spline

Strengthening A Repaired Banjo Neck

Glueing the heel

Glueing the broken heel on this banjo neck is the easy part. Thing is, the tensioning rod can put this glued-in section under a lot of strain so a simple glue-up’s not going to do the trick on its own.

I’ll need to help it out

Section showing how a dowel will be inserted to strengthen the repaired heel

So: Our old friend the spline. In a different form, this time.

I drilled two holes, at an angle, from the heel into the repaired section (being careful not to drill too far and out the bottom—that’d suck).

The dowel ends can be seen (the lighter ovals)

Then, I glued a couple of hardwood dowels in to the holes. The dowels protrude from the ‘good’ section to the repaired section, giving strength to help prevent that section shearing off under tension.

Back together and holding well. Time for tea. 

It's stayed in one piece under tension. Excellent.

Guitar Neck Repairs: Splines

Headstock repairs are nothing new in these parts. If you pop by the Haze blog from time to time, you'll probably have seen more than a couple over the last few years. We've also talked about the need to reinforce some broken headstocks with a 'backstrap' (a piece of wood that overlays the repair to add strength).

I like backstraps. They're an effective and discreet way to strengthen a neck repair. They can take a bit of time and effort to do properly, though, and splines are not the only game in town. There are times when an alternative is preferred. 

Splines are the prime candidates.

Spline Headstock Reinforcement

A spline is a slat of wood that's inlaid into a channel cut in the neck.

Like this:

Reinforcing a broken guitar neck repair with splines.

The idea is that the channel runs for a distance either side of the repaired crack. A slot is routed and the spline glued in. The newly inserted 'good' wood of the spline ties together the good wood on both sides of the crack.

As you might expect, the splines are carved down to match the neck and the finish touched up. Splines are not quite so inconspicuous as a well-executed overlay but they are an excellent way to bolster a neck repair that needs some reinforcement. 

And, in the right circumstances, you can even get inventive in your splines

 

Headstock Repairs - More on Reinforcement

So we've looked at a neck repair with an overlay for reinforcement. Let's have a look at the other main method of reinforcing a broken headstock: Splines. In guitar repair circles, splines are long (relatively speaking) narrow pieces of wood that are glued into corresponding channels to provide additional strength.

Failed, previous repair

Nasty glue residue on failed repair

The first repair is the important one.  

Remember these wise words. If the first one fails, it usually complicates any subsequent repair. This guitar arrived in the workshop with its headstock flapping about, held on by only some gummy bits of glue. There was a LOT of residue to clean up. Too much, really. Any glue I apply to repair this break needs to make a good contact with the wood. New glue, trying to grip a film of old glue is a recipe for a poor repair.

Even after cleaning up much of the earlier stuff, I felt some reinforcement was necessary to ensure a sound and lasting repair.  

Determining the truss-rod location with a magnet

Glueing up the peghead before splines

As it happens, the diamond-style volute on this instrument provided me with the perfect idea for reinforcing things. I can rout a channel through that and carve the spline to the same diamond shape. Nice and discreet. Splendid.

First up, I have to keep the truss-rod in mind. I don't want to accidentally rout into a hunk of metal. The magnet on the back of the neck tells me where the rod ends. I note that and get on with getting things back in one piece.  

Diamond volute to be 'splined'

Inset, rough-cut spline

You can see the diamond volute pretty clearly above. I'm not going to take the whole diamond—I'll effectively rout a channel through it and farther along the neck (past the break). 

It's an easy job to shape a piece of mahogany (the spline) to fit this channel. Then a little carving will replicate the original shape. Clean up, slap on a bit of lacquer and we should be able to avoid any more strings of gummy glue.

Spline reinforcement on guitar neck break