Gluing Neck Onto Guild Acoustic Guitar

Getting close to gluing the neck on.  I need to make one more check, and I need to get the dovetail to fit well.

Aside from the set (pitch, or angle) of the neck being correct, the neck also needs to be centered correctly.  It's easy for it to get off-centered with all the hacking away that's been done to the heel.

This is the quick overview.  I put tape at the nut, at the fret where the neck joins the body (in this case, the 14th), and the bridge.  I measured the center at each part and made a mark.

Then I used a straightedge to see if all the marks lined up.  If they don't, you'll need to adjust one side or the other of the heel (i.e., take a bit of material off) to get it to align.

In my case, I was off by a small margin initially - maybe 1.5mm.  I just 'tilted' the neck (side-to-side)  to line it up and from that, figured out where material needed to come off.

If you don't do this, there is a high probability that the outer strings won't lie correctly on the fingerboard - one side will be too close to the edge or may even fall off.

The neck now has the correct pitch, and it's centered.  Since I've removed material from the heel, the fit of the dovetail is a little loose.  So I want to put shims into the joint to make it tight.

I have a nice block of mahogany that I use for braces, patches and shims.  I cut a sliver and used double-sided tape to hold it onto a piece of scrap.  Then I sanded it to thickness on the belt sander.

How did I know the thickness to shoot for?  I had used some paper card stock in the neck joint as a test to get an approximate thickness.  Then I measured the thickness of my paper shims - .018 of an inch.  With that thickness of shim, the neck didn't quite sit all the way down into the joint.  Which is ok.

I wound up sanding the 'rough' wood shim down to about .022 or so.   Then I cut the piece into two shims and glued them onto the dovetail.  You'll see the shim isn't the full length of the mail dovetail - we really want to tighten up the bottom of the joint.

Mahogany is really nice to work with.  I love it.  It works easily, it's strong, it looks good, and it smells great.  What more could you ask for?

Now the shims need to be trimmed for a tight fit.

I stick carbon paper into the joint and then push the neck down.  This is a bit tedious - it took at about 15 or more fittings like this to get it accurate.

I used long strips of carbon paper held onto the guitar with drafting tape.  You're seeing top side here - the strips bend down into the joint.

The carbon paper makes a mark on the shim (see the picture).  Then we can shave that section down.   I use a small scraper to do this.  I just scrape off the darkened part - just tiny bits of material are removed.

After a number of rounds, the neck will fit all the way down into the dovetail and be tight.

I decided since I have so many neck sets to do, I should make a proper caul for the fingerboard extension.  It turned out a little wonky, but still functional.

I marked the frets onto a block of wood, then chiseled out grooves.  The block is also radiused a bit to fit closely to the curve of the fingerboard.

Now, armed with a selection of cauls and clamps, I can glue the neck back on.

I'm finding that making custom jigs and cauls is a lot of fun.  At first I wanted to rush to get them done, but now I find myself trying to make them look decent.

I used hot hide glue to put it together.  No pictures of the process - sorry, you have to work quickly!

Here it is clamped up and preparing to dry overnight.  Note the caul inside the body at the top of the soundhole.  Guilds have a fairly large brace there, so I cooked up a caul with a groove to fit over it.  I'll reuse the caul on the two other Guilds I'll be working on as well.