I'm trying to disassemble a vintage coffee grinder, so I could clean it and put back together. It is probably made in the first half of last century, mostly or all manual work. There is a joint that holds the crank in place (zoomed on photo) and I do not know how it is built. Its rather soft metal so knocking it with hammer in wrong way will disfigure it. Can anyone guess what it is? Some kind of wedge, a screw or something else?