This is how I shaped a Mini Telecaster headstock (aka peghead) on a neck from a Squier Mini Stratocaster. This is the first step in re-purposing a Mini Strat into a Tele. A set of Mini Telecaster Plans for this project is available.
First step is to make a template of the Tele headstock as seen in the picture above. As you have probably noted, the template is of a lefty. The reason is that it is supposed to be used on the back-side.
I drilled countersunk holes in the template to allow the router base to pass over unobstructed. The flat head screws I used were #10-32 about 1 1/4" long. The only nuts I had available in the right size were knock-in T-nuts, but any old nuts should work.
The neck was off the guitar, and tuning machines and string trees removed. The first and last bushing for the tuning machines were left in place to better locate the template and also prevented the nuts from rubbing directly on the wood when tightened.
In the photo above the template is tested for fit on the Squier Mini neck. The straight edge at the top (red arrows) is aligned. The green arrows mark where the bulk of the material needs to be removed.
After this picture was taken, I marked the outline (along the green arrows) with a marker and removed the template.
The three pictures below illustrate the next steps: marking, roughing out with jig saw and trimming with a pattern bit in the router.
New outline marked
Trimmed with jigsaw
Trimmed with router
When trimming with the router it is important not to run it too far (too close to the nut). In hind-sight, I should have stopped sooner and trimmed by hand. I was lucky and didn't mess it up, but got a little too close for comfort. See the blue arrow in the picture below.
Next the template was removed and the transition at the blue arrow smoothed out. I also sanded off the router burns that can be seen in the picture and rounded the edges to blend with the rest of the peghead. I used a Microplane and some 150 and 220 grit sandpaper.
Next step is to lacquer the freshly sanded wood, but I'll wait until after replacing the tuning machines.
As can be seen, I decided to keep the Squier botched logo on the front and narrowly mutilated serial number on the back, because it looks cool. I'd say, the mod was overall a success.