Lot's of ways to attach necks to bodies, and this is the method that makes the most sense to me.
I want to design in the alignment and attachment from the start. So it starts with the neck block. I hope that the following will make sense when you see it in context.
I machine up long lenghts of material with a 20mm rebate that will end up being the mortise for the tenon that will be on the neck. I cut one end square and then trim the other end at 2 degrees. This will be towards the back and coincides with the taper of my sides from butt to neck. I mark both top and back on the block. The angles are subtle and easy to get things mixed up.
All my measurements are based off of the soundboard, so the block goes into a jig that I designed for several operations. Here I will drill a cross hole in the block for the bolt that will hold the neck in place.
The neck block needs some shape on the glueing surfaces to conform to the sloped shoulders of my body. I use a 12" radius sanding beam to achieve this. Witness lines are penciled in to show progress. It only takes about 10 swipes to get the correct profile.
I glue it in place, and afterwards the tail block goes in. Masking tape to pull the joint together helps stop things from slipping about when the clamps are going on. And a great tip if you are going for a really tight joint that doesn't require an end graft.
The arrows penciled on the sides are also a reminder to me for which side the soundboard is.
After the blocks are dry, the rims are installed into the body mold and taken to the raduis dish. I have this one set up on an old potters wheel. Because I took the time to trim the sides to my template profile, as well as cut that 2 degree angle on the neck block, there is very little material to remove. It only takes about 5 seconds to fair up the profile and ready to glue on the linnnings.
And now is the first time that you can see that my body mold has a machined out area at the neck block that I slip in a 20mm wide hardwood block that also aligns with the instruments neck block. The fit on both parts is very snug. This assures me that the neck block geometry is setting me up for an easy fit to my neck later in the build.