All posts by CorkGuitars

Making ways to make music.

Neck body join. Mortice and tennon or, morbid and tedium!

After flattening and leveling the area where the mortice will go, it is cut into the neck block with this router jig.

24mm x 21mm x 74mm

The tennon is cut to match the mortice by hand with a gent saw and finally shaped with a chissel.  The tennon is cut at an angle of 1.8 degrees which is the angle of the neck body join.

The heel of the neck is shaped with a chisel and Japanese saw rasp.
Meanwhile the fret slots are cut. The fretboard was made 8.5mm thick rather than the usual 6mm to acomodate the sympathetic strings. Thus extra care and attention was needed setting up the fret slotting jig.

Tapering the frt board to match the neck.

A dab of mastik on the nuts of the truss rod stops it ratteling.

Radius the fret board to 16″

Fretboard channels for sympathetic strings.

The straight side of the channels was routed first. Then the taper was put on the fretboard and the tapering side of the channel was cut.

 The taper was put on with a block plane and sanding stick.
A plank of MDF was screwed  onto the bench to provide a straight edge and flat surface. The work was screwed onto the MDF to hold it.

Back to front

Bicycle inner tubes are used to clamp the top on.

The over hang is trimmed off with a plane , chisel, japanese saw, and sand paper

The back is glued on the same way but now the body doesn’t fit into its mold anymore so it is put in this adjustable mold 

This little shim is needed to keep the sides perpendicular in this area. 

Brace for impact!

Marking out the bracing pattern and selecting wood.

Cutting the braces from high quality quarter sawn spruce.

Found a rainbow inside! Good sign.

Housing the pieces. Notice the curve on the braces. 3mm but it should have been more I think. 

Clamp clamp clamp

Clamp clamp clamp 

Glued up an scoloped.

Shaping with a chisel

Sanding smooth 

I made a mistake here and scoloped the high part of the brace. I glued in pieces as a repair and it turned out perfect! 

rollin hills.

Mapel bridge plate glued in. It is not touching the braces.

The ends are trimmed to fit exactly up to the sides of the guitar.

The braces are housed into the kerfed lining. When it all fits the top is ready to be glued on!

1999 made in Cork mandolin!

Ow here is a tough one:

Spot anything wrong?

Yes the soundboards is smashed inwards. Looks pretty tough to fix. Especially because my hand doesn’t fit inside due to the stylish, and now annoyingly sharp, fret board end.

The inside reads:

Made in cork 


The instrument has an unusual shape and the bracing parern inside seems equally experimental. There is no x brace but rather two braces run down the length of the sound board past either side of the sound hole, under the outside of the feet of the bridge, and taper together towards the tail pice. They stop around where the crack had occured and indeed they run almost patalel to the cracks. 

This bracing pattern leaves a lot of freedom for the wood to vibrate around the bridge and I think it may be the reason it has cracked in this way. It is also the reason, I’m sure, for the reported sweet tone of the instrument. Instrument design is always a compromise between the dichotomy of strength and weakness. We want structural integrity and yet need vibrations to transmit sound. A beautiful sounding instrument that breaks reminds me of the flight of Icarus.

Anyway, philosophy asside, I have been tasked with fixing the thing! So I set about it.

Declan has a great technique for this sort of thing. I can’t push it up from the inside so I must pull it out from the outside! 

A large cleat of quarter sawn spruce will be glued in to bridge the cracked piece and sure-up the worst part of the break.

It will be pulled into place by a guitar string wound onto a guitar machine head. A hole drilled in the top of the guitar, the cleat, and a caul for the cleat, will line them all up and allow the pieces to come together by winding up the guitar string:

The cleat is shaped to meet one brace inside and to cover the other so a housing is cut out of it. The break is cleaned up to alow it to come together more easily

Long support beams hold the guitar tuner level on the sound board.

Now the g string I used snapped dramatically as I tried to tigheten it! That shows the pressure the system is under. I used an E string instead. And left it over night…

Sucsess!? The repair is still visible, as expected with such extensive damage. The edges could be sanded down and refinished but let’s string her up first and see if we’ve really succeeded…

Unfortunately when the strings came back under pressure the sound board started to bow down and it was clear that it would break again in the same way so I loosened the tension and put it back in it’s case, feeling a little dejected, but sure a solution would make itself aparent after some time…

About two weeks later I was playing a gig in The Venue, Clonakilty, with TUO Duo. Our ukulele bass caught the eye of a fellow called Steve Pawsey (www.stevepawsey com). It turned out that he was a guitar builder and we got to talking about the mandolin. He suggested that a sound post, similar to that used in violins, could solve the problem. 

I had considered the idea before, but this was the impitus I needed. Two days later the mandolin had a large mahogony sound post sitting between the back strip and the cleat I had already installed! 



Repairs IIĀ 

Here’s the guitar I made last year. I noticed a squeeking noise when a part of the back was pushed in, and sure enough a back brace has come away. It was easy enough to put glue under it with a little pallet knife and use a piece of spruce, cut to the right length, to wedge it back in place. The view inside is difficult but you can make out the wedged piece here:

I made inserts to house the brace more tightly into the kerfed lining to avoid this happening again. I’m sure the guitar sounds different after this repair. It has a brighter tone, more resonance and more projection. I also made up a label to go inside. Finally!


I wanted to compensate the bridge on my 5 string banjo. This should help keep all the note in tune up the neck. Let’s face it we need all the help we can get keeping the banjo in tune! The stepped pattern compensates for the end correction of the strings. It steps back and forward because the 5th string is the same gauge as the 1st sting. And the 4 the string is wound, making it effectively a similar gauge as the 2nd sting.

f = T/L + p(diameter)  if you like physics!

I also tuned up the head, with the strings off, and dampened it with a little rag inserted near the neck, wedges between the head and the coordinator rod.

The battlestar Galactica keeps cropping up too! I tryed one of the bridges from it for the banjo but it was too low…


This electric ESP needs the pickup wired and fitted. Also the floyd rose bridge must be set up as it has been out of action for a while. No problems here. I even wired in a phase switch in the push pull tone pot for extra tonal options! 

A rosette by any other name… Sweet.


The top of the guitar is two pieces. They are thicknesses to 3.2mm and joined on a shooting board. The nail and batton method is used to glue them.

The rosette design is made from strips of perfling. A dremmel with a special circle cutting attachment is used to route out three channels. 1.5mm 7.25mm and 1.5mm. They are 1.5 mm deep.

The perfling is glued in and clamped between a piece of MDF and perspex. A sharp scalpel and sand paper was necessary to clean up the routing. 

Job done. Off to lunch.

Put her through the drum sander the next day and finished leveling by hand with a small scraper.

It looks really great!

Some neck on ya!

Now to transform this plank of wood into a guitar neck…

While all is flat and square the router is used to channel out space for the truss rod (a metal rod which can be adjusted to counter-act the pull of the strings and keep the neck straight while playing). Two carbon fibre strips are added for extra strength, remember this guitar will have 18 strings if all goes to plan!

The half moon ends must be filled to stop any movement. The carbon fibre is epoxied in, the trust rod is held with a little mastic at either end so it can bend.

Now the head stock angle is cut with a band saw. This is where the machine heads for tuning the guitar are mounted.

Its leveled out with a plane and sanding board. Veneers of maple and rosewood are chosen and glued on top:

They’re held in place with two nails and clamped down:

Looking good. Then the taper of the neck is cut on a band saw.

Head stock design is marked out, cut on the band saw, and finished with a bobbin sander.

Now it’s looking like we might have a guitar some day!