2 x 6-string bass guitars based roughly on the "Fender 6" design from the 60's.

For bridges and fretboards I brush it straight out of a jar floating in my glue pot. The brush I use is around 3/4” wide and holds a lot of glue. Unlike other adhesives, where I put some thought into how much glue I’m spreading on a surface, with HHG I slap it on thick and just tighten the clamps. I love how the rubbery, half-cured squeezeout peels off cleanly, and a wipe with warm water deals with anything left behind. Truly a time saver and one of the great joys of lutherie.


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I cook fresh glue in a MusiCaravan double boiler for each job. So, no squeeze bottles for me; only brushes.

We had two Hold-Heet pots, one of which held an eight ounce canning jar of glue for brush work and the other a two ounce poly squeeze bottle for brace work. Both pots had shop-made 1/2" UHMWPE covers with cutouts sizes to the the appropriate glue container and suspend it in the water bath. A Rival hot pot of the sort favored by impoverished college students provided cleanup water and a place to rinse brushes (1" Zen Z93WO oval wash brushes by Royal and Langnickel sourced from Michael's replaced Japanese glue brushes made from bark... seriously... from bark).

One thing to mention... we ended up repairing our aluminum Hold-Heet liners with aluminum welding rods as electrolytic attack occurred, and the aluminum developed pitting that initiated leaks. These liners are cheaply repaired at local welding shops as well with gas or TIG as well if your own shop lacks OA gas or TIG welding capability.

On pre-warming... we had Salton brand buffet warming plates that were sized to handle neck and fretboards... still commonly found in 'antique' stores, Craig's List, and eBay. These warmers will sometimes have a 'hot spot' feature that will do a nice job of holding a ceramic or metal container at a higher temperature.... this was a nice feature when we were using heated aluminum cauls to reshape bridge patches. The alternative to those commercial aluminum cauls from Mr. T.J. Thompson's enterprise ended up being shopmade 5/8" thick aluminum cauls drilled for cartridge-style heaters and a thermo-couple tied to a PID-style controller similar to those used to control silicone bending blankets.

_________________
For the times they are a changin'

- Bob Dylan

"we had Salton brand buffet warming plates that were sized to handle neck and fretboards"
Inconceivable!

I made a pen and ink change in the original post with my seasonally appropriate, very new, very lovely Sailor Pro Gear Slim 'Christmas Pudding' fountain pen, filled with Elf Green Diamine ink (just in case the Greenridge krewe ever visits, - thanks again, gentlemen! You did not have to...but glad you did)... but apparently it did not take...

How about '...that were apparently perfectly sized to...'?

This is what happens when I have students... end of the semester cannot come soon enough.

Oh, and by the way, your Vizzini was spot-on!

_________________
For the times they are a changin'

- Bob Dylan

Hahaaaa!
Pretty cool nonetheless, to have that kind of gear on hand to assist in the gluing process.
In my little shop, the heat gun and space heater seemed to do the trick.
I glued up the second neck today, and it went even better than the first, using a larger brush as you suggested.
Thanks!
Rob