Archimedesis quoted for saying Eureka, Eureka. (I have found [it].),
when he discovered the buoyancy.
Perhaps, the inventor of these time- and woodsaving chucks luckily shouted out the same words. This type of chucks is very common in the German Ore Mountains, a worldfamous woodworking area, but I do'nt know, if it was invented there. Novadays, these chucks can be ordered from many tool stores.
Nevertheless, I found some good reasons, for making my own Eureka- chucks for myself: At the time I didn't have a standard spindle thread on my lathe. I like the chuck very small, because I specialized in miniature woodwork. and last but not least, I want everything inexpensive. The bodies of my smallest chucks are made of brass instead of steel, so eventually it can be turned on the woodworker's lathe. Additional I used the spring of a clockwork in the right size, for making the cutting rings. As we can see from the picture, there must be a slut, were we can use a wedge like tool too separate the remaining wood from the chuck. For grinding the cutting edges, I've first soldered each ring to a brass bar with a fitting diameter. So, I could handle it securely during the grinding process. After that, the rings were removed and cleaned from the tin. Some fitting brass rings have to be turned, to center the steel rings in the body of the chuck. If everything fits properly, we warm up the chuck, avoiding to burn and/or soften the the spring steel parts. Now, I added flux and soldering tin, to solder all parts together.