Avainkellon

Avainkellon is a Finnish term that translates to "key clock" or "clock key." It refers to a small, specialized tool used to wind up the mainspring of a mechanical clock. These clocks, particularly older ones, often feature a winding mechanism that requires a key to be inserted into a winding square or arbor to turn the spring. The avainkellon is designed to fit precisely into this square, allowing the user to rotate the arbor and store energy in the mainspring, which then powers the clock's movement.

The design of an avainkellon can vary depending on the clock it is intended for. Typically, they are made of metal, often brass or steel, and consist of a handle for grip and a hollow shaft that fits over the winding arbor. The size and shape of the shaft are crucial; too large and it won't fit, too small and it won't engage the winding square properly. Some older or more decorative clocks might have a dedicated keyhole specifically for their avainkellon, which might be integrated into the clock's case design. In essence, the avainkellon is a functional necessity for the operation and maintenance of many antique and mechanical timepieces.