Sunday, October 21, 2012

Making the bridge...

I spent the morning making the bridge. You can buy stock Martin style bridges ready made, but this is one area where a luthier likes to show some artistic expression. Mine are oval in shape. I start with a CNC produced template which acts as a guide for the robosander (pictured at left) on a drill press to sand down to the exact shape of the template.

The next jig profiles the top of bridge. It mounts on dowel pins in the bridge holes. First I rough cut it on the bandsaw, then back to the robosander.

One last jig has a subtle concave curve in it to match the 25' radius of the top. This ensures that the bottom of the bridge fits naturally against the top without having to force those wings down.

Finished product, and very tight fit onto the top. I'll round over those edges to make it more refined.

First look at how the body will look with bridge in place.

Thursday, October 18, 2012

Binding finished, initial look...

Here are some shots after initial sanding with all the bindings in place.





Binding the top...

Got the binding and purfling done on the top today. To the left is a test cut (under the fretboard) for fit. More pictures below.

Binding and purfling ledges.


Dry fit with tape.

Ready for gluing.

Wednesday, October 17, 2012

Binding the back...

My extra bearings for the binding cutter router bit came in from LMI today, so I set about cutting the binding ledges for the back of the guitar.  There are about 20 different bearings in the set and I only had 10 of them which were fine for the last build, but all bindings vary and this time I needed to complete the set to get the right depth. The bindings are measuring exactly .010" thick, so I routed a .090" ledge for them, then cut an addition .030" for the BWB purling. Yes, I'm measuring in thousandths of an inch! See picture captions below for more details.

Setting the depth of the binding ledge cut.

Here's the binding ledge cut, 0.090" x 0.25"

Didn't get pictures of the purfling ledge as well, but here is all the bindings and purfling copiously taped in place. Longer tape = places where the binding needed more "persuasion".

Close up showing the binding and BWB purling. This will be superglued in place!

Side fit looking good too. Time to wick in the glue.

Tuesday, October 16, 2012

The match test....

Guitar lore says that a good soundbox can put out a match when tapped on the lower bout. Let's see how we do on the match test....


Friday, October 12, 2012

Tail graft...

Time to start binding this instrument. First up is the tail graft, which covers the area where the sides meet at the tail block. They're just a rough seam now, so we cut in a nice tapered piece which allows us to get it very tight. I'm using curly Koa to match the bindings. See below for pictures of the process.

We cut it the old fashioned way..., using the graft as a starting guide.

Once the lines are defined, we cut down to the tail block.

Looking good...

Removing the ends of the sides... CAREFULLY.

Test fit is perfect!

Here it is glued in, and wetted so you can see the contrast and the curl.


Thursday, October 11, 2012

Fitting the neck...

Now that everything is flush, I can fit the neck. I need to reveal the mortise in the head block which has been covered up by the sides and the top. A simple flush trim bit in that same trim router does the job, and since it's following a pre-existing mortise, it's tough to mess up.


Second cut on the top


 

Trimming the top and bottom...

Now that the body is together, its time to trim the top and bottom plates to be flush with the sides. This can be tricky, as they aren't really flat, parallel, or perpendicular to the sides. So I have this little jig/machine to the left, which is just a home built copy of the LMII binding machine. It holds my trim router vertical and parallel to the sides, and allows it to ride up and down on the "linear bearings" (full extension drawer slides!) to follow the profile of the plate. The carriage allows me to level the body relative to the router. But more importantly, it gives me good control/handling of the body so I can do a "climb cut" on the router and avoid tearing out any wood, which is a nasty habit the router has, especially on soft spruce like the top.

The top all trimmed


 

Wednesday, October 10, 2012

Body assembly finished!

Got the back installed today, and that makes the body complete and ready for binding/trim. We got our first rain today and the humidity was at 86%, so I had to wait until 3:30 before it dropped to 52%. Why is that important? The guitar is made of wood, and wood reacts to changes in relative humidity. It will expand and contract a little. So what we want is a body that is assembled right in the middle of the range of humidity, that way we have enough room to go to either end without problems. Let's say we assembled it at 86%, then took it to Denver which is typically 5%. The shrinkage could be enough to cause cracks. In Denver, I used to run a humidifier for 2 days in a small space just to get the number close to 50%.

Side bracing added for strength and to stop any cracks if it's dropped.



Tuesday, October 9, 2012

Back kerfing...

Once again, kerfing fitted and glued for the back attachment. Tomorrow I'll glue the back on and we'll have a soundbox.


Fitting the back

The back of the guitar actually tapers about 3/4" from the bottom to the neck joint. So now I have to carefully plane the sides so that the top intersects naturally. This is one of the hardest parts, since the back has more curve, it's not a straight line. As the sides curve inward to the waist, they must get higher to meet the higher part of the back arch, then back down again at the upper bouts. This one came out perfect, and back is fitting nicely.

Attaching the soundboard...

Got the soundboard attached today. Here's front and back pics and some details.
The finished soundboard gets signed and dated. I also sign it with a latin saying, "Vita Breva Ars Longa" - Life is short, art is forever
This is what we want, a nice tight fit on the inside of the kerfing and also in the brace pockets.

Here's the underside

The glue-up, lots of clamps!



Fitting the soundboard to the sides...

With the kerning in place, I just needed to sand them at a slight bevel and then carve out pockets for the braces to sit in. Then I checked the fit to make sure everything was snug and fitting well with out too much force.

Checking the fit from the underside.