Making a classical or steel string guitar bridge is a study in design.
The bridge will directly affect the quality of sound of your guitar
so I highly recommend that you carefully study the concept of the guitar bridge
and its direct relationship to sound quality and overall playability before attempting to make one.
In this video I will show how I make my classical guitar bridges.
If you have my classical guitar building instructional DVD available from LMI,
you will find a downloadable PDF file on it with my bridge design.
To start with you will need a bridge blank.
For my classical guitars I use either Brazilian or Indian Rosewood.
I would not use ebony as I consider it a tone inhibiter for a classical guitar.
I square one edge of the blank.
Here I am using a jointer but the length of the bridge blank is borderline for using in a jointer.
This can be a dangerous step so if you feel more comfortable, a handplane can also be used.
I then use a table saw to cut the bridge to the width I use,
which is between 28 and 30mm. or 1.1 inch and 1.18 inch.
Next, I cut the length of the bridge to 186mm or 7.32 inches.
The final thickness of my bridge is between 8 and 11mm or .31 and .43 of an inch,
depending on the guitar model I am building.
Fortunately the bridge blanks that come in the LMI classical guitar kits
are around 12mm or .47 of an inch thick.
I began making the bridge at this measurement
and will thickness to my final measurement later in the bridge making process.
You will notice that there is a rough cut bridge in the picture.
I use this as a template when making a new bridge.
It makes it easier to set up the saw.
I start by making the two cross cuts that will define the width of the tie block.
They are made at about 5mm deep or about .19 of an inch.
The saw blade width is 2mm. or .078 of an inch.
I can use my bridge blank template to easily set the depth for this cut.
A spacer block placed against the fence helps me set the correct location for the cut.
The cut is made using a miter gauge that is square to the blade.
I then turn the bridge around and once again use the spacer block to set the location of the cut.
Always remove the spacer block before making the cut.
The next cut I am going to make is for the saddle slot.
Once again I use my template to set the depth to 4mm or .157 of an inch.
I set the saw fence against the bridge so the cut is in the correct location.
The cut is easily made using push sticks.
Next I will make a cut that will begin removing material in front of the tie block
where the strings exit the tie block and travel up to the saddle.
The cut is also made at 4mm deep or .157ths.
By now you are beginning to realize how useful a template can be when setting up these cuts,
so make an extra bridge blank when making your first one.
After setting the saw blade height and the correct fence location I make the cut.
I have made the saddle slot cut and a cut just in front of the tie block.
I am now going to make the first of two cuts for the two small bone pieces on both edges of the tie block.
Once again my template helps me set the fence location and the depth of cut
which in the case is 2mm or .078ths .
After the cut is made I set up for the second cut and go ahead and make it as well.
Next I use a band saw to pre radius the wings of the bridge.
This saves me some time later.
Slightly rotate the bridge and free hand it into the blade.
Be careful to not let the blade touch the end of the tie block.
The rough bridge blank should look like this.
Now I will thickness the bridge blank.
This requires a bit of an explanation.
On my classical bridges the bass side is about one half of a millimeter
or .019 taller than the treble side.
This is to compensate for the sloping of the fretboard on the bass side.
Brazilian luthier Antonio Tessarin came up with a jig that puts the radius
of the top on the bottom of the bridge as well as this graduated taper I just mentioned.
He graciously allowed me to copy it.
Notice how this jig has a radius on the back side that matches my top radius.
It is also thinner on the treble side than the bass side.
I place the bridge blank in it face down and then push it through my thickness sander.
As the bridge goes through the sander
the radius and taper are sanded into the bottom of the bridge blank.
A few passes is all it takes.
You could also use a scraper or radius block to do this.
The bridge is beginning to take shape now.
The next step is to round over the wings and I use a file to do this.
Notice how my file has a smooth edge on one side.
This allows me to get right up next to the tie block without filing it.
It is important to keep the same thickness and radius on the wings.
A scraper will then remove any marks left by the file.
Now I can attach the two small pieces of bone to the tie block.
If necessary, use a file to mark sure the slot is square.
I use thick viscosity CA glue to glue in the bone.
It helps if you hold the bone in place with something as the glue dries.
The excess on the ends can then be cut off and filed flush with the tie block.
Notice how my file is smooth on the edge.
A scraper and file can then be used to remove excess glue and level the bone with the tie block.
Next I use a chisel to shape the front edge of the bridge.
I like to slightly round it over.
I also begin removing the material in front of the tie block where the strings exit.
You want to remove enough material so that the strings
can make a gradual transition up to the saddle.
A piece of sandpaper folded in half helps clean this area.
Now I am ready to drill the holes for the strings.
It is harder than you might think to drill a series of holes in a straight line.
I clamp a fence to my drill press table.
Notice that the fence has a angle on it.
I drill a 1/16th inch hole or about 1.6mm
Be sure to set the depth stop on your drill press
After the holes are drilled, I begin sanding the entire bridge to at least 400 grit.
Sand with the grain and take your time to remove all scratch marks.
Also be careful to not alter the radius of the wings while sanding.
Now I need to bevel the edges of the bridge.
This is easily done by using a sharpening jig.
You can place the bridge in it and dial in the exact angle you like.
A few passes on progressively finer grits of sandpaper and you are done.
A quick coat of shellac and the bridge is now ready to be attached to the guitar soundboard.