neck backbow

[Joe Davisson]

When I make a fingerboard, and put the frets in, it backbows even after being glued to the neck. The string tension on the guitar isn't enough to pull it out (even with the truss rod loosened). On my last effort, I made the fingerboard thinner and got away with minimal leveling and spot treatment of a few frets, but the rod is still all the way loose.

Not sure how to end up with a flat neck after fretting, how do I compensate for the pressure of the fretting that causes the backbow?

[Chad McCormack]

Hi Joe. If you fret the board first, then glue to the neck (as your post implies you do), then make sure your board GETS flat before you glue and clamp to your neck. Do that by putting a small block under each end of the fretboard and clamp down in the middle of the board. One of those quick-clamps with the rubber pad works well. You'll need to let it sit for a while, then perhaps adjust the height of the blocks you're using and trial it a bit, but you can get the FB pretty flat. Lots of folks that do this insist that it helps the fret barbs grab and seat the frets extra well, too.

[Henrique Schneiter]

Joe, are you sure the cause of backbow are the frets? In my, well, experience (a dozen necks), the backbow is caused primarily by the glue between the fretboard and the neck, if it's water-based. Of course the frets do cause a backbow if installed on the fretboard before gluing it, but honestly I can't see it backbowing the whole neck at this point you mentioned, unless you use bar frets and a compression fretting technique.

Some people obviate that problem by using epoxi to glue the fretboard. I still prefer aliphatic, but I leave the neck clamped on a flat surface for a couple days while the glue dries, then I proceed to fretting, and then to the shaping (rounding) of the neck. I have never had a backbow in the end of the process, even without string tension. I have to mention that I have only used quarter-sawn woods for the neck so far.

You also can approach the problem by using a double-action truss-rod.

So, make sure the neck and fretboard woods are properly dried, and the gluing surfaces are DEAD FLAT before gluing or fretting (it may require a lot of block sanding and not power tools). Then install a double-action rod, glue the fretboard using epoxi, proceed to fretting after the epoxi has cured, and shape the neck. You can't go wrong with that recipe.

[Peter Wilcox]

I've only done a couple of necks, using Cumpiano's method with success, using a single action rod. Glue on the fretboard, tighten the truss rod so there is a slight (1/64 to 1/32") backbow, then plane or sand it flat. That way when you loosen the truss rod you should be able to get some forward bow. Hopefully this will still be there after fretting.

[Alain Lambert]

Your fret slots might be too narrow, causing compression fretting like Henrique mentionned.
Make sure your fret saw and your fret tang match.

[Louie Atienza]

I do necks different ways... bu when I do an acoustic neck, I do what Chad recommends, which is induce a bow on the fretboard with blocks and a clamp. I learned that from a recommendation by Mario Proulx. On an electric guitar with a Fender-stye neck, I actually slot and fret the fretboard AFTER glueing to the neck, and BEFORE shaping the neck. It's a lot easier to fret a neck when the back is completely flat. The only thing is that the fretboard has to be completely prepped beforehand, but I cover the frets and fretboard with blue painter's tape and have a special cradle for holding the neck.

[Chris Richards]

I'm certain it's the glue that's causing the problem I've had exactly the same thing happen a number of times, fortunately it's pretty easy to remove a fretboard glued with tightbond or similar (with a hot knife). To be honest rosewood isn't the easiest wood to stick anyway because of the oils in it (If the board is rosewood!). But I would remove the fretboard and re-glue it with epoxy and you won't have any problem.

[Joe Davisson]

Messed around with the frets a bit more today and got it playing ok without too much buzz. Working on a couple new builds, will probably try Peter's way first, but thanks for all the great advice.