There are three different types of neck blanks from which to make a guitar neck.
One is to use a 24 inch neck blank and attach a solid heel block to it.
Another way is to make a neck with a stacked heel from a single 35 inch neck blank.
The third way is to cut a one piece neck from a billet.
I will begin by showing how to do the scarf joint
and this is the same for either the 24 inch or 35 inch neck blank.
The neck blank should be about 3 to 3 and 1/4 inches wide or about 7.5cm to 9cm wide.
The length should be either 24 inches, about 61cm or 35 inches, about 89cm.
On my steel string guitars I measure a skoshe more than 3 inches
or about 80mm in from one end and draw a line.
I then measure another 3 and 3/8 inches or about 87mm from the first line and draw another line.
On my classical guitars I measure in from one end 5 and 1/2 inches or 14cm and draw a line.
I then measure another 2.5 inches, or 6.5 cm from this line and draw another line.
These lines are then squared down the side of the neck blank.
With a straightedge I connect these two lines diagonally across the side of the neck blank.
This should be about a 15 degree angle. However, the thickness of your neck blank can alter this.
I always check the angle with a protractor to make sure it is not more than 15 degrees.
The next step is to cut the scarf joint at the line you have just drawn.
I usually use a bandsaw to do this but you could also do it by hand.
You could even make a jig to cut it on a table saw.
After cutting the diagonal line I clean up the side that gets glued to the bottom of the neck blank using a block plane.
I then use a sanding block to remove any plane marks.
Check for fit to make sure it is a good fit before gluing it up.
There are several ways to glue the scarf joint. You can clamp the neck blank to a bench
and then use clamping cauls and C clamps like I am doing here.
You can also clamp the neck in a vise and then use clamps to apply pressure to the joint while it glues.
This method keeps the neck straight as you apply pressure.
Whichever method you use remember that you only need a little bit of glue.
Now I can thin the peghead to the correct thickness.
Don’t forget to subtract the thickness of the veneers that will be placed on the peghead from your final measurement.
For my guitars I thin the classical peghead to 18mm or .71 of an inch
and my steel string pegheads get thinned to 11mm or .43 of an inch.
My final thickness for the peghead after the veneers are applied
is 22mm or .87 for the classical peghead and 15mm or .59 for the steel string peghead.
As you work make sure the scarf joint stays square.
Now we can lay out the scale.
You will notice that after thicknessing the peghead,
the scarf joint point of intersection with the face of the neck blank
has moved back towards the heel block. This sometimes makes the neck blank too short.
At this point throw the neck blank away and order a new one.
I am kidding.
There is a little trick that can help stretch the board.
I use a joiner to plane the face of the neck blank.
This moves the scarf joint point of intersection forward and thus stretches the length of the board.
It doesn’t really stretch the board but you get the idea.
If you take complete passes along the face of the neck blank
you can make it too thin on the heel block end, especially if you want to do a stacked heel.
I therefore make three passes on the peghead end to one pass on the heel block end
just like I am showing here. When using this board stretching trick
I never plane thinner than about 17mm or .67 of an inch on the nut end of the neck.
You can join the face of the neck blank until you have enough length for the scale and tenon.
Notice how the point of intersection is now much closer to the glue line of the scarf joint.
Make sure you have enough length on the peghead for your peghead design.
You can now go ahead and lay out the scale length.
If you are using the one piece heel block on a 24 inch neck blank then just glue the heel on at this time.
If you are doing the stacked heel then cut the neck off at the end of the tenon
or flush with the appropriate fret if using a butt joint.
After cutting off the excess of the neck blank, align it with your 12th or 14th fret markings
on the side of the neck blank and calculate how much you need for each section of the stacked heel.
Don’t forget to add the measurement for your tenon if needed.
Mark the pieces and after cutting into sections align them in the same order on the bottom of the neck blank.
To glue the stacked heel pieces together just place a scrap piece of wood in your vise
and then align the pieces and apply pressure by closing the vise.
After appropriate glue time, remove the neck from the vise and you now have a stacked heel.
To cut a one piece neck from a billet I start by marking the shape of the neck onto the billet.
You can use an existing neck or your plans to do this.
Once the shape is on the billet then use a band saw to remove everything that doesn’t look like a neck.
You can cut two neck blanks from one piece of wood.
You need to have a sharp blade to execute this smoothly and may need to make relief cuts during the process.
Once the neck is cut out, or you have made the neck with a one piece heel block or a stacked heel,
go ahead and continue building your guitar.