I decided to make the centre of the key in the middle of the door. The other option I had in mind was to position the locking mechanism in the middle. I figured that most of the time, the door is going to be closed, so the keyhole position came in first.
The brass plate of the lock is about 3 mm (1/8") narrower than the stile, so I had to be careful not to burst through the sides for the shallow mortise for the plate. The mortise for the mechanism itself was not so critical, but I still tried to focus so I wouldn't break anything.
I test fitted the lock, but I then removed it again since the screws that came with the lock are actually a little large for my taste, and they also feature a Philips head. I have some better matching brass screws at home, so I'll wait with the final installation. That will also give me a chance to apply a finish without having to worry about the lock.
I had brought with me a pressed key hole insert. But now I can see that it is intended for a somewhat thicker piece of wood. My plan is to make an escutcheon out of either metal or bone, I am not sure which it is going to be.
After I removed the lock from the test fitting, I glued up the entire door.
While the glue dried, I planed and sanded the outside of the carcase a little, to remove any proud pins and tails. There is a little damage to one of the corners, so I am still a little biased about what I should do about it. Add a moulding, glue in a repair piece or soften it up and do nothing?
I'll leave that question for the time being.
After the glue had dried, I sawed of the horns and fitted the door in the opening.
The rails needed to have a little material removed, since the door was about 2 mm (3/32") too high. I did this on the shooting board, working from both sides so I wouldn't have any spelching on the far corner.
At last I sanded the door to remove my pencil marks, and the next thing will be to install the hinges.
The test fit of the door
One of the damages on the carcase, (front lower left corner)
Nice tight joint.