Frames & Ends
First I made a large hexagonal box. My plan was to take slices out of the box to form the bellows, action, and end frames The joints were very carefully formed so that they looked like mitre joints on the outside, but on the inside they were interlocked like box joints. My reasoning was that this would make a much stronger frame - if the finished concertina is ever dropped, I don't want the frames breaking apart!!
I found a lovely piece of figured cocobolo at the local lumber store, and used it to veneer the action and end frames. A solid piece is used for the ends themselves.
I made the end bolts out of 3/32" brass rod (sanded a bit to fit the die), with 3/16" rod for the heads. They're threaded with a 2.5mm x .045 metric die. The friendly folks on rec.music.makers.squeezebox said that some modern concertina makers had moved to that thread, and I figured I might as well try to follow some standard than just pick a thread myself.
Here's a picture of the parts I used to make the end bolts, along with my prototype:
Here is one of the bellows frames with the finished end bolt anchors and end bolts installed, and also a picture of the complete end: the bellows, action, and end frames all veneered and bolted together. You can click these to see larger versions.