So what I want to do here is to explain how I determine where to cut when I make a scarf neck. It was hard for me to calculate just where to cut the neck stock so that i had enough to make the headstock (pegboard if you want) but not too much. I tried math. I tried templates. I tried Zen. Then the answer was simple! You will see below.
First off, I make my scarfed necks where the scarf (headstock) is over the neck and both the neck and head are under the fretboard/fingerboard. Some of you don't put the headstock over the neck so this lesson won't help much. For that you might have to do some other calculations based on where the neck 'bends' down and how long a headstock you want. That's for someone else to decide. Me, I am not that ambitious.
Ok, so for starters, I use some sort of neck stock. What that would be is unimportant as is the thickness or width. That's totally up to you. Also the angle that you want to use. Again, not important here. What i have been using as a point of reference, is a 36" piece of stock. Lets say a standard 1"x2" piece of stock from Lowes or Home Depot (US). I want to make my headstock say, 5 1/2" long. That is, I have 5 1/2" from where the neck bends on the top to the end of the head. I lay the wood down flat (on its 2" side) and measure from one end 5 3/4" (1/4" extra for cutting or bad measurement). I will make a mark across the wood . Then I will lay the wood on its 1" side. I have a jig that I made that will measure the exact angle I want (see pic below). I lay that on the side at the previous line and make a mark of that angle. That's my cut.
Simple eh? Yeps. Can't be any simpler. Once cut, I flip the head over, glue it down, measure about 1/2" away from the topside bend an that is where the fretboard/fingerboard will end and the nut begins. From there, I can measure for my scale and then where the box will be based on where I want the bridge. Even simpler.
Here's the result:
My jig I use to make the angle.