Once the two pieces are planed flat and square they can be glued together as shown in the pictures. The thickness of the join between the headstock piece and the neck piece should be measured at 14mm.
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Place the two pieces of the neck into the vice as shown in this picture and plane the joint flat and square and keeping the angle of the scarf joint. Plane this up to the line of the nut…   Read more»

Measure 90mm from the Nut towards the end of the headstock and mark the position of the scarf joint. I cut it using a scarf joint jig on the bandsaw. 
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I started by squaring up the neck blank. Planing one of the faces flat and smooth then squaring up both of the edges. I kept the blank wider than the widest part of the headstock….80mm. I allowed 200mm…   Read more»

@nolanrathkegmail-com You certainly can use it for fretboards. I’ve seen it used a couple of times. You might be lucky enough to not need to fill in any gaps but if you do I’d follow @nsj advice and use some…   Read more»

@dhawkes1gmail-com
I agree with robin. Just mark a new centre line on the fretboard and bring the sides in evenly to match your neck profile…… double check that your neck sizes and angle are correct. 
Good luck with it.
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