Lets build a guitar neck

The neck's scarf joint glue up consists of 2 pieces of wood. The neck back and the headstock. You could make these from a single piece of wood but you would have a weak neck.
If you look at the grain in a scarfed neck you will see that the grain runs the same direction as your strings. A broken headstock is next to impossible. The weakest part of a scarfed neck is the joint itself but if its glued properly it is very strong.
For a 22 fret neck.
The neck back should be about 22" long, 2.5" wide and 13/16"+ thick.
The headstock should be about 12" long 4" wide and 5/8" thick.
Next cut a 13 degree (or whatever tip back you want) on one end of each board. I do this with a bandsaw because the joint is so steep. Clean up the joints. I use a disc sander.
They need to be glued like the picture shows with the headstock on top of the neck back.
It's a bit tricky gluing these together but I found a way thats fairly simple.
SEE PICTURE BELOW
I clamp a scrap block to my bench then stand the headstock block on its side with the top against the block. That will stop it from sliding. Now set the neck back in place. You will need to put a scrap strip under the neck back to pick it up so it's in the center of the headstock. Now clamp it to the bench. The only thing that can move now is the headstock but it cant move past its stop block.
Glue up the scarf joint and rub the joint together to spread the glue. Take it apart and wait a minute for the glue to sink in. Add more glue if need and put it back together. Clamp it together with 4 c-clamps. Leave it clamped at least overnight.
Once they dry run the flat face through your jointer. Don't go below 3/4" thickness. It needs to be flat to accept the fretboard.

This shows the rough glue up with the neck laid out. This is going to be a 25.5 scale 22 fret neck.
To start the layout draw a centerline all the way. Now grab the nut your going to use. It's important to have the nut because we need to measure from the nut for neck length. If you don't have the nut mark a 1/4" for a standard nut or 5/8" for a floyd type locking nut.
Now measure from the inside (body side) of the nut 18-7/16". Thats the total length of the neck. At this point draw a line straight across. If your making a tele type neck that line is the end of the heel. You just need to round the corners a bit. If your making a strat type neck you need a template to mark the heel. I have a template from Stewmac for this but if you have the body you can make your own heel template.
Measure 7/8" on each side of the centerline at the nut. Then 1/1/8" each side of the centerline at the heel. Connect the dots. This will give you your taper for the neck. It will be 1-3/4" at the nut and 2-1/4" at the heel. A little oversized for sanding. From here draw your headstock to whatever style you want.
Now bring it to the bandsaw (or your tool of choice) and cut it out. I normally clean up the heel at the disc sander at this point.
No need to straighten the rest as we will use the fretboard to straighten the neck.

Here I put 2 pics together to show the scarf glue up. There are 2 more bessey clamps to the right that don't show.
I did 2 pictures so it could be seen with or without the c-clamps.
As you can see in the pictures this bench has been well used.

Now that we have the basic shape I lay the truss rod on top to mark its position. I always make necks with 2way truss rods. They only need a slot to work. They don't need a tapered slot like a single rod. The slot needs to be 1/4" wide and 3/8" deep. The slot needs to be widened slightly to acomodate the cover on the adjuster at the top.

This is a jig that I made for routing the truss rod slot. It's just a board with a 1/2" slot in it. This is a view of the back just showing how the neck is held. The next picture shows the router set up.

This is the router setup that matches the jig. The router base has a 1/2" bushing that slides in the 1/2" slot in the jig. The bit is a 1/4" straight bit which is what is needed for the truss rod. The next photo shows it in use.

This is the router running in the slot in the jig. The neck was bolted in the jig from the back. The centerline we drew in the beginning is centered in the slot. The slot has a stop at the bottom that I lined up with the marks we put on previously. There is no stop for the top as there are length differences in truss rods so a stop can not be used. I just set the router in the slot where I want the slot to stop and mark the jig with a pencil.
Don't try to cut 3/8" deep all in one shot. It takes 6 or 8 passes to get to the correct depth. I just keep setting the truss rod in the slot untill it is just slightly below the surface of the neck.

Here the truss rod is installed. Notice how I had to enlarge the slot at the top for the adjuster. Just be sure the rod is flush or ever so slightly recessed or it will hold the fretboard up.
At this point you can glue on the fretboard if you have one. If you need to make one keep reading.

Here's the miter box I use to cut fretboards. These are available at most luthier supply houses. This one came from Stewmac.
This process is fairly simple. The fretboard blank is clamped to a fretting template. You just cut your fret then slide the template and board into the next pin. Very simple and extremely accurate. They tell you to connect the fretboard to the template with double sided tape but I just use 2 clamps. Just be sure you only take one clamp off at a time if they need moving so the board never moves.
Cut the fretboard to length. I usually cut it at about 3/8" past the 22 fret.
They sell different scale templates if needed. Just don't follow these directions if your using a different scale because the dimensions will be different.

Once you finish cutting your fret slots you need to taper the board. This is done with this tapering block. All it is is a block with a tab at each end. One tab is 1/4" and the other is 1/2". A couple people on the internet have claimed that they came up with this idea but this method of tapering has been used by woodworkers forever.
To use: Set your fence at 2-3/16" or ever so slightly more if you want. I usually go 1/32" over.
All cuts are made with the nut end toward the blade.
1st cut - Using the 1/4" tab run it through the saw with frets up like the picture on the left. I put a little tape on the edge to prevent tearout.
2nd cut - Using the 1/2" tab run it through the saw with frets down.

When gluing on the fretboard be sure to line the top of the fretboard up with the nut line at the top of the neck. Otherwise your scale will be wrong. The 22 fret neck hangs over just slightly depending on how much extra you left when you cut it to length.

And finally drill and install the fret markers. I usually drill the holes at 1/4" and cut the dots with a 1/4" plug cutter.
The markers go at frets 3, 5, 7, 9, 12Double, 15, 17, 19, 21.
Once the markers are in you need to radius the board. Stewmac sells sanding blocks in different radii. I personally like playing on a 16" radius. This takes a bit of sanding to do. Just keep a straight edge handy to be sure your straight. The straighter the neck is the easier it will be to fret.
Drill the tuner holes for your particular headstock..

Here is the completed neck. Continue reading for fretting instructions